Distinct impacts of two kinds of El Niño on precipitation over the Antarctic Peninsula and West Antarctica in austral spring

Abstract

Based on multiple reanalysis data, the authors investigated the distinct impacts of central Pacific (CP) and eastern Pacific (EP) El Niño events on precipitation over West Antarctica and the Antarctic Peninsula in austral spring (September–November). The results demonstrate that EP and CP events have similar impacts on precipitation over the Amundsen–Bellingshausen seas, but opposite impacts on that over the Weddell Sea, especially the Antarctic Peninsula. Mechanistically, the tropical heat sources associated with EP events drive two branches of Rossby wave trains, causing an anomalous anticyclone and cyclone over the Ross–Amundsen–Bellingshausen seas and the Weddell Sea, respectively. Anomalous southerly winds to the east (west) of the anomalous anticyclone (cyclone) advect colder and drier air into the Bellingshausen–Weddell seas and the Antarctic Peninsula, which jointly result in negative precipitation anomalies there. CP events, however, trigger only one weak and westward-shifted Rossby wave train, which induces an anomalous anticyclone and cyclone in the Ross–Amundsen seas and Bellingshausen–Weddell seas, respectively, both 20°–30° west of those generated by EP events. Consequently, anomalous northerly (southerly) winds to the east (west) of the anomalous cyclone cause an increase (a decrease) in precipitation over the Weddell Sea (Amundsen–Bellingshausen seas).摘要本文基于多种再分析资料, 研究了中部型 (CP) 和东部型 (EP) El Niño事件对南半球春季 (9–11月) 西南极和南极半岛降水的不同影响. 结果显示, EP和CP事件对阿蒙森-别林斯高晋海的降水具有相似影响, 而对威德尔海, 特别是南极半岛的降水影响相反. 由于EP事件激发两支罗斯贝波列, 分别引起罗斯-阿蒙森-别林斯高森海和威德尔海上空的异常反气旋和气旋, 从而导致别林斯高晋-威德尔海和南极半岛受到干冷的异常偏南风影响, 降水减少. 然而, CP事件仅激发一支相对较弱且偏西的罗斯贝波列, 分别引起罗斯-阿蒙森海和别林斯高晋-威德尔海上空的异常反气旋和气旋, 从而导致南极半岛以西 (东) 受异常偏南 (北) 风影响, 降水减少 (增加).