冬季亚洲—太平洋涛动年际变率与东亚气候异常

利用1948—2011年NCEP/NCAR月平均再分析资料和1951—2010年我国160站降水量资料，研究了冬季亚洲—太平洋区域的大气遥相关及其与东亚冬季风和降水的关系。结果表明:冬季在亚洲—西太平洋与中、东太平洋中低纬度对流层上层扰动温度之间存在类似于夏季的亚洲—太平洋涛动 (APO) 现象，即当东亚中低纬度对流层中、上层偏暖时，中东太平洋中低纬度对流层中上层温度偏冷，反之亦然。冬季APO可以反映冬季亚洲—太平洋东西向热力差异强度变化，与夏季相比，冬季APO遥相关在亚洲的中心位置略偏南、偏东，且冬季APO与大气环流关系与夏季也有所不同；当冬季APO指数偏高时，对流层上层东亚大槽位置偏西，而东亚热带地区的高压向北伸展，导致我国南方对流层为深厚的异常反气旋系统所控制，此时南方地区对流层低层盛行异常的偏东北气流，并伴随水汽辐散和异常下沉运动，南方降水偏少；冬季APO指数与ENSO有紧密联系。

Inter-annual Variability of Winter Asia-Pacific Oscillation and Its Relationship with the East Asian Climate Anomalies

Using 1948-2011 NCEP/NCAR monthly reanalysis data and 1951-2010 precipitation data at 160 meteorological stations of China, the empirical orthogonal function (EOF), correlation analysis and composite analysis methods, the winter (December, January and February) atmospheric teleconnection over the Asian-Pacific and its association with East Asian winter monsoon and precipitation are examined. Results show an Asian-Pacific Oscillation (APO) teleconnection in upper-tropospheric temperature disturbance between the Asian-western Pacific and the central-eastern Pacific region during winter, which is similar to the APO phenomenon during summer. When the mid-upper troposphere temperature in mid-lower latitudes of East Asia is warmer, it is colder in mid-lower latitudes of the central and eastern North Pacific, and vice versa. The APO reflects the variability of the zonal thermal contrast between Asia and North Pacific. Compared to summer, the Asian anomalous center of DJF APO is southward and eastward in position. DJF APO index does not show a significant linear trend. The power spectrum analysis shows that the APO index has the varying periods of 2-6 years. Corresponding to a higher APO index, geopotential height disturbance in mid-upper tropospheres is lower in mid-higher latitudes of East Asia and it is higher in mid-higher latitudes of central and eastern North Pacific. Also, there is a "seesaw" in lower latitudes between the Asian-western Pacific region and the central-eastern Pacific, but with a reversed phase comparing to that in higher latitudes. This anomalous feature in geopotential height in the upper troposphere indicates a westward long-wave trough in East Asia and a northward high pressure in the tropics of East Asia, with a deep anti-cyclonic anomaly over southern China. Wind anomalies of northeasterly prevail over southern China in the lower troposphere, with divergence anomalies of water vapor and downward motion anomalies in southern China. Accordingly, the local precipitation decreases. However, these relationships between DJF APO and atmospheric circulation are different from those during summer. Moreover, the APO index is highly correlated with ENSO as well.