一个适用于描述中国大陆冬季气温变化的东亚冬季风指数

利用1951年1月-2007年2月的NCEP V1格点资料和中国台站观测资料,定义了一个冬季风环流指数(IEAWM),并分析其与中国冬季气温和东亚大气环流变化的联系.结果表明该指数能够很好地反映东亚冬季风系统各成员的变化,兼顾北方和南方的环流状况和东西部热力差异的影响,改进了原有冬季风指数大多针对单一的冬季风环流成员及对中国冬季气温变化反映能力的不足,能够很好地反映中国冬季平均气温的异常变化.分析表明,当该指数为正值时东亚冬季风偏强,对应着地面西伯利亚高压和高空东亚大槽均偏强,东亚地区对流层中层的高-低纬度之间的纬向风经向切变加强,有利于中高纬度冷空气向南侵入,导致中国大陆地区气温偏低,反之亦然.IEAWM的年代际变化表明东亚冬季风在1985年之前偏强,1985年之后明显偏弱,这与1985年之后中国冬季变暖是一致的.

An index of East Asian winter monsoon applied to description the Chinesemainland winter temperature changes

Using the NCEP/NCAR reanalysis data (Version 1) and the observation data of China from January 1951 to February 2007, a new index of East Asian winter monsoon circulation (IEAWM) was defined based on comparison of previous different winter monsoon indices and circulation factors influencing the winter climate over china. Its relationships with winter temperature over China and large-scale circulation were analyzed. Results show that new index represents very well the winter temperature over China and the East Asia winter monsoon (EAWM) system. This index reflects the integrated effect of the circulations over high and low latitudes and the thermal difference between the continent and the ocean. While in the previous studies, most monsoon indices only describe the single monsoon member. The IEAWM is a good indicator of the intensity of the EAWM. Positive values of IEAWM correspond to strong EAWM, stronger than normal Siberian high and East Asian trough, and the strengthening of the meridional shear of 500 hPa zonal wind between high and low latitudes over East Asia, and therefore, the southward cold advection becomes strong and leads to the decrease in surface temperature over China; and vice versa. The obviously interdacal change is found in the IEAWM that it is positive before the mid 1980s, but negative since the mid 1980s, in good agreement with the fact of the winter warming in China after 1985.