Development of a cumulus parameterization scheme based on a new static stability criterion

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The purpose of this work is to investigate the validity of the stability theory of a saturated air parcel in an unsaturated environment in terms of the moist adiabatic lapse rate of virtual temperature using observational data and numerical experiments data, and to develop a new parameterization scheme of cumulus convection. Observational results show a good agreement with the theory.For the numerical experiment, we consider a cumulus boundary layer maintained by the balance between the surface heat fluxes, horizontal advection, and large-scale subsidence. Even if the external forcing is fixed, there occur two balanced states. One is the state with organized convection and the other is the state with randomly distributed non-organized convection. The characteristics of the boundary layer such as vertical gradient of temperature is different between the two states. In order to investigate the stability of convection, we must consider the difference between the two states.