株洲市2011年6月15日暴雨过程分析

从自组织辐合水汽流的成因出发,对株洲市2011年6月15日暴雨产生的过程进行精确到点的分析,发现其前期的一些具有物理意义的特征,这些特征为该地暴雨的精细化预报提供了有业务价值的思路和方法。在暴雨发生前12～36 h,对流层中下部存在南北力子偶,且株洲站附近存在准饱和区;对流层底层水汽通量散度对暴雨预报具有高度敏感性,其分界线位于850 hPa附近,850 hPa以下的水汽通量散度具有较强的暴雨可预见度,而850 hPa以上的水汽通量散度则不具备这种功能;暴雨中最强降水发生前24～6 h,位于850hPa以下的对流层底层水汽通量散度在株洲站及其上游附近存在明显增强的(-6～-20单位)水汽通量辐合中心区;如果上述水汽通量辐合中心区突然消失,则意味着最强降水即将发生,也意味着自组织辐合水汽流已经发展到成熟期,其即将向上发射。涡度、散度、垂直速度、假相当位温等要素场都有上述类似特征,但敏感度不及水汽通量散度;TBB与强降水呈负相关,且滞后约2 h,虽然TBB对这次暴雨过程不具有预报特征,但它表明了此次暴雨过程具有原发性特征,这对暴雨的本质研究有益;仰角越小的速度回波对暴雨越敏感,0.5°仰角的速度回波对暴雨还具有2 h左右的提前反映,这对暴雨短临预报具有指示意义。

Analyses of a Rainstorm Process in Zhuzhou on June 15, 2011

From the causes of the self-organization water vapor convergence,a rainstorm process in Zhuzhou on June 15,2011 was analyzed to find out its precursory physical features,which provided valuable thoughts and methods for the specialized forecast of local rainstorms.12-36 h before the rainstorm,there was a lizi between north and south in the middle and lower troposphere,and a quasi-saturation region existed around Zhuzhou station;The vapor flux divergence in lower troposphere was highly sensitive to rainstorms forecast,its dividing line was located near the 850 hPa,below which the vapor flux divergence had high rainstorm predictability while above which the vapor flux divergence had not;24-6 h before the occurrence of the largest rainfall,the troposphere vapor flux divergence below 850 hPa had obviously enhancing(-6——20 units) vapor flux convergence center in Zhuzhou station and its upstream area;once the convergence center disappeared,the largest rainfall was coming,indicating that the self-organization vapor convergence had become mature and began to launch.Vorticity,divergence,vertical speed and pseudo-equivalent temperature all showed the above features,but their sensitivity was lower than that of vapor flux divergence;TBB was negatively correlated with strong precipitation,but delayed about 2 h,although TBB cannot forecast this rainstorm process,it reflected the primary features of this rainstorm process,which would benefit the research on this rainstorm;the smaller the elevation of speed echo,the more sensitive it was to rainstorm,0.5° elevation of speed echo could report the rainstorm 2 hours in advance,which had great significance to the short forecast of the heavy rain.