【摘要】 利用常规观测、卫星云图、雷达探测以及自动站雨量等资料,对2010年6月27—28日和2012年5月20—22日桂西北两次严重山洪地质灾害的气象条件进行了对比分析,结果表明:（1）强降雨发生在桂西北暴雨区,最大过程雨量>350 mm,过程最大中尺度雨团和致灾区最大中尺度雨团值分别>100 mm·h^-1和>70 mm·h^-1,集中降雨时段为02—06时。灾害开始于后半夜,发生在最大过程雨量和地质条件脆弱区,不同的地质状况对应不同的灾害;灾害性天气具有区域小、降雨时段集中、过程雨量大、强度强及引发灾害重等特征。（2）暴雨发乍在欧亚地区500 hPa呈两脊一槽型、200 hPa南亚高压脊线贯穿广西上空及季风云系活跃的背景下。高空为槽或低涡、地面为干线或锋面,属低涡暴雨型。（3）高空要素变化为雨前降压升温、后降温。不稳定能量及层结、低层辐合、中低层涡旋、整层大气的上升运动、高温高湿及水汽强烈辐合是物理量特征。（4）云图上对流云团生成、合并对强降雨有指示意义.聚雨发生在云团合并发展阶段;TBB值<200 K可以作为强降雨的指标。低质心强雷达回波产生的列乍效应或回波停滞和地形作用是造成强降雨的重要因素.低层辐合、高层辐散导致了强烈的上升运动。有利于强对流的发展与维持。更多还原

【Abstract】 Based on conventional observation data,satellite cloud imagery,radar detection data and the rainfall data of automatic weather stations etc.,comparative analysis on the meteorological conditions for the two severe mountain torrent geological hazards occurred during 27—28 June 2010 and 20—22 May 2012 in northwest Guangxi was done.The results showed that:(1)The torrential rainfall occurs in the northwest of Guangxi with a maximum precipitation >350 mm.The maximum precipitation of mesoscale rain clusters is larger than >100 mm· h ~1 in the processes and over 70 mm ·h~1 in the hazard areas.The concentrated rainfall period is in 02:00—06:00 BT.The disasters begin in the late night,and occur in the area with maximum precipitation and fragile geological conditions,where different geological conditions correspond to different disasters.The severe weather has characteristics with small range,concentrated rainfall periods,intensity rainfall and triggers serious disasters.(2)The heavy rainfall is caused by circulation background with two ridges and one trough at 500 hPa in Eurasian Region and ridge line of South Asia high throughout Guangxi over at 200 hPa accompanied with active monsoon cloud system.The weather systems with upper trough or vortex and surface dry line or frontal indicate a vortex-type storm.(3)The variation of upper-air elements is the temperature decreases before the rainfall but rises after it.Unstable energy and stratification,low-level convergence,middle and low-level vortex,ascending motion of the whole atmosphere layer,high temperature and humidity,and strong convergence of water vapor are characteristics of the physical quantities.(4)Generation and mergence of convective cloud clusters on the satellite cloud images have implications to heavy rainfall.The rainstorm occurs in the developing stage of the clouds,and the TBB value less than 200 K can be used as an indicator to the severe precipitation.Train effect produced by low centroid of radar echoes and the effect of topography are important factors for the heavy rainfall. Strong vertical motion due to low-level convergence and upper-level divergence is conducive to the development and maintenance of the severe convection.更多还原