Simultaneous observation of a rain event using the MU radar and an airborne Doppler radar for simulating TRMM ground validation

The TRMM (Tropical Rainfall Measuring Mission) satellite will be the first one which installs a precipitation radar (PR) on-board. Since the planned radar is a single-frequency, single-polarization, and non-Doppler one, the retrieval of rain intensity from the echo intensity data requires careful interpretation based on sophisticated algorithms which incorporate peripheral ground validation data. The MU (Middle and Upper atmosphere) radar of Kyoto University and CAMPR (CRL Airborne Multi-Parameter Radar) of the Communications Research Laboratory are expected to play important roles in the Japanese ground validation programs. Result of the first simultaneous measurement of a rain event by two of candidate ground validation radars for TRMM precipitation radar is presented. It was found that the Z factors measured by the ground-based MU radar and the airborne CAMPR agreed well within the accuracy range of the measurements. They also showed the existence of fairly strong horizontal variation of the rain intensity inside the TRMM PR footprint size, suggesting the importance of non-uniform beam-filling (NUBF) effect