Life Cycle of Deep Convective Systems over the Eastern Tropical Pacific Observed by TRMM and GOES-W

Abstract

The life cycle of deep convective systems over the eastern tropical Pacific (30°N to 30°S, 180 to 90°W) was studied in terms of cloud types, as classified by a split window (11 μm and 12 μm). Hourly split window image data of Geostationary Operational Environmental Satellite (GOES-W) from January 2001 to December 2002 was used in this study. Deep convective systems consist mostly of optically thick cumulus type clouds in the earlier stage and a cirrus type cloud area that increases with time in the later stage. During this analysis period and over the analysis area, the life stage of deep convective system, to a large extent, can be identified by computing the percentage of cirrus type clouds within the deep convective system from a single snap shot of the split window image. Coincident Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) observations were used to study the relationship between the percentage of cirrus type clouds within a deep convective system (i.e., its life stage) and the rainfall rate. It was found that the rainfall rate tends to be larger in the earlier stage of the life cycle when a smaller percentage of cirrus type cloud is present within the deep convection.