An SST-Based Reconstruction of the Pacific Tropical Instability Wave–Associated Velocities and SSH since 1981

Abstract Tropical instability waves (TIWs) are a prominent mesoscale feature observed in satellite sea surface temperature (SST) fields over the equatorial Pacific Ocean. This study develops an SST conservation model to estimate the meridional velocities associated with TIWs ( υ ′). The model achieves a correlation coefficient of around 0.8 in υ ′ against mooring observations at the equator, surpassing the accuracy of υ ′ derived from altimeter sea surface height (SSH). Additionally, the SST-derived υ ′ reconstructs a dynamically consistent dataset for TIWs from 1981 to the present, including u ′, υ ′, and SSH′. The dataset is based on the spatial patterns of TIW modes, comprising eight Rossby modes and eight Yanai modes. Each mode exhibits enhanced amplitudes concentrated in specific longitudinal bands between 180° and 90°W, explaining 78% of the total variance in υ ′ over the basin. Validated against mooring observations, the reconstructions outperform both the SST- and SSH-derived velocities, reproducing an extended time series of the Rossby-mode TIWs centered around 5°N and the Yanai-mode TIWs along the equator. This study provides a new method for estimating TIW surface velocities and sheds light on estimating global mesoscale and smaller-scale sea surface velocities from satellite SST data. Significance Statement Tropical instability waves (TIWs) play a significant role in the dynamics of the tropical ocean and influence the ocean ecosystem and climate through nonlinear effects. However, the surface velocities associated with TIWs have been inadequately estimated from satellite observations due to the incorrect assumption of geostrophic balance near the equator. In this study, we use satellite-observed sea surface temperature (SST) to reconstruct the zonal and meridional components of TIW velocities from 1981 to the present. The reconstructions are dynamically consistent with the spatial patterns of the Rossby and Yanai modes of TIWs. This study provides a new method for estimating TIW surface velocities and sheds light on estimating global mesoscale and smaller-scale sea surface velocities from satellite SST data.