Correction of Radar Reflectivity over Beam Blocking Area and Elimination of Ground Clutter Using Accumulated Radar Reflectivity Map

The contamination of rain echoes by ground clutter and loss of energy by beam blockage may lead to significant errors for the rainfall estimation. Ground clutter results in the overestimated radar rainfall, while the radar reflectivity in beam blocking area causes the underestimation of rainfall. Ground clutter and beam blockage are caused by interactions between radar beam and topography around radar sites. Concerning the Quality Control (QC) of the radar reflectivity data, these two issues have been studied individually in the previous studies. There are not many studies on correction of underestimated reflectivity caused by beam blocking. The purpose of the present study is to develop QC technique in order to suppress ground echoes and to correct reflectivity over beam blocking areas for the improvement of radar rainfall estimation. The present QC technique is based on the climatological characteristics of ground echoes and beam blocking areas, which are analyzed on accumulated reflectivity map, Probability of Detection (POD) map, and frequency curves. The reflectivity data is acquired from volume scan data of C-band Doppler weather radar. An accumulated reflectivity map and a POD map including frequency curves are obtained by accumulation of the radar reflectivity. The number of used data for the construction of the maps is about 50,000 volume scan. The QC technique employed in the present study is evaluated by comparing the rainfall derived from 1.5km CAPPI reflectivity with the rainfall from eighteens rain gauges for the case of widespread precipitation from stratiform clouds. The result of the present study indicates that the present QC technique is very useful to eliminate the ground clutter and to correct the reflectivity over beam blocking area.