Comparing the roles of barotropic versus baroclinic feedbacks in the atmosphere's response to mechanical forcing

We present a methodology to investigate the relative importance of barotropic and baroclinic eddy feedbacks in determining the structure and amplitude of the extratropical circulation response to mechanical forcing. The study is modeled on the experiments performed in Ring and Plumb (2007), in which the dynamical core of a general circulation model is subject to mechanical torques placed over a range of extratropical latitudes. Here we perform similar experiments, but apply a wider range of mechanical forcings to a hierarchy of numerical models with varying representations of extratropical wave-mean flow interactions: an idealized general circulation model (GCM) and a barotropic model. The GCM includes both baroclinic and barotropic feedbacks. The barotropic model is run in two configurations: 1) only barotropic feedbacks are present and 2) a baroclinic-like feedback is added by allowing the stirring region to move with the jet. As such, the results provide insight into 1) the relationships between the forcing and response latitudes; 2) the relationships between the forcing latitude and climatological-mean jet position; and 3) the physical feedbacks that play a key role in determining the amplitude and structure of the atmospheric response to mechanical forcing.