Intraseasonal Oscillations during the TOGA-COARE IOP

Abstract

We examined the behavior of the convective activity and other meteorological variables such as divergence, velocity potential and total precipitable water, associated with the intraseasonal oscillation (ISO) during the TOGA-COARE IOP from November 1992 to February 1993.
During the IOP, there are two major ISOs, one in December and another in January. We confirmed that there is a hierarchic structure of the tropical convection: planetary-scale ISO, eastward-moving synoptic-scale super cluster, and westward-moving meso-scale cloud cluster. Each ISO has two super clusters. The maximum of the total precipitable water (tpw) delineated from the SSM/I data is leading the convective activity from the GMS IR TBB data by about 5-10 days. The SST is also leading the convection about by 12-13 days, which is the same as for previous results.
We also checked the surface radiation budget. The SST change is closely related with the ISO passage. The clear sky and the calm wind condition leads to the warming up of the SST east of the active convection associated with the ISO (that is, before the passage of the active convection of the ISO). During the passage of the active convection associated with the ISO, the SST decreases due to less insolation and enhanced latent heat flux from the sea surface under the disturbed wind condition.