This article demonstrates that vertical profiles of the heat flux in t
he convective boundary layer can be diagnosed through an integration o
ver height of the time change rates of observed potential temperature
profiles. Moreover, the basic characteristics of the convective bounda
ry layer, such as the mixed-layer height zi, the depth of the interfac
ial (entrainment) layer, and the heat flux zero-crossing height ho can
be uniquely evaluated based on a time evolution of potential temperat
ure profiles in the lower atmosphere.