Physical properties of maritime low clouds as retrieved by combined use of Tropical Rainfall Measuring Mission (TRMM) Microwave Imager and Visible/Infrared Scanner 2. Climatology of warm clouds and rain

Abstract

In this paper, we investigate characteristics of low clouds and warm‐rain production in terms of droplet growth based on the effective droplet radii retrieved by a combined use of visible, infrared, and microwave satellite remote sensing. We propose to categorize low clouds into the following groups: (1) nondrizzling, nonraining clouds; (2) nonraining clouds with drizzling near the cloud top; (3) raining clouds; and (4) clouds with no clear interpretation in terms of the effective radii derived using two different schemes. This categorization is supported by examination of the correlation between static stability and the retrieved results in the three “precipitating regions” (the Middle Pacific, South Pacific Convergence Zone [SPCZ], and Intertropical Convergence Zone [ITCZ] cumulus regions) and in the four “nonprecipitating regions” (the Californian, Peruvian, Namibian, and eastern Asian stratus regions). The rain rate derived by Precipitation Radar (PR) provides global characteristics consistent with our results. Californian and Peruvian stratus clouds are found to frequently have the drizzle mode near the cloud top, whereas Namibian strati have fewer chances to drizzle. The drizzle mode almost completely disappears in the eastern Asian region in the winter. The cloud–aerosol interaction is a promising candidate for suppressing the drizzle mode formation in nonprecipitating clouds.