应用FY卫星产品分析陇东半干旱区特大暴雨事件云特征

Cloud characteristics analysis of a torrential rainfall event use FY satellite in semi-arid region of Eastern Gansu Province

降水与云的发生发展密切相关,研究强对流云特征,对降水机理分析、降水监测和预报具有重要意义。2022年7月15日地处西北半干旱区的甘肃陇东出现一次特大暴雨过程,多站日降水量和小时降水量均突破历史极值,本文基于FY-4A、FY-4B静止卫星扫描成像辐射计(advanced geostationary radiation imager,AGRI)数据,FY-3D极轨卫星微波湿度计(micro-wave humidity sounder,MWHS)和微波温度计(micro-wave temperature sounder,MWTS)融合产品,分析此次特大暴雨事件中云宏微观特征、云系演变特征及大气环境条件。结果表明:(1)暴雨云系的云顶类型为过冷水云、混合云、不透明冰云和多层云等,发生强降水的云顶类型以不透明冰云为主,云顶高度达14 km以上;暴雨云系云体深厚,主要为小粒径冰云且伴有强烈上升气流。(2)此次暴雨事件存在对流云团新生、合并及加强过程,对流云团稳定维持是导致特大暴雨发生的主要原因,降水与云顶相当黑体亮温(black body tem⁃perature,TBB)及其变化的关系密切,TBB低值区对应强降水,且强降水发生前TBB迅速下降。(3)强降水发生前大气层结表现出浅层对流不稳定的特征,中低层强烈增湿是对流不稳定发展的主要原因,低层绝对湿度的差异造成了不稳定条件及降水量级的差异。

Precipitation is closely related to the occurrence and development of clouds.The study for the characteristics of convective cloud is of great significance to the precipitation monitoring and prediction,as well as researches of precipitation mechanism.A torren⁃tial rain struck Qingyang on15 July 2022,which is located in semi-arid region of Northwest China,causing the daily rainfall and hourly rainfall at several stations to exceed the historical extreme values.Based on products of the advanced geostationary radiation imager(AGRI)from FY-4A and FY-4B geostationary satellite,fusion products of micro-wave humidity sounder(MWHS)and micro-wave tem⁃perature sounder(MWTS)from FY-3D polar orbit satellite,the cloudsytem evolution,macro and micro characteristics of cloud,and the atmospheric environmental conditions during this torrential rainstorm event were analyzed.The results are as follows:(1)The rainstorm cloud top types formed from supercooled water clouds,mixed clouds,opaque ice clouds and multi-layer clouds.The cloud top types of heavy precipitation are mainly opaque ice clouds,and the height of cloud top is more than 14 km.The rainstorm cloud system is deep and mainly composed of small ice particles,and accompanied by strong updraft.(2)In this rainstorm event,there exist a process of con⁃vective cloud formation,merging and strengthening,and the continuous influence of convective clouds leds to the occurrence of ex⁃tremely heavy rain.Precipitation was closely related to the black body temperature(TBB)of cloud top and its variation.Low TBB corre⁃sponded to heavy precipitation,and the TBB drops rapidly before the heavy precipitation.(3)Before the occurrence of heavy precipita⁃tion,atmospheric stratification is shallow convective instability.The strong humidification in the middle and lower layers is the main reason for the development of convective instability.The difference of absolute humidity in the lower layers leads to the difference of in⁃stable conditions and precipitation intensity.