MOS方法在短时要素预报中的应用与检验

Application and verification of MOS statistical method for forecasting of short time meteorological elements

通过对MM5数值预报产品的释用,将MOS统计方法应用到短时要素预报中,综合利用MM5数值预报产品、自动站实况数据和雷达数据等资料,建立降水和温度的4 h预报模型;降水作为不连续变量,将其通过建立降水可能函数的方法转化为连续变量,利用统计预报方法,可以达到定量预报的目的。对4140个时次的样本进行检验。结果表明:MOS预报结果较MM5直接输出结果整体有所改进,当数值模式误差较大时,统计方法显示出一定的优势;降水预报检验结果显示,TS评分为65%,预报正确率为91%。降水明显的样本(3 h雨量大于5 mm)平均误差在8 mm以内,弱降水样本(3 h雨量大于3 mm)平均误差在1 mm以内,预报方程对非雨日样本的整体预报效果较好,优于MM5模式预报,预报正确率高达98%,但对流性降水仍是预报难点;对于温度预报,20—08时段误差较小、平均误差在1.0℃以内,而11—17时平均误差为1.5℃,但经过误差的季节订正,可以控制在1.0℃。

Through the interpretation of MM5 numerical prediction products, the MOS statistical method was ap- plied to forecast short time meteorological elements. A forecast model of precipitation and temperature with 4 hours interval was established in terms of MM5 numerical prediction products, the observational data from automatic weather stations and the radar data. Precipitation was a discontinuous variable, but it could be translated into a con- tinuous variable by establishing a possibility function of precipitation. Thus, quantitative forecasting could be real- ized. 4140 samples were tested in this paper. The results show that the MOS method is better than the MM5 meth- od, especially for the cases when errors with the MM5 method are higher. According to the test of precipitation pre- diction, TS score is 65% and the accuracy reaches 91%. The average error is less than 8mm for heavy rain samples （three hours accumulated rainfall 〉 5 mm）, while it is 1 mm or less for weak precipitation samples （three hours accumulated rainfall 〈 1 mm）. The MOS method has the higher accuracy with 98% for the prediction the non-rain day, and it is better than the MM5 prediction. However, the convective precipitation is still hard to forecast. For the temperature model,the error is less than 1.0 ℃ from 20.00 to 08.00,while it is 1.5 ℃ from 11.00 to 17：00. The error can be controlled about 1.0 ℃after season corrections.