The Atmospheric Boundary Layer: Panel Report

Abstract

Although the term planetary boundary layer (PBL) appears self-defining, the deliberations of the Panel on the Atmospheric Boundary Layer showed that PBL can mean different things to different people. For the purpose of this panel’s response, we will consider the PBL as the layer whose thermodynamic, kinematic and turbulent properties are directly influenced, on a time scale of an hour or less, by fluxes of heat, momentum and moisture at the earth’s surface. Because of the emphasis on radar here, we exclude the “constant stress” surface layer which is only a few tens of meters deep and therefore beyond the measurement capability of radar, at least for the foreseeable future. We therefore are concerned with the convective boundary layer (CBL), driven by buoyancy during the daytime, and the stable nocturnal boundary layer characterized by radiation inversions near the surface.