Results are presented from a mixed-layer model which has been used to
diagnose the average turbulent flux profiles in cumulus-capped boundar
y-layers. The model makes use of separate mixed layer models for the c
lear and cloudy parts of the broken cloud layer. It is shown, by compa
rison with aircraft observations, that the model can be applied to est
imate the area-averaged flux profiles under conditions in which the cl
ouds penetrate the capping inversion. It is also shown that a small bu
t significant part of the vertical transport results from the displace
ment of air from above the inversion around the growing clouds.