South Indian Ocean Rossby Waves

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 degrees-15 degrees S latitude band from 55 degrees to 85 degrees E. Field correlations show little coupling at 90 degrees 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 Nino in the Pacific, increased convection over the north Indian Ocean corresponds to reduced evaporation and SST warming. Mid-tropospheric heating T ' > 2 degrees 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.