陇东南暴雨动态统计PP预报模型

利用1960~2001年NCEP再分析格点资料、陇东南4市31站的降水实况资料、及4个代表站的15~40 cm的地温资料,用11种物理量设计了86个初选因子,将预报区域分东、南、西3片,将天气环流分4型,采用判别分析方法求得陇东南暴雨初级判别函数3个、二级判别函数12个,构成暴雨的动力统计PP预报模型。回检情况,初级预报判别在正例概括90%~93%暴雨日的情况下,排空率可达63%~68%;二级动态判别东片、南片性能较好,预报技巧基本在60%以上,其中东片辐合气流型可达80%以上,西片整体要差一些,但相对于暴雨的实际预报水平,12个函数均具有一定的参考性。用2004~2005年7月实际资料检验,模型预报技巧可达39.3%;试验运行,模型解释应用T213数值预报12 h、36 h的资料,对2005年6月30日至7月2日陇东南出现的暴雨有较好的反映,两方面都说明了模型的实用价值。

The Dynamic Statistical PP Forecast Model of Rainstorms in Southeast Gansu

Based on the re-analyzed grid data of NCEP,the observed precipitation of 31 stations in southeast Gansu,and the 15~40 cm ground temperature data of 4 representative stations from 1960 to 2001,86 primarily selected factors were designed with 11 kinds of physical quantities,the forecasted area was divided into 3 districts of east,south and west,weather circulation was classified as 4 patterns,3 primary and 12 two-stage discriminant functions of rainstorms in southeast Gansu were obtained through discriminant analysis approach,and the dynamic statistical PP forecast model is composed of these functions.The results of examining in return indicate that in the situation of 90%~93% rainstorm days included by positive examples,excluding rate of forecast mistake reaches 63%~68%;The two-stage dynamic discriminant in east and south districts is good,the forecast skill is basically above 60%,of which for the composite flow patterns in east district it can reach above 80%,and it is not good in west district on the whole,but relatively to actual forecast level of rainstorms,12 functions have certain reference value.The examination conducted by using observed data from 2004 to 2005 July shows that the model forecast skill can reach 39.3%;Through experimental running,applying 12 and 36 hours forecasting data of T213,the model explanation has good reflection to the rainstorm occurred in southeast Gansu from June 30 to July 2,2005,two aspects both show that the model has practical value.