Influence of the Preceding Austral Summer Southern Hemisphere Annular Mode on the Amplitude of ENSO

• 作 者: Fei ZHENG Jianping LI Ruiqiang DING
• 机 构: State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,I
• 出 处: Advances in Atmospheric Sciences
• 发表日期: 2017年11期
• 关键词: Southern Hemisphere Annular Mode ENSO Southern Ocean Dipole

There is increasing evidence of the possible role of extratropical forcing in the evolution of ENSO.The Southern Hemisphere Annular Mode(SAM) is the dominant mode of atmospheric circulation in the Southern Hemisphere extratropics.This study shows that the austral summer(December–January–February; DJF) SAM may also influence the amplitude of ENSO decay during austral autumn(March–April–May;MAM).The mechanisms associated with this SAM–ENSO relationship can be briefly summarized as follows:The SAM is positively(negatively) correlated with SST in the Southern Hemisphere middle(high) latitudes.This dipole-like SST anomaly pattern is referred to as the Southern Ocean Dipole(SOD).The DJF SOD,caused by the DJF SAM,could persist until MAM and then influence atmospheric circulation,including trade winds,over the Nio3.4 area.Anomalous trade winds and SST anomalies over the Nio3.4 area related to the DJF SAM are further developed through the Bjerkness feedback,which eventually results in a cooling(warming) over the Nio3.4 area followed by the positive(negative) DJF SAM.

There is increasing evidence of the possible role of extratropical forcing in the evolution of ENSO.The Southern Hemisphere Annular Mode (SAM) is the dominant mode of atmospheric circulation in the Southern Hemisphere extratropics. This study shows that the austral summer (December-January- The mechanisms associated with this SAM-ENSO relationship can be briefly summarized as follows: The SAM is positively (negatively) correlated with SST in the Southern Hemisphere middle (high) latitudes. This dipole-like SST anomaly pattern is referred to as the Southern Ocean Dipole (SOD). The DJF SOD, caused by the DJF SAM, could persist until MAM and then an air circulation , including trade winds, over the Nio3.4 area. Nomalous trade winds and SST anomalies over the Nio3.4 area related to the DJF SAM are further developed through the Bjerkness feedback, which eventually resu lts in a cooling (warming) over the Nio3.4 area followed by the positive (negative) DJF SAM.