陕西一次持续性强对流天气过程的成因分析

利用常规资料、地面加密资料、TBB和NCEP再分析等资料,对2006年6月23—25日陕西一次持续性的强对流天气过程进行了天气动力学诊断和中尺度特征分析。结果表明：（1）这次持续性的强对流天气发生在蒙古冷涡的大尺度环流背景下,从冷涡底部分裂的下滑冷槽是强对流天气的影响系统;中高层冷槽和低层暖温度脊、湿舌的上下叠置,有利于对流不稳定的建立和发展。（2）对流层低层850 hPa附近的逆温层所形成的干暖盖,更有利于深厚对流活动的发生;大气温度直减率越大越有利于雷暴大风的发生,对流有效位能（CAPE）和垂直风切变的大小与对流性天气的强弱有很好的对应关系。（3）23和24日的强对流天气是由生命史达6小时左右的β中尺度雹暴云团造成,而25日的剧烈天气是由生命史达10小时左右的α中尺度飑线云团造成。（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。

Cause Analysis of a Continuous Severe Convective Weather in Shaanxi

Using the observational data,intensive surface observation data,TBB data and NCEP reanalysis data,the synoptic and dynamic diagnosis and mesoscale characteristics of a continued strong convection weather process are analyzed.The results show that:(1) the Continuous downslide cold troughs,from Mongolia cold vortex,are its impact systems.High cold trough,low-level warm temperature ridge,and wet tongue overlapping are conducive to the establishment and development of convective instability.(2) The warm dry lid formed by the inversion layer near 850 hPa at the lower troposphere is more conducive to the occurrence of deep convective activity.The larger the air temperature lapse rate is,the easier the occurrence of thunderstorm and gale is.And there is a good correspondence between magnitude of the CAPE,vertical wind shear and the strength of convection weather.(3) The strong convection weather process in 23—24 June 2006 is caused by meso-βscale hailstorm cloud with a 6 h life time,but the violent weather in the 25th is caused by meso-αscale squall line cloud with a 10 h life time.(4) The surface convergence line or dry line is one of the factors which trigger the strong convection;and the convective cells or cloud cluster are generally generated close to the surface convergence line.