Assessing feedback of tropical instability wave‐induced wind stress perturbations in the equatorial Pacific

Abstract

A close relationship between tropical instability wave (TIW)‐induced sea surface temperature (SST) and wind stress (τ) perturbations (SSTTIW and τTIW, respectively) has been identified from satellite observations. In this study, we applied an empirical TIW‐induced wind stress model (τ x, τ y)TIW=F(SST) to assess τTIW feedback. This empirical model solves (τ x, τ y)TIW from TIW‐induced wind stress divergence and curl estimated from time‐evolving downwind and crosswind SST gradients. The empirical model is incorporated into a high‐resolution ocean model based on the Regional Ocean Modeling System, and the derived (τ x, τ y)TIW can be added onto the climatological component to force the ocean model, by which the effect of τTIW can be taken into account adequately. From a comparison of two experiments with and without the τTIW effect, the τTIW had a substantial effect on the equatorial Pacific heat budget, which affected the long‐term mean SST, representing an approximate 0.2°C difference. An SST budget analysis suggested that the τTIW influenced SST primarily via thermal advection and vertical mixing, the effects of which were both amplified with additional τTIW feedback and almost counteracted each other. Analysis of two additional sensitivity experiments suggested that both TIW‐induced wind stress divergence and curl components could induce comparable SST differences, with a little difference on that the latter tended to induce more salient SST cooling at the equator.