基于1962~2011年NCEP/NCAR逐日再分析资料,本文研究了北半球冬季南极涛动(Antarctic Oscillation,AAO)对欧亚大陆地表气温的影响及其物理过程。线性回归结果表明,在扣除冬季ENSO信号后,1月AAO与2月欧亚大陆地表气温呈显著正相关关系。当1月AAO处于正位相时,东南太平洋出现显著的位势高度正异常,这对应着南半球副热带高压的增强。该高度正异常在空间上从南半球向北扩展至北半球东太平洋地区,在时间上可一直持续到2月,它在南北半球相互作用过程中起重要作用。2月,北半球东太平洋高度正异常随高度向北倾斜,在对流层上层位于美国西南侧,该位置对应着北大西洋风暴轴入口处。进一步的相关分析表明,美国西南侧的高度正异常与地中海西北侧的瞬变波活动显著正相关,进而对应着斯堪的纳维亚半岛地区的高度负异常的形成。该负异常通过向下游频散波能量,引起贝加尔湖西侧高度正异常,形成典型的负位相斯堪的纳维亚环流型。该环流型对应60°N附近的西风异常,抑制了北侧冷空气南下,进而引起欧亚大陆地表气温正异常,反之亦然。
Based on the NCEP/NCAR daily reanalysis data over the period from 1962 to 2011, this study reveals the relationship between Antarctic Oscillation(AAO) and surface air temperature over the Eurasian continent during the boreal winter. The linear regression results show that after filtering out the El Nino–Southern Oscillation(ENSO) signal, the AAO in January is significantly and positively correlated with the air temperature over the Eurasian continent inFebruary. When a stronger AAO occurs in January, positive geopotential height anomaly appears over the southeastern Pacific and enhances the subtropical high in the southern Hemisphere. Furthermore, it extends northward to the eastern Pacific and persists from January to February, which acts as the key circulation in the inter-hemispheric interaction. In February, the eastern Pacific geopotential height anomaly tilts northward with altitude and anchors over southwestern America in the upper troposphere, which is right at the entrance of the climatological North Atlantic storm track. The geopotential height anomaly at southwestern America is positively correlated with the transient eddy activities over the northwestern Mediterranean Sea, which can trigger a negative geopotential height anomaly over the Scandinavian. Due to the downstream dispersion of wave energy originated from the Scandinavian geopotential height anomaly, positive anomaly develops to the west of the Lake Baikal and the negative phase of the Scandinavian pattern forms with increased westerlies around 60°N. The increased westerlies can suppress the southward invasion of cold air and thus are favorable for the development and maintenance of above-normal temperature over Eurasian continent, and vice versa.