APPLICATION EXPERIMENT OF ASSIMILATING RADAR-RETRIEVEDWATER VAPOR IN SHORT-RANGE FORECAST OF RAINFALL IN THE ANNUALLY FIRST RAINY SEASON OVER SOUTH CHINA

A scheme of assimilating radar-retrieved water vapor is adopted to improve the quality of NWP initial fieldfor improvement of the accuracy of short-range precipitation prediction. To reveal the impact of the assimilation ofradar-retrieved water vapor on short-term precipitation forecast, three parallel experiments, cold start, hot start and hotstart plus the assimilation of radar-retrieved water vapor, are designed to simulate the 31 days of May, 2013 with a finenumerical model for South China. Furthermore, a case of heavy rain that occurred from 8-9 May 2013 over the regionfrom the southwest of Guangdong province to Pearl River Delta is analyzed in detail. Results show that the cold startexperiment is not conducive to precipitation 12 hours ahead; the hot start experiment is able to reproduce well the first6 hours of precipitation, but badly for subsequent prediction; the experiment of assimilating radar-retrieved water vaporis not only able to simulate well the precipitation 6 hours ahead, but also able to correctly predict the evolution of rainbands from 6 to 12 hours in advance.