低纬南北风指数在广西暴雨预报中的应用

Application of Low Latitude South and North Wind Indices to Prediction of Rainstorm in Guangxi

利用EC风场资料设置低纬南北风指数,探讨和建立广西暴雨预报指标。采用离散格点坐标方法,对1970 2009年1115次锋面过程分析,整理出全区性暴雨事件发生时对应的南风指数和北风指数、全区性暴雨事件不发生时对应的南风指数和北风指数,由此计算得到全区性暴雨事件发生的概率(等值线)随南风指数和北风指数的分布,再通过经验订正,归纳出广西全区性暴雨开始时间、暴雨落区、暴雨强度预报指标。经过对1970一2009年440次锋面暴雨过程检验,符合暴雨开始时间指标的过程比例为74.5%,符合暴雨落区指标的过程比例为75.9%,符合暴雨强度指标的过程比例为67%,均处于合理的范围,可以应用到暴雨预报业务中。

An experiential index for prediction of regional rainstorm in Guangxi has been found, by analy- zing EC wind data and defining the south and north wind indices of low latitudes. The wind indices in the cases that regional rainstorms occur or not are collected based on 1115 front cases dur!ng 1970--2009. The distribution of probability of regional rainstorm versus the wind indices is ealculated, while the wind indi- ces are combined with experiential corrections. As a result of examining 440 front-rainstorm cases from 1970 to 2009, the proportion of the experiential index corresponding to the time of rainstorm happening is 74.5%, the corresponding to the position of rainstorm is 75.9%, and the corresponding to the intensity of rainstorm is 67 %. These facts manifest that the experiential index is reasonable and available in actual pre- dictions.