Modulation of the late summer Northeast China cold vortex by previous-winter ENSO

Abstract

The modulation of the late-summer Northeast China cold vortex (NCCV) by previous-winter El Niño–Southern Oscillation (ENSO) is investigated using reanalysis data. A significant correlation dominates in the ENSO–NCCV relationship, with El Niño (La Niña) accompanied by a weak (strong) NCCV intensity. The Indian Ocean basin mode (IOBM) plays an essential role in relaying the impact of pre-winter ENSO on the following late-summer atmospheric circulation over Northeast Asia. A positive IOBM responds passively to eastern Pacific–type El Niño and can last till late summer when El Niño has already decayed. It triggers a meridional teleconnection pattern of the cyclone over central China and anticyclone over Northeast Asia, and thereby enables a background circulation adverse to the generation of the NCCV, and vice versa. In addition, the signals of the Indian Ocean during central Pacific–type El Niño and neutral years are extremely weak, which makes their effect on NCCV generation insignificant.

摘要

本文利用再分析资料, 研究了前冬ENSO对夏末东北冷涡 (NCCV) 的调制作用. 结果表明, 前冬ENSO与夏末NCCV强度之间存在显著的相关性, El Niño (La Niña) 对应于弱 (强) 的NCCV. 印度洋海盆模态 (IOBM) 在前冬ENSO对夏末东北亚地区大气环流的影响中起着至关重要的作用. 作为东部型El Niño的被动响应, IOBM可以从前冬一直持续至夏末, 并在夏末激发“中国中部上空气旋—东北亚地区上空反气旋”的经向遥相关模态, 从而不利于NCCV增强. 反之亦然. 此外, 印度洋的信号在中部型El Niño和中性年份相对较弱, 使得它们对于NCCV的影响不显著.