A THEORY FOR THE STATISTICAL EQUILIBRIUM ENERGY-SPECTRUM AND HEAT-FLUX PRODUCED BY TRANSIENT BAROCLINIC WAVES

Obtaining a physically based understanding of the variations with spat ial scale of the amplitude and dispersive properties of midlatitude tr ansient baroclinic waves and the heat flux associated with these waves is a central goal of dynamic meteorology and climate studies. Recentl y, stochastic forcing of highly nonnormal dynamical systems, such as a rise from analysis of the equations governing perturbations to the mid latitude westerly jet, has been shown to induce large transfers of ene rgy from the mean to the perturbation scale. In the case of a baroclin ic atmospheric jet, this energy transfer to the synoptic scale produce s dispersive properties, distributions of waves energy with wavenumber , and heat fluxes that are intrinsically associated with the nonnormal dynamics underlying baroclinic wave development. In this work a metho d for calculating the spectrum and heat flux arising from stochastic f orcing is described and predictions of this theory for a model atmosph ere are compared with observations. The calculated energy spectrum is found to be in remarkable agreement with observations, in contrast wit h the predictions of modal instability theory. The calculated heat flu x exhibits a realistic distribution with height and its associated ene rgetic cycle agrees with observed seasonal mean energetics.