Climatological Analysis of Model Precipitation Forecast for China

Based on the precipitation forecast for the National Centers for Environmental Prediction (NCEP) Global Ensemble Forecast System (GEFS) reforecast for the period 1985-2010 and daily precipitation observations in China, climatological analysis of GEFS precipitation forecast is studied over China. An unbiased and robust linear moment method is used to compute the probabilistic quantitative precipitation forecast (PQPF) and assess the ability to identify the uncertainties of GEFS precipitation forecast over China.

Monthly and Seasonal mean precipitations from GEFS reforecast (first 24 hours) are fairly closed to Climate Prediction Center (CPC) longer climatological mean in terms of quantity and spatial distribution. An example of summer season, an intense rainfall center is mainly located in the southeast coast of China, GEFS reforecast indicates the same area with over 500mm which is largely agreed from climatological mean of ground observations. In this study, climatological mean of precipitation is analyzed and compared with selected ground observation. The Gamma distribution and L-moment method are used to fit precipitation forecast to each grid point for sampling the amount of daily precipitation.

The systematic characteristics (or bias) of model forecasts are investigated by selected eight observation stations over the northern, western, the Yangtze River valley and southeast coast area of China. The correlations of climatological daily forecast and observation have been calculated for these eight represented observation stations. Various results will be presented to demonstrate the values of GEFS and explore the future applications in terms of real time PQPF forecast and extreme weather forecast.