龙泉驿区夏季暴雨环流形势合成分析

Synthesis Analysis of Summer Storm Circulation Situation in Longquanyi District

摘要: 为分析龙泉驿区41年来暴雨环流形势，利用1980~2010年的NCEP再分析资料，网格距1˚ × 1˚，时间间隔为6 h，龙泉驿区本站的24小时逐日降水观测资料，对1980~2020年41年，发生在龙泉驿区共93次典型暴雨过程的高低空大尺度环流背景特征及其影响系统进行合成研究。研究表明：1) 龙泉驿区的暴雨天气过程大多受到100 hPa位势高度上的南亚高压和500 hPa位势高度上的西太平洋副热带高压的影响，同时中低层受到高原东部的弱高压和西南涡以及四川地区的切变线的共同作用。但具体每个月份环流形势都略有不同，主要的差异在于影响系统的位置有所变化，其所造成的暴雨降水程度也高低各异。2) 对比研究发现：6月南亚高压相对较低，其脊线位于30˚N左右，7，8月份的脊线位置相对较高位于35˚N附近。3) 所有月份的暴雨过程中副高脊线位置均相对较高，其中6月的脊线位置最低在20˚N，其他月份都在25˚N，最高的7月副高脊线位置可达到30˚N附近，这样的形势为暴雨的发生提供有利的水汽条件。4) 7，8月份的强降水皆受到西南涡的控制，且都伴随着强的风切变，同时来自于孟加拉湾以及南海的水汽在龙泉驿区上部得到辐合，并在上层形成了西南–东北方向的轴向急流辐合带。

Abstract: In order to analyse the storm circulation situation in Longquanyi District over the past 41 years, NCEP reanalysis data from 1980 to 2010, with a grid spacing of 1˚ × 1˚ and a time interval of 6 h. The 24-hour daily precipitation observations at this station in Longquanyi District were used to synthesize the characteristics of the high and low-level large-scale circulation background and its influence system for a total of 93 typical rainstorm processes that occurred in Longquanyi District during the 41 years from 1980 to 2020. The study shows that. 1) Most of the heavy rainfall weather processes in Longquanyi District are caused by the joint interaction of the South Asian high pressure at 100 hPa and the Western Pacific subtropical high pressure at 500 hPa, and the joint action of the weak high pressure and the southwest vortex in the eastern part of the plateau and the split low pressure trough in the northern part of Sichuan. However, the circulation situation varies slightly from month to month, the main difference being that the location of the influencing systems varies and the extent of the rainfall caused by them also varies. 2) A comparative study found that a strong South Asian high pressure was present during all the rainstorms in June the South Asian high pressure was relatively low, with its ridge at around 30˚N, and in July and August the ridge was relatively high at around 35˚N. 3) The position of the ridge is relatively high during heavy rainfall in all months, with the lowest position of the ridge in June at 20˚N and all other months at 25˚N. The highest position of the ridge in July can reach around 30˚N, which provides favourable water vapour conditions for the occurrence of heavy rainfall. 4) The heavy precipitation in July and August was controlled by a southwesterly vortex, accompanied by strong wind shear, while moisture from the Bay of Bengal and the South China Sea converged in the upper part of the Longquanyi area and formed a southwesterly-northeasterly axial rapid convergence zone in the upper layers.