CPOL Radar-Derived Drop Size Distribution Statistics of Stratiform and Convective Rain for Two Regimes in Darwin, Australia

Abstract

Abstract This note builds on prior technique development related to the classification of rain types utilizing C-band polarimetric (CPOL) radar measurements. While the prior work was preliminary and limited in scope, the authors elaborate here on the basis of the drop size distribution (DSD)-based indexing technique for rain-type classification (convective/stratiform/mixed), and place it on firmer footing by testing the methodology against texture- and disdrometer-based methods as applied to Darwin datasets. A microphysical-based methodology is attractive as it links more directly to the underlying rainfall physical processes. Statistics of the DSD parameters, namely, histograms of log10(Nw) and D0, for convective and stratiform rain types across the premonsoon buildup and monsoon regimes were derived and further separated for over land and over ocean regions. The maximum value for mean D0 (1.64 mm) and the largest histogram standard deviation (0.32 mm) occurred for convective rain over land during the buildup regime. The largest differences in D0 and NW histograms were found to be for convective rain between the buildup and monsoon regimes (independent of land or ocean areas). Stratiform rain histograms were found to be very similar during the buildup regime with little land–ocean differences. However, somewhat larger land–ocean differences were found for the monsoon stratiform rain. The main histogram characteristics of the “mixed” or “uncertain” rain type were closer to the convective rain type than to stratiform, across both regimes and land–ocean areas. Additionally, the Nw versus D0 cluster of points (mean ±1σ) for convective rain agrees very well with the previously published range of values for maritime convective (equilibrium-like) DSDs.