金阳县“7.31”泥石流灾害气象成因分析

Analysis on the Meteorological Causes of the July 31 Extreme Debris Flow Hazards in Jinyang County

以凉山州境内金阳县小银木乡松树村与布拖县四棵乡沟姑村交界处的地洛电站厂房标段钢筋场2009年7月31日发生的泥石流灾害为例,利用NCEP再分析资料、MICAPS数据资料和卫星云图等资料,从环流形势、物理量场、云系演变特征等方面研究了这次泥石流灾害形成的气象成因。结果表明,金阳县"7.31"泥石流灾害的发生与当地孕灾环境关系密切。由于阻塞高压的影响高空切变较长时间维持凉山州境内,同时配合地面冷高压不断分裂南下的冷空气和700 hPa西南暖湿气流输送的丰沛水汽,造成了这次大范围的暴雨天气过程;灾害点具备上干下湿、低层辐合高层辐散、降水中心与正涡度负散度中心的位置对应良好的特点。同时结合垂直速度剖面图和降水落区来看,负的垂直速度大值区也就是强烈上升运动中心对应着地面的强降水区,暴雨区附近的垂直环流与暴雨的启动和维持有密切关系,暴雨区往往出现在垂直环流的上升运动区。

With the debris flow occurred in Jinyang County, Liangshan Prefecture, Sichuan Pnvincc, July 31,2009 as example, using NCEI） reanalysis data, MICAPS data and satellite cloud pictures, frmn circulation situation, physi＇al quantity field, cloud ＇wJlution charact＇ristics, the meteorological causes of the debris flow were studied. The results showed that the occurance of ＂7.31 ＂ debris Iluw is closely related with tht. local environment. Due to the effect of blocking high pressure, high - altitude wind shear maintain in l.iangshan Prefecture. for a hmg p＇ri- od. Combined with southward cold air from continuous division of grouml cold high pressure and abundant water vapor conv,ying from 7（X） hPa southwest warm wet air flow, the rainstorm occurred. Disaster area has characteristics of upper dry lower wet, low hwcl convergence and a,cper level divergence, precipitation center and the positive vorticity negative divergence center positicm corresponds well. Combined with the verti- cal wlocity profile and precipitation area, vertical cireulation arnund rainstorm area is closely related with the occarance and mainraining of flu, heavy rainstorm, rainstorm area is always in ascending motion area of vertical circulation.