Simulation of polarimetric radar variables in rain at S-, C- and X-band wavelengths

• Main Authors: F. Teschl, W. L. Randeu, M. Schönhuber, R. Teschl
• Format: Article
• Language: English
• Published: Copernicus Publications 2008-04-01
• Series: Advances in Geosciences
• Online Access: http://www.adv-geosci.net/16/27/2008/adgeo-16-27-2008.pdf

Polarimetric radar variables of rainfall events, like differential reflectivity <i>Z</i><sub>DR</sub>, or specific differential phase <i>K</i><sub>DP</sub>, are better suited for estimating rain rate <i>R</i> than just the reflectivity factor for horizontally polarized waves, <i>Z</i><sub>H</sub>. A variety of physical and empirical approaches exist to estimate the rain rate from polarimetric radar observables. The relationships vary over a wide range with the location and the weather conditions. In this study, the polarimetric radar variables were simulated for S-, C- and X-band wavelengths in order to establish radar rainfall estimators for the alpine region of the form <i>R</i>(<i>K</i><sub>DP</sub>), <i>R</i>(<i>Z</i><sub>H</sub>, <i>Z</i><sub>DR</sub>), and <i>R</i>(<i>K</i><sub>DP</sub>), <i>Z</i><sub>DR</sub>. For the simulation drop size distributions of hundreds of 1-minute-rain episodes were obtained from 2D-Video-Distrometer measurements in the mountains of Styria, Austria. The sensitivity of the polarimetric variables to temperature is investigated, as well as the influence of different rain drop shape models – including recently published ones – on radar rainfall estimators. Finally it is shown how the polarimetric radar variables change with the elevation angle of the radar antenna.