A minimum bulk microphysics

Abstract. Cloud microphysics present extreme complexities, and even under bulk approaches, the formulation tends to be involved. A minimum microphysics is proposed, aimed at applications for geophysical fluid dynamics, by a maximum simplification of a standard bulk formulation. The proposed formulation is also independently derived by a simple phenomenological argument. The formulational structure of the bulk microphysics is also discussed. The autoconversion process formulation is discussed separately in a phenomenological manner, because a formal application of the bulk approach becomes involved. Four major possible formulations for autoconversion are identified. The proposed formulation is tested with a nonhydrostatic anelastic model under segmentally-constant approximation (NAM-SCA).