Adjustment of radar rainfall using rain gauge measurement

Abstract

This paper aims to apply characteristic of range dependent error in initial radar rainfall estimates to adjust radar rainfall to be equivalent to ground rainfall. Two different bias adjustment methods were tested which included 1) uniform bias adjustment method and 2) range dependent bias adjustment method. Forty-four rainfall events recorded from the Pimai radar and 50 automatic rain gauges data during 2003-2005 were used in this study. The result of this study showed that using range dependent bias adjustment factors which divided into 2 ranges (less than 70 km and greater or equal to 70 km) for each rainfall event gave the smallest RMSE between radar and rain gauge rainfall. This method can reduce RMSE between radar and rain gauge rainfall about 13% (4.7%) and 2.6% (3.8%) for the calibrated and verified rainfall events when compared to using the climatological bias adjustment factor and the varying bias adjustment factor for each rainfall event without consideration of range dependent error.