Theoretical Interpretations of the Eliassen-Palm Diagnostics of Wave-Mean Flow Interaction

Part II: Effects of Mean Damping

Abstract

In order to theoretically interpret the Eliassen-Palm diagnostics of wave-mean flow interaction, necessary and sufficient conditions are derived for the Eliassen-Palm flux divergence to balance the steady state residual circulations induced by eddies in the presence of mean damping. It is shown by a simple analytical model that this balance holds for strato spheric planetary waves when the mean Rayleigh friction coefficient is one order smaller than the mean Newtonian cooling coefficient, although the tall mean flow condition (Andrews and McIntyre, 1976) is not violated. In this case, the Eliassen-Palm flux divergence can be interpreted as approximating the steady state residual circulations (_??_Lagrangian mean circulations) induced by eddies as well as the net mean acceleration in the absence of mean damping. This balance is consistent with the stratospheric circultions of a dynamical model (Holton and Wehrbein, 1980a, b) and the GFDL "SKHI" general circulation model (Andrews et al. 1983).