Séminaire
In this talk I will discuss a recently developed moist isentropic formulation of the Eliassen-Palm (EP) flux and momentum equation. The EP flux is a useful quantity for measuring the eddy forcing on the mean flow, but its classic formulations are developed from dry theory. That is, they explicitly account for the eddy fluxes of momentum and sensible heat, but not water vapor. The moist formulation developed here relies on a conditional averaging approach because moist isentropes are generally not invertible with height and cannot be used as standard vertical coordinates. The moist EP flux is shown to be around twice as strong and extend further equatorward than the conventional dry EP flux. Physically, the increase in momentum exchange is tied to an enhancement of the form drag associated with the horizontal structure of midlatitude eddies, where the poleward flow of moist air is located in regions of strong eastward pressure gradient.
glapeyre@lmd.ens.fr