东亚夏季风异常活动的空间多模态特征

利用ERA40再分析资料，采用相关、合成、自然正交函数展开（EOF分析）等方法，探讨了东亚地区夏季风活动的多空间模态特征及其与大气环流异常的可能联系。结果表明：1）东亚夏季风活动存在3种差异明显的典型空间模态。第一模态反映了夏季风活动在我国东部沿海及以东洋面与其以西地区的反相变化，主要体现了夏季风活动主体位置的东西变动；第二模态反映了自我国华南，经长江中下游、山东半岛、渤海湾至我国东北及朝鲜半岛一带夏季风活动的一致性变化，体现了东亚夏季风活动的整体强弱；第三模态主要反映了夏季风活动在中国以东洋面、朝鲜半岛、东北亚一带与我国华南地区的反相变化，主要体现了夏季风活动主体位置的南北移动。2）东亚夏季风活动的多空间模态对应的大气环流异常存在显著差异。东亚夏季风第一空间模态与亚洲南部区域以及鄂霍次克海上空的SLP呈负相关，而与北极极区、贝加尔湖地区及日本以东洋面的SLP呈正相关；而与同期500hPa高度场的相关分布主要表现为自极地经鄂霍次克海至日本以东洋面的“＋-＋”的波列分布特征。第二模态与SLP和500hPa高度场的相关分布具有非常相似的空间分布形势，均表现为东北、朝鲜半岛、日本海一带与菲律宾洋面、鄂霍次克海地区的反位相分布，自低纬向高纬呈现“＋-＋”的波列分布特征。第三模态与SLP和500hPa高度场的相关分布，主要表现为菲律宾附近洋面、日本及以东洋面、贝加尔湖到亚洲北部的负正相间的分布形势。

Multi-spatial modes of anomalous East Asian summer monsoon activity

Based on the ERA40 reanalysis data, this paper explores the basic features of the multi-spa- tial-modes reflecting anomalous East Asian summer monsoon （EASM） activity and their relevant at- mospheric general circulation anomalies by using statistical methods, such as the correlation, composite and EOF analysis. Results suggest that： 1 ） There are three typical spatial modes of EASM with signifi- cant differences among them. The first mode represents an out-of-phase variation of summer wind be- tween the coastal area in eastern China as well as its adjacent ocean and the region to the west of the coastal area, which reflects the westward/eastward movement of EASM. And the second mode shows consistent variation of summer wind over the extensive areas, originating from South China, across the mid-lower reaches of the Yangtze River, Shangdong Peninsula, the Bay of Bohai Sea, to northeast Chinaand the Korean Peninsula, which represents the overall variation of EASM intensity. However, the third mode suggests an out-of-phase variation of summer wind between south China and the coastal area in East China,the Korean Peninsula, and northeast Asia ,reflecting the northward/southward movement of EASM. 2）The atmospheric general circulation anomalies related to the three spatial modes of EASM exhibit significant differences. The first mode bears negative correlations with SLP over South Asia and the Sea of Okhotsk, and positive correlations with SLP near the Arctic, Lake Baikal and the ocean east to Japan. The correlation between the first mode and summer 500 hPa geopotential height is featured by a ＂ ＋ - ＋ ＂ wave-train-like pattern from the polar region, across the Sea of Okhotsk, to the ocean east to Japan. The second mode shows very similar correlation patterns with both SLP and 500 hPa geopo- tential height, which represent an out-of-phase variation of SLP and 500 hPa geopotential height be- tween northeast China, the Korean Peninsula, the Sea of Japan and the Philippines as well as the Sea of Okhotsk, forming a ＂ ＋ - ＋ ＂ wave-train from the low latitudes to the high latitudes. The correlation patterns of the third mode with SLP and 500 hPa geopotential height are both alternated with positive and negative over the ocean around the Philippine, Japan as well as the ocean east to Japan, the Lake of Baikal, and northern Asia.