Contribution of Mesoscale Convective Complexes to Rainfall in Sahelian Africa: Estimates from Geostationary Infrared and Passive Microwave Data

Abstract

The contribution of mesoscale convective complexes to the July–September rainfall in Sahelian Africa is assessed using passive microwave data from the Special Sensor Microwave Image and infrared (IR) data from the European Geostationary Meteorological Satellite (Meteosat). A simple precipitation-estimation procedure, which takes advantage of the good time resolution of the IR and the strong relationship between the microwave radiance and rainfall, is developed and applied. The microwave technique uses the 37- and 86-GHz brightness temperatures to define the rain areas and the 86-GHz ice scattering signal to determine the rainfall intensity. The IR cloud shield areas are defined by the 219 K threshold. Regression analyses are used to relate the microwave-derived precipitation characteristics of the system and the IR data closest to the time of the SSM/I observation. These relationships are used to compute the precipitation characteristics of the total set of systems and to determine their monthly rainfall contribution. Results indicate that these systems have precipitation characteristics, such as rain area and volume, which are of the same order of magnitude as systems in the United States. In addition, they provide a significant fraction of the rainfall in Sahelian Africa.