EOMF-13. A Positive-Definite Solution for an EDMF PBL Scheme that Includes a Moist Adjustment Process

Abstract
The eddy diffusivity and mass flux (EDMF) planetary boundary layer (PBL) parameterization used in the operational Global Forecast System for simulating turbulent transport is shown to produce negative values of cloud water mixing ratio, primarily due to the nonlocal mixing component and its associated moist adjustment. Single-column model (SCM) simulations of a growing convective PBL are used to illustrate the unphysical distribution of temperature and moisture tendencies that are generated near the simulated PBL top. To solve this problem, the methodology to compute the mass flux is revised, and a flux-corrected transport scheme is introduced, to ensure that the solution is positive definite for the mixing of hydrometeors. Results from SCM simulations using the modified PBL scheme are shown, to illustrate the impact of this new procedure.