The relatively small footprint size of the TRMM Microwave Imager (TMI) radiometer (approximately 5.5 km) permits both the description of bulk properties of convective systems and the convective-scale analysis of the configuration of cumulonimbus clouds within these systems. The 85 GHz channels of the TMI are used to document the variety of organizational modes of convective-scale features within convective cloud systems. Satellite overpasses of Sub-Saharan Africa for four wet seasons (May-September 1998-2001) are used to make intraseasonal, interannual, and geographic comparisons of these organizational modes across the study area.

Prabhakara et al. (2000) developed an algorithm for the TMI 85 GHz channel to distinguish the relative ages of cumulonimbus clouds (young, mature, decaying) within convective cloud systems. This algorithm makes it possible to examine the frequency, orientation, and cumulative area of cumulonimbus in each stage of development within a larger system. This represents a significant advance over previous efforts to classify the bulk properties (intensity, size) of African mesoscale convective systesm using IR cloud top temperatures or the Special Sensor Microwave/Imager. Since trailing statiform anvils, if present, can contribute a significant proportion of the total rainfall, the frequency of convective cloud systems with and without decayed cumulonimbus and the sizes of these anvils are noted.