Space-based Rainfall Microwave Radiometry and Matching Radar Products: a Verification

The use of satellite-born microwave sensor for estimation of rainfall has drawing attention, and is basic to worldwide projects like TRMM and the forthcoming GPM. Promising re sults in rainfall estimates were obtained with climatologically tunned radiance – rainfall relationships derived with a leveled probability technique in the VIS/IR, suggesting that such an approach have a significant potential to explore the microwave channels. A pilot project is, then, being carried out in the area of coverage of the Bauru radar (Central S. Paulo) to investigate the utilization of the HSB (Humidity Sensor for Brazil) onboard the Aqua satellite, to perform rainfall measurements. This extends to similar sensors, like the AMSU-B. One major issue of the initial phase of the project focus on selecting the radar products in support of the rain measurements. This paper presents preliminary results on the matching of HSB ́s channel 4 (183.33 +/7 GHz) data to radar CAPPIs for typical events in the area, occurring during the dry-to-rainy trasition period of September-October, 2002. Both satellite along and cross-track directions data were analized for brightness temperature gradients vis à-vis the matching radar CAPPIs in different heights. First results show that the 3.5 km height, 240 km range operational CAPPI product matchs, to a good extent, the corresponding HSB ́s channel 4 measurements. On the other hand, brightness temperature ranges have been found to be compatible with the vertical extent of the precipitation under observation. An operational test is planned for the third quarter of 2003 and is detailed in the paper