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覃丹宇. 用滤波方法进行MαCS云团形态差异的个例分析[J]. 大气科学, 2010, 34(1): 154-162. DOI: 10.3878/j.issn.1006-9895.2010.01.14
引用本文: 覃丹宇. 用滤波方法进行MαCS云团形态差异的个例分析[J]. 大气科学, 2010, 34(1): 154-162. DOI: 10.3878/j.issn.1006-9895.2010.01.14
QIN Danyu. A Case Study of Meso-α-scale Convective System Shape Differences Using Filtering Analysis[J]. Chinese Journal of Atmospheric Sciences, 2010, 34(1): 154-162. DOI: 10.3878/j.issn.1006-9895.2010.01.14
Citation: QIN Danyu. A Case Study of Meso-α-scale Convective System Shape Differences Using Filtering Analysis[J]. Chinese Journal of Atmospheric Sciences, 2010, 34(1): 154-162. DOI: 10.3878/j.issn.1006-9895.2010.01.14

用滤波方法进行MαCS云团形态差异的个例分析

A Case Study of Meso-α-scale Convective System Shape Differences Using Filtering Analysis

  • 摘要: 利用GMS-5卫星资料, 研究了2002年6月27~28日一次强降雨过程中尺度暴雨云团的演变特征。分析表明, 整个降雨过程分两个阶段, 第一阶段, 一个近圆形中尺度对流云团从西北向东南移动, 主要造成河南省强降雨; 第二阶段, 南移的中尺度对流云团到达长江流域, 重新发展并形成东西向宽带状α中尺度对流系统 (Meso-α-scale Convective System, 简称MαCS) 云团, 造成长江中下游暴雨。为研究这次暴雨过程中尺度对流云团的组织方式演变和结构特征, 使用滤波方法对NCAR/NCEP 1°×1°再分析资料进行尺度分离, 获得中尺度扰动场, 结果表明: (1) 利用改进的Shuman-Shapiro滤波方法, 可以有效地分离出中尺度扰动。对于近圆形的MCS, 低层高度场低中心和流场辐合中心重合, 位于云顶亮温 (Black Body Temperature, 简称TBB) ≤-52℃冷云盖的西侧边缘, 这里也是新生对流活跃的地方, 而高层高度场高中心和流场辐散中心分离, 但都位于冷云盖区域。对于宽带状MαCS, 低层高度场低中心和流场辐合中心也基本重合, 位于TBB≤-52℃冷云盖的北侧边缘, 高层高度场高中心与低层低中心相对应, 但流场在冷云盖中没有表现出单一中心, 却表现为一致辐散气流。 (2) 滤波结果显示, 不论是前期的近圆形中尺度对流云团, 还是随后发展起来的宽带状MαCS, 二者都具有低空辐合高空辐散扰动结构, 只是扰动的强度后者大于前者。 (3) 这次过程的中尺度对流云团表现出的形态演变, 由近圆形变成宽带状, 是因为其组织差异造成的。两者的组织方式完全不同, 前者主要是低层中尺度气旋, 而后者主要是低层的中尺度切变线。

     

    Abstract: A Meiyu heavy rainfall event during 27-28 Jun 2002 is investigated by using GMS-5 satellite infrared images. It shows two stages of mesoscale convective system (MCS) activities with intensive precipitation. In the first stage, a circular-shape MCS moving from the northwest to southeast produces heavy rainfall in Henan Province of the central China; in the second stage, the southerly moving MCS develops and forms a persistent elongated convective system (PECS) which produces torrential rain over the Yangtze River basin. In order to understand why the cloud top shape of the MCS changes from circular to elongated, and what atmospheric processes are related, the NCEP/NCAR 1°×1° reanalysis data are filtered for scale separation. Results show that the mesoscale disturbances output by the Shuman-Shapiro filtering can well correspond to the area where the cloud top temperature is less than or equal to -52℃. Both the first stage circular-shape MCS and the second stage PECS have a similar structure with convergence at lower levels and divergence at upper levels in the troposphere. But their organizations are different: the former is mainly a mesoscale cyclone, while the latter is a mesoscale convergence zone, both at lower levels. This organizing differences cause the MCS cloud top evolution from circular to elongate.

     

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