Cloud characteristics over central Amazonia during GTE/ABLE 2B derived from multispectral visible and infrared spin scan radiometer atmospheric sounder observations

Abstract

Multispectral GOES/Visible and Infrared Spin Scan Radiometer Atmospheric Sounder (VAS) observations in the carbon dioxide absorption band at 15 μm have been used to calculate diurnal cloud statistics over central Amazonia region for 4 days during the Global Tropospheric Experiment/Amazon Boundary Layer Experiment (GTE/ABLE IIB). The CO2 technique calculates both cloud top pressure and effective emissivity from radiative transfer principles. Transmissive clouds that are partially transparent to terrestrial radiation have been reliably separated from opaque clouds in the statistics of cloud cover. A high incidence of transmissive clouds (about 47%) was found on the average. Diurnal characteristics of cloud cover over Amazonia have been linked to convective activity over this region. On days with afternoon convection, an increase in low‐altitude opaque clouds was followed by a subsequent increase in high‐altitude transmissive clouds.