Graduate Student Theses Supported by DOE's
Environmental Sciences Division:
Fiscal Year 2000 Update
(ORNL/CDIAC-130)
(http://cdiac.esd.ornl.gov/epubs/cdiac/cdiac130/cdiac130.htm)
Compiled by
Robert M. Cushman
Carbon Dioxide Information Analysis Center
and
Alisa Harrison
Katie Stevens
National Institute for Global Environmental Change National Office
University of California, Davis
September 2000
Carbon Dioxide Information Analysis Center
Environmental Sciences Division
Oak Ridge National Laboratory*
U.S. Department of Energy
Oak Ridge, Tennessee
*managed by University of Tennessee-Battelle, LLC, for the
U.S. Department of Energy under Contract DE-AC05-00OR22725
1
Ahn, SoEun. 1997. Economic Analysis of the Potential
Impact of Climate Change on Recreational Trout
Fishing in the Southern Appalachians. Ph.D. Thesis,
North Carolina State University, 137 pages.
This study focuses on economic analysis of the
potential impacts of climate change on recreational
trout fishing in the Southern Appalachian Mountain
area of North Carolina. Significant decreases in trout
habitat and/or populations are expected in the study
area if water temperature increases due to global
warming. The main purpose of this study is to estimate
the trout angler's welfare loss from the reductions of
trout habitat and/or population in recreational trout
fishing based on the climate change scenarios. Nested
multinomial logit random utility models (RUMs) were
used for the economic assessment and two nesting
structures were examined -- the first with two decision
levels and the second with three decision levels -- to
describe an angler's choice behavior given a single
occasion. The five scenarios used for estimating trout
angler's welfare changes were 10, 20, 30, 40, and 50%
reductions in both stream length and trout populations.
An angler's median compensating variation (CV)
measures, the measure of an angler's monetary welfare
loss, for each of the five scenarios from the two-level
nested model were -$1.36, -$2.66, -$3.92, -$5.14, and -
$6.32 per trip in 1995 dollars. With the three-level
nested model, median CV measures for each of the five
scenarios were -$0.35, -$0.69, -$1.02, -$1.34, and -
$1.64.
Major Professor(s): de Steiguer, J. Edward
Department: Forestry
Principal Investigator(s): Abt, Robert C.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CLIMATE, ECONOMICS, FISH,
MODEL
2
Arunachalam, Valli. 1996. Ultrafine Aerosol Particles:
Long-Range Interactions, Aggregation Kinetics and
Structure. Ph.D. Dissertation, Texas A&M University,
131 pages.
A theoretical and computational study of ultrafine
aerosol particle aggregation including the long-range
van der Waals interaction force is presented.
Previously, studies of aggregation have not rigorously
incorporated the effects of particle interactions. The
significance of this work lies in the use of physically
motivated interaction potentials in calculations of
aggregation. In the first part of this study, a highly
accurate approximation is developed whereby, for the
first time, the van der Waals energy can be calculated
for any geometry. In the aggregation process considered
here, the geometry of interest is an irregular aggregate
of adhering, spherical primary particles and an
approaching primary particle (monomer). The effect of
retardation of the long-range energy is also
incorporated. In the second part of this study, the effect
of these retarded, long-range van der Waals
interactions, particle transport and ambient pressure
and temperature on aggregate-monomer collision rate
constants and aggregate structure are investigated by
performing molecular dynamics simulation
calculations. Glassy carbon is chosen as the prototype
material for simulations. In general, the aggregates
grown with the interaction potential tend to have
relatively open structures, with few branches, while the
aggregates grown without the potential tend to be more
compact and branched. Further, the interaction
potential results in enhancements in the collision rate
constants over the corresponding geometric rate
constants. The effects are smaller in the transition
regime than in the free molecular regime. Simulations
performed with the non-retarded and the retarded
interaction potential show that the percentage of
relatively open aggregates, and the magnitude of the
collision rate constants are greater in the latter case
than in the former. An increase in temperature resulted
in a collapse of aggregate structure and decrease in
collision rate constants. The effects are more
pronounced in the free molecular than in the transition
regime. No significant difference was observed in the
structure of the aggregates or in the aggregate-
monomer collision rate constants as a result of
changing the pressure of the simulations from 760 mm
to 3040 mm.
Major Professor(s): Marlow, William H.
Department: Nuclear Engineering Department
Principal Investigator(s): Marlow, William H.
Program Area: Atmospheric Chemistry
KEYWORDS: AEROSOL, AGGREGATE
3
Bahrmann, Chad. 1997. The Influence of Air Mass
History on Black Carbon Concentrations in the
Southeastern US. M.S. Thesis, North Carolina State
University, 64 pages.
Atmospheric black carbon concentrations in the
southeastern US have been measured at a regionally
representative site near Mt. Mitchell, NC (35o 44' 05"
N, 82o 17' 15" W, 2038 m elevation), the highest peak
in the eastern US, during a nine month period from
June to October 1996 and March to June 1997. Black
carbon concentrations are measured by an
Aethalometer, which operates by measuring the
attenuation of light through a sample. This attenuation
is attributed to accumulated black carbon on the sample
medium. All measured black carbon concentrations are
reported in terms of air mass histories determined from
back trajectory analysis using the Hybrid Single-
Particle Lagrangian Integrated Trajectory (HY-SPLIT)
model. Air masses influencing the site have been
classified as polluted, marine, and continental
according to sulfate and nitrate emission inventories.
The average BC mass concentrations for each sector
are: 216.6 ~ 47.8 ng m-3 for polluted air masses, 65.6 ~
23.5 ng m-3 for marine air masses, and 169.9 ~ 50.6 ng
m-3 for continental air masses. A strong positive
relationship between cloud condensation nuclei and
black carbon concentrations suggest at times the black
carbon measured at the site may be internally mixed.
The average black carbon concentration found in cloud
water is 74.2 g of black carbon per kilogram of cloud
water. Clear air black carbon to sulfate mass ratios
ranged from 0.01 to 0.06 and will therefore, only
slightly reduce the cooling effect caused by the direct
forcing of sulfate aerosols.
Major Professor(s): Saxena, Vinod K.
Department: Marine, Earth and Atmospheric Sciences
Principal Investigator(s): Saxena, Vinod K.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: AEROSOL, CARBON, CLOUDS,
CONDENSATION
4
Barnes, Diana H. 2000. Urban Pollution of Mitigated
Greenhouse and Ozone-depleting Gases. Ph.D. Thesis,
Harvard University, 328 pages.
The Montreal Protocol in 1987 and its subsequent
London (1990) and Copenhagen (1992) Amendments
mandated control measures on the production and
consumption of ozone-depleting substances. The
majority of the substances, including CFC-11, CFC-12,
CFC-113, Halon-1211, CCl4, and CH3CCl3, were
scheduled for 100 percent reductions by 1 January 1996
in developed countries. Global background
measurements taken in remote (far from the pollution
sources) locations over the last decade have indeed
indicated a deceleration in the atmospheric growth
rates for many of the species and, for some of the
shorter lived molecules, notably CH3CCl3, declining
atmospheric concentrations are now being observed
[list references of NOAA papers]. While these
remotely-based measurements give insight to the health
of the atmosphere at large, our ability to tally the
spatial and temporal emissions of these chemicals on a
regional basis during production, transport, and
consumption may now be compromised, given that
today such activities are subject to fines and may not be
reported willingly. Atmospheric modelers, concerned
about ozone depletion, are constrained to rely on either
remote observations or county and state emission
reports to the EPA, which in turn are based on factory
inventories. To address this difficulty, this study
provides an independent measure of emissions of
ozone-depleting species for the years 1996 through
1998, well beyond the year in which they were fully
banned by the Montreal Protocol. The measurements
were taken every 24 minutes at Harvard Forest, MA,
downwind of the Northeast urban-industrial corridor,
including the greater metropolitan region of New York
City. Using the well-documented EPA CO emissions
inventory and a combination of the Midgely and
McCulloch PCE sales-based inventory and EPA/TRI
PCE emissions inventory, we estimate the annual
urban/industrial emissions of CFC-11, CFC-12, CFC-
113, CH3CCl3, Halon-1211, CHCl3, H2, CH4, and SF6
all on a per capita basis for the New York City--
Washington, D. C. corridor. We compare our results to
those of inventories for the Northeastern, U.S., for the
U.S. as a whole, for Europe, and for the world, where
available.
Major Professor(s): Wofsy, Steven C.
Department: Earth & Planetary Sciences
Principal Investigator(s): McElroy, Michael B.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: AIR QUALITY, HALOGEN SPECIES,
HALOGENATED HYDROCARBON, HYDROGEN,
METHANE, MONTREAL PROTOCOL, URBAN
ENVIRONMENT
5
Bauerle, William L. 1997. Diurnal Water Potential
Gradients in Relation to Water Loss from Old Growth
Douglas-Fir (Pseudotsuga menziesii) Trees. M.S.
Thesis, University of Washington, 67 pages.
The use of a high rise canopy crane installed in an old
growth Douglas-fir forest aided in the collection of
xylem pressure potential and water loss measurements.
Predawn and solar noon xylem pressure potential
measurements were made along a 64.7 meter gradient
of Douglas-fir canopy height. The measured gradient at
predawn or under no flux conditions was about -0.01
MPa per meter of height. This value matches the
theoretical hydrostatic gradient. Thermocouple
psychrometry and porometry were used to confirm
xylem pressure potential measurements made by the
pressure chamber. The data in this study support the
pressure chamber as a valid eco-physiological
instrument to estimate water potential and describe
water transport in plant material.
Major Professor(s): Hinckley, Thomas M.
Department: Forest Resources
Principal Investigator(s): Hinckley, Thomas M.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: FLUX, PRESSURE, SAP, STOMATE,
TRANSPIRATION, VEGETATION, WATER
6
Bowling, David Randall. 1999. Stable isotope analysis
of carbon dioxide exchange in a Tennessee hardwood
forest. Ph.D. Thesis, University of Colorado, 204
pages.
Observations of the patterns of biosphere-atmosphere
exchange of CO2 and its isotopic forms, and of the
diurnal and seasonal dynamics of these molecules have
the potential to substantially increase our knowledge of
the processes controlling carbon cycling in ecosystems.
In this dissertation, new techniques have been
developed and associated experiments conducted in a
temperate deciduous forest in eastern Tennessee
(Walker Branch Watershed) to elucidate the biological
and physical processes controlling forest-atmosphere
carbon dioxide exchange. Measurements of canopy-
level fluxes of isoprene are described and compared to
eddy covariance measurements. Excellent agreement
was obtained between the two techniques, providing the
first direct comparison between these two methods for a
reactive compound. The relaxed eddy accumulation
technique was modified to produce measurable
atmospheric signals in isotopic composition of CO2.
Direct measurements of the fluxes of CO2 and its
component stable isotopes were made using relaxed
eddy accumulation and standard eddy covariance
combined with flask sampling. These data are the first
flux measurements reported for these compounds over
natural ecosystems. Mass balance equations are derived
to use net isotopic flux measurements to partition net
ecosystem exchange into its component fluxes, net
photosynthesis and respiration.
Major Professor(s): Monson, Russell K.
Department: EPO Biology
Principal Investigator(s): Monson, Russell K.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: ATMOSPHERE, CARBON DIOXIDE,
FLUX, FOREST, PHOTOSYNTHESIS, RESPIRATION,
TERRESTRIAL ENVIRONMENT
7
Bowman, Jean Ann. 1999. The Role of Continental
Moisture Recycling in Climate Model Precipitation and
Climate Change Impact Research. Ph.D. Thesis, Texas
A&M University, 72 pages.
This research examines the effect of continental
moisture recycling on climate model precipitation to
determine the extent to which land surface hydrologic
process approximations contribute to imprecise model
precipitation simulations. The inability of climate
models to accurately simulate regional precipitation
patterns may be attributed to inaccuracies in (1)
atmospheric moisture transport processes, and (2)
moisture exchanges between the land surface and the
atmosphere. It is difficult, however, to quantify the
relative role each of these plays in the problem.
Estimation of model moisture recycling is evaluated as
a potential method of differentiating between the
sources of model error. Two climate simulations are
performed using the National Center for Atmospheric
Research (NCAR) global atmospheric general
circulation model (GCM) known as the Community
Climate Model (version 2) (CCM2). Moisture recycling
is also estimated using results from a reanalysis climate
modeling project. Total model precipitation for four
large continental regions is partitioned into
contributions from moisture transported into the region
and moisture recycled locally through evaporation.
Moisture recycling is expressed as Pm/P, where Pm is
locally-recycled moisture (from a specified land surface
region) and P is total precipitation. The moisture
recycling ratio, inward moisture flux, moisture
divergence, precipitation and evaporation quantities are
compared as monthly means to observations of those
quantities for each of the four geographic regions, and
to estimates of the quantities published by Brubaker et
al. (1993). Monthly mean CCM2 precipitation from the
non-BATS simulation is also compared to both sets of
model results and to the Brubaker et al. (1993) results.
Differences in monthly mean precipitation originating
from all four of the sources (three models and one set of
published results) are clarified by comparing the annual
cycles and through an analysis of variance. To further
evaluate the extent to which the moisture recycling
process describes model precipitation error, model
precipitation is adjusted using the difference between
the Brubaker et al. (1993) recycling and computed
model recycling. This is done for each of the four
geographic regions of interest, and the resulting scaled
precipitation series are again compared to observed for
each region respectively.
Major Professor(s): North, Gerald R.
Department: Geography
Principal Investigator(s): Wurbs, Ralph A.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CLIMATE, HYDROLOGY, MODEL,
MOISTURE, PRECIPITATION
8
Bremer, Dale. 1998. Effect of Burning and Grazing on
Carbon and Energy Fluxes in a Tallgrass Prairie. Ph.D.
Dissertation, Kansas State University, 129 pages.
Burning and grazing are the two most common forms
of land management on grasslands and may influence
ecosystem energy, carbon (C),and water budgets.
Increasing concentrations of atmospheric CO2 may also
affect these factors. The objectives of this study were to
measure the effects on a tallgrass prairie of: 1) grazing
on soil-surface CO2 flux (Fs); 2) burning on energy
fluxes and evapotranspiration (ET); and 3) elevated
CO2 on Fs, soil water content, and microbial C under
severe drought. Comparative measurements of Fs were
collected from grazed and ungrazed pastures, and from
plots hand-clipped to simulate grazing. Annually, Fs
ranged from 8.8 x 10-3 mg m-2 s-1 during the winter to
0.51 mg m-2 s-1 during the summer, following the
patterns of soil temperature and canopy phenology.
Clipping typically reduced Fs by 21 to 49% within 2
days of defoliation. Cumulative annual Fs was 4.94 kg
m-2 in unclipped plots and 4.08 kg m-2 in clipped plots;
thus, clipping reduced annual Fs by 17.5%. Daily Fs in
grazed pastures was 20 to 37% less than in ungrazed
pastures. The surface energy balance and ET were
measured during the growing season on burned (B) and
unburned (UB) watersheds. During the first 6 weeks
after the burn, lower albedo on the B site raised
available energy (net radiation minus soil heat flux) by
8.6% compared with the UB site. The absence of dead
biomass on the B site induced a three-fold increase in
surface conductance to water vapor and consequently,
average ET was higher on the B (2.97 mm d-1) than on
the UB site (1.40 mm d-1). Differences in albedo and
available energy between sites diminished by June 1,
but ET remained higher on the B site because of its
greater leaf area index. By July 1, the effects of the
burn on ET were negligible. Cumulative estimates of
seasonal ET were 503 mm on the B site and 367 mm
on the UB site; thus, burning increased seasonal ET by
23.4%. Measurements of Fs, soil water content, and
microbial C were collected from CO2-enriched and
ambient CO2 open-top chambers during an induced
drought. The average soil water content in the 1.5 m
profile was significantly higher under elevated CO2, but
extremely dry soils in the upper part of the profile kept
Fs low in both treatments. Nevertheless, Fs was
significantly higher under elevated CO2. However, no
differences in microbial C between treatments were
apparent. Results indicate that land management
factors such as grazing and burning have strong
impacts on energy, C, and water budgets in grasslands.
Increased atmospheric CO2 may also affect C dynamics
in prairies during severe drought.
Major Professor(s): Ham, Jay
Department: Agronomy
Principal Investigator(s): Ham, Jay
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON, CARBON DIOXIDE,
COMBUSTION, ENERGY FLUX,
EVAPOTRANSPIRATION, FERTILIZATION,
GRASSLAND, GRAZING, MICROBE, RADIATIVE
PROCESS, RESPIRATION, SOIL, STRESS, WATER,
WATER USE
9
Brogan, Sean. 1997. Expert Estimates of Climate
Change Impacts On Southern Appalachian Coldwater
Fisheries. M.N.R. Thesis, North Carolina State
University, 95 pages.
Regional climate warming may increase ground and
streamwater temperatures resulting in the loss of fish
habitat. This study summarized the opinions of thirty-
eight coldwater fisheries experts regarding the impacts
of climate change on Southern Appalachian brook trout
(Salvelinus fontinalis), brown trout (Salmo trutta) and
rainbow trout (Oncorhynchus mykiss). A 4.6 degree C
and 25% reduction in summer water levels represented
future climate change conditions. Median responses by
experts indicated stream and groundwater temperature
increases of 3.0 degrees C and 1.0 degree C,
respectively; a 5% rise in trout metabolic rates; a 3%
decline in dissolved oxygen content; a 5% decrease in
brown trout habitat and a 10% reduction in brook and
rainbow trout habitat.
Major Professor(s): de Steiguer, J. Edward
Department: Forestry
Principal Investigator(s): Abt, Robert C.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CLIMATE, FISH
10
Brondizio, Eduardo. 1996. Forest Farmers: Human
and Landscape Ecology of Caboclo Populations in the
Amazon Estuary. Ph.D. Dissertation, Indiana
University, 481 pages.
This is a study of agricultural and agroforestry
intensification in the Amazon estuary and its socio-
economic and environmental implications. Remote
sensing, vegetation ecology, and socio-economic
assessment are integrated in a multiscale fashion, and
different land use systems are compared with special
emphasis to ACAI agroforestry systems (Euterpe
oleracea). Agroforestry intensification in the
floodplains carried out by Caboclo populations presents
an economically and ecologically viable alternative for
food production in the region that provides reliable
incomes for local populations without increase in
deforestation rates.
Major Professor(s): Moran, Emilio
Department: School of Public and Environmental
Affairs
Principal Investigator(s): Moran, Emilio
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: AGRICULTURE, ESTUARY, FOREST,
LAND USE, TROPICS
11
Brown, Kimberly J. 2000. Canopy Architecture of
Clonal Hybrid Populus: Implications for Light
Reflectance, Interception, and Physiology. Ph.D.
Thesis, University of Washington, 160 pages.
Various-sized monoculture plantation blocks of P.
deltoides x P. nigra (DN) and P. trichocarpa x P.
deltoides (TD) hybrid poplars were distinguishable in
an AVIRIS image of a fiber farm in eastern
Washington State. Presuming an operational plantation
would use clones of equal productivity, three
hypotheses were posited and tested: (1) the two Populus
hybrids would have equal above-ground productivities;
(2) clonal differences in canopy architecture would be
linked to differences in canopy light dynamics; and (3)
for equal clone productivity, differences in clonal
hybrid leaf morphology and physiology must exist to
compensate for differences in canopy architecture and
light interception. Repeated destructive harvests and
canopy architectural and leaf physiological
measurements were made from 1996 to 1998. Mean
whole-tree aboveground biomasses and leaf areas were
similar between the two clones (DN=57.97 ñ 9.89 s.e.,
TD= 54.77 ñ 16.62 kg, DN=5.9 ñ 1.5, TD= 4.6 ñ 2.1
m2 leaf area tree-1). Significant clonal canopy
architectural differences were: the DN clone had more
branches, narrower branching angles, a deeper live
crown, a more vertical upper canopy leaf angle
distribution, and a lesser light extinction coefficient (k
= 0.33); the TD clone had fewer, more open branches, a
shorter live crown, a more horizontal upper canopy leaf
angle distribution, and a greater k (0.46). For DN and
TD, leaf mass per unit area, chlorophyll, leaf nitrogen,
leaf thickness, and cell size were influenced by relative
canopy position but did not differ interclonally.
Similarly, both clones shared similar leaf
photosynthetic responses to controlled manipulations of
light or CO2 conditions within a relative canopy
position. A multi-layered canopy model with equal leaf
photosynthetic parameters but different canopy
architectural and light interception parameters was
used to simulate whole-tree maximum potential net
photosynthesis (MPNP) for DN and TD (after Bond et
al. 1999). In the model, the interactions of vertical leaf
area distribution (VLAD), k, and leaf angle
distributions in each clone resulted in equally
illuminated leaf area and similar MPNP for the two
clones. Clonal differences in leaf angle most strongly
influenced MPNP by altering whole-canopy leaf area
illumination.
Major Professor(s): Hinckley, Thomas M.
Department: Ecosystem Sciences
Principal Investigator(s): Hinckley, Thomas M.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: LEAF AREA INDEX (LAI),
MORPHOLOGY, PHOTOSYNTHESIS, PHYSIOLOGY,
STOMATE, TRANSPIRATION, TREE
12
Burba, Georgiy G. 1996. Energy Fluxes in a Mid-
Latitude Prairie Wetland Ecosystem. M.S. Thesis,
University of Nebraska at Lincoln, 95 pages.
Components of the energy budget (net radiation, energy
storage, and sensible and latent heat fluxes) were
measured in three communities (Phragmites australis,
Scirpus acutus, and open water) in a marsh located in
north central Nebraska during the growing season of
1994. The Bowen ratio-energy balance method was
used to calculate sensible and latent heat fluxes. During
daytime, the energy storage term (G) consumed 45-
60% of the net radiation (Rn) in open water, and 20-
30% in the two emergent communities (Phragmites and
Scirpus). During nighttime, G was a significant source
of energy in all three communities and, therefore, the
daily (24 hours) averaged values of G were small.
Evapotranspiration (ET) was a major consumer of the
incoming solar energy in Phragmites and Scirpus.
During early and peak growth, the daily ET in the two
emergent communities ranged between 2.5 and 6.5 mm
d-1 utilizing around 80-90% of Rn. As compared to the
ET from Phragmites and Scirpus, the evaporation (E)
from open water was about 25% smaller during
daytime, and 2-3 times larger during night. For the
entire measurement period, the daily integrated E in
open water was 4.1 mm d-1, and the daily integrated ET
was 3.8 mm d-1 in Phragmites and 3.5 mm d-1 in
Scirpus. Before senescence, the daily ET in Phragmites
and Scirpus was between 75 and 100% of the potential
rates (ETp). During senescence, the percentage was 10-
75%. In open water, the daily E was 60-100% of the
potential rate throughout the measurement period. ET
in Phragmites was partitioned into transpiration (Ev)
and evaporation (Es) using a dual-source modification
of the Penman-Monteith equation. During the early and
peak growth stage, Ev contributed 40-62% of the total
ET (Ev ranged from 1.7 to 3.5 mm d-1 and Es ranged
from 1.0 to 3.2 mm d-1). During senescence, Ev
decreased, and by the end of the season, the Ev/ET ratio
reached negligible values. The daytime variation of Es
in Phragmites (as well as that of E in open water) did
not follow Rn. The variation was primarily controlled
by thermal stability and air dryness.
Major Professor(s): Verma, Shashi B.
Department: Agricultural Meteorology
Principal Investigator(s): Verma, Shashi B.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: ENERGY FLUX, EVAPORATION,
FLUX, HEAT, PRAIRIE, TRANSPIRATION,
VEGETATION, WETLAND
13
Chen, Wanchun. 2000. Assessment of Land Surface
Energy Budgets in GCIP CART/ARM Region. M.S.
Thesis, University of Maryland, 21 pages.
The surface energy budgets of the operational Eta and
GEM models were evaluated with in-situ observations
and satellite products. Time series output from the Eta
and the GEM models were evaluated by comparison to
measured values at CART/ARM region for winter
1998/1999. Surface energy budget components, soil
moisture and cloud indicators were examined. The
correlation between downward short wave radiation
and cloud cover fraction was also computed. It was
found that for ETA model, the bias in latent heat flux
and Bowen ratio are consistent with the bias in soil
moisture: the positive bias in soil moisture results in
larger than observed latent heat flux and, consequently,
smaller Bowen ratio. The GEM model has a
remarkable representation of the downward short wave
radiation and the net radiation at the surface, but
surface heat fluxes, particularly the ground heat flux,
reveal biases.
Major Professor(s): Stenchikov, Giorgiy L.
Department: Department of Meteorology
Principal Investigator(s): Stenchikov, Giorgiy L.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: BOWEN RATIO, ETA MODEL, GEM
MODEL, LATENT HEAT, SENSIBLE HEAT, SOIL
MOISTURE
14
Chung, Hong-Fu. 1996. Measuring Economic Welfare
Effects of Supply Shifts in the Southern Softwood
Stumpage Market: With Application to Climate
Change Impact Analysis in the Forest Sector. Ph.D.
Dissertation, North Carolina State University, 125
pages.
Price shifts in a given market could cause prices in
other markets to shift. Such multi-market price effects
could make the measurement of economic welfare
difficult. This is because changes in welfare - as
measured in changes in producer and consumer
surpluses under compensated market schedules - may
not be confined to the original market; instead, they
may cross over to horizontally and vertically integrated
markets upstream and downstream from the original
market. A test was made to determine whether such
crossover price effects were significant in the Southern
softwood timber market. To perform such a test, a two
separate market models were estimated from the same
cross sectional data set of timber harvests and standing
live volume. One timber market model was partial
equilibrium (PE) in nature while the other was general
equilibrium (GE). The PE model assumes that prices in
adjacent markets are held fixed; in contrast, the GE
model drops non-timber prices from the specification.
The resulting models showed incongruous results for
the market for sawtimber, but a well behaved pulpwood
market. A statistical test of the slopes of the demand
curves of the two models on the pulpwood market failed
to reject the null hypothesis that they were equivalent.
Consequently, this study is not able to provide strong
evidence that price effects and therefore welfare effects
in the Southern softwood pulpwood market transfer
over to other markets in the economy. Nevertheless, the
study did find that the GE demand curve for timber was
more own-price inelastic than the PE demand curve.
The result conforms to what microeconomic theory
would predict. Finally, a case application was made
applying both PE and GE market models to scenarios
of global climate change. Differences in welfare
impacts as large as two fold were found. It helps to
illustrate the potential range of welfare measures that
could occur if a PE modeling framework was used
instead of a GE modeling framework.
Major Professor(s): de Steiguer, J. Edward
Department: Forestry
Principal Investigator(s): Abt, Robert C.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: ECONOMICS, FOREST, MODEL
15
Croker, Jennifer. 1997. Ecophysiological Significance
of Nonhydraulic Root-to-shoot Signaling in Control of
Stomatal Behavior During Soil Drying. M.S. Thesis,
University of Tennessee, 82 pages.
The objectives of this study were to: (1) characterize
stomatal response of six deciduous tree species to
nonhydraulic root-sourced signals of soil drying, and
(2) test whether species sensitivity to nonhydraulic
signaling is allied with their drought avoidance and
tolerance profiles. Saplings were grown with roots
divided between two pots. Three treatments were
compared: half of the root system watered and half
droughted (WD), half of the root system watered and
half severed (WS), both halves watered (WW). Drying
about half of the root system caused nonhydraulic
declines in stomatal conductance (gs) in all species,
with gs of WD plants reduced to from 40% to 60% of
WS controls. Declines in gs were closely related to
declining soil matric potential between -0.01 and -0.10
MPa. Soil matric potential required to cause declines in
gs of WD plants to 80% of WS controls varied from a
high of -0.013 to a low of -0.044 MPa. Stomatal
inhibition varied somewhat with leaf age in half of the
species. Leaf osmotic potentials during soil drying were
mostly similar among treatments. Although stomatal
sensitivity to the nonhydraulic, root-sourced signal
(characterized as decline in gs per unit decline in soil
matric potential) was not closely correlated with
previously identified lethal leaf water potentials or
capacity for osmotic adjustment, species having the
highest stomatal sensitivity also had the least
dehydration tolerance. This suggests that stomatal
sensitivity to nonhydraulic root signals may be
mechanistically linked to a limited extent with other
characteristics defining relative species drought
tolerance.
Major Professor(s): Aug‚, Robert M.
Department: Institute of Agriculture
Principal Investigator(s): Aug‚, Robert M.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: ROOT, SOIL, STOMATE, STRESS,
VEGETATION, WATER
16
DeLuca, Cecilia. 1996. Means and Variability of Some
Aspects of the Hydrological Cycle. M.S. Thesis,
Massachusetts Institute of Technology, 114 pages.
Means and interannual variability of moisture flux
divergence and precipitable water are calculated for the
years 1965 through 1989 from a GFDL global
atmospheric dataset. An empirical orthogonal function
(EOF) analysis assesses portions of the variability due
to long-term trends, the effect of the El Nino Southern
Oscillation, and other factors. Apparent long term
trends are discussed in light of the deficiencies- of the
dataset, other studies, and statistical significance tests.
Little conclusive evidence that the trends reflect
physical phenomena is found, with a convergent trend
in northern high-latitudes a possible exception. In the
latter part of the thesis, the monthly-mean moisture
flux divergence is equated with runoff and is used to
drive a GISS river model, which routes moisture
collected on land to oceans. Based on the results of the
model and divergence data over land and ocean
regions, the annual mean and interannual variability of
the freshwater flux into the Atlantic is computed for 4o
latitude strips and for the northern, mid- and southern
Atlantic. For the northern Atlantic, mean fluxes are in
good agreement with models and observational studies.
For the mid- and southern Atlantic there are
inconsistencies between this and other studies that
reflect the scarcity of radiosonde data over tropical
oceans and the southern hemisphere. A possible
application of the computed fluxes and their variances
is the validation and forcing of atmosphere, ocean or
coupled models. This may be feasible with the results
obtained for high northern latitudes, but is not likely to
yield meaningful results south of about 40oN. Included
in an appendix is a catalogue of graphical statistics,
with seasonal and annual means, interannual variability
(including EOF analyses), and zonal means of a
number of hydrological fields, including moisture
fluxes.
Major Professor(s): Peter Stone
Department: Earth, Atmospheric and Planetary
Sciences
Principal Investigator(s): Rosen, Richard
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: FLUX, HYDROLOGY, MODEL,
MOISTURE, PRECIPITATION, RIVER, TEMPORAL
DISTRIBUTION, WATER
17
Dyhrman, Sonya T. 1999. Cellular Markers of
Phosphate Stress in Phytoplankton. Ph.D. Dissertation,
University of California San Diego, 156 pages.
Primary production in the world ocean sustains marine
organisms and modulates global climate. As a result,
the factors that regulate phytoplankton production are a
source of extensive investigation. Much attention
focuses on the role of nutrients, such as nitrogen and
phosphorus, in the regulation of phytoplankton growth
and bloom dynamics. However, such studies have been
hampered by the difficulties involved in assessing
single-cell phytoplankton physiology in situ. This
research discusses the development of two in situ assays
for phosphate stress in the dinoflagellate Prorocentrum
minimum. This work also elucidates aspects of
phosphate nutrition in this species and the
coccolithophoris Emiliania huxleyi. For both organisms
cell-surface proteins regulated by phosphate were
characterized in laboratory cultures. The induction and
repression of these proteins in response to phosphate
supply were studies and compared with alkaline
phosphatase activity which is a commonly used marker
of phosphate stress. In P. minimum one phosphate
regulated protein was purified and identified as an
alkaline phosphatase. The phosphate regulated proteins
of E. huxleyi were partially purified, consistently
associating with each other as well as with alkaline
phosphatase activity. One of these proteins appears to
be a phosphatase with an affinity for 5' nucleotides.
Antibody probes were generated to the purified alkaline
phosphatase in P. minimum. The antibody probes were
tested for specificity to the target protein and for cross
reactivity with other species of phytoplankton. An
immunofluorescence assay using these antibody probes
distinguished phosphate-stressed from phosphate-
replete cells in culture and in a field sample. In P.
minimum an additional assay for phosphate stress was
developed using the fluorescent alkaline phosphatase
substrate ELF-97. The phytoplankton population in
Narragansett Bay, Rhode Island was sampled in the
summer of 1998 and tested for phosphate stress using
this assay. Cell-specific, P. minimum alkaline
phosphatase activity was detected in the field samples.
This study demonstrates the importance of phosphate in
aspects of phytoplankton physiological ecology,
particularly in this important estuary. It also confirms
that the tools developed here may be used successfully
in future studies of cell-specific phytoplankton
physiological ecology.
Major Professor(s): Palenik, Brian P.
Department: Scripps Institution of Oceanography
Principal Investigator(s): Palenik, Brian P.
Program Area: Coastal Margins
KEYWORDS: COMMUNITY DYNAMICS, GROWTH
AND DEVELOPMENT, NUTRIENT, PHOSPHATE,
PLANKTON, STRESS
18
Foster, Sara. 1997. Decomposition of Populus
tremuloides Leaves Grown Under Elevated
Atmospheric Carbon Dioxide. M.S. Thesis, University
of Illinois at Chicago, 16 pages.
I determined the C:N ratio of Populus tremuloides
leaves grown under ambient and elevated CO2, and the
decomposition rates of the leaves under the conditions
in which they had been grown. The N concentration of
senescent leaves when they were put into litter bags was
significantly affected by soil N and CO2 treatments, but
these differences in leaf "quality" did not affect
decomposition rate. Leaf nitrogen concentration was
26% higher in leaves from trees in high N compared
with low N soil (p<0.0005, 3-way ANOVA), and 38%
higher in leaves grown under ambient compared with
elevated CO2 (p<0.0001, 3-way ANOVA). Soil N and
CO2 affected leaf N independently; there was no
interaction effect. After 233 days, there were no
treatment effects on mass loss rates of the leaves.
Further, when the leaves were moistened and CO2
production measured, there were no treatment
differences. In summary, although the C:N ratio of
Populus tremuloides leaves grown under elevated CO2
was higher than that of control leaves grown under
ambient conditions, the difference did not affect
decomposition rate.
Major Professor(s): Lussenhop, John
Department: Biological Sciences
Principal Investigator(s): Teeri, James
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON CYCLE, CARBON DIOXIDE,
DECOMPOSITION, FERTILIZATION, LEAF,
NITROGEN CYCLE, PHOTOSYNTHESIS,
RESPIRATION, SOIL
19
Fraser, Rolland. 1996. Multiscale (Spatial, Spectral,
Temporal) Remote Sensing of Biogeochemical
Conditions in Nebraska Sand Hills Lakes. Ph.D.
Dissertation, University of Nebraska at Lincoln, 250
pages.
This dissertation applied remote sensing to several
questions regarding lake water quality in the Nebraska
Sand Hills. In Chapter 2, baselines of reflectivities were
defined, from May to October, 1972 through 1986, as
measured by the Landsat Multispectral Scanner, for
130 lakes in Garden and Sheridan counties, Nebraska.
This yielded multispectral signatures and records of
variation for the individual lakes. Chapters 3 and 4
addressed the basic problem of associating lake
reflectivities with water quality parameters specific to
Sand Hills lakes, using: a) 252 bands of hyperspectral
reflectance data collected with a spectroradiometer
from a helicopter, b) 7 bands of multispectral
reflectance data collected by the Landsat Thematic
Mapper, and c) water quality conditions of turbidity,
algal chlorophyll-a and alkalinity. Results from both
chapters yielded significant correlations of turbidity and
chlorophyll-a with the spectral information. A record of
hyperspectral reflectance from 32 lakes was established.
Chapter 5 was a cursory study on the spatial variability
expressed by waterscape (landscape ecology analog)
metrics within and among lakes, using reflectance
classes as surrogates to aquatic habitats. Results showed
that spatial metrics vary among lake spectral classes.
Chapter 6 provided estimates of albedo, from
hyperspectral reflectance data among lakes, and then
used the results to examine the variability in lake
radiation budgets. There were shifts in relative
dominance between reflected shortwave and longwave
components, which may be important in assessing lake
impacts on local and regional climate or biological
production. Each of these studies presented either new
approaches to the study of water resources with remote
sensing, or new and useful information about the many
lakes in Nebraska's Sand Hills. Both aspects should
prove useful in regional monitoring or comparisons
with other regions of the world. Overall, the results
provided evidence that remote sensing is a useful tool
for studying water quality, and a developing science
with new basic questions to be addressed.
Major Professor(s): Rundquist, Donald C.
Department: Geography
Principal Investigator(s): Rundquist, Donald C.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: PRAIRIE, RADIATIVE PROCESS,
REFLECTANCE, REMOTE SENSING, SPATIAL
DISTRIBUTION, WATER QUALITY
20
Friedman, Karen. 1997. Global Atmospheric Water
Vapor Flux Climatology in the NCEP/NCAR
Reanalysis and the Oort Data Set. M.S. Thesis,
Massachusetts Institute of Technology, 122 pages.
The integrated water vapor flux is calculated for the
National Centers for Environmental Prediction/
National Center for Atmospheric Research
(NCEP/NCAR) reanalysis and the Oort objective
analysis data sets with the purpose of intercomparison.
The period of study is 1979 to 1995 for the
NCEP/NCAR data and 1964 to 1989 for the Oort. Such
lengthy time-series allow the estimation of interannual
variability in the atmospheric branch of the hydrologic
cycle. Global fields and zonal averages are displayed
for the annual, December/January/February, and
June/July/August averages. As part of the analysis, the
data sets are each separated into years with and without
an El Nino occurrence. The difference and divergence
are calculated to investigate if the data sets can resolve
the anomalies known to exist during El Nino Southern
Oscillation (ENSO). Power spectra analysis is also
performed to look for events within certain frequency
ranges. Both data sets appear to resolve the global
water vapor flux and ENSO conditions reasonably, but
the Oort data does not perform as well possibly due to
regions with inherently poor data.
Major Professor(s): Dara Entekhabi
Department: Civil and Environmental Engineering
Principal Investigator(s): Rosen, Richard
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: EL NI¥O - SOUTHERN OSCILLATION
(ENSO), FLUX, MOISTURE, TEMPORAL
DISTRIBUTION, WATER VAPOR
21
Gray, Sean. 1998. Diagnosis of energy divergence in
the GEOS-1 Reanalysis. M.S. Thesis, University of
Maryland, 16 pages.
In single column modeling, boundary conditions must
be specified to reproduce the climate. For our modeling
efforts, we attempt to impose large-scale advective
transport of latent and sensible heat, derived from data
assimilation, as the horizontal boundary condition to
our radiative-convective model. The computation of the
divergence of advective fluxes is not a simple
numerical procedure, because high levels of accuracy
are needed. Here the advective fluxes for summer
(averaged for 1988-1995) from the NASA GEOS-1
reanalysis is presented. The boundary conditions were
calculated from the divergence of latent and sensible
energy flux. The integrated effect of this flux was tested
against the observed column energy convergence.
Major Professor(s): Stenchikov, Georgiy
Department: Department of Meteorology
Principal Investigator(s): Stenchikov, Giorgiy L.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CIRCULATION, CLIMATE, FLUX,
HEAT, MODEL, RADIATIVE PROCESS
22
Green, Mark A. 1996. The Biogeochemical
Mechanisms Driving Calcite and Aragonite Saturation
States in Long Island Sound Sediments: The Effects on
Juvenile Bivalves, Benthic Foraminifera, and
Carbonate Debris Preservation. Ph.D Dissertation,
State University of New York at Stony Brook, 257
pages.
Few studies have considered dissolution of calcium
carbonate in nearshore temperate, mud deposits where
sediments are seldom more than 1-3% CaCO3 by
weight. However, knowledge of the processes that
control CaCO3 dissolution-preservation in all types of
depositional environments are essential to fully
understand the global CaCO3 cycle. The purpose of this
study was to better constrain the role of nearshore-
temperate regions in the cycling of biogenic calcium
carbonate by studying the seasonal patterns of CaCO3
build-up and dissolution in Long Island Sound
sediments. Pore water saturation state with respect to
calcite and aragonite minerals in Long Island Sound
sediments fluctuate from saturated and near saturated
conditions during late fall, to undersaturated during
winter, before slowly changing to supersaturated
conditions during late spring. Higher äCO2 production
rates during warmer periods cause the CO32-
concentration to become supersaturated for both calcite
and aragonite. äCO2 production is controlled by both
temperature and substrate availability so that benthic
deposition of organic matter produced during the
spring bloom accelerates the seasonal progression of
pore waters to supersaturation. Undersaturation occurs
during winter time when lower rates of äCO2
production and oxidation of reduced minerals such as
FeS lower CO32- below saturation. Large benthic losses
of Ca2+, Mg2+, Sr2+, and F- occur when sediments are
undersaturated with respect to carbonate minerals over
a period of ~160 days. The prorated annual average
flux range of -0.53 to -3.3 mmol Ca2+ m-2 d-1 (-2.0 ñ
1.02 mmol Ca2+ m-2 d-1) is comparable to or greater
than fluxes of Ca2+ documented from other nearshore
carbonate regions as well as the deep sea, where little if
any temporal variability in pore water saturation state
occurs. Mass fluxes of Ca2+ from this study imply that
between ~31.0 g CaCO3 m-2 dissolves during winter in
LIS sediments. This translates to a Sound-wide loss
during winter of ~5.6 x 1010 g CaCO3. Rapid,
significant declines in the total foraminifera
assemblage of Elphidium clavatum and Buccella
frigida, and the abundance of bivalves Tellina agilis,
and perhaps to some extent Nucula annulata, correlate
with the winter-time period of calcite/aragonite mineral
undersaturation. Declines in the density of individuals
can be explained by dissolution of the carbonate tests.
Dissolution of some calcareous organisms during
winter in LIS suggests one mechanism by which
systematic biases exist in the taxonomic and age class
composition of the fossil record. What is ultimately
preserved as a fossil may not actually represent all
ecological groups that existed at the time of burial or
reflect their actual abundances while living and/or
shortly after death. A laboratory experiment showed
that calcite undersaturation resulted in dissolution of
previously discarded tests of the foraminifera E.
clavatum and B. frigida, and also increased mortality of
live individuals approximately 3 times relative to
controls. SEM observations of foraminifera support the
notion that dissolution was greater in experimental-
undersaturated chambers relative to control-saturated
chambers. No significant difference was seen between
treatments for the bivalves T. agilis or N. annulata.
However, dissolution-induced mortality in meiofauna
other than foraminifera, such as juvenile bivalves,
should not be discounted and deserves future attention.
Major Professor(s): Aller, Robert C., and Josephine
Aller
Department: Coastal Oceanography
Principal Investigator(s): Aller, Robert C., Josephine
Aller, Cindy Lee, and J. Kirk Cochran
Program Area: Marine Transport
KEYWORDS: CARBON CYCLE, COASTAL
ENVIRONMENT, OCEAN, SEDIMENT, TEMPORAL
DISTRIBUTION
23
Gu, Lianhong. 1998. Modeling Biophysical Exchanges
and Micro-Meteorology in Soil-Vegetation-Atmosphere
Continuums: Results from a Two-Story Boreal Aspen
Forest. Ph.D. Thesis, University of Virginia, 265 pages.
While the description of vertical differentiation in the
light environment has become a routine part of plant
canopy process modeling, air temperature, water vapor
partial pressure and CO2 concentration have been often
assumed to be constant over the canopy depth. Yet
these variables exhibit vertical variations in most plant
canopies. Since plant physiological activities are
sensitive to temperature, water vapor partial pressure
and CO2 concentration, these often coupled gradients
could have important impact on energy and mass
exchanges between vegetation and the atmosphere. In
this study, a multi-layer canopy process model for the
exchanges of radiative energy, sensible heat, water
vapor and CO2 between vegetation and the atmosphere
is developed. The mode l is designed to be applied to
both one-story and two-story canopies. It first predicts
profiles of temperature, water vapor and CO2 partial
pressures in plant canopies. Then from these predicted
profiles, exchanges of sensible heat, water vapor and
CO2 in each layer of the canopy are computed. Finally,
canopy level fluxes are obtained by integrating these
exchanges over the canopy. In the multi-layer model
developed, short-wave radiative transfer within plant
canopies is described by a modified two-stream model
which can address the problem of canopy clumpiness.
A longwave radiative transfer matrix (LRTM)
technique is developed to model longwave radiative
transfer in plant canopies. The revised localized near-
field (LNF) theory is used to describe sensible heat,
water vapor and CO2 transfers within and just above the
canopy. Stomatal conductance is computed by the Ball-
Berry-Leuning model. Photosynthesis is described by a
biochemical model. Soil moisture and temperature are
modeled by the force-restore method. Soil respiration is
described by an empirical temperature function. Stem
respiration is modeled from temperature and sapwood
taper in the canopy. Sapwood taper is estimated based
on the pipe-model theory. Because of the complex
relationships among different biophysical processes,
some variables, such as leaf temperature, stomatal
conductance for water vapor and internal CO2 partial
pressure, can not be expressed explicitly and
independently. These variables are solved through a
system of nonlinear equations which has 3m+5
independent equations where m is the total number of
foliage layers in the canopy. The numerical solution of
this system by the Broyden's method is the core of the
program of the model. A random fluctuation technique
is developed to overcome the possible failure in the
convergence of the iteration process and has been
proved to be effective in the application. The model was
tested comprehensively against measurements from a
two-story boreal aspen forest in the southern study area
of the boreal ecosystem-atmosphere study (BOREAS)
project. The tests included diurnal cycles of canopy net
radiation, sensible heat flux, water vapor flux, CO2 flux
and friction velocity, and profiles of air temperature,
water vapor partial pressure and CO2 concentration and
their diurnal cycles. After being fully tested, the model
was used to decompose fluxes of sensible heat, water
vapor and carbon dioxide into contributions from
ecosystem elements. Major conclusions obtained in this
dissertation study can be summarized as follows:
-- The model can make accurate predictions for fluxes
of radiative energy, sensible heat, water vapor and CO2
over this two-story forest, and profiles and diurnal
patterns of air temperature, water vapor partial pressure
and CO2 concentration within and just above the
canopy.
-- Energy and mass exchanges in this boreal forest was
largely controlled by the abovestory even through its
LAI was smaller than that of the understory. However,
to model energy and mass exchanges, it is not sufficient
to consider leaves only, and contributions from other
elements of the ecosystem can not be neglected in
general. In particular, respiration of stems and soil is a
significant part of the carbon budget for this forest and
must be included in the study of ecosystem productivity.
-- Ecosystem elements can have significantly different
roles in determining canopy sensible heat fluxes than in
determining canopy evapotranspiration or CO2
assimilation. For example, the understory had a much
bigger role in contributing to the fluxes of H2O and CO2
than in contributing to the sensible heat flux. In
addition, their roles may change from nighttime to
daytime.
-- The results showed that scalar transfers in this boreal
forest can be described by the revised localized near-
field theory, and problems of soil-vegetation-
atmosphere transfers can be solved through a system of
non-linear equations.
Major Professor(s): Shugart, Herman H. Jr.
Department: Environmental Sciences
Principal Investigator(s): Emanuel, William R.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: BOREAL REGION, FOREST, MODEL,
RADIATIVE PROCESS, TERRESTRIAL
ENVIRONMENT
24
Heffernan, Lisa. 1996. Measuring the Effects of
Increased Levels of Carbon Dioxide on Soil Bacteria in
a Mediterranean Type Ecosystem. M.S. Thesis, San
Diego State University, 51 pages.
The levels of carbon dioxide have steadily increased
over the past 200 years due to the clearing of land, use
of fossil fuels, and tillage of soil. There are a number of
different studies being conducted on both above-ground
fauna and below-ground microbial life. Since there is a
diversity of organisms in the soil it is often difficult to
identify certain groups of organisms. For instance,
methods for identifying nitrogen-fixing bacteria are
variable, time consuming, and sometimes unreliable.
With advances in molecular biology, more accurate
methods in identification can be designed. This study
addressed the question of how increased levels of CO2
affect bacterial population numbers. CO2-controlled,
long-term greenhouse system (CO2LT) and Free-Air
CO2 Enrichment (FACE) were used to simulate levels
of CO2 from 250 ppm to 550 ppm and the response of
this change in CO2 on bacteria was measured during
the first growing season. There were no significant
changes in total bacterial numbers during the first
growing season. At six months the dominant bacteria
were also identified. The dominant bacteria at all CO2
levels were identified as Bacillus species and potential
nitrogen-fixing bacteria were identified from the lower
concentration chambers. Finally, progress was made
towards a molecular method to identify nitrogen-fixing
bacteria.
Major Professor(s): Allen, Michael
Department: Biology
Principal Investigator(s): Oechel, Walter
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON DIOXIDE, CHAPARRAL,
FERTILIZATION, MICROBE, NITROGEN CYCLE,
SOIL
25
Hellstrom, Robert. 2000. Modeling Meteorological
Forcing of Snowcover in Forests. Ph.D. Thesis, Ohio
State University, 335 pages.
The architectural properties of a forest are known to
modify significantly meteorological forcing of
snowcover. Current numerical snow models utilize a
wide range of vegetation representations that limit their
application to particular biomes or for basic research on
specialized problems. Most do not explicitly represent
the combined effects of the canopy on processes of mass
and energy transfer beneath the canopy. This project
develops forest canopy sub-models that estimate the
below-canopy solar and longwave irradiance, wind
speed, and accumulation of precipitation, based on
meteorological measurements above the canopy and
parameters of forest architecture. The wind and solar
radiation sub-model predictions were independently
compared with meteorological observations at
deciduous and coniferous sites in the snowbelt region of
northern Michigan. The solar radiation and wind
models required adjustments to match sub-canopy
measurements. The primary experiment compared the
simulations and measurements of snow depth for eight
modified versions of the Utah Energy Balance (UEB)
snow model during the 1998-99 snowcover season at
the two forest sites and a near-by open site.
Independent inclusion of each sub-model and a new
stability scheme in the UEB model revealed significant
sensitivity of modeled snow depth to stability and each
of the four processes estimated by the sub-models. The
original UEB model uses a simple forest canopy
parameterization that does not consider precipitation
interception. Comparison of the original and modified
UEB models significantly improved simulations of
snow depth at the open and coniferous sites, but
performance was slightly worse for a leafless deciduous
site. Unlike the modified model, the analysis suggests
that the original model produces inconsistent results,
which reduces its potential for application to different
biomes. Results suggest that opposing processes of
energy and mass exchange tend to moderate
meteorological forcing beneath a forest canopy. Each
process can substantially affect snow depth, depending
on the above-canopy meteorological conditions and
architecture of the forest. Future work should consider
refinement of the sub-models, testing in different
biomes, inclusion of soil substrate processes, and
comparison of these results with those of other snow
models under similar environmental conditions.
Major Professor(s): Arnfield, John
Department: Department of Geography
Principal Investigator(s): Teeri, James A.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: FOREST, MEASUREMENTS,
METEOROLOGICAL FORCING, MODEL,
SNOWCOVER
26
Henning, Frank Porter. 1995. Effects of Elevated
Atmospheric Carbon Dioxide on Carbon and Nitrogen
Cycling in Soybean and Sorghum Agroecosystems.
M.S. Thesis, Auburn University, 127 pages.
The concentration of carbon dioxide (CO2) in the
atmosphere has been rising rapidly since the onset of
the Industrial Revolution. Currently, the concentration
of CO2 in the atmosphere is approximately 370 æmol
mol-1, and that level is expected to double within the
next century. Atmospheric CO2 supplies nearly all of
the carbon in plant tissues, and thus to the food
chains of most life on Earth. Previous research has
demonstrated that elevated atmospheric CO2 stimulates
plant growth and increases dry matter yield.
Consequently, elevated CO2 will probably dilute plant
nutrient concentrations and increase C inputs to soil
systems. A field scale study was conducted to
investigate alterations in C and nitrogen (N) cycling in
two soil-plant systems cropped with soybean [Glycine
max (L.) Merr.] (C3 species) and sorghum [Sorghum
bicolor (L.) Moench] (C4 species). Open top field
chambers were used to maintain CO2 concentrations at
ambient (÷360 æmol mol-1) and elevated (÷370 æmol
mol-1) during the 1992 and 1993 growing seasons. The
study site was an outdoor soil bin which contained a
uniform Blanton loamy sand topsoil (loamy, siliceous,
thermic, grossarenic Paleudult) located at the USDA-
ARS National Soil Dynamics Laboratory on the campus
of Auburn University, Auburn, Alabama. Elevated CO2
increased soybean and sorghum yields and altered
many of the parameters used to investigate plant C and
N dynamics. Elevated CO2 had little or no effect on soil
C and N concentrations, or on soil microbial biomass.
However, soil respiration in plots cropped with soybean
and sorghum was greater under elevated compared to
ambient CO2. These data suggest more C entered the
soil system, but no more C was stored in soil under
elevated than ambient CO2. In the short-term it appears
that greater C is lost from agroecosystems under
elevated atmospheric CO2, which may be explained by
shifts in soil microbial communities. In a separate
laboratory investigation, Norfolk loamy sand (fine,
loamy siliceous, thermic Typic Kandiudult) was
amended with soybean and sorghum leaf and stem
tissue residues from plants grown under elevated and
ambient atmospheric CO2. Plant litter N concentrations
decreased and C:N and lignin:N increased under
elevated CO2, suggesting a decrease in litter quality.
However, despite decreased litter quality, C and N
mineralization were higher in soils amended with
soybean leaf and sorghum stem tissues grown under
elevated compared to ambient CO2. Results from this
study indicated that some residue tissues from crops
grown under elevated CO2 may alter microbial
community composition and thus enhance soil C
turnover.
Major Professor(s): Wood, C. Wesley
Department: Agronomy and Soils
Principal Investigator(s): Rogers, Hugo H.
Program Area: Carbon, Climate, and Vegetation
KEYWORDS: AGRICULTURE, ATMOSPHERE,
CARBON CYCLE, CARBON DIOXIDE, CROP,
LITTER, NITROGEN CYCLE, PARTITIONING,
PRODUCTIVITY, SOIL, VEGETATION
27
Hnilo, Justin J. 1996. A Comparison of GCM and
MSU Temperatures for the AMIP Experiment (1979-
1988). Ph.D. Dissertation, University of Alabama at
Huntsville, 256 pages.
The Atmospheric Model Intercomparison Project
(AMIP) was an experiment in which nearly all of the
available atmospheric General Circulation Models
(GCMs) were systematically driven by a common set of
sea surface temperatures (SSTs) over the 1979-88
period. The GCMs of AMIP, given this common
forcing, were thus more easily intercompared with one
another, and compared with actual observations. In the
following study gross measures of tropospheric
temperatures were studied in comparison with the
tropospheric temperatures observed by the Microwave
Sounding Units (MSUs) for the same 1979-88 period.
Two measures of temperature from AMIP GCMs were
utilized: 1) zonal mean pressure-level temperatures
from which a simulated MSU temperature is derived
and 2) the 850-200hPa thickness (gridpoint). GCM
simulated temperatures were found to have mimicked
the general interannual differences, related to El Ni¤o
events, quite well. However, a more subtle measure of
model variation-decadal trend-showed that in nearly all
GCMs, the trend was greater than observed. Most
GCMs also demonstrated a thickness response that was
less than what was observed; a consequence of GCM
atmospheric heating that was deposited too low in the
modeled atmospheric column. The appropriateness of
using these GCMs as regional climate predictors is
questioned as it was found that regional anomalies in
the GCMs are often more persistent and severe than
those observed in the real world. Therefore, while
providing relatively good global and tropical response
to SSTs, further GCM improvements are required to
more accurately represent decadal trends and regional
variations-two key parameters for studying global
climate change.
Major Professor(s): Christy, John R.
Department: Atmospheric Science
Principal Investigator(s): Christy, John R.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: ATMOSPHERE, CLIMATE, MODEL,
REMOTE SENSING, SATELLITE, TEMPERATURE,
TEMPORAL DISTRIBUTION
28
Holden, Gerold. 1998. Impact of Increased
Atmospheric CO2 on the Greening of the Sand-Sage
Prairie, Finney County Kansas. M.A. Thesis, Kansas
State University, 51 pages.
The explosive growth of human population and
associated industrial expansion has had far reaching
repercussions for the Earth system. Most of the
anthropogenic alterations to the environment are
detrimental and most are poorly understood. Are
human activities changing the climate of the earth? If
so, are these changes affecting the vegetative
communities found on the landscape? There is a
pressing need to answer these questions. Within the
broad scope of these questions lies the focus of this
study. Atmospheric levels of CO2 have been rising since
continuous data collection began in 1958. This change
in atmospheric composition has the potential to alter
the climate. For this study Landsat MSS images were
used to evaluate change in the vegetative communities
of the sand sage prairie in Finney County Kansas from
1972 to 1993. The response of the vegetation to
changing environmental conditions was monitored
through the use of the Normalized Difference
Vegetation Index (NDVI). Although it is evident that
the vegetation is responding to its environment, it is
questionable as whether atmospheric CO2
concentrations can be isolated as a cause of increased
vegetative vigor due to the overwhelming influence of
precipitation. The result of this study was a positive
linear regression relationship between NDVI values
and atmospheric concentrations of CO2 as measured at
the Mauna Loa collection site.
Major Professor(s): John Harrington, Jr.
Department: Geography
Principal Investigator(s): Harrington, John
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON DIOXIDE, NORMALIZED
DIFFERENCE VEGETATION INDEX (NDVI),
PRAIRIE, SATELLITE, VEGETATION
29
Horsfall, Fiona M. C. 1996. The Effect of Variable
Atmospheric Forcing on Oceanic Subduction of a
Passive Tracer in a Numerical Model: Implications for
Global Warming. Ph.D. Dissertation, University of
Miami, 230 pages.
The idealized geometry, isopycnic ocean model of
Bleck et al. (Miami Isopycnic Coordinate Ocean Model
- MICOM) is used to investigate the oceanic response
to changes in atmospheric forcing. The forcing changes
were made to depict changes in the model buoyancy
input, momentum input, and turbulent kinetic energy
(TKE) input. Each forcing factor was varied uniformly
throughout the model domain, separately and together,
to examine the oceanic sensitivity, and the possible
adjustment of the thermohaline circulation, to a
changing climate. The ocean responses examined in
this qualitative study are the maximum depth of the
mixed layer and the distribution of a passive tracer
maintained at 100% in the mixed layer and subducted
into the interior and deep ocean by dynamical
processes. The model response to the enhanced surface
forcing shows wind stress drives lateral advection
within the model, which changes subduction rates but
not mixed layer depth. Increased air temperatures
provide a downward buoyancy flux, which dampens
TKE and thus the mixed layer shallows and subduction
rates are reduced. An increase in wind speed enhances
TKE in the mixed layer which causes the mixed layer
to deepen, but does not directly affect subduction rates.
The combined effect of more than one forcing
mechanism acting together indicates that the individual
forcing effects show dominance at different latitudinal
regions: wind stress forcing is dominant in mid-
latitudes whereas wind stirring and buoyancy forcing
are dominant at low and high latitudes within the
model domain. The next generation of the model,
which includes more realistic topography and a greater
model domain, was then used with latitude-dependent
atmospheric forcing changes that simulate a global
warming scenario, a cooling scenario, and a
combination of these representing an alternative
warming scenario. The results show the latitudinal
dominance of the applied forcing seen in the sensitivity
experiments, but in all cases, there is a reduction in the
amount of tracer subducted into the interior. The model
does not reach a steady state during the integration
period, and the data suggests further integration may
produce a different result with respect to the amount of
tracer subducted in one of the global warming scenario
experiments, where the deep ocean gains tracer with
time.
Major Professor(s): Bleck, Rainer
Department: Meteorology and Physical Oceanography
Principal Investigator(s): Hanson, Howard P.
Program Area: Computer Hardware, Advanced
Mathematics, and Model Physics (CHAMMP)
KEYWORDS: CIRCULATION, CLIMATE, ENERGY
FLUX, MIXED LAYER, MODEL, MOMENTUM,
OCEAN, SPATIAL DISTRIBUTION, TEMPERATURE,
TRACER, WIND
30
Houston, Robb E. 1999. Reconstruction of Eastern
Pacific Climate Variability Using Multiple
Geochemical Tracers in Cocos Island Corals. M.S.
Thesis, Rice University, 110 pages.
The tropical ocean-atmosphere climate system plays a
key role in regulating global climate variations and
despite numerous and intensive studies, the range of
natural variability in the tropics remains largely
uncertain. Past variations in the climate system must be
well established before current environmental trends
can be evaluated to make predictions for the future.
Corals growing in the shallow tropical ocean may
provide some of the answers. Massive coral species can
live for centuries, faithfully incorporating chemical and
isotopic tracers into their skeletal structure that reflect
ambient water conditions. By analyzing variations in
the chemical and isotopic composition of cores from
such corals, it is possible to reconstruct proxy records of
tropical climate variability that extend for the past
several decades. However, chronologic control and data
interpretations are inhibited by indistinct growth
banding, hiatuses, and competing effects of multiple
environmental parameters. This study attempts to solve
some of the problems of corals-based climate
reconstructions by using precise 230Th dating techniques
for chronologic control and coupled 18O, Sr/Ca, and
U/Ca measurements to try to separate the relative
effects of SST and SSS. In addition, Cocos Island is a
centrally located open ocean site that will be essential
to verify previous results and to construct a regional
synthesis of eastern Pacific tropical climate variability.
Major Professor(s): Linsley, Brad
Department: Geology
Principal Investigator(s): Linsley, Brad
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CLIMATE, CORAL, EL NI¥O -
SOUTHERN OSCILLATION (ENSO), ISLAND,
OCEAN, TEMPORAL DISTRIBUTION, TROPICS
31
Hu, Tianmiao. 1998. A Study of Applying Artificial
Neural Network Techniques to Regional Climate
Downscaling under Global Climate Change. M.S.
Thesis, Tulane University, 95 pages.
In this thesis feedforward neural networks were
successfully used for regional temperature and wind
speed downscaling. A semi-empirical downscaling
approach similar to an approach widely used in the
weather forecast community was adopted. Free
atmospheric output from the Community Climate
Model (CCM1) and observational regional surface
variables were used to generate the empirical models
and future predictions. The strength of this approach is
that the large-scale atmospheric forcings were
accounted for by the CCM1 and the mesoscale forcings
were accounted for by the empirical models. In
temperature downscaling the neural network approach
gave similar results to those from the multiple linear
regression approach. Both approaches significantly
improved the original CCM1 predictions. While the
previous multiple linear regression approach had to
resort to seasonal models with smoothed data in
temperature downscaling, the neural network approach
could produce a single yearly model with unsmoothed
data. The strong modeling ability of the neural network
was demonstrated by its regional wind speed
downscaling where the multiple linear regression
approach failed to generate useful models. In
conclusion, neural networks are powerful alternatives
to statistical tools and are very suitable for analysis of
complex systems like those of the global climate.
Major Professor(s): Sailor, David
Department: Mechanical Engineering
Principal Investigator(s): Sailor, David
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CLIMATE, DOWNSCALING, MODEL,
NEURAL NETWORK, REGIONAL ANALYSIS
32
Hubbard, Carter. 1998. Hydrologic Modeling of the
Missouri River Basin in a Climate Change Model. M.S.
Thesis, University of Nebraska-Lincoln, 531 pages.
A computer model of the Missouri River basin has been
developed to simulate climate change impacts on water
resources in the Great Plains. The model is based on
the SWAT (Soil and Water Assessment Tool)
hydrologic code developed by the Agricultural Research
Service (ARS) and the Texas Agricultural Experiment
Station (TAES). The input data set for the model was
obtained from the HUMUS (Hydrologic Unit Modeling
of the United States) project. Modifications were made
to the SWAT model (Jorgensen, 1996) to simulate the
operation of the six main stem reservoirs on the
Missouri River. The reservoir algorithms effectively
simulate the operating procedures used by the Missouri
River Region of the U.S. Army Corps of Engineers.
Climate change data sets were provided by the National
Center for Atmospheric Research. Using historical
climate data and climate change data for 2xCO2 climate
conditions, simulations of the SWAT model were run.
Impacts of climate change on the spatial and temporal
distribution of water resources and agricultural
production were evaluated by comparing differences in
outputs between the baseline and double CO2
simulations. Results indicate overall water yield from
the Missouri River basin will decrease for 2xCO2
climate conditions. Results also indicate that an
additional 1.5 million hectare-meters of water will be
available annually in the main stem reservoir system
for 2xCO2 climate conditions. The water could be
diverted from the reservoirs for use in the surrounding
agricultural areas in South and North Dakota,
Montana, and Nebraska. Main stem reservoir system
inflows for baseline climate conditions show SWAT
consistently underpredicts water yield values in the
northern Missouri River basin. The model responds to
changes in inputs but simulated runoff values are
consistently low. Work is being performed to improve
precipitation lapse rate and snowmelt algorithms for
mountainous regions of the Missouri River basin. These
improvements should allow a full analysis of climate
change impacts and management strategies.
Major Professor(s): Hotchkiss, Rollin H.
Department: Civil Engineering
Principal Investigator(s): Hotchkiss, Rollin H.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON DIOXIDE, CLIMATE,
HYDROLOGY, MODEL, RIVER, RUNOFF, SPATIAL
DISTRIBUTION, TEMPORAL DISTRIBUTION
33
Jorgensen, Steven F. 1996. Hydrologic Modeling of
Missouri River Reservoirs in a Climate Change Model.
M.S. Thesis, University of Nebraska at Lincoln, 109
pages.
A computer model of the Missouri River basin has been
developed to simulate the impacts of climate change on
water resources in the Great Plains. It uses the
hydrologic model SWAT (Soil and Water Assessment
Tool) developed by the Agricultural Research Service
(ARS) and the Texas Agricultural Experiment Station
(TAES). The data for the initial model was obtained
from the HUMUS (Hydrologic Unit Modeling of the
United States) project also developed by the ARS and
TAES, funded through the Natural Resources
Conservation Service. New algorithms were compiled
in the model to simulate operation of the six main stem
reservoirs on the Missouri River in Montana and South
Dakota. These were developed to investigate the
potential of the reservoirs to mitigate effects of global
climate change. The reservoir algorithms effectively
simulate the operating procedures used by the Missouri
River Division of the Corps of Engineers. The routines
seek to maintain the reservoirs in the normal operation
range by monitoring total system storage and individual
reservoir storage and adjusting outflow accordingly. A
simplified version of the HUMUS dataset was compiled
and calibrated for use in testing the reservoir routines.
The algorithms were successfully implemented and
tested in this model. The reservoir subroutine
reproduced system storage and reservoir release rates
very well using historical data. Further, simulations
with logical bounds showed that the routines perform
well for many ranges of input. The computer model is
now prepared for further development and the
simulation of the effects of climate change in the region
including economic analyses, adaptation scenarios, and
mitigation scenarios.
Major Professor(s): Hotchkiss, Rollin H.
Department: Civil Engineering
Principal Investigator(s): Hotchkiss, Rollin H.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CLIMATE, HYDROLOGY, LAKE,
MODEL
34
Keightley, Keir Edward. 1999. Mapping Productivity
and Boundary Layer Conditions Using the Airborne
Visible and Infrared Imaging Spectrometer. M.A.
Thesis, University of California, 103 pages.
In the past 30 years research has sought to measure and
model the physiology of naturally occurring vegetation
from the scale of stoma to the scale of the entire planet.
Review of the relevant body of literature reveals the
complexity of this task. The objective of this research is
to use high spatial resolution imaging spectrometer
data to establish a relationship between atmospheric
water vapor and the corresponding underlying
vegetation and to investigate the feasibility of
generating realistic estimates of boundary layer
conditions. Ultimately, this and other research is
intended to provide accurate estimates of terrestrial
carbon and energy flux as well as indications of
biologically active trace gas flux from the scale of the
plant organ to the continent and entire planet. These in
turn can be used to monitor environmental change.
AVIRIS data of a site in Southern Washington State
were processed to produce water vapor, liquid water
and reflectance products. This was done for three
separate dates during the summer months of 1996 and
1997. These products were then used in combination
with USGS 30-meter DEM and surface temperature
measurements to generate regional maps of 'anomalous'
water vapor. Statistical analysis revealed that for
forested areas, stands of old growth forest were
associated with significantly greater amounts of
atmospheric water vapor than were stands of second
growth (previously harvested) forest. The surface
meteorological data and water vapor data were
integrated to calculate boundary layer parameters that
influence evapotranspiration and respiration. No
attempt was made to quantify the forest productivity in
relation to the measured vapor anomalies due to the
lack of data describing the near-surface distribution of
water vapor and the lack of productivity control site
data. The technique developed has the potential to
provide an alternative approach to the vegetation
indices currently used as input to regional
ecophysiological modeling for the remote detection of
physiological activity (e.g. photosynthesis). This
technique provides, as well, the spatial resolution to
link small scale (tree to stand) research results with
regional scale (watershed to biome) modeling.
Major Professor(s): Roberts, Dar A.
Department: Geography
Principal Investigator(s): Roberts, Dar A.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: ATMOSPHERE, BOUNDARY LAYER,
EVAPOTRANSPIRATION, FOREST, LAND
SURFACE, MODEL, RESPIRATION, WATER VAPOR
35
Khisty, Mohan. 1996. Simulation of the Shift in
Position of Hinge Lines Between Two Lakes. M.S.
Thesis, University of Nebraska at Lincoln, 40 pages.
Groundwater flow between two hypothetical, shallow,
flow-through lakes was numerically simulated in steady
state and transient conditions for two cases. In the first
case the lakes are at identical surface water elevations
and in the second case there is a small difference in
surface water elevations between them. Simulation
results from both cases indicate a direct relation
between movement of hinge lines, which indicate
changes in the direction of groundwater-lake seepage
components, and the seasonal persistence and decline
of a groundwater mound that exists between the two
lakes. A comparison between steady-state simulation
results for both cases indicates that a small difference
in surface water elevation between two lakes results in
differences between the relative proportions of
groundwater-lake seepage components of the two lakes
and is reflected in the difference in position of hinge
line locations between the two lakes. A comparison
between transient simulation results for both cases
shows that the small difference in surface water
elevations between two lakes results in a fairly constant
difference in the rates of groundwater-lake seepage
components. Hinge line positions between the two lakes
also maintain a fairly constant difference in position
during the course of the simulation. Lake level
fluctuations produced by the model compare well with
the range and seasonality of actual lake level
fluctuations on which the modeled system is based.
Simulation results establish the usefulness of the lake
package addition to MODFLOW in simulating
groundwater-lake interactions involving multiple lakes.
Further, these results provide guidance in locating
sampling wells because the bounds of hinge line
traverse, for each lake, delineates a zone of transition
characterized by groundwater-lake flow reversals.
Major Professor(s): Gosselin, David C.
Department: Geology
Principal Investigator(s): Gosselin, David C.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: FLOW, HYDROLOGY, LAKE, LAND
SURFACE, SPATIAL DISTRIBUTION
36
Klassen, Jane F. 1997. Climate Change Impacts on the
Hydrology of Spring Creek Basin in the Black Hills of
South Dakota Using Soil and Water Assessment Tool.
M.S. Thesis, South Dakota School of Mines and
Technology, 67 pages.
An increase in atmospheric CO2 levels and temperature
from a changing global climate may affect the
availability of water on and beneath the earth's surface.
Changes in water availability in the north central
United States are expected to be particularly critical
because water availability is limited. Therefore, the
physical hydrologic processes need to be well
understood in order to determine the consequences of
climate change on regional water resources. The
objective of this paper is to evaluate the ability of the
hydrologic modeling program called Soil and Water
Assessment Tool (SWAT) to simulate the hydrologic
response of a pine forest watershed located in the steep
sloping terrain of the Black Hills of South Dakota. This
paper also evaluates the models sensitivity to potential
climate change effects. The calibration results show
that the coefficient for linear regression, r2, between the
actual annual water yield and the calibrated model is
0.94. The results of the climate change sensitivity
analysis show increased annual water yield of up to
74% due to doubled atmospheric CO2, up to 110% due
to increased precipitation, and decreased annual water
yield of up to 75% due to increased temperature and
63% due to decreased precipitation. From both the
climate change models, it appears that
evapotranspiration, which includes both leaf
photosynthesis processes and soil moisture processes,
could become a limiting or contributing factor in the
amount of annual water yield from the watershed under
climate change conditions. Changes in precipitation
due to climate variations would also have an effect on
the evapotranspirational processes of the forest, in turn
contributing to an increase or decrease in annual water
yield from the basin.
Major Professor(s): Fontaine, Thomas A.
Department: Civil and Environmental Engineering
Principal Investigator(s): Hotchkiss, Rollin
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CLIMATE, HYDROLOGY, MODEL,
RUNOFF, WATER
37
Lightsey, Jack Wilson I. I. I. 2000. Input Preparation
and Execution of the PnET-IIS Hydrological Model on
the Six-Digit HUCs of the Southeast. M.S. Thesis,
University of Alabama, Tuscaloosa, 83 pages.
The PnET-IIS model is a coupled photosynthesis,
productivity, and hydrological model designed to
project regional forest changes from observed monthly
time step data. It is capable of predicting runoff for a
watershed on the basis of climatic, soil, and vegetation
inputs. Comparisons of runoff predictions for the past,
present, and future is a way of predicting the impacts of
global climate change. The research described in this
thesis consists of two major parts. The first of these
concerns validation of the PnET-IIS model, and the
second concerns input preparation for execution of the
model for the entire southeastern United States. The
first stage of this research focused on validation of the
PnET-IIS model as a tool for predicting runoff from a
watershed based on necessary model input parameters.
The model was first validated on 12 test sites within the
southeastern United States. These sites were chosen
based on spatial distance from one another, dominant
forest type, and digital input availability. Once the
necessary model inputs had been assembled, execution
of the PnET-IIS model on these sites was performed.
This allowed for comparisons with existing historical
streamflow data provided by the United States
Geological Survey (USGS). The second stage of this
research focused on input preparation for each of the
144 6-digit hydrological unit codes (HUCs) that
comprise the southeastern United States. Individual
GIS databases were constructed from various internet
sites for the inputs necessary to perform PnET-IIS runs.
Compilation, modification, and storage of the inputs
were then carried out using the GIS software ArcInfo
and ArcView. Input files created using these tools will
provide the basis for future PnET-IIS runs to assess the
implications of potential climate change for the water
resources of the southeastern United States.
Major Professor(s): Durrans, S. Rocky
Department: Civil and Environmental Engineering
Principal Investigator(s): Abt, Robert C.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CLIMATE, FOREST, HYDROLOGY,
MODEL, PHOTOSYNTHESIS, PRODUCTIVITY,
RUNOFF, SOIL, VEGETATION
38
Liptay, Karen. 1998. The Use Stable Isotopes to
Constrain Anthropogenic Methane Sources: Coal
Mines and Landfill. M.S. Thesis, Florida State
University, 121 pages.
Seasonal variations in the oxidation of methane during
its transport across the soil cap of a landfill in Leon
County, Florida USA were determined in situ with a
stable isotopic technique. The approach contrasted the
ë13C values of emitted and anoxic zone CH4 and
utilized measurements of the isotopic fractionation
factor (à) which varied inversely with temperature from
1.025 to 1.049. Anoxic zone CH4 did not vary
seasonally and had a ë13C average value of -55.18 ñ
0.15o/oo. Methane emitted from the landfill soil surface
and captured in chambers ranged in ë13C from -54o/oo
in winter, when emission rates were high to -40o/oo in
summer when emission rates were lower. The
antipathetic variation between the ë13C of emitted CH4
and the rate of CH4 emission is consistent with control
of the emission rate by bacterial oxidation. Our
interpretation of the isotope data indicates that methane
oxidation consumed from 3 to 5% of the total flux in
winter, to a maximum of 43 ñ 10% in summer. There
was variation in the extent of methane oxidation in soil
types with mulch/topsoil averaging 55 ñ 14%, and clay
averaging of 33 ñ 13% in summer. The seasonally
integrated value for methane oxidation for areas of the
landfill covered with mulch/topsoil was 26 ñ 4% of the
flux towards the soil surface, while for clay soil it was
only 14 ñ 2%. The overall annual average which
includes both types of soil was 20 ñ 3%. Covering
landfills with additional mulch, which can be generated
from yard waste, may attenuate methane emission by
providing a loose non-compact substrate for bacterial
attachment and an environment with moisture,
methane and oxygen. At specific sites within the
landfill we studied, temperature was the main factor
controlling methane oxidation. Models for the global
methane budget use stable isotopic signature to
constrain methane sources. The current value for coal
mines (-37o/oo) is based on a review of studies done in
the 1960's and does not include methane from
ventilation systems. Coal mine samples for this study
were taken from four basins in the USA for a total of 78
samples. The average value for our sites was -51 ñ 7o/oo
a value more depleted than previously recorded. Our
study shows that coal basin of the USA have unique
isotopic signatures and that the isotopic ratio used in
models should be less enriched than the current value.
Major Professor(s): Chanton, Jeffrey P.
Department: Oceanography
Principal Investigator(s): Chanton, Jeffrey P.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: ATMOSPHERE, LANDFILL, METHANE
39
Liu, Shuguang. 1996. Evapotranspiration from
Cypress (Taxodium ascendens) Wetlands and Slash
Pine (Pinus elliottii) Uplands in North-Central Florida.
Ph.D. Dissertation, University of Florida, 258 pages.
In order to investigate the difference, if any, of
evapotranspiration between cypress wetlands and slash
pine uplands, the rainfall interception, evaporation
from water surface, transpiration and stomatal
conductance at the leaf/needle level, leaf area index,
soil moisture and water table fluctuations were
measured in three cypress (Taxodium ascendens)
wetlands and their surrounding slash pine (Pinus
elliottii) plantations from April 1993 to March 1994
near Gainesville, Florida. The feasibility and potential
methods of estimating evapotranspiration from water
table fluctuations were appraised and developed. A
multi-species and multi-layer evapotranspiration model
at ecosystem level, ETM, was developed in order to
simulate the change of evapotranspiration and its
components (i.e., transpiration, rainfall interception,
and evaporation from water or soil surface) under
various environmental and biological conditions. The
transpiration submodel, which scales transpiration up
from the leaf/needle level using the acquired stomatal
conductance data and information about stand structure
and micrometeorology, was verified with field scale
measurements obtained in a slash pine plantation by an
eddy-correlation method. There were no empirical
parameters in the newly-derived interception submodel,
which was tested by field measurements and compared
with Gash and Mulder models using data from the
literature. A submodel of evaporation from open water
surfaces was also developed, based on field
measurements. There was no significant difference (à =
0.05) between cypress and slash pine with respect to
transpiration and stomatal conductance at the leaf level
during the growing season. No significant difference (à
= 0.05) has been detected in terms of annual
transpiration, rainfall interception and total
evapotranspiration between cypress wetlands and slash
pine uplands. Therefore, the difference in
evapotranspiration between cypress wetlands and slash
pine uplands was primarily determined by the
magnitude of water surface evaporation in wetlands,
which could be as high as 500 mm per year or about
1/3 of the potential evaporation.
Major Professor(s): Riekerk, Hans
Department: School of Forest Resources and
Conservation
Principal Investigator(s): Gholz, Henry L.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CONDUCTANCE, EVAPORATION,
HYDROLOGY, LEAF AREA INDEX (LAI), MODEL,
STOMATE, TRANSPIRATION, VEGETATION,
WETLAND
40
Lombardi, Joanne E. 1999. A technique for carbon
isotopic analysis of rhizospheric methane oxidation and
atmospheric methane. Ph.D. Thesis, Florida State
University, 196 pages.
The objectives of this dissertation were to constrain
estimates of rhizospheric methane oxidation in detailed
greenhouse and field studies and to evaluate the gas
chromatograph isotope-ratio mass spectrometer for
determination of excess CH4 over ambient air.
Significant differences were observed for rhizospheric
methane oxidation between greenhouse and field
studies. In the greenhouse, oxidation percentages were
62% while only 26% and 40% were determined in the
filed. Differences were associated with higher root
density in greenhouse plants, which was caused by
potting effects and fertilization. To model methane
oxidation in the rhizosphere, turnover times and the
concentration and d13C signatures of sedimentary,
lacunal, and emitted CH4 were measured. Fractionation
factors for rhizospheric methane oxidation were
calculated to be 1.021 for greenhouse rhizosphere soil
and ranged from 1.041-1.018 for two field sites. Using
a transport reaction model, the measured d13C and
concentration values for the filed were reproduced. To
reproduce the field data, production and oxidation
zones had to be in close contact with each other,
produced methane had to be significantly 13C depleted
relative to sedimentary methane, and a fractionation
factor for rhizospheric methane oxidation greater than
1.015 had to be applied. Differences in produced and
bubble methane were a result of fractionation due to
methane oxidation and transport from the oxidation
zone into the plant. The results of the model
application indicate that rhizospheric methane
oxidation occurs not along the rhizoplane, as has been
generally assumed, but in the bulk sediment or
rhizosphere, supported by O2 leakage from the plant
roots. The precision and accuracy of the GC-IRMS
system operated with a cryogenic pre-concentration
device allowed determination of the source of excess
methane over and above clean background ambient air
at several sites. Excess CH4 in the air at a swamp forest
tower was within range of the sedimentary CH4 at the
site, even though the methane concentration in the air
samples was elevated by only 0.3 ppm or less. Air
collected at four sites in the northeastern USA
contained excess methane from such sources as
combustion, landfill methane emission and biogenic
methane.
Major Professor(s): Chanton, Jeffrey P.
Department: Chemistry
Principal Investigator(s): Chanton, Jeffrey P.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: METHANE, OXIDATION, ROOT
41
Mansfield, Jennifer. 1996. Genotypic Variation for
Condensed Tannin Production in Trembling Aspen
(Populus tremuloides) under Elevated CO2 and in High
and Low Fertility Soil. M.S. Thesis, Ohio State
University, 30 pages.
The Carbon/Nutrient Balance Hypothesis suggests that
leaf C:N ratios influence the synthesis of secondary
compounds such as condensed tannins. Levels of CO2
are rising in the atmosphere, resulting in increased C:N
ratios in leaves. Six genotypes of Populus tremuloides
were grown under elevated and ambient CO2 partial
pressure and high and low fertility in field open-top
chambers at the University of Michigan Biological
Station. During the second year of exposure, leaves
were harvested three times (June, August, and
September) and analyzed for condensed tannin
production. Significant genotype, fertility and CO2
effects as well as a significant genotype by CO2
interaction were found. The Carbon Nutrient Balance
Hypothesis was supported overall, but not all genotypes
responded in the same way to the CO2 treatment. Some
genotypes increased tannin production at elevated
compared to ambient CO2 while others showed no CO2
response. These results suggest that with rising
atmospheric CO2, plant secondary compound
production may vary within species. This could have
consequences for plant-herbivore and plant-microbe
interactions, as well as the evolutionary response of this
species to global climate change.
Major Professor(s): Curtis, Peter
Department: Plant Biology
Principal Investigator(s): Curtis, Peter
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON DIOXIDE, FERTILIZATION,
LEAF, SOIL
42
Mays, Kennetha. 1996. Photosynthetic Responses of
Quaking Aspen, Populus tremuloides, Genotypes under
Elevated CO2 and in High and Low Fertility Soils. M.S.
Thesis, Ohio State University, 42 pages.
Plants often increase their photosynthetic rate under
elevated CO2 conditions but this response may be
limited by low soil fertility levels. To determine the
photosynthetic response of quaking aspen genotypes to
elevated CO2, with and without nutrient stress, trees
were grown from root cuttings for 15 months under 35
or 70 Pa CO2 in soils of low or high N fertility in open
top chambers at the University of Michigan Biological
Station. Light saturated net CO2 assimilation was
measured three times over a single growing season
using a portable infrared gas analyzer, or IRGA. All
plants were measured at both 35 and 70 Pa CO2.
Genotypes were organized into two groups according to
timing of leaf drop. In June at the CO2 X soil fertility
phenotypes, all phenotypes responded positively to
increased CO2, but only in the high fertility soil
treatment. In June and August, early leaf drop
phenotypes responded positively at both levels of soil
fertility while late leaf drop phenotypes responded
positively only at high soil fertility. In September, using
27 Pa to measure negative adjustment early leaf drop
phenotypes grown at elevated CO2 and low soil fertility
had significantly downregulated photosynthetic
capacity while late leaf drop phenotypes had not. When
using 56 Pa to measure negative adjustment no
downregulation took place. Our data indicated that
high CO2 stimulation of photosynthesis in quaking
aspen was sensitive to soil fertility but that this
sensitivity varied temporally and according to plant
phenotype.
Major Professor(s): Curtis, Peter
Department: Plant Biology
Principal Investigator(s): Curtis, Peter
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON DIOXIDE, FERTILIZATION,
PHOTOSYNTHESIS, SOIL, STOMATE, VEGETATION
43
Montes-Helu, Mario. 1997. Tracked Vehicle
Disturbance in a Rangeland and Design of Sapflow
Gauges for Desert Shrubs. Ph.D. Dissertation, New
Mexico State University, 300 pages.
Rangelands of the arid southwest are used extensively
for military training. The impact of track-vehicle traffic
on the Ft. Bliss military reservation were evaluated in
soil water balance. Military training can reduce
vegetation and accelerate erosion. Sustainable
management will result from balancing disturbance
intensity with recovery times. Military activities can
occur during all seasons and the possible impact in the
ecology can vary. Season and soil types produce
different impact. The objectives of this study were to
measure the soil disturbance caused by track-vehicles
and the resulting change in site water balance. Soil
disturbance was analyzed with the change in the bulk
density, microrelief and erosion rods. Bulk density
changed (increased) depending the number of tank
passes and season. The surface micro-topography was
modified by the tank and remained months after the
tank passed. Erosion rods showed soil removal and
deposition. Water storage increased about one to 2 cm
for 5 pass treatments in one site. There was a slight
increase of water storage right after the tank because
the destruction of the vegetation reducing plant
transpiration. The Penman method estimated a lower
potential evapotranspiration (PET) values than
expected under irrigation conditions. Dry soil surface
and low vegetative covers produced low net radiation.
A relationship between total rain and runoff measures
was used in the water balance to estimate runoff. The
overall water balances, assuming zero drainage shows
that all the rain was used in ET. The actual
evapotranspiration (AET) was about 15% of PET.
During the growing season the AET is 0.25 cm day-1 in
the wettest sites. Dry sites had a maximum AET of 0.15
to 0.20 cm day-1. Direct measurement of plant
transpiration has always been a problem under natural
conditions. One way to estimate of plant transpiration
is the heat balance method. This is an application of
heat and accounting the heat input and output used to
measure the water flow assuming steady-state
conditions. The main objective was design a sap flow
gauge that can regulate the quantity of heat required
depending on sap flow conditions and avoid the stem
damage by overheating when there is low flow.
Controlling heat input to maintain constant
temperature difference keeping steady-state condition
does not appear to damage the stem. The simple design
does not allow adequate correction for conduction
losses. The three thermocouple design allows correction
for conduction losses. However, calibrations before
installation in the field are not possible. Portable heat
balance design allows laboratory calibrations before
field installation. There was a good agreement between
the measurements and the calculated water flux under
laboratory conditions. Under greenhouse conditions,
the heat balance method calculated the water flow in
potted pecan plants quite well when compered with
measured water loss.
Major Professor(s): Jones, Timothy L.
Department: Agronomy and Horticulture
Principal Investigator(s): Gutschick, Vincent
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: DISTURBANCE, EVAPORATION,
FLOW, LAND SURFACE, PRECIPITATION,
RUNOFF, SAP, SOIL, TRANSPIRATION, WATER
44
Munoz, Ricardo. 1997. Energy Sector Sensitivity to
Climate and Climate Change. M.S. Thesis, Tulane
University, 60 pages.
In this work methodologies for determining the climate
sensitivity of the energy sector are developed. In
addition, the potential impact of climate change on
energy supply and demand is assessed using various
case studies. In the demand side, models that relate per
capita electricity and natural consumption to degree
days and temperature respectively were developed for
eight key states of the U.S. The final models are quite
robust, with R-square parameters generally larger than
0.8. These models predict increases in electricity
consumption up to 20% for increments in temperature
of 3oC. Natural gas consumption will decrease
significantly under climate change at a rate
proportional to the exponential of the temperature
increase. In the supply side, the Sacramento, Eel and
Russian rivers basin was used as an example of the
implementation of the methodology we developed. The
final model relates the total hydrogenating availability
in any given season to present and past (as far back as
five seasons) basic climatic parameters. Possible
impacts of climate change on hydrogeneration for the
basin depend strongly on the accuracy of climate
change predictions, especially precipitation levels. The
climate change scenarios used in this work are within
climate predictions given by General Circulation
Models, however. Finally, recommendations that could
lead to conceptual improvements and to increased
predictive capabilities of the models were made.
Major Professor(s): Sailor, David
Department: Mechanical Engineering
Principal Investigator(s): Sailor, David
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CLIMATE, ENERGY USE, MODEL,
TEMPERATURE
45
Osborn, Timothy J. 1995. Internally-Generated
Variability in Some Ocean Models on Decadal to
Millennial Timescales. Ph.D. Thesis, University of East
Anglia, 650 pages.
Passive variability, generated by the modulation of
random weather events by the inertia of the oceans, is
studied with a range of simple ocean models of the
upwelling-diffusion type. Earlier work is extended by
parameterising global-mean vertical heat transport in a
number of depth-dependent and time-dependent ways.
These are developed from theoretical and empirical
considerations, as well as from comparison with a more
complex ocean general circulation model (OGCM).
They are an attempt to separate the effects of isopycnal
and diapycnal advection and diffusion. The spectra of
passive variability is shown to be sensitive to these
parameterisations. The highest sensitivity is to the
replacement of a completely mixed layer by a layer of
enhanced mixing, which results in all the combinations
tested exhibiting weaker low frequency variability than
some previous studies found. Active variability,
generated by instabilities and interactions within the
ocean and between ocean and atmosphere, requires
more complex ocean models which explicitly model
ocean dynamics. Previous work, which found
considerable Southern Ocean and Atlantic Ocean
variability in the LSG OGCM under mixed boundary
conditions, was extended in a number of ways. First, a
similar experiment was performed, but with a rather
different OGCM. Numerical problems greatly reduced
the usefulness of the results. Second, the sensitivity of
the internal variability to some of the model's physical
and numerical details was investigated. Using an
alternative convective adjustment scheme can reduce
the magnitude of the internal variability by 70%. Using
an improved parameterisation of brine rejection from
sea-ice freezing also reduced the magnitude of
variability, although stronger stochastic forcing could
induce large North Atlantic oscillations. Third, it was
shown that the dominant variability was purely a
Southern Ocean phenomenon, since the signals which
propagate around the Atlantic Ocean play no active role
in that mode. A second type of propagation was
identified - westward around the Antarctic continent -
and was explained as a coupled 'salinity - coastal
upwelling' wave motion. Finally, the active variability
of a hybrid coupled model was studied. This model
consisted of the same OGCM, but coupled to a
statistical atmosphere model rather than to mixed
boundary conditions. The atmosphere model was
constructed on the basis of results from a 19 year
simulation with an atmosphere general circulation
model forced by observed sea surface temperatures. It
included active air-sea fluxes of fresh-water,
momentum and heat. The fresh-water flux model
appeared to reduce the magnitude and period of the
ocean variability, but this was shown to have little
significance. In fact, when the statistical model was
improved it acted to slightly strengthen and lengthen
the oscillation maxima and minima. The air
temperature (i.e., heat flux) model weakened the
convective feedback which causes the model's
variability, so that the oscillations were weaker. But it
was unable to prevent the variability from occurring,
and was unable to prevent a partial collapse of the
North Atlantic thermohaline circulation under stronger
forcing.
Major Professor(s): Wigley, Tom M. L.
Department: School of Environmental Sciences
Principal Investigator(s): Wigley, Tom M. L., and
Philip D. Jones
Program Area: Carbon, Climate, and Vegetation
KEYWORDS: CIRCULATION, FLOW, FLUX, HEAT,
MODEL, MOMENTUM, OCEAN, SALINITY, SPATIAL
DISTRIBUTION, TEMPERATURE, TEMPORAL
DISTRIBUTION
46
Pacheco, Gerardo. 1996. Empirical Modeling of
Timber Supply in the U.S. South. Ph.D. Dissertation,
North Carolina State University, 215 pages.
Periodic assessments from the USDA Forest Service
analyze the timber resource situation and project the
changing resource conditions, providing information
used to formulate policy changes or identify
opportunities for public or private investment at the
national level. Recent wider data availability has
allowed modelers in the South to produce alternative
projections to the national assessments given concerns
about reliability of state and substate projections from
national models. The three papers in this research deal
with data and modeling issues in the modeling of
timber supply for the US South. Chapter 1
characterizes the US South forest resource from the
perspective of empirical timber supply modeling.
Summaries of relevant timber supply indicators at the
South-wide, state, and survey region level, for the
common forest types, species groups, and ownerships
are provided as guidelines for the commonly used levels
of aggregation in modeling. An assessment is made of
the use of Eastwide data base data from the USDA
Forest Service for timber supply modeling. Insights
provided may be relevant to the modeling process and
to the elaboration of assumptions. The information
provided can contribute to the development of
improved models and it might be useful to resource
analysts in industry, government, and universities.
Results from a South-wide timber supply projection to
the year 2020 are examined and compared against
national projections in chapter 2. Using the latest FIA
survey unit data for the South (excluding Kentucky and
public ownerships) individual state inventories where
updated to 1994 as a common starting point for the
projection. Only private ownerships were considered in
the model. Softwood prices are projected to increase
seven times and hardwood prices over two and a half
times over the projection period. The largest projected
price increases for softwoods occur during the decade
2010 to 2020. Inventory of softwoods is projected to
decrease by 30% relative to the starting year, and
hardwoods to increase only slightly by 2%. South-wide
softwoods growth to removal ratio is expected to
decline from 0.94 to 0.71, and from 1.36 to 0.87 for
hardwoods. Price projections are sensitive to growth per
acre assumptions. The results in this paper are
conservative in that they assume constant productivity
levels in planted pine forest types. Chapter 3 examines
the effects of differing assumptions about the future
productivity levels of pine plantations. Empirical
models of growth and yield are developed for each of
the major forest types in the US South with the purpose
to evaluate the impact on empirical timber supply
projections from possible increases in the productivity
of pine plantations of 20%, 40% and 60% by the year
2020. The resulting equations were used to generate
data and to modify the empirical timber supply model
SERTS. Total increases of 60% in pine plantation
growth per acre by the end of the projection results in
total softwood price increases (174%) that are less than
one fourth of those produced by the base projection
(788%). Improved projections can be made with better
quality and availability of data on projected pine
plantation areas and the extent of current and projected
level of intensive management in pine plantations.
Major Professor(s): Abt, Robert C.
Department: Forestry
Principal Investigator(s): Abt, Robert C.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: ECONOMICS, FOREST, GROWTH
AND DEVELOPMENT, MODEL, PRODUCTIVITY,
REGIONAL ANALYSIS
47
Pantoja, Silvio. 1997. Reactivity of Proteins, Peptides
and Amino Acids in the Marine Environment: Effects
of Molecular Size and Structure on Degradation. Ph.D
Dissertation, State University of New York at Stony
Brook, 279 pages.
This dissertation investigates basic principles of
reactivity of organic matter, focusing on amino acids,
peptides and proteins as model compounds. I explore
the lability of these compounds in seawater and
sediments, the relationship of degradation rate and
extent to chemical structure, and the changes in
molecular size of the compounds with depth in
sediments. Microbial degradation of proteins and
peptides in the ocean is thought to proceed via
extracellular hydrolysis to oligopeptides and amino
acids, which can be subsequently mineralized. A new
approach to studying extracellular hydrolysis of
peptides in seawater and sediments was developed by
synthesizing fluorescent peptide substrates of varying
length and with different amino acid constituents. It
was shown that extracellular peptide hydrolysis in
seawater and sediments does not proceed in a random
manner, but at specific peptide linkages, and that size
and structure of peptides influence hydrolysis rates.
Hydrolysis of dipeptides was slower than of longer
peptides; kinetics of these reactions suggest the
occurrence of multiple hydrolytic enzymes in seawater
and sediment, each with different specificity.
Laboratory incubations suggest that performance of
these hydrolytic enzymes under different environmental
may cause preferential degradation of certain
substrates. Consistent with their role as a link between
protein deposition and microbial mineralization in
sediments, field observations suggested that
extracellular hydrolysis of peptides could supply most
of the consumed free amino acids consumed. Protein is
a reactive fraction of the nitrogen pool and can account
for most of the NH4+ produced in coastal sediments. In
field experiments off the coast of Chile, rate constants
for protein decomposition were among the highest
reported for marine sediments. In Long Island Sound
sediments, the magnitude of the protein decomposition
rate constant was affected by deposition of labile
substrate and biological benthic activity. Enrichment of
larger proteins was detected in deeper sediments,
suggesting selective preservation, adsorption or
condensation with other resistant organic matter.
Major Professor(s): Lee, Cindy
Department: Coastal Oceanography
Principal Investigator(s): Aller, Robert C., Josephine
Aller, Cindy Lee, and J. Kirk Cochran
Program Area: Marine Transport
KEYWORDS: COASTAL ENVIRONMENT,
DEGRADATION, ORGANICS, SEDIMENT, SPATIAL
DISTRIBUTION, WATER
48
Pontius, Robert G., Jr. 1994. Modeling Tropical Land
Use Change and Assessing Policies to Reduce Carbon
Dioxide Release from Africa. Ph.D. Dissertation, State
University of New York at Syracuse, 177 pages.
Humans could be causing the climate to change in ways
that could threaten the welfare of future generations.
The alteration by humans of the earth's remaining
tropical forests is a component of the atmospheric flux
of carbon dioxide, the most important greenhouse gas.
It is especially important to investigate this flux
because our understanding of it is highly uncertain, and
it is a component of the global carbon cycles that
humans can regulate. This dissertation supplies
scientific tools and socioeconomic insights that policy
makers may use to help to decide how much, if at all, to
reduce the anthropogenic release of carbon dioxide
from tropical landscapes. Chapter 1 presents a new GIS
model called GEOMOD2, which is a computer
program written in FORTRAN. GEOMOD2 simulates
land use change forward and backward in time using a
digital map of land use, and produces a map of
simulated carbon dioxide flux due to land use change.
GEOMOD2 selects land for conversion according to
patterns of previous land use and rates of change.
Chapter 1 applies GEOMOD2 to tropical Africa, but
the model could be used in other parts of the world and
for a wider variety of applications. Chapter 2 uses the
kappa parameter and an extraordinarily complete data
set for Costa Rica to examine the accuracy with which
GEOMOD2 predicts land use patterns. GEOMOD2
simulates the pattern of land use in Costa Rica over a
duration of more than four decades with a success rate
between 74% and 84% (kappa between 0.32 and 0.44).
Chapter 3 uses an ecological economics approach to
assess policies to reduce the amount of carbon dioxide
being released from African agriculture. It concludes
that the application of fertilizer to existing African
fields would supply additional needed food to Africans
at a minimum carbon dioxide release, compared with
other methods such as food importation, expanded
shifting cultivation, or newly created permanent
cultivation.
Major Professor(s): Hall, Charles A.S.
Department: Graduate Program in Environmental
Science
Principal Investigator(s): Hall, Charles A.S.
Program Area: Carbon, Climate, and Vegetation
KEYWORDS: CARBON CYCLE, EMISSION, LAND
USE, MODEL, POLICY, TROPICS
49
Pressley, Shelley Noelle. 1999. Biogenic Hydrocarbon
Emissions from an Old Growth Forest and a Poplar
Plantation. M.S. Thesis, Washington State University,
94 pages.
Measurements of natural hydrocarbon emission fluxes
are reported for an old growth Pacific Northwest
coniferous forest. The emission data were collected for
the two dominant species (Douglas fir and western
hemlock) during the growing season in 1997 and 1998
using a branch enclosure technique. Monoterpene
emissions were standardized to 30oC by block-
averaging the data into 2oC temperature intervals and
using an emission algorithm E(T) = Es exp[ (T-Ts)].
Combining all samples from both years, the standard
emission rate for Douglas fir is Es = 0.39 ñ 0.14 æg C g-
1 h-1 (using a = 0.14oC-1) and for western hemlock Es
= 0.95 ñ 0.17 æg C g-1 h-1 (using a = 0.06oC-1).
Significant differences between the standard emission
rates for each year were observed indicating some type
of long term control of emission rates possibly related
to variations in nutrient availability or larger scale
ecological events. Overall there was no significant
correlation between time of season, or location within
the canopy and emission rates. In general, the Douglas
fir data fit the temperature-emission algorithm better
than the western hemlock data. Biogenic hydrocarbon
branch enclosure measurements are also reported for a
young managed poplar plantation. Emission samples
collected at the managed poplar plantation were
measured by subjecting the leaf to photosynthetic
photon flux density (PPFD) levels of 1000 æmol m-2 s-1
and a temperature of 30oC. The average isoprene
emission rate for the poplars was Es = 105.0 ñ 27.6 æg
C g-1 h-1 on a mass basis and Es = 170.4 ñ 39.3 æg C m-2
s-1 on a leaf area basis. The role of biogenic
hydrocarbon emissions in terrestrial carbon exchange is
quantified and compared for these two different
ecosystems. On a leaf level basis, the average fraction
of assimilated carbon emitted in the form of BHCs is
relatively high (0.99%) for the poplar trees and much
lower for the old growth conifers (0.2% for western
hemlock and 0.06% for Douglas fir). Depending on the
amount of light received and ambient temperatures
western hemlock can emit rather high (up to 1.0%)
amounts of fixed carbon. Emissions are also compared
to physiological parameters such as PPFD, relative
humidity, temperature, photosynthesis rates, and
transpiration rates. The strongest correlation was
between biogenic emissions and temperature as
expected, although there was a large degree of scatter
with the western hemlock data. The emission
measurements reported here represent one of the first
extensive datasets for an old growth forest. Very few
studies are based on such a large number of enclosure
samples from a limited number of species. Most
enclosure studies involving a large dataset have also
been conducted in controlled environments. Thus,
emission inventory standard emission rates are typically
based on limited emission samples from ambient
conditions, or samples from seedlings in controlled
environments. The emission rates presented in this
thesis will contribute to improving the biogenic
emission inventory factors used for future modeling.
Major Professor(s): Lamb, Brian K.
Department: Civil and Environmental Engineering
Principal Investigator(s): Lamb, Brian K.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON CYCLE, EMISSION, FOREST,
HYDROCARBON, ORGANICS, TERRESTRIAL
ENVIRONMENT, TREE
50
Pritchard, Seth. 1998. The Influence of Elevated
Atmospheric Carbon Dioxide on Longleaf Pine
Needles. Ph.D. Thesis, Auburn University, 182 pages.
The influence of rising atmospheric CO2 on leaf
structure and tissue quality of trees must be understood
before it will be possible to predict the fate of trees,
ecosystems, and entire biomes to atmospheric CO2
levels predicted for the next century. Therefore,
longleaf pine (Pinus palustris Mill.) seedlings were
grown for 20 months at two levels of CO2 (365 and 720
mol mol-1), in two levels of soil N (4 and 40 g m-2), and
with two levels of soil moisture (-0.5 and -1.5 MPa
xylem pressure potential). Leaf tissue was collected 4,
8, 12 and 20 months after initiation of the experiment
and prepared for light microscopy, scanning electron
microscopy (SEM), and transmission electron
microscopy (TEM). Needle phenolic content was
determined using the Folin-Denis method, and
condensed tannins were estimated with a protein
precipitation Assay at the final (20 month) harvest.
Although significant interactions of soil N with CO2
were observed for leaf anatomy and morphology at the
first harvest (4 months), few significant main effects or
interactions of CO2, soil N or water levels were detected
at later harvests. At the 12 month harvest, a CO2 by N
by water interaction was observed for the size of starch
grains within chloroplasts. Disruption of chloroplast
integrity by large starch inclusions was pronounced in
needles from trees grown in elevated CO2 when water
and N were both limiting. At 20 months, chloroplasts
grown in high CO2 exhibited stress symptoms including
increased numbers of plastoglobuli and shorter grana.
Needle surface wax density was decreased and
epicuticular wax morphology was altered by growth in
elevated CO2 only when soil N was limiting. Total leaf
polyphenol and condensed tannin contents were
increased by main effects of elevated CO2, low soil N
and adequately watered conditions. Elevated CO2 and
low N decreased deposition of calcium oxalate crystals
within needle phloem compared to ambient CO2 and
high N. Needle tissue quality, and thus interactions
between pathogens/herbivores and longleaf pine, may
be altered under elevated CO2. Furthermore, decreasing
effects of elevated CO2 on needle morphology and
anatomy with increasing length of the study, coupled
with negative effects of elevated CO2 on ultrastructural
characteristics of the photosynthetic apparatus suggest
that some degree of photosynthetic acclimation may
have occurred. Results from this study provide data
useful in understanding how the longleaf pine
ecosystem will respond to future CO2 levels.
Furthermore, they suggest that pine species may be
inherently less able to exploit extra carbon in a high
CO2 world than broadleaf species.
Major Professor(s): Peterson, Curt M.
Department: Botany and Microbiology
Principal Investigator(s): Rogers, Hugo
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON DIOXIDE, CHLOROPLAST,
FERTILIZATION, HERBIVORY, LEAF,
MORPHOLOGY, PHOTOSYNTHESIS
51
Pyles, R. David. 2000. The Development and Testing
of the UCD Advanced Canopy-Atmosphere Soil
Algorithm (ACASA) for Use in Climate Prediction and
Field Studies. Ph.D. Thesis, University of California
Davis, 191 pages.
The UCD Advanced Canopy-Atmosphere-Surface
model is presented and its output is compared with a
comprehensive set of observations at six diverse sites.
ACAS is a multi-layer canopy-surface-layer model that
solves the steady-state Reynolds averaged fluid flow
equations to the third order. These equations include
explicit representation of the full steady-state,
horizontally homogeneous, diabatic set of vector and
scalar fluxes and flux transports. ACAS includes a
fourth-order, near-exact technique to calculate leaf,
stem, and soil surface temperatures and surface energy
fluxes at various levels within the canopy. Plant
physiological response to micro-environmental
conditions from a groomed grass field in the
Netherlands, deciduous and coniferous forests in
Canada, tropical pasture and forest in Brazil, and
ancient temperate rainforest in the Pacific Northwest of
the United States are compared with simulated values.
Major Professor(s): Paw U, Kyaw Tha, and Bryan C.
Weare
Department: Land, Air, and Water Resources
Principal Investigator(s): Paw U, Kyaw Tha
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CANOPY, ENERGY FLUX, MODEL
52
Qi, Ye. 1994. Human-Induced Biospheric Change and
the Global Carbon Cycle: A Spatial Modeling
Approach and its Application to Tropical Asia. Ph.D.
Dissertation, State University of New York at Syracuse,
250 pages.
I have developed a computer model, called GEOMOD,
to simulate land use change and its consequences on
biotic carbon exchanges between terrestrial ecosystems
and the atmosphere, using a spatial modeling approach.
Land use change is a most important part of the
anthropogenic disturbance to the terrestrial biosphere.
Its contribution to the atmospheric carbon dioxide
accumulation is only second to fossil fuel combustion.
Therefore modeling land use change has drawn great
interest among the scientist community of global
environmental change. Conventional models of land
use change usually neglect the geographical
heterogeneity within a region and thus cannot provide
the spatial distribution of various land uses and their
changes. We adopt a spatial modeling approach in this
study. First, the input and output of the model are
geographically-explicit. Spatial patterns of land use and
factors that are related to land use change are
represented with matrix-format raster data files. Each
raster is dealt with independently; Secondly, the change
of land use patterns are made driven by local features of
geographical, ecological, and societal variables. I first
tested my model by applying it to Peninsular Malaysia
and Chiang Mai, Thailand, two relatively small areas
in tropical Asia. I found that a satisfactory accuracy can
be obtained for simulating the changes in land use
patterns, when using only one initial land use pattern,
topography, and land use change rates. This result
suggests that land use pattern can be considered as a
function of the initial pattern and topography in these
cases. Then, I applied the model to thirteen countries
in Tropical Asia, a much larger region than the test
areas. In this application I made two model runs for
comparison purpose. One is national level and the
other sub-national. The national levels uses land use
change rates for each country, while the sub-national
run for each sub-national unit, or ecological zone. In
addition, the spatial patterns of carbon content are also
simulated. In chapter 4, I have developed a method,
called normalized distance method, or RDM, for spatial
pattern comparison and model validation. I analyzed
the weakness of previous methods and construct a new
index, normalized distance. The new index improves
the previous methods by incorporating the locational
information, as well as the number of matched
gridcells. I analyzed the effects of changing spatial
scales on spatial pattern analysis, by computing the
responses of four spatial autocorrelation coefficients to
varying grid sizes. I found that all spatial
autocorrelation coefficients are scale dependent for the
data sets I used. This result suggests that scale effects
be carefully incorporated when interpreting the results
of spatial modeling. The overall objective of the study
is to explore the approaches and tools for studying land
use change and its impacts on the global carbon cycle.
However, we have found our results of model
simulations could be used to feed three dimensional
atmospheric transport models.
Major Professor(s): Hall, Charles A.S.
Department: Graduate Program in Environmental
Science
Principal Investigator(s): Hall, Charles A.S.
Program Area: Carbon, Climate, and Vegetation
KEYWORDS: CARBON CYCLE, MODEL, SPATIAL
DISTRIBUTION, TERRESTRIAL ENVIRONMENT,
TROPICS
53
Reimer, Paula J. 1998. Carbon Cycle Variations in a
Pacific Northwest Lake During the Late Glacial to
Early Holocene. Ph.D. Dissertation, University of
Washington, 188 pages.
Carbon isotopes and elemental analysis of lake
sediments and macrofossils from a Pacific Northwest
lake are used to constrain climate and atmospheric 13C
changes since the Late Glacial. An increase of 1.6o/oo in
13C of bulk organic matter is seen at the transition to
the Holocene. When corrected for mixing of terrestrial
and lacustrine carbon based on the C:N ratio, the
residual 13C decreases by about 1o/oo at the Late
Glacial/Holocene transition, which probably reflects the
change in atmospheric 13C, and then rises to about
0.5o/oo above the expected value as productivity
increases drive the lacustrine 13C upward.
Major Professor(s): Stuiver, Minze
Department: Geological Sciences
Principal Investigator(s): Stuiver, Minze
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON, CARBON CYCLE, CLIMATE,
HOLOCENE, ICE AGE, ISOTOPE, LAKE, SEDIMENT
54
Remillard, Suzanne Marie. 1999. Soil Carbon and
Nitrogen in Old-Growth Forest in Western Oregon and
Washington. M.S. Thesis, Oregon State University, 121
pages.
Soil organic carbon (SOC, kg C m-2) is an important
component in evaluating global C stores. The nitrogen
(TN, kg N m-2) cycle is closely linked to C and
understanding its role is also important. Contents and
distributions of SOC and TN in soil profiles, to 1-meter
depth, were estimated from 79 soils pits, in old-growth
forests, in 7 physiographic provinces in western Oregon
and Washington. Soils were sampled in four layers,
forest floor, 0- to 20-cm, 20- to 50-cm, and 50- to 100-
cm, and analyzed on a LECO CN Analyzer. Material
<2-mm was analyzed, as well as C-bearing material
>2-mm. Forest floor SOC ranged from 0 to 14 kg C m-2
(mean = 2.7) and forest floor TN ranged from 0 to 0.4
kg N m-2 (mean = 0.07). The SOC of mineral soil
ranged from 1.0 to 18 kg C m-2 (mean = 6.6) for 0- to
20-cm depth and 2.2 to 57 kg C m-2 (mean = 17) for 0-
to 100-cm depth. The TN of mineral soil ranged from
0.04 to 1.0 kg N m-2 (mean = 0.31) for 0- to 20-cm
depth and 0.12 to 3 kg N m-2 (mean = 1.0) for 0- to
100-cm depth. Up to 66% of SOC and TN measured
was found below 20-cm, illustrating how failing to
sample at depth can grossly underestimate SOC. As
much as 44% of SOC and TN measured was found in
C-bearing material >2-mm, material for which many
methods neglect to account. Longitudinal differences in
SOC and TN contents were evident between Coastal,
Cascade, and Eastside Cascade sites, implying effects
from site and climatic factors. Regression analysis was
used to quantify relationships of SOC and TN to site
and climatic factors. Response variables included forest
floor, forest floor plus 0- to 20-cm, 0- to 20-cm, and 0-
to 100-cm layers. Moisture and soil texture played
important roles in most cases examined. The results of
this study, and of other studies assessing the effects of
site and climatic characteristics on the factors
controlling soil organic matter accumulation, suggest
the relationships are regionally specific.
Major Professor(s): Homann, Peter S., and Bernard T.
Bormann
Department: Forest Science
Principal Investigator(s): Harmon, Mark E.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON, CARBON CYCLE, CLIMATE,
FOREST, NITROGEN CYCLE, ORGANICS, SOIL,
SPATIAL DISTRIBUTION
55
Riemer, Daniel D. 1998. Marine and Terrestrial
Sources of Reactive Volatile Organic Compounds and
Their Impact on the Tropospheric Ozone Chemistry of
the Earth. Ph.D. Dissertation, University of Miami, 187
pages.
Two areas integral to the global cycle of tropospheric
ozone were studied. The first segment of this
investigation involved the study of marine ecosystems
to define the sources of nonmethane hydrocarbons
(NMHCs) in the surface ocean. This included
laboratory and field investigations conducted to
determine the function and importance of dissolved
organic matter (DOM) in the abiotic photochemical
production of nonmethane hydrocarbons in surface
seawater. Concurrently, phytoplankton were
investigated as a biogenic sources of NMHCs in the
surface ocean. Low molecular weight alkenes,
compounds observed in the greatest concentrations in
the surface ocean, are formed almost exclusively as a
result of DOM-mediated photochemistry. Isoprene was
found to be produced by all phytoplankton species
investigated. The primary sink for NMHCs found in
surface seawater was gas exchange. The second
segment of this study focused on the prevalence of
NMHCs and oxygenated volatile organic compounds in
the rural southeastern United States. (Note: Research
supported also by the Office of Naval Research and the
Environmental Protection Agency)
Major Professor(s): Zika, Rod G.
Department: Marine and Atmospheric Chemistry
Principal Investigator(s): Milne, Peter J.
Program Area: Atmospheric Chemistry
KEYWORDS: ATMOSPHERE, EMISSION,
HYDROCARBON, OCEAN, ORGANICS, OZONE,
PLANKTON, TROPOSPHERE
56
Saros, Misa. 1995. Sensitivity of Pulse Heights to
Pressure for Ultrafine Particles in the Ultrafine
Condensation Particle Counter (UCPC). M.S. Thesis,
University of Minnesota Twin Cities, 71 pages.
Previous work has shown that for particles smaller than
about 15 nm in diameter there is a dependence of pulse
heights produced by the optical detector in an ultrafine
condensation particle counter (UCPC) on initial
particle size. Using this technique with the UCPC
described by Stolzenburg and McMurry (1991) valuable
information has been obtained about size distributions
and concentrations of atmospheric particles in the 3 to
4 nm diameter range. In future work this technique will
be used with aircraft measurements; information on the
dependence of pulse heights on pressure in the 0.25 to
1.0 atm range will be required to interpret this data.
This thesis describes a laboratory study of the
sensitivity of UCPC pulse heights to pressure.
Possibilities for improvement of the pulse height
analysis technique are also discussed. Monodisperse
sodium chloride (NaCl) or ammonium sulfate
((NH4)2SO4) particles in the 3 to 12 nm diameter range
were delivered to the UCPC which was operated at
pressures ranging from 0.25 to 1 atm. The calibration
aerosols were generated by rapidly cooling a hot vapor
to induce nucleation of ultrafine particles followed by a
differential mobility analyzer (DMA) to select particles
of known size. A short DMA (classifier length = 10.5
cm) was used to minimize diffusional broadening. A
calibration of the UCPC optics was also performed
using monodisperse oleic acid particles (between 5 and
15 æm in diameter) from a vibrating orifice aerosol
generator (VOAG). The results of the experiments
demonstrate that pulse heights increase for particles of
all sizes as the pressure drops from 1 atm to about 0.6
atm. Below 0.6 atm, pulse heights decrease
monotonically with pressure. At a pressure of 0.25 atm,
pulse heights are reduced by more than 50% relative to
those at 1 atm. While the absolute pulse heights change
with pressure, the relative spacing of the pulse height
distribution does not. That is, the pulse height
difference between two particles of different sizes
remains nearly constant over the pressure range in
question. While the pulse height difference is
insensitive to pressure, it does depend on particle
composition. Indeed, the pulse height difference was
consistently greater for NaCl particles than for
(NH4)2SO4 particles. It seems likely that this is a result
of particle shape and not of chemical composition.
Nonetheless, it is clear that care must be taken to
calibrate with aerosols that are representative of those
being measured. Finally, these experimental results are
also compared with the predictions of a particle growth
model developed by Stolzenburg. While there is
qualitative agreement between the model and
experimental results, modifications to the model will be
required if quantitative accuracy is to be achieved.
Major Professor(s): McMurry, Peter H.
Department: Mechanical Engineering
Principal Investigator(s): McMurry, Peter H.
Program Area: Atmospheric Chemistry
KEYWORDS: AEROSOL, CONDENSATION, GASES,
NUCLEATION, PARTICULATE
57
Schoof, Justin T. 1999. Synoptic Circulation
Classification and Downscaling for the Midwestern
United States. M.S. Thesis, Indiana University, 174
pages.
This thesis is the culmination of a synoptic circulation
classification for the Midwestern United States and the
application of the derived circulation indices in a
downscaling methodology for surface air temperature
and precipitation. The variables used in the
classification are twice daily observations of: 500mb
and 700mb height, 850mb temperature, and 850mb
dew point temperature, plus a single derived value;
precipitable water content (from the surface to 500mb
level). These data are used to develop the synoptic
circulation classification for the growing and non-
growing seasons (defined based on surface temperature)
and are taken from 7 radiosonde sites within the study
area for the period 1971-1990. The classifications are
undertaken using Varimax orthogonally rotated
principal components analysis and validated by
comparison with obliquely rotated components and
using hierarchical cluster analysis of the component
scores. Half of the randomly chosen component scores
from the 5 significant growing and non-growing season
components are then used to construct feed-forward
backpropagation neural networks to predict surface
temperature and precipitation at Indianapolis, IN. The
neural networks are then tested using the remainder of
the classification data set. The results are discussed in
terms of prediction accuracy and compared to a
downscaling methodology based solely on multiple
regression analysis.
Major Professor(s): Pryor, Sara C.
Department: Geography
Principal Investigator(s): Pryor, Sara C., Rebecca J.
Barthelmie, Margaret Carreiro, C. Susan Grimmond,
and Hans P. Schmid
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: ATMOSPHERE, CIRCULATION,
CLIMATE, NEURAL NETWORK, PRECIPITATION,
SPATIAL DISTRIBUTION, SURFACE LAYER,
TEMPORAL DISTRIBUTION
58
Sea, William B. 1999. Measures of spatial variability
in turbulent fluxes of carbon dioxide and water vapor at
the WLEF site during summer 1997. M.S. Thesis,
University of Minnesota, 35 pages.
Fluxes from three levels on the WLEF tower were
subdivided into wind sectors and analyzed to detect
significant differences in flux as a function of wind
direction. It was established with summer 1997 data
that midday CO2 uptake did vary with wind direction.
Wind sectors were divided into upland and lowland
fractions and compared to the flux data. No significant
correlation between this simple footprint model and the
observed flux variability was found. Water vapor fluxes
from the same period were modeled using the Penman-
Monteith equation. Good agreement was found.
Discrepancies were related to the time since last
rainfall.
Major Professor(s): Davis, Kenneth J.
Department: Water Resources Science
Principal Investigator(s): Bakwin, Peter S.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON CYCLE, FLUX, MODEL,
SPATIAL DISTRIBUTION, WATER VAPOR, WIND
59
Shen, Jinmei. 1996. Interactions Between Land
Surface and the Atmosphere and the Role of GCM Sub-
Grid Heterogeneity. M.S. Thesis, Iowa State University,
102 pages.
This thesis consists of two papers to be submitted for
publication: 1) Comparison of the influences of land
surface properties on mesoscale circulations using two
land surface process schemes. 2) The influence of
surface heterogeneity on subgrid heat fluxes and
boundary layer turbulence structure. In the first paper,
comparison is made between two surface
parameterization schemes: the Simple Biosphere Model
SiB2 of Sellers and the Biosphere Atmosphere Transfer
Scheme (BATS) of Dickinson, et al. Sensitivity
analyses are carried out on soil and vegetation
parameters by comparison with observations from three
locations. The second paper examines the effects of
subgrid heterogeneity on surface fluxes and mesoscale
circulations. A series of sensitivity simulations
demonstrates the role of GCM subgrid heterogeneity.
Major Professor(s): Arritt, R.W., and E.S. Takle
Department: Geological and Atmospheric Sciences
Principal Investigator(s): Brandle, J.R., W.E.
Easterling, and E.S. Takle
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: BOUNDARY LAYER, CIRCULATION,
FLUX, HEAT, LAND SURFACE, MODEL, SOIL,
SPATIAL DISTRIBUTION, TURBULENCE,
VEGETATION
60
Shipham, Mark. 1997. An Analysis of High
Frequency Methane Measurements in Central New
England. Ph.D. Thesis, University of New Hampshire,
76 pages.
A unique high resolution ambient air methane data set
consisting of approximately 125,000 independently
measured data points for the years 1991-1995 has been
collected at a site in the northeastern United States.
This data base is used to examine the long term trend,
seasonal and diurnal cycles, and the frequent pollution
events that affect the site on a year round basis. The
annual median mixing ratio of methane for all
measurements was 1808 ppbv in 1992, increasing at a
variable rate to 1837 ppbv in 1995. The lower 10-30%
of the data from each month was defined as
representative of background air and was compared to
the global CMDL data set. The background data exhibit
a variable upward trend of 5.5 +/- 2 ppbv/year during
the 4-year time period, with most of the increase
observed during 1993 and 1994. The seasonal cycle for
the background data set is similar to what is observed
by CMDL stations and varies from 24 to 35 ppbv. The
amplitude of the seasonal cycle for the full data set was
larger, ranging from 35 to 44 ppbv. Differences
between the full and background mixing ratios vary on
a seasonal basis and are largest in the winter and
smallest in the summer. These differences appear to be
controlled by changes in atmospheric stability and
changes in emissions from local and regional sources
throughout the year. Wind roses of chemical species are
examined for annual and seasonal time periods with
enhancements in anthropogenic species corresponding
to the location of large cities and landfills. Methane is
strongly correlated to species that have an
anthropogenic component, including acetylene,
propane, ethane, and hexane. The southwest quadrant
is subjected to the most severe pollution events and is
impacted by outflow from large cities in that sector,
including Northampton and Springfield, MA.
Emissions from cities in other quadrants, including
Boston and Worcester, MA, Providence, RI, and the
near by town of Petersham, MA also affect the site, but
to a lesser degree. Case studies are used to identify
atmospheric conditions that lead to high concentrations
of methane and other species. The co-occurrence of a
persistent wind direction, light wind speed, and stable
atmospheric conditions is the ideal scenario in which
emissions from nearby cities and landfills are advected
to the site. Emissions from local and regional, rather
than distant sources, are the primary cause of elevated
events.
Major Professor(s): Harriss, Robert, and Patrick Crill
Department: Earth Sciences
Principal Investigator(s): Crill, Patrick
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: ATMOSPHERE, EMISSION,
METHANE, SPATIAL DISTRIBUTION, TEMPORAL
DISTRIBUTION
61
Siqueira, Andrea. 1997. The Ecology of Food and
Nutrition: Patterns of Land Use and Nutritional Status
Among Caboclo Populations on Maraj¢ Island, Par ,
Brazil. Ph.D. Dissertation, Indiana University, 402
pages.
During the past 30 years, the magnitude of
environmental, economic and political change taking
place in Amazonia have had profound impact on the
social, economic, nutritional and health status of native
populations. Caboclos, the native Amazon peasant,
practice an economy based on multiple resource use,
including agriculture, fishing, hunting, management
and extraction of forest products. These activities of
subsistence and economy have been directly and/or
indirectly affected by the changes taking place in the
region as a whole. Some of these effects can be
observed in changes in land use and in the strategies of
subsistence and economy of these rural populations.
Others, however, need to be understood at the level of
social organization and biological adaptation of these
populations. This study investigates the relationships
between land use and nutritional status among Caboclo
populations on Maraj¢ Island, Par , Brazil. Different
land use and patterns of subsistence and economy are
compared. Nutritional status is assessed through food
intake surveys and anthropometric measurements of
physical growth and development. Changes in land use
are assessed through ethnographic research and data
from remote sensing analysis. The study presents and
discusses qualitative and quantitative data collected in
different field seasons between 1989 and 1994. The
results show that indeed land use changes affect food
availability and security at the household and
population levels. Overall, however, the study
populations present signs of chronic malnutrition. Food
with high energetic content is seasonally available. In
addition, sanitary conditions and health services are
also limited. Interestingly enough, the incidence of
malnutrition is not biased towards any specific
category, such as gender, age group or landownership.
Nevertheless, factors such as social organization, land
tenure and household decision-making processes are
important dimensions to understand land use and
nutritional status variations among and within
populations.
Major Professor(s): Moran, Emilio F.
Department: Anthropology
Principal Investigator(s): Moran, Emilio F.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: ESTUARY, GROWTH AND
DEVELOPMENT, HEALTH, TROPICS
62
Tian, Hanqin. 1996. Metabolism of the Biosphere in
Changing Global Environments: Carbon Flux and
Land Use Change as Studied at Scales From Landscape
to Global. Ph.D. Dissertation, State University of New
York at Syracuse, 240 pages.
The basic pattern of the metabolism of the biosphere
appears to be changing, based on my analysis of
monthly records since the 1950's of atmospheric CO2
concentration, fossil fuel consumption, and oceanic
absorption of carbon dioxide. The changes determined
by my method include a significant increase in both
production and respiration of the biosphere since the
1970's. Nevertheless, the ratio of production and
respiration (P/R) remains a constant 1.0 during the past
35 year period. Terrestrial ecosystems in the middle
and high latitudes of the northern hemisphere appear to
be more sensitive in their response to changing global
environments than other areas as shown by the rate of
metabolism change. I developed a simple metabolism
model to conduct simulation experiments and
uncertainty analysis about what possible changes in
ecosystem function might lead to the observed changes
in atmospheric CO2. I also investigated the role of
changing land use in the changes of global metabolism
through two case studies in tropical and boreal Asia.
My study in boreal Asia shows that many of these
ecosystems are in early successional changes due to
their recovery from deforestation. The high rate of
metabolism in early successional stages may be one of
the important factors that has enhanced the metabolism
of the biosphere. My study in South and Southeast Asia
shows an increase in agricultural area and a decrease in
carbon storage. Specially, I applied a spatially-explicit
model of land use change, called GEOMOD, to
quantify spatial and temporal patterns of land use
change in South and Southeast Asia. The expansion of
agricultural land into forested land may be the cause of
the increase in seasonal amplitude of atmospheric CO2
if the annual net production of crops is greater than the
annual net production of forests.
Major Professor(s): Hall, Charles A.S.
Department: Department of Environmental Forest and
Biology
Principal Investigator(s): Hall, Charles A.S.
Program Area: Carbon, Climate, and Vegetation
KEYWORDS: BOREAL REGION, CARBON CYCLE,
LAND SURFACE, LAND USE, METABOLISM,
MODEL, NORTHERN HEMISPHERE, SPATIAL
DISTRIBUTION, TERRESTRIAL ENVIRONMENT,
TROPICS
63
Vanyarkho, Olga V. 1996. Seasonal changes in
vegetative characteristics and gas exchange properties
of Phragmites australis and Scirpus acutus in a mid-
latitude prairie wetland ecosystem. M.S. Thesis,
University of Nebraska at Lincoln, 75 pages.
Our research was conducted in the Sandhills region of
Nebraska as a part of a comprehensive field experiment
on trace gas and energy fluxes in mid-latitude wetland
ecosystems. Field measurements were conducted from
April to October, 1994 at Ballards Marsh and Dewey
Lake Fen near Valentine, Nebraska. We measured
single leaf physiological properties and water surface
CO2 fluxes using a portable gas exchange system. Total
canopy foliage index, biomass accumulation, and
related vegetative parameters were determined by
destructive sampling. Phragmites australis and Scirpus
acutus, dominant plant community types for these
wetlands, had similar seasonal trends in canopy
heights, biomass accumulation, and leaf area index at
both sites. However, the Dewey Lake Fen communities
had taller canopies and greater biomass and leaf area
indices. At Ballards Marsh, both species exhibited
similar seasonal patterns of single leaf CO2 assimilation
and stomatal conductance. Assimilation rates for
Phragmites under full sunlight in mid-July were higher
(20-22 æmol m-2 s-1) than for Scirpus (17-20 æmol m-2 s-
1). Stomatal conductance was higher for Scirpus (0.5-
0.6 mol H2O m-2 s-1) than for Phragmites (0.3-0.4 mol
H2O m-2 s-1), which was, probably due to higher internal
CO2 concentration in Scirpus than in Phragmites.
Surface CO2 fluxes reached a maximum in the
beginning of August (Phragmites-dominated areas:
2.95 æmol m-2 s-1, Scirpus-dominated areas: 2.05 æmol
m-2 s-1). The total canopy foliage indices reaches
maximum values by the beginning of August. We used
a simple radiative transfer model (Norman 1992) to
scale up net CO2 assimilation and conductance from
leaf to canopy level for selected days. In general,
canopy net CO2 assimilation for Phragmites was higher
(16-17 æmol m-2 s-1) than for Scirpus (12-13 æmol m-2 s-
1); however, canopy conductance was higher in Scirpus
than in Phragmites (0.6 mol H2O m-2 s-1 versus 0.5 mol
H2O m-2 s-1). The magnitude of these differences was
related to the proportion of incident radiation that was
direct beam.
Major Professor(s): Arkebauer, Timothy J.
Department: Agronomy
Principal Investigator(s): Verma, Shashi B.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: BIOMASS, CARBON CYCLE, FLOW,
GASES, LEAF, MODEL, PRAIRIE, STOMATE,
TEMPORAL DISTRIBUTION, VEGETATION, WATER,
WETLAND
64
Venkatesh, Ramasubbu. 1995. A Classical Trajectory
Study of Collisions of 2-15 Atom Nickel Clusters.
Ph.D. Dissertation, Texas A&M University, 158 pages.
The collisions of 2 - 15 atom nickel clusters have been
studied using the classical trajectory method. Three
cases were considered: cluster-monomer, cluster-dimer
and cluster-cluster collisions. The interaction between
the nickel atoms is modeled using a semi-empirical
many-body potential based on the second moment
approximation of the tight-binding scheme. The cross
section results obtained in this study are consistent with
the smooth and featureless distributions observed for
nickel and other transition metal clusters. The two
major assumptions made in cluster growth model, the
substitution of cluster formation rate by hard sphere
collision rate and the estimation of decay rate by
assuming exponential decay of collisionally formed
clusters, were examined and found to be reasonable
assumptions. The results pertaining to the study of
cluster decay however suggest that in addition to the
decay rate dependence on energy, its angular
momentum dependence should also be taken into
account in cluster decay rate calculations. The cluster-
monomer and cluster-cluster collisions were also
studied using bulk and dimer fitted Lennard-Jones
potentials. A comparison of the cross section results for
these two potentials with those obtained using the
many-body potential suggest that the rate calculations
may be sensitive to the nature and Parameterization of
the interaction potential depending on the temperature
considered and cluster growth process simulated. This
work has systematically addressed the basic issues
related to cluster growth modeling for a material of
technological interest.
Major Professor(s): Marlow, William H.
Department: Nuclear Engineering Department
Principal Investigator(s): Marlow, William H.
Program Area: Atmospheric Chemistry
KEYWORDS: METAL, MODEL, MOMENTUM
65
Voss, Michael. 1996. Estimating Global Monthly
Mean Vertical Cloud Amount: Method and Result.
M.S. Thesis, University of California at Davis, 77
pages.
Existing cloud climatologies fail to provide information
regarding the vertical extent of clouds. A methodology
is developed whereby a global vertical clod climatology
is created. Cloud bulk microphysical properties are
estimated and combined with satellite derived optical
depth to determine cloud thickness. Monthly mean
cloud amounts form the International Satellite Cloud
Climatology Project (ISCCP) are then assembled with
cloud thickness distributions to produce a three
dimensional cloud climatology. The resulting monthly
mean vertical cloud climatology provides height
specific cloud amount between 60oN and 60oS. The
methodology employed does introduce large systematic
uncertainties which are difficult to assess. Nonetheless,
the results are compared with the Atmospheric General
Circulation Model (AGCM) simulated cloud amount
revealing large discrepancies in both the magnitude
and relative spatial distribution of cloud amount. The
elevation of maximum cloud amount is significantly
higher in the AGCM's than found in this research.
Major Professor(s): Weare, Bryan C.
Department: Land, Air and Water Resources
Principal Investigator(s): Weare, Bryan C.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CLIMATE, CLOUDS, MODEL
66
Wang, Xianzhong. 1999. Gender-specific and
intraspecific response of trembling aspen (Populus
tremuloides) to elevated atmospheric carbon dioxide.
Ph.D. Thesis, Ohio State University, 129 pages.
I studied gender-specific and intraspecific variations in
the physiological responses of Populus tremuloides to
elevated CO2 as affected by soil N availability. I also
synthesized leaf dark respiration data from independent
studies using meta-analysis. Net CO2 assimilation rate
(A) of male P. tremuloides was 17.8 and 26.2 micro
mol m-2 s-1 at ambient and elevated CO2, significantly
higher than A of females of 15.6 and 21.0 micro mol m-
2 s-1. Male trembling aspen had a higher maximum rate
of CO2 fixation by Rubisco and area-based leaf dark
respiration (Rda). Mass-based leaf Rd (Rdm), however,
was unaffected by gender and CO2 concentration,
although the results of meta-analysis on 44 independent
observations showed that Rdm was reduced 18.4% by
elevated CO2. We found a positive correlation between
Rda and leaf starch content, which was higher at
elevated CO2, but no correlation between Rda and leaf
N content was observed, suggesting the importance of
starch content in determining the magnitude of
respiration. Total biomass accumulation of female P.
tremuloides was higher than that of males in low-N soil
and at ambient CO2, but not in other treatments.
Elevated CO2, on the other hand, significantly
increased total biomass of both male and female trees
in low- and high-N soil, with the increase ranging from
22-70% for female and 58-66% for male trees. There
was a significant CO2 x genotype interaction in
photosynthetic responses to CO2 enrichment, wherein A
was significantly enhanced by elevated CO2 for five
genotypes in high-N soil and for four genotypes in low-
N soil. Enhancement of A by elevated CO2 ranged from
14% to 68%. We found a correlation between the
degree of A enhancement to elevated CO2 and stomatal
sensitivity to CO2. Stomatal conductance and A of
different genotypes also responded differentially to
drought stress. Our results suggest that P. tremuloides
genotypes and genders respond differentially in A and
Rd to rising atmospheric CO2, with the degree of
responses dependent upon other environmental factors.
These differential responses will likely alter the
distribution and population structure of this
ecologically important species in a CO2 enriched
environment.
Major Professor(s): Curtis, Peter S.
Department: Environmental Science
Principal Investigator(s): Teeri, James A.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON DIOXIDE, GENETICS,
PHOTOSYNTHESIS, RESPIRATION, TREE
67
Wang, Xiaoli. 1997. Global Thermohaline Circulation
and Ocean-Atmosphere Coupling. Ph.D. Thesis,
Massachusetts Institute of Technology, 134 pages.
A global ocean general circulation model of idealized
geometry, combined with an atmospheric model based
on observed transports of heat, momentum, and
moisture, is used to explore the sensitivity of the global
conveyor belt circulation to the surface freshwater
fluxes, in particular, the effects of meridional
atmospheric moisture transports. The numerical results
indicate that the equilibrium strength of the North
Atlantic Deep Water (NADW) formation increases as
the global freshwater transports increase. However, the
global deep water formation, i.e., the sum of the
NADW and the Southern Ocean Deep Water formation
rates, is relatively insensitive to changes of the
freshwater flux. Perturbations to the meridional
moisture transports of each hemisphere identify
equatorially asymmetric effects of the freshwater fluxes.
The equilibrium NADW formation is primarily
controlled by the magnitude of the Southern
Hemisphere freshwater flux. The Northern Hemisphere
freshwater flux only has a significant impact on the
transient behavior of the North Atlantic overturning.
Increasing this flux leads to a collapse of the conveyor
belt circulation, but the collapse is delayed if the
Southern Hemisphere flux also increases. The
perturbation experiments also illustrate that the rapidity
of the collapse is affected by random fluctuations in the
wind stress field. The atmospheric component of the
coupled ocean-atmosphere model is modified to
investigate the stability of the thermohaline circulation
(THC) to an increase in the surface freshwater forcing
in the presence of interactive meridional transports in
the atmosphere. The atmospheric model still assumes a
fixed latitudinal structure for the heat and moisture
transports, but the amplitudes are now calculated
separately for each hemisphere from the large scale sea
surface temperature (SST) and SST gradient, using
parameterizations based on baroclinic stability theory.
The ocean-atmosphere heat and freshwater exchanges
then are calculated as residuals of the steady-state
atmospheric budgets. Owing to the ocean component's
weak heat transport, the model has too strong a
meridional SST gradient when driven with observed
atmospheric meridional transports. When the latter are
made interactive, the conveyor belt circulation
collapses. A flux adjustment is introduced in which the
efficiency of the atmospheric transports is lowered, to
match the too low efficiency of the ocean component.
The feedbacks between the THC and both the
atmospheric heat and moisture transports are positive,
whether atmospheric transports are interactive in the
Northern Hemisphere, the Southern Hemisphere, or
both. However, the feedbacks operate differently in the
Northern and Southern Hemispheres, because the THC
upwells and causes equatorward heat transport in the
latter. The feedbacks in the two hemispheres do not
necessarily reinforce each other because they have
opposite effects on low-latitude temperatures. The
model is qualitatively similar in stability to one with
conventional "additive" flux adjustment, but
quantitatively more stable.
Major Professor(s): Stone, Peter H.
Department: Earth, Atmospheric and Planetary
Sciences
Principal Investigator(s): Stone, Peter H.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: ATMOSPHERE, CIRCULATION,
CLIMATE, MODEL, OCEAN
68
Weber, Rodney. 1995. Studies of New Particle
Formation in the Remote Troposphere. Ph.D.
Dissertation, University of Minnesota Twin Cities, 183
pages.
Particle formation and growth play key roles in
determining the size distribution of remote tropospheric
aerosols. Since these aerosols can have significant
global climatic influences, understanding such
processes is critical for accurate predictions of future
climate. In this research, a method for measuring
ultrafine particle concentrations (~3-4 nm diameter)
was developed and applied to studies of tropospheric
particle formation. Laboratory experiments showed that
ultrafine condensation particle counter photo detector
pulse heights provide a robust and sensitive
measurement of ultrafine particle concentrations. Pulse
heights were insensitive to particle size and
composition, and were affected by the presence of large
particles (diameters > 15 nm) only when concentrations
were larger than ~4x103 cm-3. Tropospheric
measurements were made at a remote marine (Mauna
Loa Observatory, HI) and continental site (Idaho Hill,
CO). At both sites, ultrafine particles were frequently
detected and appeared to be from recent nucleation.
Measurements show that sulfuric acid (H2SO4) was
likely a primary precursor vapor whereas water (H2O)
was not. Preexisting aerosol surface area limited
ultrafine concentrations by limiting the H2SO4
concentration and by scavenging newly formed
particles. At both sites, measured 3 nm particle
formation rates were much higher than nucleation rates
predicted by classical H2SO4-H2O theory and were
observed at much lower H2SO4 concentrations (105-107
cm-3) than predicted by this theory (108-109 cm-3).
Furthermore, while binary theory predicts nucleation
rates vary as ~[H2SO4]10, the measured particle
formation rates varied as [H2SO4]2, suggesting that
kinetically, nucleation is H2SO4 collision limited. These
discrepancies may result from additional species, such
as ammonia (NH3), participating in nucleation. A
simple new (collision limited) H2SO4-NH3-H2O
nucleation model is proposed. At both sites, the median
particle diameter growth rate was 0.1 nm h-1, calculated
by assuming condensation of only hydrated H2SO4
vapor. Measurements indicate that growth rates were
actually higher by factors of 1.5-2 at Mauna Loa and 5-
10 at Idaho Hill. Higher growth rates may be from
coagulation of molecular clusters with ultrafine
particles, or condensation of additional species such as
secondary organics.
Major Professor(s): McMurry, Peter H.
Department: Mechanical Engineering
Principal Investigator(s): McMurry, Peter H.
Program Area: Atmospheric Chemistry
KEYWORDS: AEROSOL, CONDENSATION, GASES,
NUCLEATION, PARTICULATE
69
Winterson, Kristin. 1999. Carbon Sinks in Vegetation
of the Southern Appalachian Mountains. M.S. Thesis,
University of Virginia, 80 pages.
Forest Service data were analyzed for counties in the
Southern Appalachian Region of Tennessee, North
Carolina, Georgia, and Kentucky. Utilization of the
diameter at breast height (DBH) measurements showed
carbon sinks to exist in all counties. North Carolina
and Georgia averaged 264 and 275 g C m-2y-1,
respectively while Tennessee and Kentucky sequestered
161 and 80 g C m-2y-1. Analyses of varying allometric
equations proved inconsequential; all equations, when
used for the entire region, passed an ANOVA test with
à = 0.05. Variations in carbon sequestration were most
pronounced across state boundaries. Variations in stand
age, human populations, and survey techniques are the
most likely reasons for this observation. Eddy
covariance data from Walker Branch Watershed,
Harvard Forest, and boreal regions in Canada were
comparable to the FIA results. To insure this region is a
sink in the future, continued use of DBH measurements
from the FIA data set should be utilized. Furthermore,
data should be corroborated with atmospheric tower
data wherever possible to test for accuracy.
Major Professor(s): Emanuel, William R.
Department: Environmental Sciences
Principal Investigator(s): Emanuel, William R.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: CARBON, CARBON CYCLE, FOREST,
SPATIAL DISTRIBUTION
70
Yu, Shaocai. 1996. The Spatial, Temporal, and
Seasonal Variations of Climatological Variables, and
the Impact of Stratospheric Volcanic Aerosols on
Radiative Forcing in the Southeastern U.S. M.S. Thesis,
North Carolina State University, 109 pages.
SECTION I. The monthly and yearly climatic data on
the duration of growing season, mean, maximum,
minimum and daily temperatures, diurnal temperature
range (DTR), and precipitation in 52 stations over the
Southeast US were statistically analyzed by SAS model
during the period of 1949 to 1994 (46-year interval).
The results showed that the growing season became
longer in 61.5% of stations, and significantly longer in
13.5% of stations at the 0.05 level in the past 46 years.
The arithmetic average of duration of growing season
for 52 stations became longer by 1.7 days in past 46
years. The earlier start and later end of growing season
led to the dominant longer duration of growing season
in the Southeastern US. The annual mean daily
temperature decreased in 51.9% of stations, and
decreased significantly in 13.5% of stations at the 0.05
level in the past 46 years. The arithmetic average of
annual mean daily temperature for 52 stations
decreased by -0.09oC in the past 46 years. There were
slightly cooling trends in the Southeastern US in the
past 46 years. The annual total precipitation increased
in 82.7% of stations, and there was dominant
increasing trend of total precipitation in all seasons
except Summer in past 46 years. The annual total
precipitation increased significantly in 9.6% of stations
at the 0.05 level. The arithmetic average of annual total
precipitation for 52 stations increased by 81 mm in the
past 46 years. The annual, winter and summer mean
maximum temperatures decreased in 67.0%, 90.4% and
63.5% of stations in the Southeastern US in the past 46
years, respectively. The annual mean maximum
temperature decreased significantly in 15.4% of
stations at the 0.05 level. The arithmetic average of
annual mean maximum temperature for the 52 stations
decreased by -0.28oC in the past 46 years. For mean
minimum temperature, the annual, summer and fall
mean values showed increasing trends in 59.1%, 69.2%
and 82.7% of stations, respectively. The annual mean
minimum temperature increased significantly in 19.2%
of the stations at the 0.05 level. The arithmetic average
of annual mean minimum temperature for the 52
stations increased by 0.09oC in the past 46 years. The
annual, winter, summer and fall mean temperature
range (DTR) became smaller in 69.2%, 67.3%, 76.9%
and 75.0% of the stations, respectively. The annual
mean DTR decreased significantly in 28.9% of the
stations at the 0.05 level. The arithmetic average of
annual mean diurnal temperature range for the 52
stations became shorter by -0.37oC in the past 46 years.
SECTION II. Major explosive volcanic eruptions inject
massive amounts of dust and gases into the lower
stratosphere and upper troposphere. Stratospheric
volcanic aerosols can influence the radiation balance of
Earth by scattering and absorbing radiation. Volcanic
aerosols can scatter incoming solar radiation to space,
increasing planetary albedo, reducing the total amount
of solar energy reaching the troposphere and the earth's
surface, decreasing the daytime maximum temperature
(aerosol shortwave forcing). They can also absorb and
scatter terrestrial longwave radiation, warming the
nighttime minimum temperature (longwave forcing).
Downward longwave radiation from the warming
stratosphere also acts to warm the surface. However,
persuasive evidence of climate response to this forcing
has thus far been lacking. Here we examine patterns of
annual and seasonal variations in mean maximum and
minimum temperature trends over the two periods
1992-94 and 1985-87 relative to that over the period
1988-90 at 47 stations in Southeastern US for evidence
of such climate responses. The stratospheric volcanic
aerosol microphysical characteristics over the
Southeastern US during the period 1985-1994 were
inferred from the Stratospheric Aerosol and Gases
Experiment (SAGE) II satellite extinction measurement
using a modified randomized minimization search
technique (RMST). The dominant decreasing trends of
mean maximum temperature and the dominant
increasing trends of mean minimum temperature over
period 1992-94 and 1985-87 relative to that over the
period 1988-90 are consistent with the distribution of
stratospheric volcanic aerosol and model calculation of
aerosol forcing in the Southeastern US. The
stratospheric volcanic aerosol forcing also has an effect
on daily temperature, diurnal temperature range and
precipitation in Southeastern US.
Major Professor(s): Saxena, Vinod K.
Department: Marine, Earth, and Atmospheric Sciences
Principal Investigator(s): Saxena, Vinod K.
Program Area: National Institute for Global
Environmental Change (NIGEC)
KEYWORDS: AEROSOL, CLIMATE, RADIATIVE
PROCESS, SPATIAL DISTRIBUTION, TEMPORAL
DISTRIBUTION, VOLCANO