一次雷暴大风引发的强沙尘暴天气的中尺度系统分析

Analysis on Mesoscale System of a Strong Dust-storm Triggered by Thunderstorm

使用探空、地面和张掖多普勒天气雷达观测资料对2013年7月30日发生在河西走廊的一次强沙尘暴天气进行了分析。结果表明:这次雷暴大风沙尘天气是对流层低层冷平流作用下,不稳定能量释放形成的β、γ中尺度对流系统造成的,雷暴下击暴流的辐散流和密度流是引发地面强风和沙尘暴的直接因素。高层干、中层相对湿和低层干的层结,易产生雷暴大风天气。1 h正变压和负变温演变能很好地反映雷暴下击暴流形成的雷暴高压和冷池的强弱变化,同时也反映了下击暴流的辐散气流和冷池密度流造成的地面大风及沙尘天气的变化。

Based on the sounding data,observation data from automatics weather station and the radar data in Zhangye of Gansu Province,the forming mechanism of a strong sandstorm occurred in Hexi Corridor on 30 July 2013 was analyzed. The results showed that the thunderstorm and dust storm weather was caused by the mesoscale β or γ convective system which triggered by instable energy from cold advection in the lower troposphere,and the divergence flow and density flow of downburst were the direct factors producing strong wind and dust storm. The stratification with dry upper level,wet middle troposphere and dry boundary layer was easy to produce thunderstorm weather. The 1 hour positive variable pressure and negative variable temperature could well reflect the intensity of thunderstorm high pressure and cold pool. And also the variation of strong wind and dust storm caused by the divergence flow of downburst and density flow of cold pool.