Atmospheric response to oceanic mesoscale variability

Much attention has been paid of late to the mesoscale variability in the tropical oceans since recent satellite data clearly demonstrates that the lower atmosphere responds to oceanic internal variability. Forced OGCM studies have shown that such internal variabilities, mainly manifested as the tropical instability waves (TIWs), do make a net contribution to the mixed layer heat budget and hence have the potential for a lower frequency rectification of the sea surface temperatures (SSTs). The precise mechanisms by which the atmospheric boundary layer responds to TIWs is not fully understood yet. To undrstand the mechanisms of coupled air-sea interactions engendered by the TIWs, we employ a regional ocean model coupled to a regional atmosphere model in the tropical Atlantic. The horizontal resolution of the component models is varied from the climate prediction model type resolution to high resolutions required for explicitly resolving the TIWs and the associated coupled response. The differences in the simulations are diagnosed to understand the net rectification of the SSTs by the TIWs and the related atmospheric responses at seasonal to interannual time-scales. External forcings such as ENSO are suppressed in these early experiments to quantify the role of the TIWs on the variability of the tropical marine ITCZ and the cascading effects on the trade winds and hence the meridional mode. The details of the analyses and the processes involved in the atmospheric response to TIWs and potential impacts on regional climate variability are discussed.