Satellite observations of the Pacific tropical instability wave characteristics and their interannual variability

Descriptions of tropical instability wave (TIW) characteristics in the tropical Pacific Ocean as a function of the large-scale climate conditions and interannual variability, such as the El Nino southern oscillation, are made based on satellite data. As others have found, the TIW ocean–atmosphere coupling is caused by atmospheric boundary layer instability and mixing. Our observational investigation extends some of these previous findings and suggests that this mechanism of coupled variability of the wind and sea surface temperature may occur not only during La Nina years, when TIWs are more active, but whenever the TIWs are active. The sea surface temperature and height anomaly covariability phase shift might occur also independent of the TIW season activity. There is evidence that TIW activity increases when under strengthened wind stress conditions either in La Nina years or, by analogy, when oceanic numerical simulations are carried out with stronger wind stress. Observational results show larger TIW wavelengths and shorter periods when the ocean is under the action of strengthened wind stress. On this observational study this occurs when La Ninna conditions prevail on the equatorial Pacific