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Vertical Structure of Convective Cloud in a Cold Vortex over Northeastern China Using CloudSat Data
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摘要: 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, 中部为锢囚锋主体对流区, 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现象，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，冰水含量多的对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。Abstract: 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.
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Key words:
- CloudSat;
- cold vortex;
- occlusion;
- cold-dry air
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图 1 2006年7月20日06:00位势高度场 (实线，单位：gpm)、位温场 (灰色) 及水平风场 (矢量)
(长虚线为CloudSat轨道1206 03：50扫过的轨迹) (a) 500 hPa，(b) 950 hPa
Fig. 1 500 hPa (a) and 950 hPa (b) geopotential height (solid line, unit: gpm), potential temperature (grey) and wind (vector) fields at 06:00 20 July 2006
(the long dashed line represents CloudSat section of granule 1206 at 03:50 20 July 2006)
图 2 2006年7月20日04:00 FY-2C可见光云图
(实线为CloudSat扫过的轨道)
Fig. 2 FY-2C visible light cloud image at 04:00 20 July 2006
(the solid line represents CloudSat granule)
图 3 2006年7月20日04：53 CloudSat轨道1206扫过轨迹 (a) 雷达反射率因子 (灰色) 和假相当位温 (等值线，单位：K) 剖面，(b) 冰水含量 (灰色) 和液态水含量 (黑色区域，不低于100 mg·m-3) 与温度 (等值线，单位：℃) 剖面
Fig. 3 CloudSat of granule 1206 cloud profiling at 04:53 20 July 2006 (a) radar reflectivity (grey) and equivalent potential temperature (contour, unit: K), (b) ice water content (grey), liquid water content (black area, no less than 100 mg·m-3) and temperature (contour, unit:℃)
表 1 CloudSat卫星数据产品代码及相应产品名称
Table 1 CloudSat data code and its relevant product
产品编码 产品名称 1B-CPR, 1B-CPR-FL 雷达散射剖面 2B-GEOPROF 云的几何剖面 2B-CLDCLASS 云的分类 2B-CWC-RO 组合 (液态、固态) 水含量 (单雷达) 2B-CWC-RVOD 组合水含量和可见光光学厚度 2B-TAU 云光学厚度 2B-FLXHR 通量和加热率 2B-CLDCLASS-LIDAR 激光雷达云几何剖面 
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