Abstract
In order to theoretically interpret the Eliassen-Palm diagnostics of wave-mean flow interactions, necessary and sufficient conditions are derived for the Eliassen-Palm flux divergence to approximate the zonal acceleration in the absence of mean damping.
It is shown by a simple analytical model that a violation of these conditions due to the effect of the lower boundary condition may explain why some observational diagnostic studies indicate that transient eddies accelerate westerlies in the mid-latitude upper troposphere in the absence of mean damping, although the transient E-P flux divergence is easterly there. It is also suggested on the basis of simple diagnostic relations that the steady state upper tropospheric westerlies can be either enhanced or reduced by transient eddies depending on mean damping and radiative heating.
