A Further Study of the Preferred Mode of Cumulus Convection in a Conditionally Unstable Atmosphere

Abstract

Numerical experiments are made to determine a preferred mode of cumulus convection in a conditionally unstable atmosphere. The model developed in the previous study (Asai and Nakasuji, 1977) is extended to deal with water vapor explicitly. The preferred mode of cumulus convection is regarded as the steady convection cell attained eventually after a random potential temperature disturbance is imposed initially. It is shown that the preferred scale of the convection cell and the preferred cloud coverage depend on mean vertical velocity, static stability and relative humidity. It is confirmed that the preferred cumulus convection minimizes the potential energy and consequently the mean temperature lapse-rate in the convective layer.