Comparison of Two Verification Methods for 6 h Precipitation Forecasts of Regional Models

6 h precipitation forecast for different lead times of operational models for North China Regional Center, South China Regional Center, East China Regional Center and Numerical Weather Prediction Center of CMA (NWPC) are verified and compared from May to September in 2011. The two methods which are used to average verification results for some period are discussed in detail.The verification results show the forecasting performance is different according to the observational time, the forecasting lead time and coverage area of models. Compared with NWPC GRAPES_Meso model in the same area, the performance for most lead times of operational models of three regional centers is better, particularly for over 24 h lead time forecast. Furthermore, verification score of East China Regional Center model is the best, TS of this model is higher than that of NWPC model except that 0.1 mm or more precipitation of 18 h forecast with 0600 UTC observation and 24 h forecast with 1200 UTC observation, and the bias is close to 1 for most verification grades. Moreover, TS of intense precipitation of three Regional Centers models is higher than that of NWPC model most of the time, but TS of North China regional center model is lower for 6 h and 18 h forecast with 0600 UTC observation and for 6 h forecast with 1800 UTC observation. On the other hand, the verification results derived from the different averaging approaches have few impacts on TS comparison results for regional model and NWPC model, but the TS value by new method is higher than that of the former method, except when the difference of TS between the two models is very small. For the new method, the model performs better for the large-scale rainfall process perhaps getting higher TS than the model that is only good at meso-scale rainfall. But the difference for heavy rain with little probability, especially for precipitation heavier than 13 mm is significant. If there is more false alarms for the forecast of greater grades small meso-scale precipitation, and there is some missing for the large scale rainfall, the differences between the two methods will be larger. Under this condition, the bias of the new method shows that forecast rainfall is less obviously comparing with observation, but that of the former method indicates more. Such situation usually occurs in North China. Because the two averaging approaches show distinct differences, more studies are needed so that users can understand the differences better and make a correct decision on how to use the forecasts of models properly.