Accurate measurement of tropical rainfall is essential to understanding interannual variability, climate change, the hydrologic cycle and its link to the general circulation. There are numerous methods for estimating tropical precipitation including rain gauges, the Special Sensor Microwave Imager (SSM/I) satellite, Outgoing Longwave Radiation (OLR) measurements and, more recently, the Tropical Rainfall Measuring Mission (TRMM) satellite that carries as one of its precipitation measuring instruments the first space-borne precipitation radar (TRMM PR). These data sources produce differing rainfall estimates over the tropics due to differences in horizontal resolution as well as spatial and temporal sampling. In this study, the interannual variations in rainfall estimates are compared for 1998 and 1999 during the West and Central Africa rainy seasons from TRMM PR, TRMM Merged (TRMM and other data sources), Geostationary Operational Environmental Satellite (GOES) Precipitation Index (GPI) Global Precipitation Climatology Project (GPCP), Special Sensor Microwave Imager (SSM/I) satellite data and gauge data.

Previous results for West Africa have shown that the TRMM PR and TRMM Merged rainfall estimates differ in the intensity and occurrence of maximum rainfall during June-August 1998. The results from this research indicate differences in the amount of rainfall estimated by the different datasets and the occurrence of maximum rainfall during the rainy season. The results also illustrate differences in the interannual difference of the rainfall estimates from the data and changes in precipitation characteristics throughout the wet seasons of West and Central Africa.