2019年7月11日双流一次强降水过程成因分析

Analysis of a Heavy Precipitation on July 11, 2019 in Shuangliu

摘要: 为了研究2019年7月11日02时到13时成都市双流区一次强降水过程的特征和成因，利用常规天气图、欧洲中心(ERA-interim)的再分析资料和温江站探空资料，从环流形势、水汽条件、不稳定能量的释放和动力抬升作用等方面对此次强降水过程进行分析。结果表明：1) 本次降水是在高低层系统的相互作用下产生的对流性强降水过程。双流上空的对流层中高层辐散，低层有气旋性辐合，冷暖气流在降水区交汇，释放了对流层中低层的不稳定能量，是造成此次强降水的主要原因。2) 双流上空较强的水汽辐合和较大的比湿场为此次强降水提供了强大的水汽条件。来自于孟加拉湾以及南海的水汽在双流上空汇合，在该地形成水汽辐合中心。不稳定能量方面，降水发生时，双流地区850 hPa的假相当位温高值中心值为80℃，∆θse500-850达到−10℃。大气为不稳定层结，川南地区存在的能量锋区不断向双流输送不稳定能量，为双流暴雨提供了不稳定条件。动力方面，500 hPa高原低槽前的正涡度平流使地面气旋性辐合加强，双流上空产生一个强度为−1.0 Pa∙s−1的上升中心。高空强烈的辐散促使低层的垂直上升运动增强，为本次强降水的发生和发展提供了良好的动力抬升条件。3) 通过温江站探空资料分析，在暴雨发生前，不稳定能量就开始积累，当能量积累到一定程度后，一旦大气层结受到扰动，暴雨就发生了，随着能量释放完毕，降雨也随之结束。CAPE指数可以反映出能量的积累，对暴雨的发生有一定的指示意义。

Abstract: In order to study the characteristics and causes of a rainstorm in Chengdu Shuangliu on July 11, 2019, the process of heavy precipitation was comprehensively analyzed from the different aspects such as influence system, water vapor transport, unstable energy and dynamic conditions based on the conventional weather data, sounding data in Wenjiang and the European Central ERA-Interim reanalysis data. The results showed that: 1) The precipitation is a convective short-time heavy precipitation process under the joint action of high and low layer system. This precipitation is a convec-tive heavy precipitation process under the interaction of high and low layer systems. The middle and upper troposphere of the double stream is dispersed, and the lower layer has cyclonic convergence. The cold and warm air flows meet in the precipitation area, releasing the unstable energy in the middle and low layers of the troposphere, resulting in this heavy precipitation. 2) The strong water vapor convergence and the larger specific wet field provide strong water vapor conditions for this heavy precipitation. From the Bay of Bengal and the South China Sea, water vapor converges over the Shuangliu, forming a water vapor convergence center. In terms of unstable energy, when precipitation occurs, the high-value center of potential pseudo-equivalent temperature of 850 hPa in Shuangliu is 80˚C; ∆θse500-850 is −10˚C. The energy front in the south of Sichuan region continuously transports unstable energy to Shuangliu, which provides enough energy conditions for the occurrence of heavy precipitation. In the dynamics aspect, 500 hPa Positive vorticity advection in front of low trough in the plateau enhances cyclonic convergence on the ground; there is an ascending center with strength of −1.0 Pa s−1 over the Shuangliu. The strong divergence at high altitude leads to the Intensive convergence of the lower layer by the pumping action, which promotes the vertical upward movement and provides a good dynamic condition for the occurrence and development of this heavy precipitation. 3) Through the analysis of Wenjiang sounding data, the unstable energy begins to accumulate before the rainstorm occurs. When the energy accumulates to a certain extent, once the atmospheric junction is disturbed, the rainstorm occurs until the energy release is completed at the end. CAPE index reflects the accumulation of energy and has certain indicative significance for the occurrence of rainstorm.