Structure and Mechanisms of South Indian Ocean Climate Variability*

作者：Shang‐Ping Xie, Hariharasubramanian Annamalai, Friedrich A. Schott, Julian P. McCreary · 发表于：Journal of Climate · 年份：2002 · DOI：10.1175/1520-0442(2002)015<0864:samosi>2.0.co;2 · 被引用次数：866 · 研究领域：Oceanographic and Atmospheric Processes、Tropical and Extratropical Cyclones Research、Climate variability and models

A unique open-ocean upwelling exists in the tropical South Indian Ocean (SIO), a result of the negative wind curl between the southeasterly trades and equatorial westerlies, raising the thermocline in the west. Analysis of in situ measurements and a model-assimilated dataset reveals a strong influence of subsurface thermocline variability on sea surface temperature (SST) in this upwelling zone. El Niño–Southern Oscillation (ENSO) is found to be the dominant forcing for the SIO thermocline variability, with SST variability off Sumatra, Indonesia, also making a significant contribution. When either an El Niño or Sumatra cooling event takes place, anomalous easterlies appear in the equatorial Indian Ocean, forcing a westward-propagating downwelling Rossby wave in the SIO. In phase with this dynamic Rossby wave, there is a pronounced copropagation of SST. Moreover, a positive precipitation anomaly is found over, or just to the south of, the Rossby wave–induced positive SST anomaly, resulting in a cyclonic circulation in the surface wind field that appears to feedback onto the SST anomaly. Finally, this downwelling Rossby wave also increases tropical cyclone activity in the SIO through its SST effect. This coupled Rossby wave thus offers potential predictability for SST and tropical cyclones in the western SIO. These results suggest that models that allow for the existence of upwelling and Rossby wave dynamics will have better seasonal forecasts than ones that use a slab ocean mix...