肇庆市切变线暴雨的精细化时空分布及其环流型特征

Refined Spatiotemporal Distributions of Shear-induced Heavy Rain in Zhaoqing City and the Characteristics of the Associated Circulation Patterns

利用肇庆市2008—2017年近10年20个典型切变线暴雨过程的降水量资料,通过EOF分析等方法研究了暴雨的空间分布特征,并在此基础上对比分析不同分布雨型的环流背景场特征。分析结果表明:(1) EOF展开方法表明肇庆切变线暴雨前3个特征向量累积方差贡献比例为93. 6%。(2)切变线暴雨过程出现频率最多的3种分布雨型为:全市一致偏多(少)型(南部变率高于北部)、南多(少)北少(多)型、南北多(少)中部少(多)型。(3)第1模态最大正负相关的2个典型个例环流场特征的主要区别在于高空槽南伸位置和切变线移动路径以及西南气流的强弱;第2模态的区别在于切变线南压滞留的位置和时间差异;第3模态区别在于切变线是否断裂为东西两段以及低层风速风向辐合区域的差异。

Using the rainfall data of 20 typical shear-induced heavy rains over the ten years of 2008- 2017, this work studies the spatial distributions of the heavy rains using the method of EOF and compares the characteristics of circulation patterns associated with different rainfall patterns. The results are shown as fol- lows. （1） As shown in the EOF expansion, the contribution ratio is 93.6% by the accumulated variance of the first three eigenvectors for the shear-induced heavy rain in Zhaoqing. （2） The following three patterns of shear-induced heavy rain occur most frequently： unanimously more （less） rainfall across the whole city （with the variability larger in the south than in the north）, more （less） rain in the south than in the north, and more （less） rain in the south and north than in the middle part. （3） For two typical patterns of circulation in the maximum positive and negative con＇elation of the first mode, the difference is mainly in the south-extending position of an upper-level trough, the path on which the shear moves and the intensity of a south-westerly flow; for the second mode, it mainly differs in the position at which the south-going shear stagnates and the time it gets there; for the third mode, the difference is whether the shear breaks into two sections and how a converging area of low-level wind speed and direction differs from each other.