92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Thursday, 26 January 2012: 2:45 PM
Natural Variations of Central Pacific El Niņo: Statistical Evidence
Room 354 (New Orleans Convention Center )
Jin-Soo Kim, Seoul National University, Seoul, South Korea; and K. Y. Kim and S. W. Yeh

Spatial patterns and principal component (PC) time series of the Eastern Pacific (EP) El Niņo and the Central Pacific (CP) El Niņo were extracted via cyclostationary Empirical Orthogonal Function analysis from recent 60-year (1951-2010) observed Sea Surface Temperature (SST) data sets in the tropical Pacific. Evolution patterns obtained from the several data sets are nearly similar: EP and CP El Niņo patterns explain about 50%, and 10%, respectively. Recent extensive studies claimed that CP El Niņo has occurred more frequently and strongly because of increased SST over the West Pacific Warm Pool and Niņo4 region since 1990s. However, PC time series of the CP El Niņo have not significantly changed before and after 1990s. Since the 1990s, two types of El Niņo are in phase although their phases appear to be statistically independent based on the 60-year data sets. For this reason, superposition of two types of El Niņo results in significant warming in the Central Pacific during the past twenty years and this is interpreted as the strengthening of CP El Niņo in recent years. A similar analysis is conducted on the Geophysical Fluid Dynamics Laboratory Climate Model version 2.1 pre-industrial conditions 500-year control run data, and the results are generally consistent with those from the observational dataset, which suggests that CP El Niņo is one of natural physical modes occurring in the equatorial climate system.

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