A combined infrared and microwave technique for studying the diurnal variation of rainfall over Amazonia

The development of a combined microwave/infrared satellite technique for estimating convective and stratiform rainfall and its application in studying the diurnal variability of rainfall in Amazonia is presented. The current technique, takes advantage of the 30-minute sampling and 4 km spatial resolution of the infrared channel and the better physics of the microwave retrieval. The resultant method is subsequently used to derive the diurnal variability of rainfall over the entire northern half of South America, and includes the partition of the rainfall into the contributions from its convective and stratiform components. The technique is applied to the four-month period beginning January 1999, which coincided with the TRMM/LBA ground validation program over Rondonia, Brazil. Radar data from the TOGA radar, available every 10 minutes, are used as validation in an area approx. 150 km around the radar site (11 N, 62W). Results are compared to the same four-month period in 1996. Derived differences between morning (5-7 LT) and evening (17-19 LT) rainfall are compared to a 10-year microwave-based climatology. Using an earlier version of this technique, promising results were found in the intercomparison between instataneous estimates and independent passive microwave-based rainfall. The diurnal variation of rainfall in early 1996 in brazil was well-described by the technique, as was the variation of the convective and stratiform components of the rainfall.