A model of decadal middle-latitude atmosphere-ocean coupled modes

Jason Goodman and John Marshall
Program in Atmospheres, Oceans and Climate
Department of Earth, Atmospheric and Planetary Sciences
Massachusetts Institute of Technology

Abstract:

An analytical model of the mutual interaction of the middle-latitude atmosphere and ocean is formulated and studied. The model is found to support coupled modes in which oceanic baroclinic Rossby waves of decadal period grow through positive coupled feedback between the thermal forcing of the atmosphere induced by associated SST anomalies and the resulting windstress forcing of the ocean. Growth only occurs if the atmospheric response to thermal forcing is equivalent barotropic, with a particular phase relationship with the underlying SST anomalies. The dependence of the growth rate and structure of the modes on the nature of the assumed physics of air-sea interaction is explored, and their possible relation to observed phenomena discussed.