Effect of nonlinear advection on the Indian Ocean diploe asymmetry

Abstract

The asymmetry of sea surface temperature anomaly (SSTA) amplitudes between the positive and negative phases of the Indian Ocean dipole (IOD) are studied. The dynamic effects on it are analyzed using a hybrid coordinate ocean model (HYCOM). It suggests that the IOD is still asymmetric even when forced by a symmetric wind stress, and the asymmetry of the SSTA in the eastern pole is strong while that in the western pole is almost insignificant during the mature phase (September-November (SON)). Thus, the IOD asymmetry is primarily caused by the asymmetry in the IODE. A heat budget analysis is also conducted for the mixed-layer temperature in the eastern Indian Ocean (IODE), which indicates that a nonlinear ocean advection cools both the positive and negative IOD events. Therefore, the nonlinear ocean advection is responsible for the asymmetry of the IOD.