Spatio-temporal structure of SST in El Niño regions and its relationships with zonal displacement anomaly of western Pacific warm pool

Using the monthly averaged NOAA PSD optimal interpolation sea surface temperature (OISST) data from December 1981 to April 2009, this paper adopted the empirical orthogonal function and power spectral density to analyzing the SST fields' spatial-temporal structure of El Niño1, El Niño2, El Niño3 and El Niño4, respectively. The first modal analysis has shown that: (1) time coefficients of El Niño1, El Niño3 and El Niño4 are well associated with zonal displacement anomalies at eastern edge of western Pacific warm pool (WPWP), and the main periods of the coefficients are almost same as ENSO with about 57 months. But the time coefficient of El Niño2 does not show this characteristic in term of time cycle; (2) the corresponding spatial structure of SST fields of El Niño1 and El Niño2 distributes along the northwest 45° with the positive center at northeast and the negative center at southwest, and El Niño3 region and El Niño region 4 distributes longitudinally along 2°N with transformation of positive to negative from right to left. Also, the correlation analysis between zonal displacement anomalies at eastern edge of western Pacific warm pool and ENSO indices has shown that the former is ahead of about a 2-month leading of El Niño indices in the duration of El Niño, while during the La Niña, the former lags behind about a 4/5-month of La Niña indices.