Time development of the upper cloud edge in one-dimensional approximation based on moist thermodynamics

Abstract. It is commonly accepted, that cloud formation is caused by the humidity flux directed from the warm bottom atmospheric layers towards the cold dry heights, and the transportation mechanism in stable stratification is due to development of so-called turbulent boundary layer. The transportation of vapor can be described by buoyancy profile, and requires two significant characteristics of the atmosphere. The first is the heat and water vapor fluxes from the underlying surface which has been investigated by Smith (1988). The second is the temperature profile in the atmosphere, which is usually approximated and parameterized in various ways, because the exact solution is complicated and difficult to use. In this paper we construct a theory of three-component gas mixture, containing air, vapor, and water droplets. This model can be applied for the internal cloud region. Later we use buoyancy to investigate the dynamics of cloud formation, taking into account condensation of the water vapor inside the cloud. The obtained results suggest a typical time of 10 h required for development of intense cloud layer over a sea surface.