Simulation of deep convection by use of an assumed PDF parameterization

Poster PDF

Description

Parameterization of deep convection is difficult in part because deep convective events precipitate strongly, and the precipitation interacts closely with thermodynamic fields. To parameterize the coupling between precipitation and convective drafts, there are advantages to using the assumed probability density function (PDF) method. Namely, samples can be drawn from the subgrid PDFs and input into a microphysics parameterization, yielding tendencies that can be fed back into the thermodynamics. In this way, a parameterization of convective drafts can be closely coupled to a sophisticated microphysics scheme that includes, for instance, prognostic precipitation. In order for the assumed PDF method to succeed, a sufficiently accurate PDF shape must be chosen for the hydrometeors. An improved shape has been formulated and tested. This poster will present simulations of tropical deep convection observed during the ARM TWP-ICE field experiment, which took place near the coast of Australia. The TWP-ICE case will be simulated by a single-column PDF parameterization (“CLUBB”) coupled to a Monte Carlo sampler (“SILHS”). The parameterized simulation will be compared with a cloud-resolving simulation. The parameterized simulation satisfactorily emulates the profiles and time evolution of the cloud-resolving simulation.