Satellite-inferred morning-to-evening cloudiness changes.

Abstract

Outgoing infrared radiation (IR) values inferred from radiance measurements in the water vapor window (10.5-12.5 micrometer) taken at approximately 0900 and 2100 LT by scanning radiometers aboard NOAA satellites are compared in order to determine whether a significant diurnal variation exists. Data with a resolution of 2.5o in latitude and longitude are mapped for latitudes between 50oN and 50oS for two seasons, June-August 1975 and December 1975-February 1976. On the basis of these maps it is possible to identify broad categories of geographical regions which display similar patterns of 12h differences in outgoing IR. For several of these categories composite histograms are constructed in order to investigate the morning to evening difference in outgoing IR for ranges of values corresponding to high clouds, middle clouds and low clouds. -from Authors