Two types of El Niño and their related atmospheric and oceanic dynamics

Recent extensive studies on two types of El Niño, the Eastern-Pacific (EP) and Central-Pacific (CP) types, have led to a need for an in-depth understanding of their differences. Their related atmospheric and oceanic dynamics are investigated during 1958-2007 by using various datasets such as the Extended Reconstruction of Historical Sea Surface Temperature version 3 (ERSST V3), Atmospheric Model Intercomparison Project (AMIP) SST, and Simple Ocean Data Assimilation Reanalysis (SODA). Physically consistent patterns of wind stress, sea surface height, vertical structures of subsurface temperatures, salinity and currents in the upper tropical Pacific with each type of El Niño are obtained using the Cyclostationary Empirical Orthogonal Function (CSEOF) technique and multiple regression analysis. Comparisons between them allow us to better understand the atmospheric and oceanic dynamics related to the different types of El Niño. Recent increase of occurrence frequency of the CP El Niño will also be discussed.