A CUMULUS PARAMETERIZATION WITH MULTIPLE CLOUD-BASE LEVELS

We have generalized the Arakawa-Schubert cumulus parameterization to a llow multiple cloud-base levels. A spectrum of cloud-top levels is all owed for each cloud-base level. We use a linear (rather than exponenti al) mass flux profile, because this greatly simplifies the determinati on of the entrainment rate and reduces the computational requirements of the parameterization. Cloud-top entrainment is included. The linear mass flux profile and the multiple cloud bases are separately tested in a general circulation model. Results show that the linear mass flux profile tends to lead to smoother precipitation distribution with a d ecrease in the depth and intensity of deep convection and that cumuli with cloud bases above the boundary layer tend to occur at night over land.