Simulation of interannual SST variability in the tropical Indian Ocean

A 2.5-layer thermodynamic ocean model is used to investigate interannual variability in sea surface temperature (SST) of the tropical Indian Ocean. Simulated SST agrees well with the data. Model and observed SSTs exhibit large seasonal and interannual variability in the western and southeastern tropical Indian Ocean. Three processes, namely, latent heat flux, radiative Aux, and entrainment, play major roles in the evolution of model SST anomalies. Interannual heat flux is found to have greater influence on the SST anomalies in most parts of the model domain. On the other hand, influence of interannual wind is only pronounced near the coasts in the Arabian Sea during the Asian summer monsoon season and a region in the central part of the southern tropical Indian Ocean (STIO) during boreal winter Besides the El Nino-Southern Oscillation related basinwide warming, empirical orthogonal function analysis shows a dipole structure in both model and observed SST anomalies in the STIO. The eastern pole is anomalously cold with a peak occurring 4-8 months prior to the negative peak of the Southern Oscillation. A similar dipole structure in the latent heat flux anomalies explains the dipole in the SST anomalies.