We present an analytical evaluation and interpretation on how diabatic heat
ing of the convective boundary layer (CBL) is transported upward into the m
idtroposphere by mesoscale flows, and how the air mixes with the environmen
t and therefore weakens the atmospheric static stability. The thermodynamic
imprint on the free atmosphere due to the irreversible processes such as m
ixing, dissipation, and diffusion, associated with the mesoscale flow, is m
ore clearly shown when the forcing is periodic in time. Convective mixing i
n the CBL accounts for a thermodynamic perturbation of the order of a few d
egrees, while mixing associated with the mesoscale activity accounts for a
perturbation of the order of hall: a degree. To isolate this last effect, w
e prescribe a periodic forcing with a 1 day period, so over 24 hours, the n
et diabatic input averages to zero, and the contribution due to the advecti
on cancels out. Tn this formulation the perturbation is solely due to irrev
ersible processes associated with the mesoscale. These perturbations are re
levant, since they are smaller, but of the same order of magnitude as pertu
rbations associated with mesoscale advection and the CBL mixing. A more com
plete evaluation of the relative contribution to the atmospheric perturbati
ons due to the mesoscale activity was completed using an initial value prob
lem approach. In this case, there is a net transport of the diabatic heat i
nduced by the mesoscale flow. As a consequence, when the mesoscale flow per
sists for several days, the static stability of the atmosphere is eroded by
the combined action of the diabatic heat, CBL mixing, and transport and mi
xing due to the mesoscale activity. In this paper we first evaluate the con
tribution of the irreversible processes using a periodic in time forcing. T
hen we examine the atmospheric impact due to a sequence of several sea bree
ze days, starting from rest at time zero and letting the flow evolve as an
initial value problem. Results suggest that perturbations associated with m
esoscale flows generated by landscape variability are of climatological imp
ortance and need to be introduced in a parametric form in coarser large-sca
le models, as presently is done with turbulent subgrid CBL processes.