THE DEVELOPMENT OF SSM I RAIN-RATE RETRIEVAL ALGORITHMS USING GROUND-BASED RADAR MEASUREMENTS/

Rainfall algorithms developed for the DMSP Special Sensor Microwave/Im ager are presented and then ''calibrated'' against ground-based radar measurements to develop instantaneous rain-rate retrieval algorithms. These include both scattering- and emission-based algorithms. Radar da ta from Japan, the United States, and the United Kingdom have been use d in the investigation. Because of the difficulties in accurately matc hing the satellite and radar measurements in both time and space, an a pproach where both measurements are grouped in 1 mm h(-1) rain-rate bi ns provides a much more accurate set of measurements to be used in the derivation of coefficients for instantaneous rain-rate retrieval. Bot h linear and nonlinear relationships are developed, with the nonlinear fits being more accurate and supported by model simulations. An appli cation of the derived instantaneous rain-rate relationships to an inde pendent case is presented, with approximately a 10% error for the scat tering algorithm when compared with radar-derived rain rates.