一次强雷雨过程中对流参数对潜势预测影响的分析

The Analyses of Convective Parameters and Their Potential Predictability in a Severe Thunderstorm Rain

在利用观测资料和1°×1°NCEP再分析资料对2003年7月4～5日的一次强雷雨过程的天气形势、暴雨特征分析基础上,从雷暴和强暴雨的发生条件入手,探讨了一些强对流参数的物理意义、计算方法及其在此次强雷雨发生潜势预测中的指示意义。结果表明:始终稳定维持在乌拉尔山、鄂霍茨克附近的高压脊为此次强雷雨提供了有利的环流背景;来自孟加拉湾、印度洋一带和南海地区的暖湿气流与南下的冷空气在淮河流域交汇,并形成一条东西向稳定的梅雨锋;梅雨锋及其上发生发展的中尺度扰动是此次强降雨的主要制造者;对流有效位能[ConvectiveAvialablePotentialEnergy(CAPE)]、对流抑制指数[ConvectiveInhibition(CIN)]、K指数、沙瓦特指数[ShowalterIndex(SI)]、垂直切变和稳定度的组合———粗里查森数[BulkRichardsonNumber(BRN)]等对流参数的分布、演变可以较好地揭示出此次强雷雨的发生、发展。选取合理、适当的对流参数对于短时局地强雷雨天气的潜势预测、强度判别是有指示意义的。

The observational data and NCEP data are used to analyze the heavy rain on 45 July 2003. It is found that 1) the large scale systems are very favorable for the occurrence of heavy rain in the Huaihe River. From 29 June 2003 the subtropical high maintained in South China, the warm, moisture air and cold, dry air coming from the trough met in the Huaihe River areas, which was favorable for the maintenance of Meiyu front and the occurrence of the heavy rain. 2) The southwesterly to the south of convergence line transports a great deal of moisture to the convective region. 3) Accompanying with the ascending motion, the strong convergence, positive vorticity in the middle and lower troposphere and the strong divergence, negative vorticity in the upper troposphere contribute greatly to the occurrence and maintenance of the heavy rain. 4) The distribution and variation of the convective parameter, such as Convective Avialable Potential Energy (CAPE), Convective Inhibition (CIN), Lifting Index (LI), K index, indicate successfully the local physical characteristic, which are favorable for the occurrence of heavy rain. The CAPE assembles obviously 23 h earlier than beginning of rain and decreases quickly after its occurrence.