Different impacts of two type El Niño on the Western North Pacific summer monsoon

This study examines the different impacts of two type El Niño events ,the Eastern Pacific El Niño (EP-EL) and the Central Pacific El Niño (CP-EL), on the Western North Pacific summer monsoon (WNPSM) based on the observations and numerical experiments. It is found that the major difference of WNPSM occurs during the El Niño developing year. That is, the retreating of WNPSM of both types El Niño is significantly earlier than the climatological mean in El Niño developing year. The retreating of EP-EL is about two pentads earlier than that of CP-EL. The differences of the onset of WNPSM between the two types El Niño, however, are insignificant. Thus, the duration of WNPSM during EP-EL is significantly shorter that during the CP-EL. This difference is attributed to the change of the Western North Pacific High, occurring in boreal autumn, shifts westward during CP-EL compared to that during EP-EL. The AGCM experiments suggest that the warm equatorial Pacific SST (sea surface temperature) anomaly shifts westward and the warming trends of SST over western Pacific during CP-EL compared to that of EP-EL are crucial to result in the above difference.