2010年8月8日舟曲特大泥石流暴雨天气过程成因分析

A Study of Rainstorm Process Triggering Zhouqu Extremely Mudslide on 8 August 2010

利用地面加密雨量站、常规探空资料、卫星云图黑体辐射亮温(TBB)资料以及每6 h一次的1°×1°NCEP再分析资料,使用天气学诊断方法,初步剖析了2010年8月7—8日引发舟曲特大泥石流暴雨天气过程的降水特征、天气背景、对流暴雨中尺度系统演变特征及其成因。结果表明:引发舟曲特大泥石流暴雨的是一具有长生命史的移动性中尺度对流系统;暴雨前期的水汽积累与热带低压"电母"外围的偏东偏南气流将西太平洋的水汽远距离地输送到舟曲及其以北地区密切相关;热带低压外围向西北方向传播的东风波扰动和大陆高压北侧东移南压的西风带短波槽共同作用导致前期控制我国长江以北大部地区的副热带高压带断裂,为舟曲暴雨发生提供了必要的动力条件;高原地形对北方冷空气阻挡绕流迫使其与西进北上的暖湿气流交汇在甘南地区形成辐合、东风气流下高原东坡动力强迫抬升以及高原东坡热力作用在舟曲强降水形成过程中也可能起到重要作用。

With intensive surface rain gauge data,conventional sounding data,satellite-sensed temperature of black body（TBB） and 6-hourly 1°×1° NCEP reanalysis data,synoptic diagnosis method was used to investigate the rainfall characteristics,weather background,mesoscale systems of convective rainstorms and its formation causes.The results indicated that the rainstorm was triggered by a long-lived moving mesocale convective system.The moisture accumulation was closely related to the long-range moisture transported from the west Pacific Ocean to Zhouqu and its north area by south flow sometimes and east flow sometimes in the outside of tropical depression ＂Dianmu＂.The combined action of a north-west moving easterly wave perturbation on the north side of tropical depression and a south-east moving westerly short wave on the north side of the subtropical high led to the breaking of the subtropical high,which controlled the most part of north China in early days,and provided necessary dynamic condition for the rainstorm formation.The convergence in the south of Gansu province formed by the bypassing flow of north cold air due to the Plateau blocking and the north-moving warm and moist air,the dynamic lifting and thermodynamic effect of the Plateau east slope under easterly flow may also play an important role in the formation of Zhouqu heavy rainfall.