Sensitivity of the eddy momentum flux to meridional resolution in atmospheric GCMs

GCM experiments with zonally symmetric climates are used to demonstrate that the increase in the meridional eddy momentum fluxes and zonal surface winds that occurs when resolution is increased is primarily due to the increase in meridional rather than zonal resolution. It is argued that the sensitivity to meridional resolution reflects the need to resolve the small scales generated in the Rossby wave field as waves radiate from the midlatitude baroclinic eddy source region into regions with small mean winds. Some additional experiments highlight the sensitivity of surface winds and eddy momentum fluxes to the subgrid-scale horizonal mixing formulation in low-resolution models. -Authors