一次上海春季强对流天气过程的诊断分析

Diagnostic Analysis of a Strong Convictive Weather Process of Spring in Shanghai

摘要: 本文利用上海市气象自动站实况资料和NECP的FNL (1˚ × 1˚，逐6小时)再分析资料，对2022年4月13日上海市强对流天气过程进行了诊断分析。结果发现：此次上海强对流过程是在春季江淮气旋形成和发展中所造成的。850 hPa上江淮气旋形成，在气旋和切变线经过区域，冷暖空气交汇，强对流天气触发；700 hPa垂直速度场上存在一个垂直上升运动大值区，该垂直上升运动中心与对流云系发展强盛区对应；水汽方面，上海925 hPa上形成两条水汽输送带，水汽通量大值区靠近长江出海口。不稳定条件方面，上海市上空存在上干冷、下暖湿的不稳定层结；中低层风垂直切变大，0℃层高度为3.5 km，有利于强降水的发展。从比湿场来看，强比湿出现层次较低，所以本次强对流过程是由动力条件和不稳定条件主导的。

Abstract: Using FNL reanalysis data (1˚ × 1˚, every 6 hours) from NECP and automatic observation data from Shanghai Meteorological Services, a strong convective weather process in Shanghai on Apr. 13th, 2022 is diagnostically analyzed. The results show that this strong convective weather process is mainly caused by the formation and development of Jianghuai cyclone in spring. In 850 hPa, Jianghuai cyclone is formed, cold and warm air are converged in the area where the cyclone and shear line pass, by which strong convective weather is triggered. There is a large region of fast vertical ascent motion in the vertical velocity field of 700 hPa, which corresponds to the strong development of convective cloud system. Two water vapor conveyor belts are formed on Shanghai in 925 hPa, and the large water vapor flux area is close to estuary of the Yangtze River. In terms of unstable conditions, there are unstable layers of dry-and-cold upper layer and warm-and-humid lower layer above Shanghai. In addition, the vertical wind shear of the middle and low layers is large and the height of the 0˚C layer is 3.5 km, which is conducive to the development of heavy precipitation. The level of strong specific humidity is lower on the vertical specific humidity field, which indicates that this convective weather process is dominated by dynamic conditions and unstable conditions.