Evaluation of the gap filler radar as an implementation of the 1.5 km CAPPI data in Korea

Abstract

This study evaluated the gap filler radar as an implementation of the 1.5 km CAPPI (constant altitude plan position indicator) data in Korea. The use of the 1.5 km CAPPI data was an inevitable choice, given the topography of the Korean Peninsula and the location of the radar. However, there still exists a significant portion of beam blockage, and thus there has been debate about the need to introduce the gap filler radar (or, the gap-filler). This study evaluated the possible benefits of introducing gap-fillers over the Korean Peninsula. As a first step, the radar data error was quantified by G/R ratio and root mean square error (RMSE), and the radar data over the Korean Peninsula were evaluated. The gap-fillers were then located where the error was high, and their effect was then evaluated by the decrease in the G/R ratio and RMSE. The mean values of the G/R ratio and RMSE of the 1.5 km CAPPI data over the Korean Peninsula were estimated to be about 2.5 and 4.5 mm h–1, respectively. Even after the mean-field bias correction, the RMSE of the 1.5 km CAPPI data was not decreased and mostly remained very high, around 4.4 mm h–1. Unfortunately, the effect of the gap-filler on the 1.5 km CAPPI data was also found to be very small, just 1–2%. However, the gap-filler could be beneficial, if the lowest elevation angle data were used instead of the 1.5 km CAPPI data. The effect of five gap-fillers could be up to 7% decrease in RMSE.