Upper-Ocean Heat Budget in Response to the Madden–Julian Oscillation in the Western Equatorial Pacific

Abstract

The upper-ocean heat budget in response to the atmospheric Madden?Julian oscillation (MJO) in the western equatorial Pacific is examined using a tropical Pacific basin general circulation model. 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 from the European Centre for Medium-Range Weather Forecasts and independent satellite data. A 10-event composite of the model results was formed. The simulated composite SST agrees well with the observed composite from weekly SST analyses. Also, the simulated intraseasonal SST variation for the large MJO event during TOGA COARE (December 1992) agrees reasonably well with SST observed at a mooring. The strong equatorial jet associated with this MJO event is also well simulated. The heat budget of the warm pool is calculated from the model output in order to investigate the role of three-dimensional processes in driving the intraseasonal SST variability. Although 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 and vertical processes.