Footprinting: A seasonal connection between the tropics and mid-latitudes

A connection between the mid-latitude and tropical Pacific is identified in a coupled general circulation model (CGCM). The connection involves a seasonal coupling between winter mid-latitude atmospheric circulation anomalies, and summer equatorial wind stress anomalies. The seasonal coupling results from a footprinting mechanism, in which the summer tropical atmosphere responds to subtropical sea surface temperature (SST) anomalies that are generated by the mid-latitude atmospheric variability during the previous winter. Details of the connection, and of the footprinting mechanism are presented. Implications for interannual ENSO and decadal ENSO-like variability are discussed.