Toward Convective Boundary Layer Parameterization: A Scalar Transport Module

Abstract

Recent results from large-eddy simulations indicate that the eddy diffusivity for scalar diffusion through the top of a convective boundary layer is different from that for diffusion through the bottom. From this, one can show that the eddy diffusivity is not well behaved in general and can have singularities. As an alternative to the high-resolution approach using eddy-diffusivity closure, we propose an improved integral method for calculating scalar transport in the convective boundary layer. Based on an analytical parameterization for the mean scalar profile, it is computationally as simple as the familiar ?mixed-layer? integral method but is physically more realistic, allowing a mean scalar gradient within the mixed layer. We present sample results for the evolution of humility, CO and O3 profiles during the day.