Different features of super and regular El Niño events and their impacts on the variation of the West Pacific Subtropical High

Using the NCEP/NCAR reanalysis, the GODAS ocean data and the Hadley sea surface temperature (SST) and National Climate Center (NCC) circulation indices data, the super and regular El Niño events are investigated with focus on the features of sea surface and subsurface layers as well as their possible impacts on the West Pacific Subtropical High (WPSH). It is demonstrated that for super El Niño events, positive sea surface temperature anomalies (SSTA) appear relatively earlier and develop faster with a stronger zonal gradient of SSTA. The maximum of positive SSTA is located in Nino3 region. However, for regular El Niño events, positive SSTA are located more westward and the zonal gradient of SSTA is weaker. During the El Niño episodes, the subsurface ocean temperature anomalies (SOTA) propagate eastward with Kelvin waves and reach up to the sea surface along the thermocline. The vertical currents in front of Kelvin waves play an important role in the change of SOTA. Stronger oceanic waves can be excited in the thermocline when air-sea couples more intensively, which are favorable for higher SOTA and thus possibly induce a super El Niño event. In both types of El Niño events, abnormal anticyclonic circulations are generated over the western Pacific and South China Sea due to the Gill-type responses. As the intensity of the anomalous atmospheric circulation forced by SSTA is closely related to the intensity of forcing sources, the WPSH is stronger in super El Niño cases than in regular ones. Besides, the lagged warming of SST in the Indian Ocean in response to El Niño is favorable for the persistence of atmospheric circulation anomalies in the Asian-Pacific region. These results are helpful for better understanding the features of different types of El Niño events and their impacts on the WPSH.