ABSTRACT South Indian Ocean Rossby waves (SIO-RW) are identified in the Global Ocean Data Assimilation System (GODAS) 1.5–7 yr filtered sea surface height (SSH) time series. There is a persistent three-year oscillation in the 5°–15°S latitude band from 55° to 85°E. Field correlations show little coupling at 90°E, but as the SIO-RW undulates westward at approximately 0.19 m s−1 across the mid-basin, a northwest–southeast axis of warm sea surface temperatures (SSTs) and deep convection forms. Many teleconnections in earlier work are confirmed: interannual pulses of zonal wind in the eastern basin trigger the SIO-RW via anticyclonic wind stress curl. New insights derive from an understanding of links with the upper troposphere. As the SIO-RWs move westward with the onset of an El Niño in the Pacific, increased convection over the north Indian Ocean corresponds to reduced evaporation and SST warming. Mid-tropospheric heating T′ > 2°C over the northwest Indian Ocean accelerates the southern sub-tropical jet to greater than 10 m s−1 over the southeast Indian Ocean, reinforcing the anticyclonic vorticity. The downstream acceleration of the jet generates upper-level divergence and moist convection over the western basin, anchoring an atmospheric Rossby wave in a northwest–southeast alignment underpinned by differential propagation of the SIO-RW. As the ocean Rossby wave reaches Africa, the coupling fades and transitions. What distinguishes Indian Ocean from Pacific Ocean Rossby waves are their southern latitude and higher frequency. The tropical mid-tropospheric heating that accelerates the southern sub-tropical jet shifts westward in tandem with the SIO-RW.

中文翻译：

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南印度洋罗斯比波

摘要 南印度洋罗斯比波 (SIO-RW) 在全球海洋数据同化系统 (GODAS) 1.5-7 年过滤海面高度 (SSH) 时间序列中被识别。在从 55° 到 85°E 的 5°–15°S 纬度带中存在持续三年的振荡。场相关性显示在 90°E 几乎没有耦合，但随着 SIO-RW 在盆地中部以大约 0.19 m s-1 向西波动，温暖海面温度 (SST) 的西北-东南轴和深对流形成。早期工作中的许多遥相关被证实：东部盆地的纬向风的年际脉冲通过反气旋风应力旋度触发 SIO-RW。新的见解源于对与上层对流层联系的理解。随着太平洋厄尔尼诺现象的发生，SIO-RW 向西移动，北印度洋上空的对流增加对应于蒸发减少和海温升高。印度洋西北部的对流层中层加热 T' > 2°C 使南部副热带急流在印度洋东南部的上空加速至 10 m s-1 以上，从而加强了反气旋涡度。急流的下游加速在西部盆地产生上层发散和湿对流，将大气罗斯比波锚定在由 SIO-RW 的差分传播支撑的西北-东南方向。随着海洋罗斯比波到达非洲，耦合逐渐消失并转变。印度洋与太平洋罗斯比波的区别在于它们的南纬度和更高的频率。