The Diurnal Cycle of Diabatic Heating and TRMM Precipitation Estimates in West Africa

Numerous investigations have examined the diurnal cycle of convective activity in West Africa based exclusively on satellite observations. However, a unique opportunity exists to study this problem using combined in situ and satellite data thanks to the African Monsoon Multidisciplinary Analysis (AMMA)/NASA AMMA (NAMMA) field campaign that took place in 2006. In particular, a network of radiosonde launch sites was set up from June through September 2006, with the most intensive observations collected over parts of Niger, Nigeria, Benin, Togo, and Ghana. In the present study, composite vertical profiles of diabatic heating through the diurnal cycle are computed within this region of West Africa, based on the AMMA sounding data. Then, these heating profiles are placed within the context of precipitation estimates derived from several TRMM products for the same time period. In particular, the structures and timing of the heating profiles are compared with precipitation feature information provided by the TRMM database of the University of Utah Tropical Meteorology Group. This dataset includes precipitation features based on applying thresholds to data from several different instruments, including the PR, TMI, and VIRS. Differences in the composite diurnal timing of rainfall as detected by these various types of precipitation features are explored and compared with the signatures of convective and stratiform precipitation suggested by the observed diabatic heating. Alignment between the timing of the diabatic profiles and more-processed satellite products, such as 3B42 rain estimates, is also assessed.