2023年双流地区一次强降水过程的数值诊断分析

Numerical Diagnostic Analysis of a Heavy Precipitation Process in Shuangliu Area in 2023

为了进一步研究四川省成都市双流区的强降水过程,文章使用成都信息工程大学实习台提供的天气形势场,探空资料和欧洲中期天气预报中心网站获取的ERA5数据集,通过天气学诊断分析和物理量场数值分析,对发生在2023年7月12日凌晨的暴雨过程进行诊断分析,结果表明:1) 500 hPa上四川盆地位于一个低槽前部,副热带高压位于长江流域。由于副热带高压外围的反气旋环流和槽前西南气流的共同作用,有利于引导低层西南暖湿气流向四川盆地输送。700 hPa高度上四川盆地以西存在低槽,成都位于低槽前部,受偏南气流影响,存在西南暖湿气流的输送。盆地以北为偏北风,向盆地内输送干冷气流。850 hPa高度上四川盆地处在暖区内,存在低压区和气旋性旋转的风,为降水提供动力条件。暖湿气流通过重庆进入盆地。2) 本次强降水天气过程的水汽来自于偏南气流,经贵州、重庆到达成都,高温高湿水汽的到来使得成都上空大气变得非常不稳定。下层暖湿,上层干冷,有利于对流的产生。水汽输送持续了整个暴雨过程,使得在暴雨结束后成都市850 hPa比湿略有上升,伴随着一个较强的水汽辐合中心。3) 暴雨过程中的垂直运动较为强烈;散度场上500 hPa辐散、850 hPa辐合的配置,利于上升运动的发展和加强;500 hPa成都地区位于低槽前部,槽前正涡度平流促使低层低压发展,加强低层气流上升运动,为暴雨的发生发展提供了良好的动力条件。4) 在热力条件上,成都市上空假相当位温场存在一个高值区,并且IC −1,CIN为130.2 J·kg−1,在以上的环流形势中,气块能够获取到足够能量越过LFC从而产生对流,使得暴雨产生。To further investigate the process of heavy precipitation in Shuangliu District, Chengdu City, Sichuan Province, this paper utilizes weather situation fields provided by the internship station of Chengdu University of Information Technology, sounding data, and the ERA5 dataset obtained from the website of the European Centre for Medium-Range Weather Forecasts. Through meteorological diagnostic analysis and numerical analysis of physical fields, the heavy rain process occurring in the early morning of July 12, 2023, is diagnosed and analyzed. The results show the following: 1) At 500 hPa, the Sichuan Basin is located at the front of a trough with the subtropical high situated over the Yangtze River basin. Due to the anticyclonic circulation on the periphery of the subtropical high and the combined action of the southwest airflow in front of the trough, it is conducive to guiding the low-level southwest warm and moist airflow towards the Sichuan Basin. At 700 hPa, there is a trough to the west of the Sichuan Basin, with Chengdu located at the front of the trough, influenced by the southerly airflow, which facilitates the transport of southwest warm and moist air. To the north of the basin, there is a northerly wind, transporting dry and cold air into the basin. At 850 hPa, the Sichuan Basin is within a warm sector, with a low-pressure area and cyclonic wind rotation, providing dynamic conditions for precipitation. The warm and moist airflows into the basin through Chongqing. 2) The moisture for this heavy precipitation weather process comes from the southerly airflow, passing through Guizhou and Chongqing to reach Chengdu. The arrival of high-temperature and high-humidity moisture makes the atmosphere above Chengdu very unstable. The lower layer is warm and moist, while the upper layer is dry and cold, which is conducive to the occurrence of convection. The moisture transport lasted throughout the heavy rain process, resulting in a slight increase in specific humidity at 850 hPa in Chengdu after the rain, accompanied by a strong moisture convergence center. 3) The vertical movement during the heavy rain process is relatively strong;the divergence at 500 hPa and convergence at 850 hPa are favorable for the development and strengthening of upward motion;at 500 hPa, the Chengdu area is at the front of the trough, and the positive vorticity advection in front of the trough promotes the development of low-level low pressure, strengthening the upward motion of the airflow at low levels, providing good dynamic conditions for the occurrence and development of heavy rain. 4) In terms of thermal conditions, there is a high-value area in the pseudo-adiabatic potential temperature field above Chengdu, and IC −1, and CIN is 130.2 J·kg−1. Under the above circulation conditions, the air mass can obtain enough energy to cross the LFC, thus generating convection and resulting in heavy rain.