Ensemble Sensitivity Analysis of Heavy Rainfall Associated With Three MCSs Coexisting Over Southern China
Ensemble Sensitivity Analysis of Heavy Rainfall Associated With Three MCSs Coexisting Over Southern China
复制标题
华南地区三种MCS共存的暴雨集合敏感性分析
DOI：
10.1029/2019jd031266
复制
发表时间：
2020
影响因子：
4.4
通讯作者：
Chen Guixing
中科院分区：
文献类型：
--
作者：
Shen Yian;Du Yu;Chen Guixing
利用集合敏感性分析方法，对一次华南暴雨过程进行了分析，探讨了影响降水量及其可预报性的主要控制因子。这次暴雨是由中国西南地区（MCS-A）、中国南部沿海（MCS-B）和台湾北方（MCS-C）三个中尺度对流系统（MCS-A）共同存在引起的。这三个MCS在预报精度和对降水中心有贡献的相关关键因素（如低空涡/切变线和低空急流）方面表现出不同和相似之处。西南低涡是一个位于中国西南部200-600 km水平尺度的中尺度低涡，其强度和形状对MCS-A和MCS-B有显著影响，而中国东部沿海切变线的增强则伴随着MCS-C降水的增加。此外，根据低空急流的位置、强度、高度和方向，低空急流及其相关的水汽输送对三个MCS产生了强烈的影响。位于西南低涡东南面、纬向风分量较强、轴向偏北（南）的天气性低空急流与MCS-A（MCS-B）相应区域的降水增加有关。除了天气LLJ，MCS B的降雨还受到海洋边界层急流的影响。上述关键因素的不一致可能进一步影响三个MCS的可预测性，从而导致其预测精度的差异。
Using ensemble‐based sensitivity analysis, a heavy rainfall event over southern China was analyzed to investigate the key controlling factors of rainfall amount and relevant predictability. The heavy rainfall event was caused by three coexisting mesoscale convective systems (MCSs) over southwestern China (MCS‐A), the south coast of China (MCS‐B), and northern Taiwan (MCS‐C). The three MCSs exhibited differences and similarities with respect to their forecast accuracy and relevant key factors contributing to the rainfall centers, such as low‐level vortex/shear lines and low‐level jets. The strength and shape of the southwest vortex, a mesoscale vortex usually located over southwestern China with a horizontal scale of 200–600 km, exerted a significant effect on MCS‐A and MCS‐B, whereas the stronger shear line near the east coast of China was accompanied by increased precipitation in MCS‐C. In addition, the low‐level jets (LLJs) and their associated moisture transports had a strong influence on the three MCSs according to the LLJ location, strength, height, and direction. A synoptic LLJ located to the southeast of the southwest vortex with a stronger meridional (zonal) wind component and an axis more to the north (south) was related to increased precipitation in the corresponding region of MCS‐A (MCS‐B). In addition to the synoptic LLJ, the rainfall of MCS‐B was also influenced by a boundary layer jet over the ocean. Uncertainties in the aforementioned key factors might further influence the predictability of the three MCSs and thus lead to the differences in their forecast accuracy.