A NEW STATISTICAL METHOD OF ESTIMATING SURFACE RADIANCES FROM CORRESPONDING SATELLITE WINDOW-CHANNEL RADIANCES
Abstract Stepwise linear regressions for the specification of blackbody surface radiances are computed using a set of 103 model atmospheres chosen originally by Wark et al. and the corresponding simulated values of Nimbus 2 window-channel (10–11 µ) radiances. Two stratifications are considered: (a) precipitable water vapor, u>1, and (b) u<1 gm cm–2. For each of five zenith angles considered, significant contributions are made in both regression formulas by inclusion of parameters representing the radiative transfer effects of water vapor and ozone. This regression formulation makes use of empirically derived expressions related to these effects over long atmospheric paths. The specification of the sample of surface radiances is in accordance with a multiple correlation coefficient, exceeding 0.990 and 0.995 in the respective stratifications. Corrections for atmospheric effects to be applied to Nimbus 2 window-channel radiances in estimating the corresponding surface values are displayed in nomogramic as w...
Airborne Radiometer Measurements of Effects of Particulates on Terrestrial Flux
Abstract Thin layers of particulates or clouds in the high troposphere and lower stratosphere are generally not visible to an observer at the surface, even under the favorable viewing conditions at sunset. They are not easily detected by a television camera in a satellite from above. Yet these layers affect upwelling infrared flux. A flight program, employing balloon-borne radiometers and a jet aircraft from which visual observations of particle layers were made, was conducted to measure the attenuating effects of these layers on upwelling. terrestrial flux. An estimate of the error such attenuation can cause in surface temperatures deduced from the upward flux measurement was then made. The balloon-borne radiometers were launched from a desert area of California. During the ascents the presence of cirrus or particle layers could not he visually or photographically detected from the surface. They were, however, detected by the radiometer during ascent and by observers in a jet aircraft. The observations i...
Climatology of the cusp-related thermospheric mass density anomaly, as derived from CHAMP observations
We report on the thermospheric mass density anomaly in the vicinity of the ionospheric cusp. A systematic survey of the anomalies is presented, based on a statistical analysis of 4 years of data (2002–2005) obtained by the accelerometer onboard CHAMP. The anomalies are detected during all years and seasons in both hemispheres but with stronger signatures in the Northern Hemisphere. For the same geophysical conditions, solar flux and geomagnetic activity the anomalies in the north are larger by a factor of about 1.35. Over the course of the survey period the amplitude decreases by more than a factor of 5 while the level of solar flux reduces by a factor of 2. The anomaly strength also depends on the solar wind input. The merging electric field, E merg , is generally enhanced for about an hour before the anomaly detection. There is a quadratic response of the anomaly amplitude to E merg . For geophysical conditions of P10.7 E merg E merg , where the weight of E merg , in mV/m, is by about 50 times higher than that of the solar flux level. The solar zenith angle and the influence of particle precipitation are found to play a minor role as a controlling parameter of seasonal variation. The well-known annual variation of the thermospheric density with a minimum around June also influences the formation of the cusp anomalies. This leads to a clear hemispheric asymmetry with very weak anomalies in the south during June solstice, which is supposed to be a combined effect of the minimum in annual variation and the seasonal decrease of solar insolation in this region.