Different impacts of the two types of El Niño on Asian summer monsoon onset

In this study, we investigate the features of Asian summer monsoon onset during the decaying phases of central Pacific (CP) and eastern Pacific (EP) types of El Niño. The Asian summer monsoon onset is late during the EP El Niño while it is generally normal during the CP El Niño. Compared to the CP El Niño, the EP El Niño exerts a stronger impact on the climate over the Indian Ocean and the western North Pacific. Warmer sea surface temperature (SST) develops in boreal spring in the southern Indian Ocean and thus forms a large cross-equatorial SST gradient during the EP El Niño, which induces asymmetric patterns of winds and precipitation over the Indian Ocean. The asymmetric precipitation and circulation patterns contribute to a late monsoon onset. In addition, the anomalous anticyclone over the western North Pacific during the EP El Niño also contributes to late onset of the monsoon. (letter)