[A-CG30] Multi-scale ocean-atmosphere interaction in the tropics

[ACG30-11] Asymmetry in sea surface temperature anomalies and atmospheric teleconnection associated with the Indian Ocean Dipole

Mai Nakazato¹, Shoichiro Kido², *Tomoki Tozuka^1,2 (1.Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 2.Application Laboratory, Research Institute for Value-Added-Information Generation, Japan Agency for Marine-Earth Science and Technology)

Keywords:Indian Ocean Dipole, Mixed layer heat budget analysis, Atmospheric teleconnection, Tropical Indian Ocean

One of the important features of the Indian Ocean Dipole (IOD) is its asymmetry; negative sea surface temperature (SST) anomalies in the eastern pole during the positive IOD are stronger than positive SST anomalies during the negative IOD. Based on an online mixed layer heat budget analysis using the Regional Ocean Modeling System, it is shown that the vertical diffusion term plays an important role in generating this asymmetry in addition to the contributions from the nonlinear advection and the thermocline feedback proposed by some previous studies. To understand the origin of the asymmetry in the vertical diffusion term, a detailed decomposition is carried out. It is found that the asymmetry is primarily explained by differences in subsurface temperature anomalies; during positive IOD events, anomalous cooling below the mixed layer contributes to SST cooling via vertical mixing. However, such effects are weaker in the case of negative IOD events due to weaker subsurface temperature anomalies. Furthermore, analyses of the Rossby wave source and wave activity fluxes suggest that the SST asymmetry in the IOD indeed have asymmetric impacts on the mid-latitudes via atmospheric teleconnection.