黑龙江省一次伴有龙卷的暖区暴雨成因分析

2014年7月19日夜间黑龙江克山出现雨强超过90 mm的短时强降水,利用常规观测资料、区域站资料、NCEP/NCAR再分析资料等对此次冷锋前部的暖区强降水成因进行分析。结果表明:(1)此次强降水出现在580 dagpm线附近,副高诱发的超低空急流为强降水提供了充沛的水汽和不稳定能量。(2)地面辐合线和地形抬升触发对流。高空急流东移,高空急流出口区左侧和辐散区与低层辐合相耦合促使对流快速发展增强。耦合消失,强降水则快速减弱。(3)低层暖平流明显,尤其地面具有暖锋锋生特征。强降水出现在不稳定层结和上升运动快速增强的阶段。(4)地面～200 hPa辐合层形成深厚的上升运动区,促使对流快速发展。(5)中尺度对流雨带沿地面辐合线生消。降水先出现在暖湿舌前部。随后,强降水产生的冷空气抬升暖湿空气形成冷锋特征的降水,由于强降水和冷空气的正反馈作用,降水持续时间长。冷空气势力最强时,伴随中尺度气旋性环流及0～1 km强垂直风切变有利于龙卷产生。(6)开口状地形的辐合作用、抬升及局地地形导致的中尺度环流风场对暖区降水的形成和维持作用显著。

Analysis on the Formation of a Warm sector Torrential Rain Case with Tornado in Heilongjiang

Based on conventional observations and NCEP reanalysis date, the causes of warm sector Torrential Rain in front of the cold front in the night of July 19, 2014 are analyzed. The results show that: (1)The heavy precipitation appears near the 580dagpm line, the ultra-low-level jet induced by subtropical anticyclone provides abundant moisture and unstable energy for heavy precipitation. (2) The surface convergence line and the uplift of topographic trigger convection As the upper-air jet moves eastward, coupling of high level jet and Low level jet accelerates the development of convection. While the heavy rainfall decreases rapidly with the coupling disappeared. (3)The lower level, especially the ground temperature, has strong warm convection and is characterized by a warm front. The heavy precipitation appears in the rapid enhancement stage of unstable stratification and ascending motion. (4) The surface -200hPa convergence layer forms a deep ascending motion zone, which promotes the rapid development of convection. (5)The mesoscale convective rain belt grows and vanishes along the convergence line of the ground. First, the northern precipitation appears in front of the warm and wet zone. Subsequently, the cold air generated by heavy precipitation uplifts warm and wet air and produces the southern cold front precipitation. Due to the positive feedback effect between heavy precipitation and cold air, the precipitation lasted for a long time.. When the cold air force is the strongest, it is beneficial to tornado generation with mesoscale cyclonic circulation and 0-1km strong vertical wind shear. (6)Topograrphy plays a significant role for warm sector torrential rain.