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

The modulation of the late-summer Northeast China cold vortex (NCCV) by previous-winter El Niho-Southern Oscillation (ENSO) is investigated using reanalysis data. A significant correlation dominates in the ENSO-NCCV relationship, with El Niho (La Niha) 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 Niho and can last till late summer when El Niho 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 Niho and neutral years are extremely weak, which makes their effect on NCCV generation insignificant.