A Fractal Interfacial Entrainment Model for Dry Convective Boundary Layers. Part I: Model Description

Abstract

An entrainment model for the convective planetary boundary layer is presented. It is based upon an ensemble-averaged view of the local entrainment interface that caps the convective mixed layer. Fractal and variational methods are used to estimate the areal enhancement of the convoluted, discontinuous interface. A momentum budget involving critically damped ?tracer? particles is used to find ?h, the mean capping inversion depth, and lh, and lv, the mean interfacial thicknesses along the horizontal and vertical directions, respectively. Entrainment rate estimates are consistent with the results of day 33 of the Wangara experiment. Due to the local scaling, the model is more responsive than previous models to conditions near the inversion that affect entrainment.