Upper ocean heat budget in the western Pacific warm pool in response to Maden-Julian Oscillation

Upper ocean heat budget associated with the atmospheric Maden-Julian Oscillation (MJO) in the western equatorial Pacific is examined using a tropical Pacific basin model (Gent and Cane, 1989). The model is forced with surface fluxes associated with 10 well-defined MJO events from the period 1986-93. Surface fluxes were estimated from gridded operational analyses and independent satellite data.

10-events composite of the model results was formed. The simulated composite SST agrees well with the observed composite from the weekly SST analyses. Also, the intraseasonal SST variation from the model agrees reasonably well with SST observed at a mooring during TOGA COARE. The eastward jet is generated 140E-150E on the equator and it reaches the dateline during the active convective phase of MJO. The heat budget of the warm pool is calculated from the model output in order to investigate the role of 3-dimensional processes in driving the intraseasonal SST variability produced by the MJO. While horizontal advection of heat is locally large, it is incoherent on the scale of MJO. It is confirmed that the intraseasonal SST variation in the western Pacific warm pool is primarily controlled by the surface heat flux variation.

During COARE, intraseasonal Kelvin waves are generated by westerly winds in the western Pacific and they propagate to the east of 140W. The upper ocean heat budget associated with the intraseasonal Kelvin waves in the central Pacific is also calculated. The zonal heat advection and strong vertical mixing of colder water below due to the anomalous upwelling associated with kelvin waves significantly affect the SST.