EXAMINATION OF GLOBAL ATMOSPHERIC-TEMPERATURE MONITORING WITH SATELLITE MICROWAVE MEASUREMENTS .2. ANALYSIS OF SATELLITE DATA

Using Microwave Sounding Unit (MSU) channel 2 (Ch. 2, 53.74 GHz) data, Spencer and Christy (1992a) determined that the earth exhibits no tem perature trend in the period 1979-90, while other authors find a tempe rature increase of roughly 0.1 K. Based on a theoretical analysis Prab hakara et al. (1995) showed that the information about the global atmo spheric temperature deduced from MSU Ch. 2 observations has a small co ntamination, delta T-2, as a result of the attenuation due to hydromet eors in the atmosphere. A method is developed in this study, that util izes coincident measurements made by MSU in Ch. 1 (50.3 GHz), to estim ate this delta T-2 over the global oceans. The magnitude of delta T-2 is found to be about 1 K over significant parts of the tropical oceani c rain belts and about 0.25 K over minor portions of the mid-latitude oceanic storm tracks. Due to events such as El Nioo, there is variabil ity from year to year in the rain areas and rain intensity leading to significant change in the patterns of delta T-2. The patterns of delta T-2 derived for March 82 and March 83 reveal such a change. When aver aged over the global oceans, from 50 degrees N to 50 degrees S, delta T-2 has a value of 0.25 and 0.29 K for March 1982 and 1983, respective ly. Due to these reasons the interannual temperature change derived by Spencer and Christy from MSU Ch. 2 will contain a residual hydrometeo r effect. Thus in evaluating decadal trend of the global mean temperat ure of the order of 0.1 K from MSU Ch. 2 data one has to take into acc ount completely the contamination due to hydrometeors.