南极涛动和北半球大气环流异常的联系

使用ECMWF逐日再分析资料分析研究了北半球冬季南极涛动和北半球大气环流异常之间的联系。资料的分析结果表明, 南极涛动和滞后其25～40天位于北大西洋地区的一个弱的类似于北大西洋涛动 (North Atlantic Oscillation, 简称NAO) 的偶极子模态, 以及伴随这一偶极子模态而出现的北半球中纬度纬向风异常之间存在着统计上的联系。处于正 (负) 位相的南极涛动对应着滞后25～40天后, 北大西洋高纬极区出现位势高度负 (正) 异常, 副热带大西洋出现位势高度正 (负) 异常; 同时, 在北半球中高纬度地区(45°N～65°N) 出现西 (东) 风异常, 中低纬度地区(25°N～40°N)出现东 (西) 风异常。文中也对资料分析结果进行了简单的动力学分析, 表明与南极涛动相联系的涡动动量异常是驱动北半球纬向平均纬向风异常的主要原因。

The Linkages between the Antarctic Oscillation and the Northern Hemisphere Circulation Anomalies

Using ECMWF daily reanalysis data, this paper investigates the linkages between the Antarctic Oscillation (AAO) and the tropospheric circulation anomalies of the Northern Hemisphere (NH) during Northern winter. Statistical analyses show that the AAO is associated with a weak but significant North Atlantic Oscillation (NAO)-like dipolar pattern accompanied by anomalous zonal-mean zonal wind over the North Atlantic lagging 25－40 days during boreal winter. Positive (negative) phase of the AAO corresponds to anomalous low (high) geopotential height over the Arctic and anomalous high (low) geopotential height over the subtropical Atlantic accompanied by anomalous westerlies (easterlies) in middle－high latitudes (45°N－65°N) and anomalous easterlies (westerlies) in middle-low latitudes (25°N－40°N) of the troposphere. These results indicate that the AAO has some linkages with the NH tropospheric circulation anomalies during Northern winter. And the simple dynamic diagnoses also indicate that the anomalous eddy momentum flux associated with the AAO tends to cause the emergence of the anomalous NH zonal-mean zonal wind.