南极极涡与南极涛动对大气环流异常影响的统计分析

Statistical Analysis of the Effects of the Antarctic Polar Vortex and the Antarctic Oscillation on Atmospheric Circulation Anomalies

摘要: 本文利用1979~2018年7~9月NCEP/NCAR月平均再分析资料和AAO指数，分析了季节平均时间尺度南极极涡和南极涛动与南半球大气环流异常和南半球向北的越赤道气流的关系。研究发现，南极极区500 hPa位势高度异常EOF分解第一模态可反映南极涛动的位相变化，第二模态反映极涡“偏心”形态分布。南极涛动的不同位相对应的极地外西风带内大气环流异常具有明显的区域特征，并非呈环状分布。极地与极地外冷暖空气交换的关键区域主要在南印度洋至澳大利亚南部，南太平洋以及南美洲东部大西洋上空，其中南印度洋上空与极地的冷暖空气交换最为显著。当极涡偏向西半球时，极涡与南太平洋上空和南美洲南部的冷空气活动联系更密切。季节平均时间尺度南极极涡与季风环流强度具有密切的联系，当极区位势高度偏高，极涡偏弱时，季风环流增强。

Abstract: Based on the NCEP/NCAR monthly mean reanalysis data from Jul to Sep in 1979~2018 and the AAO index, this paper analyzes the relationship between the Antarctic Polar Vortex and the Antarctic Oscillation on the seasonal time scale and the Southern Hemisphere atmospheric circulation anomalies and the southern hemisphere northward cross-equatorial flow. It is found that the first mode of EOF decomposition can reflect the phase change of the Antarctic Oscillation, and the second mode can reflect the eccentricity distribution of the polar vortex. The anomaly of the atmospheric circulation in the outer westerly zone corresponding to the different phases of the Antarctic Oscillation has obvious regional characteristics and is not distributed as a ring. The key regions of cold and warm air exchange between polar and extra-polar regions are mainly from the southern Indian Ocean to the southern part of Australia, the southern Pacific Ocean and the Atlantic Ocean over the eastern part of South America, among which the cold and warm air exchange between the southern Indian Ocean and the polar region is the most significant. When the polar vortex is tilted over the Western Hemisphere, it is more closely associated with cold air activity over the South Pacific and southern South America. The intensity of Asian monsoon circulation is closely related to the Antarctic polar vortex. When the polar potential height is high, which means that the polar vortex is weak, the 55˚E~65˚E cross-equatorial airflow from south to north increases, and the intensity of Asian monsoon circulation increases.