Indian Ocean Intraseasonal Variability in an Ocean General Circulation Model

Abstract

Abstract The impact of atmospheric intraseasonal variability on the tropical Indian Ocean is examined with an ocean general circulation model (OGCM). The model is forced by observation-based wind stresses and surface heat fluxes from an atmospheric boundary layer model. Composites of 26 well-defined boreal spring and summer intraseasonal events from 1985 to 1994 are used to explore surface and subsurface impacts of intraseasonal oscillations in the ocean. The phase and amplitude of simulated intraseasonal sea surface temperature (SST) variations agree well with observations. The net surface heat flux dominates the composite mixed layer heat budget on intraseasonal timescales, while entrainment through the base of the mixed layer contributes locally. Horizontal advection is of secondary importance in the composite heat balance. However, inspection of individual events suggests that in individual intraseasonal events different processes may control their dynamics. A characteristic feature of equatorial intr...