A new satellite-based census of precipitating and nonprecipitating clouds over the tropics and subtropics

Abstract

Cloud properties retrieved from TRMM VIRS measurements analyzed for PR-determined precipitating clouds (P-PCs) and nonprecipitating clouds (PN-PCs), respectively. The total cloud amount (CA) averaged across the tropics and subtropics in boreal summer is about 55.9 and 40.1, over ocean and land, respectively, with P-PCs contributing less than 10% to the total CA. Low P-PCs that have cloud top lower than 680 mb are extremely scanty, while low PN-PCs account for near half of total PN-PCs. The mean cloud optical thickness (COT) of P-PCs exceeds 60, approximately 10 times that of PN-PCs. According to ISCCP cloud classification, four primary cloud types of PN-PCs, cumulus, stratocumulus, altocumulus and cirrus are revealed, whereas deep convective clouds and cirrostratus are proved to be the first and second primary cloud type of P-PCs, implying a considerable amount of P-PCs with high cloud top but moderate COT. Copyright 2008 by the American Geophysical Union.