Intraseasonal Perturbations in Sea Surface Temperatures of the Equatorial Eastern Pacific and Their Association with the Madden–Julian Oscillation*

Abstract

Abstract A particular pattern of intraseasonal perturbations in sea surface temperature (SST) is observed in the eastern Pacific Ocean following events of strong surface winds associated with the Madden–Julian oscillation (MJO). This intraseasonal SST pattern straddles at the equator with its longitudinal scales of 2–5 × 103 km and meridional scales of about 500 km. The amplitude of the perturbations is 0.5°C or greater. Positive and negative perturbations sometimes follow one another. They show tendencies of both eastward and westward movement. Such equatorially elongated perturbations in SST in the eastern Pacific are hypothesized to be caused by intraseasonal oceanic Kelvin waves forced by the MJO over the western/central Pacific. As the Kelvin waves propagate eastward, changes in the vertical temperature gradient in the upper ocean due to the fluctuations in the depth of the thermocline modify the thermal effect of the equatorial upwelling. As a result, mixed layer and surface temperatures may fluctua...