Grant and Brown (Quart. J. Roy. Meteorol. Soc., 125, 1913-1936) proposed a
similarity hypothesis for shallow cumulus convection and evaluated it using
large-eddy simulation results. Here, results from an additional independen
t simulation are used to provide further support for the basic theory. At t
he same time, some extensions to the theory are proposed. It is shown that
the effects of non-zero fluxes at cloud base can be conveniently accounted
for by a simple representation of the transport of scalar variance into the
convecting layer. The effects of having more complex mean profile shapes w
ithin the layer (and hence changes in the gradient production of variance)
are also investigated.