基于H8卫星的昆明大暴雨过程对流云特征及触发机制分析

Analysis of Convective Cloud Characteristics and Trigger Mechanism of Kunming Rainstorm Based on Himawari-8 Satellite Data

利用葵花8号(H8)卫星、NCEP FNL再分析、地面加密观测及探空资料,针对2019年7月20日发生在昆明的一次大暴雨天气,分析该过程中对流云初生、发展的演变特征及其触发的物理机制。结果表明:(1)500 hPa低涡切变是此次过程产生的主要影响系统,对流云团的快速发展以及云团的合并使得降雨增强和持续。(2)降雨发生初期,云顶高度较低;随着对流云发展,红外亮温降温率达−30℃·(30 min)^(-1),降雨迅速增强;当云顶高度接近水汽层顶即水汽与红外亮温差小于2℃时,降雨进一步增强;红外亮温快速降低,以及水汽与红外亮温差可作为预判对流云产生短时强降水的参考标准。(3)对流有效位能呈细长条型,并有一定的对流抑制能,在地面辐合的作用下,容易触发对流;当冷空气侵入时,在地形抬升作用配合下,对流发展为深对流;整层比湿积分高达3554g·kg^(-1)并配合南北两侧水汽输入,为此次强降雨的发生提供了十分有利的水汽条件。

Using Himawari-8(H8)satellite data,NCEP FNL reanalysis data,surface and upper air observation data,the characteristics of the convective initiation and the triggering mechanism of the rainstorm event occurred in Kunming on July 20,2019 were divided and analyzed.The results are as follows:(1)The 500 Hpa low-vortex shear was the main impact system of the process,and the rapid development of convective cloud and the merger of cloud made precopitation aggravation and continue.(2)In the initial stage of precipition,the convective cloud was low.With the development of the convective clouds,the cooling rate of infrared brightness temperature reached−30℃·(30 min)^(−1),the precipition rapidly enhanced.When the convective cloud top was close to the water vapor top,the temperature difference between water vapor and infrared bright temperature was less than 2℃,the precopitation enhanced.The rapid decrease of infrared brightness temperature and the temperature difference between water vapor and infrared brightness was used as a reference indicator for the forecast of short-term heavy precipitation.(3)CAPE shape was elongated,and a certain convection inhibition was easily triggered.When the cold air invaded,the convection developed into deep convection under the cooperation of terrain unlift.The entire layer of moisture reached up to 3554 g·kg^(−1)and the water vapor inflowed from the north-south sides,which provided advantageous water vapor conditions for this rainstorm.