A Comparison between Polarimetric Radar and Wind Profiler Observations of Precipitation in Tropical Showers

Abstract

This paper describes the results of an experiment that combines the data from a 5-cm-wavelength polarimetric radar and multiple-frequency wind profilers to examine the polarimetric signatures associated with the microphysical structure of several relatively shallow thunderstorms and also to examine quantitative rainfall measurements made with the polarimetric radar. These shallow storms produce considerable amounts of centimeter-sized hail. The presence and size of this hail are deduced from the wind profiler data. The melting hail particles produce a distinctive polarimetric signature with large values of differential reflectivity ZDR and suppressed values of the correlation coefficient between the signals at horizontal and vertical polarization. Comparisons between the mass-weighted mean drop diameter and differential reflectivity have been performed and show reasonable agreement with theoretical expectations, although the observed ZDR are somewhat smaller than expected. This may be associated with the theoretical assumption of the Pruppacher?Beard oblateness relationship even though there is evidence to suggest that real raindrops may be less oblate on average in convective rain. Quantitative polarimetric rainfall estimators have been compared with rainfall rates derived from the profiler drop size distribution retrievals and show reasonably good agreement when reflectivity values are matched.