The distribution of large-scale drought/flood of summer in China under different configurations of monsoon and polar vortex
The distribution of large-scale drought/flood of summer in China under different configurations of monsoon and polar vortex
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DOI：
10.7498/aps.63.059201
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发表时间：
2014-03
影响因子：
5.4
通讯作者：
F. Ji;Jh H. Zhao;Q. Shen;R. Zhi;Z. Gong
中科院分区：
文献类型：
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作者：
F. Ji;Jh H. Zhao;Q. Shen;R. Zhi;Z. Gong
从冷暖系统配置的角度，选取东亚夏季风（EASM）和7月亚洲区极涡面积（APVA），分析了二者的气候特征与中国夏季降水分布之间的关系. 在此基础上，将1951–2010年EASM和APVA的异常配置分为四种类型：A：季风强、极涡大；B：季风强、极涡小；C：季风弱、极涡大；D：季风弱、极涡小.利用合成分析方法，发现在季节尺度上，7月份东亚夏季风和亚太夏季风的不同配置下，中国夏季旱涝的大尺度分布呈现出多面性特征。A型年我国夏季降水总体偏少，西北地区东部与华北地区西部之间、东北地区东部洪涝灾害严重，长江流域干旱; B型年南涝北旱，长江流域北方地区南部降水偏多，北部降水偏少; C型年华北洪涝，华南干旱，淮河流域北方降水偏多;长江中下游及其以南地区降水偏少; D型年夏季降水总体偏多，降水核心位于长江中下游。由此可以看出，夏季降水的分布不仅与东亚夏季风有关，而且与7月的太平洋夏季风有关。在两者不同配置下，降水量及其分布表现出明显的差异性和规律性，对夏季降水的总体趋势预测有一定的影响。此外，通过对不同环流结构下大气环流异常特征的讨论，以及不同气象因子对季风与极涡关系的影响分析，得出夏季降水的差异性和规律性直接取决于环流结构的结论。其中，西太平洋副热带高压和中高纬度地区的阻塞形势是压倒性的因素。
From the view of warm and cold system configuration, an East Asian summer monsoon (EASM) index and the Asian polar vortex area (APVA) index in July were selected, and their climatic characteristics and relationships with the distribution of summer rainfall over China were analyzed. On this basis, the relationships between the EASM and APVA in July from 1951 to 2010 were divided into four types: type A, stronger monsoon and bigger polar vortex area; type B, stronger monsoon and smaller polar vortex; type C, weaker monsoon and bigger polar vortex; type D, weaker monsoon and smaller polar vortex. Based on the method of composite analysis, we found that on the seasonal scale, large-scale distributions of summer droughts and floods over China showed multi-faceted characteristics in different configurations of the EASM and the APVA in July. In A type years, the summer rainfall of China was overall less than normal, the region between eastern parts of Northwest and the western parts of North China, and the eastern regions of Northeast suffered from flood, while Yangtze River valley suffered from drought; in B type years, it had flood in South and drought in North, and the precipitation in the south/north of northern regions in the Yangtze River valley was more/less than normal; in C type years, North China was flooded and South of China suffered from drought, while the precipitation in the northern parts of the Huaihe River valley was more than normal; and in the middle and lower reaches of Yangtze River and to its south the precipitation was less than normal; in D type years, the overall summer rainfall was more than normal, with the precipitation core lying in the middle and lower reaches of Yangtze River. Thus, it can be seen that the distribution of summer rainfall is not only related to the EASM, but also to the PAVA in July. Under different configurations of the both, the precipitation and its distribution display obvious difference and regularity, which, to some extent, have effects on predicting the total trend of summer rainfall. Besides, by discussing the anomaly characteristics of atmospheric circulation due to different configurations and by analyzing the influences of different meteorological factors on the relationship between the monsoon and the polar vortex, we can conclude that the difference and regularity of summer rainfall directly depend on the configurations of circulation. Among them, the western Pacific subtropical high and the blocking situation in the mid and high latitudes are the overriding factors.