Stable Boundary Layer Mixing in a Vertical Diffusion Scheme

This paper examines a role of the parameterization of the stable boundary layer (SBL) in forecasting weather and climate. The SBL scheme based on the bulk Richardson number between the surface layer and the top of the boundary layer was implemented on the Yonsei University (YSU) planetary boundary layer (PBL) scheme, and evaluated against the local scheme in which the mixing coefficient is a function of the local Richardson number at a given model level. In the new SBL scheme, the vertical diffusion coefficients are computed by a prescribed parabolic shape function as in the case of the unstable conditions in the YSU PBL. The critical bulk Richardson number for the determination of the SBL top is set as a constant value of 0.25 over land, whereas it is a function of the surface Rossby number over the oceans, following the study of Vickers and Mahrt.