Combined wind profiler/polarimetric radar studies of the vertical motion, thermodynamic and microphysical characteristics of tropical thunderstorms

An experiment using 920 and 50 MHz wind profiler radar combined with polarimetric radar data was undertaken in Darwin, northern Australia during the 1997/98 wet season. The profilers scans were coordinated in time and height sampling. The polarimetric radar cycle included a volume scan (for TRMM commitments) followed by an RHI scan over the profilers and a fixed elevation/azimuth dwell of 2 minutes over the profilers. The combined data allows a detailed examination of the vertical motion field and precipitation microphysics of several short lived storms that developed on sea breeze fronts passed over the profilers. These storms were quite shallow with tops only up to about 8 km, but reached reflectivities in excess of 55 dBZ. They had intense updrafts, often exceeding 15 ms-1 on the periphery of the cells and strong downdrafts of several ms-1 within the cell reflecting the short lifetimes of these cells. There was extensive ice production within these storms with the growth of cm sized hail above the freezing level. This large ice then extended down to heights as low as 2.6 km (~ 2 km below the freezing level) near the strong updrafts. The ice was unambiguously identified in the polarimetric data and in the profiler data where spectral peaks were found at fall speeds far in excess of the maximum fall speed for large rain drops. There are distinctive radar signatures associated with the melting of these particles that have significant implications on radar rain estimation of these storms and polarimetric radar based precipitation algorithms. These data provide an ideal test for cloud resolving models.