Abstract
Using empirical orthogonal function (EOF) analysis of the monthly tropical Pacific subsurface ocean temperature anomalies (SOTA) from 1979 to 2014, we detected three leading modes in the tropical Pacific subsurface temperature. The first mode has a dipole pattern, with warming in the eastern Pacific and cooling in the western Pacific, and is closely related to traditional El Niño. The second mode has a monopole pattern, with only warming in the central Pacific subsurface. The third mode has a zonal tripole pattern, with warming in the off-equatorial central Pacific and cooling in the far eastern Pacific and western Pacific. The second and third modes are both related to El Niño Modoki. Mode 1 is linked with a Kelvin wave that propagates from the central to the eastern Pacific and is induced by the anomalous westerlies that propagate from the western to the central Pacific. Mode 2 is also linked with a Kelvin wave that propagates from the western to the central Pacific induced by the enhancement of westerlies over the western Pacific. Mode 3 is linked with a Rossby wave that propagates from the central to the western Pacific driven by the anomalous easterlies over the eastern Pacific.
Highlights
Centre observation datasets: EN4, quality-controlled subsurface ocean temperature (SOT) and salinity profiles and objective analyses[17]
Mode 1 is generated by a Kelvin wave that propagates from the central to the eastern Pacific
The monthly subsurface ocean temperature (SOT) data were obtained from the Met Office Hadley
Summary
Centre observation datasets: EN4, quality-controlled SOT and salinity profiles and objective analyses[17]. The data version number used in this study is EN4.1.1, and we downloaded the data on 8 August 2015. The data are available from 1900 until present, with 1° × 1° horizontal resolution and 42 levels in the vertical direction from 5 m to 5350 m. We chose a time period from Jan 1979 to Dec 2014 to avoid the possible influence of the climate shift in 197618,19. We selected a depth from 5 m-300 m (20 levels) to properly contain the thermocline. The Simple Ocean Data Assimilation Reanalysis dataset[20] (SODA version 2.0.2) was used to examine th
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