用L指数作广东暴雨短期落区预报

本文分析了产生暴雨的大气热力条件和暴雨与特定低空急流的关系。发现某些物理量在暴雨开始前18—30小时有突变现象。这种现象在其它的段不明显。把上述物理量组合成暴雨落区预报指数。在确定有暴雨产生的情况下,该指数参考低空急流的特定位置,能预报未来24小时前后暴雨产生的范围,7年来预报准确率在80％以上。这个方法对大雨落区预报也有参考价值。

SHORT RANGE FORECASTING OF TERRENTIAL RAIN LOCATION IN GUANGDONG WITH L INDEX

The thermodynamic conditions of atmosphere resulting in tcrrential rain in Guangdong as well as the relationship between terrential rain and specific low-level jet stream are analysed in this paper. It is found that some physical quantities fluctuate sharply 18 to 30 hours before the onset of terrential rain. The phenomena is not obvious in other time. The above mentioned quantities are combined into L index to predict the location of intense rain. When terrential rain is predicted to occur, the index can foretell the rainfall domain in the coming 24 hours or so, with reference to the position of low-level jet. The average forecast accuracy has been above 80 percent for the past seven years. This method can also be applied to the forecasting of heavy rain location to some degree.