冬季极赤温差年际变化及其与东亚气候异常的联系
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.