Interannual variations of North Equatorial Current transport in the Pacific Ocean during two types of El Nino

Interannual variations of Pacific North Equatorial Current(NEC) transport during easternPacific El Ni?os(EP-El Ni?os) and central-Pacific El Ni?os(CP-El Ni?os) are investigated by composite analysis with European Centre for Medium-Range Weather Forecast Ocean Analysis/Reanalysis System 3.During EP-El Ni?o,NEC transport shows significant positive anomalies from the developing to decay phases,with the largest anomalies around the mature phase.During CP-El Ni?o,however,the NEC transport only shows positive anomalies before the mature phase,with much weaker anomalies than those during EP-El Ni?o.The NEC transport variations are strongly associated with variations of the tropical gyre and wind forcing in the tropical North Pacific.During EP-El Ni?o,strong westerly wind anomalies and positive wind stress curl anomalies in the tropical North Pacific induce local upward Ekman pumping and westward-propagating upwelling Rossby waves in the ocean,lowering the sea surface height and generating a cyclonic gyre anomaly in the western tropical Pacific.During CP-El Ni?o,however,strength of the wind and associated Ekman pumping velocity are very weak.Negative sea surface height and cyclonic flow anomalies are slightly north of those during EP El Ni?o.