2015年6月湖南一次暴雨天气过程分析

Analysis of a Heavy Rainfall Process in Hunan Province in June 2015

湖南是暴雨较为频发的地区,暴雨天气过程较多,对2015年6月湖南省的一次暴雨天气过程进行分析,以明确该次暴雨天气过程的特点。此次暴雨天气过程前期降水强,后期减弱南压,主要是受高空南支槽和中低层切变影响,地面有弱冷空气侵入地面倒槽之中,冷暖空气交汇,是一次较为典型的低涡冷槽型暴雨天气过程。高空急流与中低层急流通过强烈的垂直运动互相促进,急流的加强不断输送水汽,在湖南地区建立了持续的水汽通道,暴雨区域假相当位温等值线密集,有利于形成明显的深厚湿对流环境场,促进暴雨的形成和持续发展;在600-1 000 h Pa,假相当位温都随高度升高而减小,表明该地上空为对流不稳定区域,K指数及不稳定能量都较大,低层辐合抬升,触发不稳定能量释放,形成多个连续的对流云团不断东移,有利于暴雨的维持和发展,从而造成了该次大范围的暴雨天气过程。

Heavy rainfall is more frequent in Hunan Province.A heavy rainfall process in Hunan Province in June 2015 was analyzed in order to identify its characteristics.The early rainfall was relatively strong, and the late rainfall weakened and moved？ southwards, which was main-ly affected by the high altitude southern trough and low level shear line.A weak cold air invaded the ground inverse trough.Thus, the inter-section of cold and warm air was a typical heavy rainfall process with low vortex cold trough type.Upper-level jet stream and low-level jet stream promoted each other through strong vertical movement, which continually strengthened the jet stream to transport water vapor.A contin-uous passage of water vapor was established in Hunan Area.Pseudo-equivalent temperature contours was intensive in the area of heavy rain-fall, which was helpful to form a clear deep moist convection environmental field, and to promote the formation and sustainable development of heavy rainfall.Within the range of 600-1000 hPa, pseudo-equivalent temperature decreased with the increase of height, showing that there was convective instability over the area.K index and unstable energy were both relatively large; low-level convergence uplifted, which trig-gered the release of instable energy, which led to the eastward movement of continuous convective cloud clusters.It was conducive to the ma-intenance and development of the heavy rainfall, resulting in a wide range of this rainstorm.