A Study of the Incoming Longwave Atmospheric Radiation from a Clear Sky

Abstract

A band model for atmospheric absorption is used to calculate the incoming longwave atmospheric radiative flux for some typical clear sky conditions. The sky radiation is also measured using a specially-designed calorimetric apparatus over a wide range of ground-level atmospheric conditions. Good agreement is obtained between the measurement and the calculation using appropriate atmospheric conditions. Two simple equations are proposed for the prediction of seasonal values of sky radiation: one for summer-type conditions without a quasi-permanent temperature inversion, and one for winter-type conditions with a quasi-permanent temperature inversion. Spectral information of the atmospheric radiation is presented, and the spectral flux in the wavelength range 8–14 μm is computed for typical conditions.