Climate Features and Formation Causes of Autumn Rain over Southwest China
Climate Features and Formation Causes of Autumn Rain over Southwest China
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发表时间：
2004
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通讯作者：
Bai Hu-zhi
中科院分区：
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作者：
Bai Hu-zhi
在分析西南地区秋雨气候特征的基础上，利用秋季降水量和降雨日数设计了秋雨指数，同时对EOF和REOF技术进行了分解，分析了影响秋雨的主要因素。结果表明：第一模态表明，长江中上游降水向北、向南的趋势正好相反；第二荷载特征向量场反映了西南地区降水的一致性。利用REOF技术将西南地区秋雨划分为6个气候带。气候变化趋势表明，20世纪60年代至70年代初和80年代，西南地区秋季降水相对较多，70年代中后期和80年代中期至90年代末降水相对较少，但21世纪初也出现了明显的秋雨。西太平洋副热带高压、印缅槽和贝加尔湖槽是西南地区秋雨的主要影响系统。如果贝加尔湖槽和印缅槽发育良好，西太平洋副热带高压增强，则有利于西南地区秋季降水偏多，反之，如果条件翻转，则会导致西南地区秋季降水偏少。
On the basis of analying the climatic characterstics of autumn rain over Southwest China, the autumn rain index was designed by using the autumn precipitation and rain day numbers, meanwhile, the decompositions of EOF and REOF technique were carried out, and the main effective factors about autumn rain were analyzed. The results showed that the first mode indicates the precipitation trend to the north and to the south over the mid-and-upper reaches of Changjiang River is just oposite. The second load eigenvector fields reflectes the consistency of precipitation over Southwest China. The six climatic zones of autumn rain over Southwest China were respectively divided by REOF technique. The trend of climatic change indicated that there is more rain comparatively over Southwest China in autumn in the periods of from 1960′s to early 1970′s and 1980′s, and for less rain in the periods of mid-and-late 1970′s, from middle 1980′s to late 1990′s, however the autumn rain appeared obviouslyin early 21~(st) centurytoo. Western Pacific subtropical high, trough located at India and Burma, and Baikal trough were the main influence systems of autumn rain over southwest China. If the Baikal trough and India-Burma trough were well-developed and west Pacific subtropical high were strengthened, which would be favorable for more rain over Southwest China in autumn, on the contrary, if the condition was overturned, and then which would resulted in rainless.