多模式短期集合降水概率预报试验

Experiments of Multi-model Short-range Ensemble Precipitation Probability Forecasts

利用AREM、MM5和WRF3个中尺度数值模式,通过积云参数化和边界层方案组合构成15个集合成员,对中国2003年7月汛期降水分别采用平均法、相关法、Rank法开展多模式短期集合降水概率预报试验。结果表明:用上述3种方法制作的多模式短期集合概率预报都能对降水落区及中心做出较准确的预报,但平均法和相关法易使降水落区虚假放大,Rank法则能较好地刻画降水落区边界及强度,其概率预报效果优于平均法和相关法结果。采用BS(Brier score)、RPS(ranked probability score)评分和ROC(relative operating characteristic)曲线对3种方法的降水概率预报效果评价时发现,对某一临界值等级的概率预报,3种方法结果差异较小;但对某一天降水概率预报结果的综合评价表明,Rank法显著优于前两种方法;降水强度大、范围广的降水的RPS评分和各级的BS评分较高,表明多模式降水概率预报也具艰巨性。

Experiments of 15 ensemble members are performed by using AREM,MM5 and WRF models with different model physical process parameterization schemes and identical initial values for rainy season in July 2003,and multi-model short-range ensemble precipitation probability forecasts are made by means of ＂Average＂,＂Correlation＂ and ＂Rank＂.Results indicate that the ensemble precipitation probability forecasts made by the three methods above-mentioned all can give accurate estimation of center and region of the precipitation,and the ＂Rank＂ is superior to the ＂Average＂ and ＂Correlation＂ for performing better in forecasting the areas,intensity and boundary of precipitation but the other two expand improper areas.Evaluation results of ranked probability score（RPS）,Brier score（BS） and relative operating characteristic（ROC） show there is little difference in a certain critical grade precipitation of the ＂Rank＂ results and that of the other two,but for synthetic effect of someday in the rainy season the ＂Rank＂ surpasses the ＂Average＂ method and ＂Correlation＂ method obviously.The higher score of RPS and every grade BS for the heavier and wider precipitation case means that multi-model short-range ensemble precipitation probability forecasts are a challenge.