2000, Heat transport and weakening of the atmospheric stability induced by mesoscale flows

Abstract. We present an analytical evaluation and interpretation on how diabatic heating of the convective boundary layer (CBL) is transported upward into the midtroposphere by mesoscale flows, and how the air mixes with the environment and therefore weakens the atmospheric static stability. The thermodynamic imprint on the free atmosphere due to the irreversible processes such as mixing, dissipation, and diffusion, associated with the mesoscale flow, is more clearly shown when the forcing is periodic in time. Convective mixing in the CBL accounts for a thermodynamic perturbation of the order of a few degrees, while mixing associated with the mesoscale activity accounts for a perturbation of the order of half a degree. To isolate this last effect, we prescribe a periodic forcing with a 1 day period, so over 24 hours, the net diabatic input averages to zero, and the contribution due to the advection cancels out. In this formulation the perturbation is solely due to irreversible processes associated with the mesoscale. These perturbations are relevant, since they are smaller, but of the same order of magnitude as perturbations associated with mesoscale advection and the CBL mixing. A more complete evaluation of the relative contribution to the atmospheric perturbations due to the mesoscale activit