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

摘要

Polarimetric radar variables of rainfall events, like differentialreflectivity Z_DR, or specific differential phase K_DP, are bettersuited for estimating rain rate R than just the reflectivity factor forhorizontally polarized waves, Z_H. A variety of physical and empiricalapproaches exist to estimate the rain rate from polarimetric radarobservables. The relationships vary over a wide range with the location andthe 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 forthe alpine region of the form R(K_DP), R(Z_H, Z_DR), andR(K_DP), Z_DR. For the simulation drop size distributions of hundredsof 1-minute-rain episodes were obtained from 2D-Video-Distrometermeasurements in the mountains of Styria, Austria. The sensitivity of thepolarimetric variables to temperature is investigated, as well as theinfluence of different rain drop shape models – including recentlypublished ones – on radar rainfall estimators. Finally it is shown how thepolarimetric radar variables change with the elevation angle of theradar antenna.