摘要:本文利用美国航空航天局戈达德空间研究所地表气温、美国国家海洋和大气局—环境科学协作研究所20世纪再分析资料，以及第六次国际耦合模式比较计划的多模式Historical试验结果，去除外强迫影响后，研究1910/1911～2019/2020年冬季（DJF）欧亚中高纬地区“暖北极—冷欧亚”（WACE）模态的年代际变化特征及其物理原因。结果表明：WACE具有显著的年代际变化，在WACE正位相时期，乌拉尔阻塞发生频率偏高，有利于热量向极区输送使得极区出现异常暖平流，且水汽向极区输送导致极区水汽辐合，向下长波辐射增加，另外对流活动增强导致潜热释放，进而极区温度上升。与此同时，极涡及欧亚大陆西风减弱且乌拉尔阻塞发生频率偏高，有利于冷空气侵袭欧亚大陆造成异常冷平流，且欧亚地区水汽辐散，向下长波辐射减少，对流活动减弱进而潜热释放减少，导致欧亚大陆温度降低。最后利用CAM3.0大气环流模式模拟了北大西洋海温正异常对WACE的影响，模式结果与统计结果相符合，进一步说明了北大西洋海温正异常可以通过强迫低层与高层大气环流异常，导致极区水汽辐合，欧亚大陆水汽辐散，进而影响WACE的年代际变化。
关键词:暖北极—冷欧亚/
北大西洋海温/
年代际变化/
物理机制
Abstract:Based on the surface air temperature datasets from NASA (National Aeronautics and Space Administration)’s Goddard Institute for Space Studies, 20th century’ s reanalysis data from National Oceanic and Atmospheric Administration–Cooperative Institute for Research in Environmental Sciences, and the historical experiments of the Coupled Model Intercomparison Project Phase 6, this study analyzes the interdecadal variation characteristics of the Warm Arctic–Cold Eurasia (WACE) mode in the Eurasia and Arctic region from 1910/1911 to 2019/2020 during the boreal winter after removal of external forcing. The results show that the WACE displays remarkable interdecadal variability. When WACE is in the interdecadal positive phase, the high-frequency Ural block favors heat transport to the polar regions, leading to warm advection and water vapor transport. This, in turn, causes water vapor convergence in the polar region, leading to an increase in downward long-wave radiation and an increase in convective activity and latent heat release. This results in increasing temperatures in this region. At the same time, the weakening of the polar vortex and westerly winds in Eurasia and the high-frequency of Ural blockage favor cold air advection into Eurasia. Divergence of water vapor in Eurasia reduces downward long-wave radiation, leading to decreased convective activity and latent heat release, which in turn decreases the temperatures in Eurasia. The authors used the CAM3.0 atmospheric circulation model to simulate the North Atlantic SST (Sea Surface Temperature) influence on WACE. Model results are consistent with the statistical results, further illustrating that the North Atlantic SST positive anomaly can force the lower and upper atmospheric circulation anomalies, leading to water vapor convergence in the polar regions and divergence in Eurasia, thus affecting decadal variability of WACE.
Key words:Warm Arctic–Cold Eurasia/
North Atlantic Sea Surface Temperature/
Interdecadal variation/
Physical mechanism
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