Energy of Midlatitude Transient Eddies in Idealized Simulations of Changed Climates
As the climate changes, changes in static stability, meridional temperature gradients, and availability of moisture for latent heat release may exert competing effects on the energy of midlatitude transient eddies. This paper examines how the eddy kinetic energy in midlatitude baroclinic zones responds to changes in radiative forcing in simulations with an idealized moist general circulation model. In a series of simulations in which the optical thickness of the longwave absorber is varied over a wide range, the eddy kinetic energy has a maximum for a climate with mean temperature similar to that of present-day earth, with significantly smaller values both for warmer and for colder climates. In a series of simulations in which the meridional insolation gradient is varied, the eddy kinetic energy increases monotonically with insolation gradient. In both series of simulations, the eddy kinetic energy scales approximately linearly with the dry mean available potential energy averaged over the baroclinic zones. Changes in eddy kinetic energy can therefore be related to the changes in the atmospheric thermal structure that affect the mean available potential energy.
© 2008 American Meteorological Society. (Manuscript received 14 June 2007, in final form 2 April 2008) We are grateful for support by the National Science Foundation (Grant ATM-450059), the Davidow Discovery Fund, and a David and Lucile Packard Fellowship. The simulations were performed on Caltech's Division of Geological and Planetary Sciences Dell cluster. We thank Dargan Frierson for providing code for the convection and radiation schemes and Chris Walker for development of the postprocessing code.
Published - OGOjc08b.pdf