Contrasts of Bimodal Tropical Instability Waves (TIWs)-Induced Wind Stress Perturbations in the Pacific Ocean among Observations, Ocean Models, and Coupled Climate Models

The coupling between wind stress perturbations and sea surface temperature(SST)perturbations induced by tropical instability waves(TIWs) in the Pacific Ocean has been revealed previously and proven crucial to both the atmosphere and ocean. However, an overlooked fact by previous studies is that the loosely defined “TIWs” actually consist of two modes, including the Yanai wave-based TIW on the equator(hereafter eTIW) and the Rossby wave-based TIW off the equator(hereafter vTIW).Hence, the individual feedbacks of the wind stress to the bimodal TIWs remain unexplored. In this study,individual coupling relationships are established for both eTIW and v TIW, including the relationship between the TIW-induced SST perturbations and two components of wind stress perturbations, and the relationship between the TIW-induced wind stress perturbation divergence(curl) and the downwind(crosswind) TIW-induced SST gradients. Results show that, due to different distributions of eTIW and vTIW, the coupling strength induced by the eTIW is stronger on the equator, and that by the vTIW is stronger off the equator. The results of any of eTIW and vTIW are higher than those of the loosely defined TIWs. We further investigated how well the coupling relationships remained in several widely recognized oceanic general circulation models and fully coupled climate models. However, the coupling relationships cannot be well represented in most numerical models. Finally, we confirmed that higher resolution usually corresponds to more accurate simulation. Therefore, the coupling models established in this study are complementary to previous research and can be used to refine the oceanic and coupled climate models.

Journal of Oceanology and Limnology