利用美国国家环境预报中心/大气研究中心(NCEP/NCAR)再分析资料, 定义了冬季极赤温差(temperature difference between polar and equatorial regions, TDPE)指数, 分析了地面以上2 m 处极赤温差指数(I_(TDPE-S))的年际变化及其与同期东亚冬季降水、气温的关系. 结果表明:I_(TDPE-S)可反映出全球变暖过程中北半球高纬地区冬季地面温度显著升高, 且在年际时间尺度上存在4~8 a的周期变化. I_(TDPE-S)与东亚冬季降水和气温存在很好的相关. 当I_(TDPE-S)偏高(偏低)时, 中国东北、新疆、河西走廊、日本海以及南中国海到菲律宾岛地区冬季降水增加(减少), 对应着中国华北到东北地区冬季平均气温降低(升高). 进一步研究发现, I_(TDPE-S)高值年, 东亚中纬度地区异常水汽主要来自西北太平洋, 低纬度地区降水异常时的水汽主要来自热带海洋上空.水平温度平流引起的异常降温可部分解释东亚中纬度地区冬季平均气温异常偏低. 这些结果对深刻认识大气环流异常的形成机理及其影响具有重要意义.
英文摘要:
Based on NCEP/NCAR reanalysis data, we develop an index of the temperature difference between polar and equatorial regions (TDPE) and investigate interannual variability of this index (I_(TDPE-S)) at 2 m height above the surface, in relation to winter rainfall and temperatures over East Asia. Results suggest that I_(TDPE-S) is able to reveal the remarkable increase of winter surface temperature at boreal high latitudes during global warming, with 4-8 year periodic variation. I_(TDPE-S) correlates well with winter rainfall and temperature in East Asia. As the index increases (decreases), winter precipitation increases (decreases) over Northeast China, Xinjiang,the Hexi Corridor, Sea of Japan, South China Sea, and the Philippines, corresponding to a drop (rise) of winter mean temperature in northern and northeastern parts of China. Further study reveals that in years of higher I_(TDPE-S), anomalous water vapor in mid-latitude East Asia originates mainly from the western North Pacific. Water vapor related to rainfall anomalies at the low latitudes has its origin mainly in tropical oceans. A horizontal temperature advection-caused anomalous reduction of temperature partially explains an abnormally low mean temperature in winter at mid-latitude East Asia. These results are important for in-depth understanding of the formation mechanisms and effects of atmospheric circulation anomalies.