A closer look at the central Pacific El Nino and warm pool migration events from 1982 to 2011

In recent years, it has been observed that there are different types of El Nino events. The warm events can be divided into two categories: those centered in the central Pacific (CP) and those centered in the eastern Pacific (EP). We examined the variability of western Pacific warm pool (WPWP) horizontal migration and size from January 1982 to December 2011 by applying Ensemble Empirical Mode Decomposition (EEMD) and Hilbert-Huang Spectrum (HHS) to the optimally interpolated sea surface temperature (OISST) data set. The analysis shows that the long-term residual trend of the zonal centroid movement is migrating to the west by 3.78 degrees from the mean location during the past 30 years. The size of the warm pool has also increased 18% during this period. These analysis techniques isolated two separate time series for the migration of the zonal component of the WPWP for both CP and EP events and showed that these two types of El Nino generally operate at different time scales. The EP time series shows the strong traditional EP El Nino and the transition between strong El Nino conditions and La Nina conditions. The CP time series shows that CP El Ninos occur more often than EP El Ninos. The changes of El Nino type in conjunction with westward drift and increasing warm pool size shows an interesting multidecadal change in the warm pool. Potential mechanisms relating the Pacific Decadal Oscillation to El Nino typologies were also discussed. Key Points Analysis of 30 yrs of SST data HHT/EEMD analysis of data Investigated CP and EP time-series of El Nino