Varied changes in the intensity of extratropical transient eddies in response to global warming

Extratropical storm tracks are widely known to shift poleward in simulations of greenhouse-gas-driven global warming. But there are also changes in their intensity, as measured, for example, using high-pass filtered velocities. To characterize the response in intensity, we examine the changes in eddy kinetic energy that occur in climate model simulations of global warming. Results are shown for a range of simulations from the Coupled Model Intercomparison Project (CMIP3). The changes in eddy kinetic energy are shown to depend strongly on the hemisphere and season under consideration. The eddy kinetic energy has previously been found to scale with the dry mean available potential energy in simulations with idealized general circulation models. We show that this also holds for changes in energy over the seasonal cycle in reanalysis data and comprehensive climate model simulations. We discuss the extent to which this relationship can be used to understand the varied changes in eddy kinetic energy with global warming.