2017年6月湖南致洪暴雨的天气分析

利用实况观测资料和欧洲中长期天气预报中心再分析资料,对2017年6月底湖南一次致洪暴雨过程进行诊断分析。结果表明:高空冷涡和副高的稳定维持为暴雨发生提供了有利的大尺度环流条件,中低层低涡切变线和地面锢囚锋是此次暴雨的主要影响系统。2支高空急流增强和靠近诱发了低空急流爆发,高低空急流耦合形势的增强促进了暴雨的持续和加强。低空急流为暴雨发生提供了充沛的水汽和不稳定能量,暴雨区表现为显著的对流不稳定,并且在假相当位温垂直梯度增加的阶段对应暴雨强度亦增大。水汽通量以及辐合大值区对暴雨落区预报具有一定的指示意义。

Diagnostic Analysis of Flood-resulting Rainstorm over Hunan Province in June 2017

Based on the real-time observed data and ERA-Interim 1°×1° 6h reanalysis data, the flood-resulting rainstorm overHunan Province in June 2017 were diagnostically analyzed. The results show that the upper cold vortex and subtropical high wereremain steady, which formed a favorable large scale environment for the rainstorm occurring, and the low vortex shear line andground occluded front were the major influencing systems. The enhancement and proximity of 2 high level jet induced the eruptionof the low level jet. Because of the enhancement of the coupling of high and low level jet, the rainstorm was strengthened andsustained. The low level jet provided abundant water vapor and unstable energy for the occurrence of the rainstorm. The rainstormarea showed significant convective instability, and the intensity of rainstorm increased with the increase of vertical gradient ofpseudo equivalent temperature. The large area of water vapor flux and convergence provided references for forecasting the fallingarea of rainstorm.