桂北后汛期一次持续性暴雨天气过程分析

Analysis of a Continuous Rainstorm Process in Later Flood Season in Northern Guangxi

运用常规资料、区域自动站资料以及NECP再分析资料,对2017年8月9—15日发生在桂北地区的持续暴雨过程进行了深入分析。结果表明:此次持续暴雨过程发生在500 hPa中高纬两槽一脊的形势下,副热带高压脊线稳定维持在15°N附近、西脊点稳定在110°E以西,副高的阻挡使西风槽前与副高西北侧的西南暖湿气流形势得以长时间维持,为桂北持续暴雨的发生提供了不稳定条件。季风涌增强北推,与南半球冷空气爆发造成的索马里越赤道气流增强,共同为此次持续暴雨提供了源源不断的水汽供应。南亚高压强大、稳定地维持在青藏高原上空,桂北地区位于南亚高压东部脊线上的强辐散区,低层位于低空西南风急流左侧强辐合区,形成很好的低层辐合上升、高层辐散下沉的垂直环流形势,与高低空急流耦合共同为此次持续暴雨提供了较好的动力机制。

Using conventional data,regional automatic station data and NECP reanalysis data,the continuous rainstorm process occurred in northern Guangxi on August 9-15,2017 was analyzed.The results show that the continuous rainstorm process occurred in the situation of two grooves and one ridge in the middle and high latitudes of 500 hPa.The subtropical high ridge line is stable near 15°N,the western ridge point is stable to the west of 110°E.Blocking effect of subtropical anticyclone can maintain the southwest warm and wet air flow in front of the westerly trough and the northwest side of the subtropical high for a long time,which provides unstable conditions for the occurrence of continuous rainstorm in northern Guangxi.The monsoon surge intensified and pushed north,along with the enhancement of Somali cross equatorial flow caused by cold air bursts in the southern hemisphere,provided a steady supply of water vapor during the continuous rainstorm.The South Asian High is strong and stable over the Qinghai Tibet Plateau,the northern Guangxi is located in the strong divergence area on the eastern ridge of the South Asian high,and the lower layer is located in the left strong convergence area of the southwest wind jet at low altitude.Form a good vertical circulation situation of low convergence rise and high divergence sink,coupled with high and low altitude jet,it provides a better dynamic mechanism for the continuous rainstorm.