Hypercooling in the Nocturnal Boundary Layer: Broadband Emissivity Schemes

Abstract

roadband flux emissivity schemes are often used to model infrared radiative exchanges in the atmosphere. In particular, such schemes help highlight the interaction of radiation with other transport processes, an aspect that is crucial to an understanding of phenomena relevant to the nocturnal boundary layer (NBL). Although the original schemes were restricted to radiatively black bounding surfaces, an extension of the same to nonblack surfaces has since been frequently used in NBL modeling. Herein, it is shown that the nonblack extension is erroneous and leads to a spurious yet intense near-surface cooling in the opaque bands. This paper presents the correct formulation that eliminates this cooling and discusses in some detail earlier NBL calculations affected by this error.