冬季北半球大气对秋冬季巴伦支海海冰异常的敏感性研究

Sensitivity of the boreal winter atmosphere to sea ice anomalies in autumn and winter over Barents Sea

中文关键词:  巴伦支海  海冰异常  环流  气温

英文关键词:The Barents Sea  Sea ice anomalies  Circulation  Temperature

中文摘要:

      基于ERA-Interim再分析资料，借助大气模式CAM4，分析了北半球冬季不同月份的平均大气对巴伦支海不同振幅及不同季节海冰扰动的敏感性，并考察了中高纬度典型大气模态的分布变化情况。结果表明，冬季巴伦支海海冰的减少，会导致湍流热通量异常向上、局地异常变暖及水汽含量的异常升高，且相关异常的强度和范围随着海冰减少幅度的减小而减弱。这种局地响应会通过大气环流调整扩散开来，产生远程影响。具体地，冬季大气环流与欧亚地面温度异常对于不同幅度海冰异常的响应是非线性的，且在不同月份也呈现出不同特征。秋季巴伦支海海冰减少虽未引起局地显著的温度异常，但欧亚大陆温度及环流场异常响应的强度更强、范围更广，这表明秋季海冰可以独立地对冬季中纬度大气产生影响。此外，冬季不同月份西伯利亚高压强度、位置对巴伦支海海冰减少的响应是不同的，北大西洋涛动位相的倾向变化对不同季节、不同振幅海冰减少的响应也不相同。冬季海冰减少时，12月和1月，西伯利亚高压强度更易偏强、位置易偏东，2月则与之相反。与冬季相比，秋季海冰偏少时，西伯利亚高压更易稳定维持在欧亚大陆，晚冬时发生北大西洋涛动负位相的概率增大，但出现极端负位相概率降低。这为了解巴伦支海海冰异常对北半球天气、气候的影响提供了参考。

英文摘要:

      Based on the ERA-Interim reanalysis data, sensitivity of the boreal winter atmosphere to sea ice anomalies with different amplitudes in autumn and winter over the Barents Sea is explored by boundary forcing the Community Atmosphere Model 4.0 (CAM4). Both the winter mean atmospheric responses and the typical modals at the mid-high latitudes are studied. The results show that sea ice loss over the Barents Sea in winter can generate anomalous upward turbulent heat flux, which warms the local lower atmosphere and increases local atmospheric moisture with the magnitudes and extents consistent with sea ice anomalies. Specifically, the responses of atmospheric circulation and surface air temperature over the Eurasian continent are nonlinear and change with time. Although the reduction of the Barents Sea ice in autumn does not cause significant local temperature anomalies in winter, it leads to stronger and wider temperature and circulation anomalies over the Eurasian continent. The results indicate that autumn sea ice change can independently affect the mid-latitude atmosphere in winter. In addition, the intensity and location of the Siberian high and the North Atlantic Oscillation（NAO）phases in different months during winter have different responses to the reduction of the Barents Sea ice. In December and January, the Siberian high tends to become stronger and shifts more eastward in response to winter sea ice loss over the Barents Sea, and opposite is true in February. However, with the sea ice loss in autumn, the Siberian high is more likely to be stationary. And the negative phase of NAO (NAO^-) occurs more frequently in late winter, but strong NAO^- occurs less frequently. The above results provide a reference for understanding the impact of the Barents Sea ice loss on weather and climate in the Northern Hemisphere.