Comparisons of Numerical Simulations of the Planetary Boundary Layer by a Mixed-Layer and a Multi-Level Model

Abstract

Abstract A series of increasingly complicated meteorological circulations is modeled by a two-dimensional, multi-level primitive equation model (MLM) and a one-dimensional mixed-layer model (XLM) in order to determine the extent to which the simple mixed-layer model can provide accurate predictions of the mean structure of the planetary boundary layer (PBL). Under horizontally homogeneous conditions, the PBL structure in the XLM agreed closely with the average structure in the MLM. When horizontal inhomogeneities associated with differential heating over complex terrain and across a land-water boundary were introduced, the XLM solutions became less accurate when compared to the MLM solutions. For these conditions a multi-level model appears to be essential to the correct prediction of flow within the PBL, because mass-wind adjustments in the flow above the PBL produce important changes on the pressure gradient within the PBL.