Large-sample evaluation of two methods to correct range-dependent error for WSR-88D rainfall estimates

The vertical variability of reflectivity is an important source of error th at affects estimations of rainfall quantity by radar. This error can be red uced if the vertical profile of reflectivity (VPR) is known. Different meth ods are available to determine VPR based on volume-scan radar data. Two suc h methods were tested. The first, used in the Swiss Meteorological Service, estimates a mean VPR directly from volumetric radar data collected close t o the radar. The second method takes into account the spatial variability o f reflectivity and relies on solving an inverse problem in determination of the local profile. To test these methods, two years of archived level-II r adar data from the Weather Surveillance Radar-1988 Doppler (WSR-88D) locate d in Tulsa, Oklahoma, and the corresponding rain gauge observations from th e Oklahoma Mesonet were used. The results, obtained by comparing rain estim ates from radar data corrected for the VPR influence with rain gauge observ ations, show the benefits of the methods-and also their limitations. The pe rformance of the two methods is similar, but the inverse method consistentl y provides better results. However, for use in operational environments, it would require substantially more computational resources than the first me thod.