The characteristics and classification of eastward-propagating mesoscale convective systems generated over the second-step terrain in the Yangtze River Valley
The characteristics and classification of eastward-propagating mesoscale convective systems generated over the second-step terrain in the Yangtze River Valley
复制标题
长江流域二级地形东传中尺度对流系统特征及分类
DOI：
10.1002/asl.874
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发表时间：
2019
影响因子：
3
通讯作者：
Li Jun
中科院分区：
文献类型：
--
作者：
Yang Ruyi;Zhang Yuanchun;Sun Jianhua;Fu Shenming;Li Jun
2000年5月至2016年8月（2005年除外）期间，使用每小时的黑体温（TBB）数据集总共检测到了316个在第二阶梯地形上形成的向东传播的中尺度对流系统（MCS）。这些 MCS 持续三个到几十个小时，并沿着不同的轨迹移动。这些检测到的 MCS 根据其关键特征分为四类（即 C1、C2、C3 和 C4）。 C1 MCS 通常向东北方向移动至中国北部，平均持续时间约为 16 小时，而其 C2 对应物大多以在第二阶梯地形东部边缘上的准静止行为为特征，平均寿命约为 9 小时。相比之下，大多数 C3 MCS 向东移动，平均持续约 21 小时，引发从第二阶梯地形东缘到海岸线的强降雨。 C4 MCS 具有与 C3 MCS 相似的特征，但平均持续时间短得多（约 8 小时），影响范围主要限于长江中游地区。对这四个 MCS 类别的综合分析表明，所有类别中较强的低水平气旋涡度有利于 MCS 的维持；中上层转向流的差异导致了四类运动方向的不同；输入水蒸气的强度与 MCS 的寿命成正比。
A total of 316 eastward‐propagating mesoscale convective systems (MCSs) that form over the second‐step terrain are detected during May to August 2000–2016 (except 2005) using an hourly black body temperature (TBB) dataset. These MCSs last from three to dozens of hours and moved along various trajectories. These detected MCSs are divided into four categories (i.e., C1, C2, C3, and C4) according to their key characteristics. C1 MCSs generally move in a northeastward direction to northern China and have a mean duration of ~16 hr, while their C2 counterparts are mostly characterized by quasi‐stationary behavior over the eastern edge of the second‐step terrain and have a 9‐hr mean life span approximately. In contrast, most C3 MCSs move in an eastward direction and tend to last ~21 hr on average, inducing heavy rainfall from the eastern edge of the second‐step terrain to the coastline. The C4 MCSs possess similar features to C3 MCSs but have much shorter mean durations (~8 hr) and exert influences within an area mainly limited to the middle reaches of the Yangtze River Valley. Composite analyses of these four MCS categories show that a strong lower‐level cyclonic vorticity in all categories favors the MCSs' sustainment; the differences of the steering flow from middle‐to‐upper levels account for the different moving directions of the four categories; the intensity of imported water vapor is proportional to the longevity of MCSs.