Performance verification of Desert Oasis Gobi Regional Assimilation andForecast System for precipitation forecast

Based on the 6 h rainfall forecasts of Desert Oasis Gobi Regional Assimilation and Forecast System （DOGRAFS）and observationsat four initialized times daily during 1 November 2012 to 31 October 2013，the capabilities to precipitation forecast is evaluated preliminarilyin terms of Threat Score，Equitable Threat Score and Bias Score. The results indicate that the performance of DOGRAFS changes closelycorresponding to the seasonal variation as a whole，which tends to be better in summer and autumn than in winter and spring. With the samethreshold，the difference in performance among the results of different initialized times is small，although the result at 12 UTC is slightly betterthan the others. The forecast skill decreases with the threshold increasing，among which the 0.1 mm·(6 h)-1 threshold behaves the most stableand the 3.1 mm·(6 h)-1 and 6.1 mm·(6 h)-1 are at the second place. For larger rainfall thresholds such as 12.1 mm·(6 h)-1 and 24.1 mm·(6 h)-1，the performance is relatively poor. In addition，the strong precipitation event occurred in the southwest of Xinjiang during 26th —29th May2013 is analyzed as an example. In this case，the forecast at different initialized times has an uneven performance for the rainfall area andgrade by comparing the observed and forecast precipitation; among which the forecast at 12 UTC 26th behaves the best. Furthermore，the assimilateddata have improved wind，temperature and humidity fields remarkably and have a positive effect on the forecast results by means ofanalysis increments.