基于CloudSat资料的冷涡对流云带垂直结构特征

Vertical Structure of Convective Cloud in a Cold Vortex over Northeastern China Using CloudSat Data

利用CloudSat卫星资料、NCEP再分析资料和FY-2C卫星可见光云图分析了2006年7月20-24日我国东北一次冷涡过程不同时期对流云的垂直结构以及云内中小尺度的结构,发现在冷涡发展阶段的初期,暖锋对流结构表现为孤立的回波系统多,强对流深厚,对流系统体现为孤立、深厚的特征。在冷涡发展成熟阶段,回波强度比冷涡发展初期的对流系统有所减弱,且为浅薄的对流系统。冷涡系统影响下发展的锢囚锋回波系统顶部呈现独特的结构特征:东南部为干冷空气侵入造成的回波区,中部为锢囚锋主体埘流区,西北部为暖锋遇冷锋抬升作用形成的回波区。在锢囚锋尾部存在冰水含量与液态水含量分层脱象,干冷空气侵入层在5 km高度左右,在干冷空气侵入层上部为冰水含量分布的弱回波区,下部为液态水分布的弱回波区。在冷涡成熟阶段,对流系统分布在冷涡外沿,表现为孤立的对流系统,冰水含最多的埘流系统主要在冷涡的北面,而液态水主要分布在冷涡中心零度层以下。

Cold vortex（or cold low,also called cut-off low）,characterized by a cold core and low pressure center over 500 hPa level,is one of the most frequent weather systems over Northeast China.It is often accompanied by strong convective incident,and can bring a wide range of continuous rainfall.However,most of the past researches mainly focus on the environmental conditions and large scale of the cold vortex systems. There is little analysis on meso-scale structure of the convective systems of cold vortex,especially using satellite and radar data,and the understanding on the vertical structure of the meso-scale convective systems is limited.CloudSat data,NCEP reanalysis data and visible light satellite data has been used to analyze the convective rain bands and meso-scale cloud structure of different stages of a cold vortex over Northeast China during 20-24 July 2006. The results show that at the beginning of development stage,the structure of the warm front is characterized with isolated and deep convective systems.At the development and matured stage,the intensity of radar echo is weaker than its development stage,and the convective systems are shallow.The echo top of occlusion under the cold vortex system presents some special characteristics：In the southeast of occlusion, the echo area is driven by the cold-dry air;in the middle area of occlusion is the main convective system and in the northwest area echo is caused by the lifting effect of warm front confront the cold front. There is delamination between ice water and liquid water at the tail of the occlusion front.The height of incursion layer of dry-cold air is about 5 km,above which is the weak echo consisting of ice water,and below the incursion layer is the echo with liquid water.At the mature stage of the cold vortex,the convective systems are located mainly outside the cold vortex in the form of isolated convective systems.Convective systems which contains plenty of ice water content are mainly located in the north of the cold vortex,while liquid water content exists below the 0℃layer of the cold vortex center.