Parameterization of Radiative Flux Profiles within Layer Clouds

Abstract

The vertical structure of radiative flux profiles within clouds can have a significant impact on the thermodynamic processes that maintain and dissipate the clouds, particularly in the case of marine stratus and stratocumulus. However, dynamic models of these and other cloud systems have tended to include radiative transfer physics in only the most rudimentary fashion. This has caused potentially important feedback processes in the clouds to be neglected. We present here simple formulations for the vertical structure of solar and infrared radiative fluxes within a layer cloud overlying a partially reflective surface. The parameterized profile shapes are analytic, with governing parameters derived from bulk radiative properties and more physically based radiative transfer models. The bulk cloud, subcloud layer and surface radiative properties are assumed to be known. The parameterizations are based on exponential functions of height, with decay scales related to cloud liquid water content. Although the results presented here are based on very simple assumptions about the cloud structure in the vertical, the method used is applicable to more general cases as well as to various other analytic and/or numerical radiative transfer calculations.