ugh biogeophysical and biogeochemical processes that modify both surface-atmosphere exchanges of momentum, energy and greenhouse gases and surface roughness.
The feedback mechanisms between the land surface and the atmosphere have been increasingly investigated during last decade due to the increasing computational power. Therefore, in order to study the potential impacts of LCC on local climate, the simulations performed by General Circulation Models (GCMs) have been complemented by the use of Regional Climate Models (RCMs): in fact, the coarse resolution of the GCMs limits their capability to capture mesoscale features that play a pivotal role in regional dynamics.
Figure. Differences of deforestated and control simulations of horizontal wind vectors (arrows, m/s) and temperature (shaded area, K) at 960 hPa over the summer season (JJA). The contour lines indicate where these differences are statistically significant (t test for 90% confidence level).
River discharge data analysis
River discharge is one of the five components of the Mediterranean Sea water budget, together with the net inflow of Atlantic water through the Strait of Gibraltar that from the Black Sea at the Dardanelles Strait, evaporation, and precipitation. In terms of absolute values, river discharge (R) represents the smallest contributionto this budget. In fact, climatological annual mean discharge is less than 20% of the atmospheric water budget evaporation minus precipitation (E - P), and the amplitude of its seasonal cycle is almost negligible with respect to the seasonal cycle of E-P. Nevertheless, discharge together with precipitation is the only freshwater input into the basin, and during spring the two basin-integrated components E -P and R are fairly comparable.
We collected historical river discharge monthly series from different hydrological database in order to assess the river discharge contribution to the Mediterranean fresh water input. We identified 68 rivers discharging into the Mediterranean and we estimated the climatological annual mean Mediterranean discharge with an accuracy of about 78%, see Fig.1
Fig. 1 Climatological seasonal cycle of total discharge into the Mediterranean Sea and its decomposition by continent of origin. Represented here is at least 78% of the actual Mediterranean totals (solid line), 76% of discharge from Europe (short dashed), 40% of that from the Middle East (dotted), and 86% of discharge from North Africa (long dashed). (Values are in m3/s.) From "River Discharge into the Mediterranean Sea: Climatology and Aspects of the Observed Variability" , M.V. Struglia, A. Mariotti, A. Filograsso, Journ. Clim. Vol.17 (2004), No. 24 pp. 4740-4751.
Regional projections of river discharge in the Mediterranean catchment
Among all the possible physical impacts of climate change in the Mediterranean area, the one related to the availability of water resources is crucial both for natural equilibrium of biological ecosystems and for social and economic activities of the inhabitants of the Mediterranean countries. Projected variations in river discharge deriving from altered rainfall distribution will dramatically affect both natural equilibriums and people, as some areas are liable to experience large increases in flood flows, whereas others will be subject to water stress.
We developed IRIS (Interactive River Scheme) which is a numeric tool to estimate river discharge from modelled total runoff fields. Runoff fields are computed by atmospheric models via a soil parameterization scheme, which accounts for energy and water fluxes at the atmosphere-biosphere-land interfaces, thus determining the moisture content of soil, the quantity of water returned to the atmosphere through evapo-transpiration and the excess rainfall that goes into runoff.
Fig.2 Mediterranean and Black Sea catchments in IRIS. Reconstruction based on TRIP datase
On sufficiently long time scales, vertical balance between the four components of the terrestrial hydrological cycle should be achieved:
where P is the cumulated precipitation, E is the cumulated eva