Independence of SST skewness from thermocline feedback in the eastern equatorial Indian Ocean

Abstract

The observed sea surface height (SSH)‐sea surface temperature (SST) in east equatorial Indian Ocean (EEIO) shows a significant asymmetric relation between the positive and negative SSH anomalies during boreal autumn. Whether or not the thermocline‐ SST feedback is responsible for the negative SST skewness in the EEIO is explored by diagnosing various air‐sea feedback processes and a mixed layer heat budget. Our analysis based on observations suggests that the SSH‐subsurface temperature relation is approximately symmetric between the positive and negative episode, which is significantly different from the asymmetric SSH‐SST relation. This implies that the observed SSH‐SST asymmetry is not attributed to the ocean thermocline feedback. A further analysis of the SST‐precipitation, precipitation‐wind stress and wind stress‐SSH relations demonstrates that the asymmetry arises from asymmetric atmospheric heating/wind responses to the SST anomaly. A mixed layer heat budget analysis reveals that the ratio of the mixed‐layer temperature tendency between the positive and negative events keeps approximately unchanged with and without vertical temperature advection, suggesting that the thermocline‐feedback is not crucial for generating the negative SST skewness in the EEIO.