【摘要】 暴雨落区预报目前已成为我国普遍应用的预报方法,但还存在如何抓住主要因子以便更好提高预报准确率的问题.本文用北京45次特大暴雨实例的六次探空资料及部分诊断分析资料,对比分析暴雨出现前某些因子变化情况,探讨了暴雨发生条件以及哪些因子和过程更为重要的问题,目的是供预报员做改进落区预报的参考.主要结果为: （1）暴雨的产生不但须850毫巴水汽含量高,高层也须水汽充沛.最大可降水量和各层温度露点差之和（sum from i=1 to 7（T-T_d）_i）是适应这一特点的暴雨预报的二个水汽因子,它们能同时反映高、低层水汽含量状况,并能较好地反映水汽增长特点——当水汽由缓增变为快增时,它们有明显量变,而单用一层参数,则反映不明显. （2）所以能产生暴雨的位势不稳定层结,主要不在于Δpθ₅ 大,而在于该处要有足够强的自下而上增温增湿过程和冷空气迫近过程.此特征在700毫巴图上表现为有尺度不大的T-T_d≤3℃、T≥8℃高温高湿区以及温度或θ_5β的密集带. （3）产生暴雨的基本动力因子为正涡度和深厚的强上升运动,预报时要结合天气系统的移动来估计这种有利的动力区域位置.文中提出四种天气图特征,它们可预示上升运动的加强. （4）在上述热力和动力因子齐备的条件下发生暴雨,其中的关键为动力因子,但高温高湿过程是先兆更多还原

【Abstract】 The forecasting technique for the region of occurrence of heavy rains has been widely used in our country. However, it still is very important to capture the essential factors in order to improve the forecasting accuracy.In this paper, based on the 6 sounding data and diagnostic results obtained from 4-5 eases of Beijing rainfalls with great intensity, the variations of some factors prior to rainfalls and the conditions of the rainfall occurrence, as well as rainfall itself are analysed in order to understand which factor or process may be more important and to provide some useful references in improving forecasting.更多还原