引发甘肃白银市严重山洪地质灾害的暴雨过程分析

Analysis of Rainstorm Which Caused Severe Mountain Torrent Geology Disaster in Baiyin of Gansu Province

摘要: 利用常规气象观测资料、自动站逐小时雨量、物理量、NCEP再分析资料和卫星云图等资料，对2011年5月28日发生在甘肃白银市的局地暴雨引发山洪天气过程进行诊断分析。结果表明：1)这次暴雨天气过程发生在西伯利亚冷涡东移的大尺度环流背景下，冷涡底部不断有分裂的冷槽携带干冷空气和西太平洋副热带高压西北侧的西南暖湿气流交汇，大气不稳定度增大，触发对流产生。2)700hpa低涡、切变线和850 hpa鞍形场环流配置，有利于耦合导致上升运动加强，触发不稳定能量的释放，成为暴雨天气的中尺度影响系统。3)散度场、涡度场、垂直速度场等物理量场的高低空配置和时空变化与暴雨过程的时空变化高度吻合。4)地面辐合线或干线是触发强对流天气的因子之一，对流单体一般生成于地面辐合线附近，在地面辐合线与干线结合处易于对流单体或云团的新生和发展。5)引发山洪的暴雨强度大，持续时间短，在卫星云图上表现为一个水平尺度200~400 km，云顶亮温最低为−80℃的中β尺度对流云团。6)山洪发生在地质条件脆弱区，不同的地质状况对应不同的灾害。

Abstract: Based on the data of routine meteorological observation, hourly precipitation of automatic weather station and NCEP reanalysis data, the local rainstorm in Baiyin of Gansu province on 28 May 2011 was analyzed. The results show that this rainstorm occurred on large scale circulation background of the Siberia cold vortex moved eastward; the dry cold air which constantly split from the bottom of the cold vortex converged with southwest airflow of warm; the atmospheric instability increased that triggered convective weather. The meso-scale influential systems of this rainstorm were vortex and shear line of 700 hPa and saddle type of 850 hPa. This circulation pattern was beneficial to strengthen ascending movement and trigger off instability energy releasing. The allocation at different heights and temporal and spatial variation of physical field was consistent with the rainstorm. Surface convergence line was one of triggering factors contributed to convection. The convection cells were easily formed near the joint of surface convergence line and dry line. The characteristics of rainstorm which caused mountain torrent geology disaster were high intensity and short duration. There was a meso-β-scale convective cloud cluster in satellite cloud image. Its horizontal scale was 200 - 400 km and the minimum of TBB was −80˚C. The mountain torrent occurred in the geological conditions of vulnerable areas, different geological conditions can form different disasters.