## Abstract

The influence of ground level temperature and humidity on the intensity and spectral distribution of the thermal radiation reaching ground level from the clear sky has been investigated in the spectral region between 4*μ* and 15*μ*. The influence of the thickness of the emitting layer or atmospheric path viewed by the detector has also been studied by making measurements of the sky radiation from various zenith distances. Empirical relationships between the intensity of the atmospheric emission spectrum in various spectral intervals and the ground-level conditions of temperature and humidity are developed and presented in graphical form.

© 1956 Optical Society of America

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### Equations (4)

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(1)
$${R}_{S\mathrm{\lambda}}={D}_{S\mathrm{\lambda}}/{K}_{\mathrm{\lambda}},$$
(2)
$${R}_{S}({\mathrm{\lambda}}_{1},{\mathrm{\lambda}}_{2})={\int}_{{\mathrm{\lambda}}_{1}}^{{\mathrm{\lambda}}_{2}}{R}_{S\mathrm{\lambda}}d\mathrm{\lambda}={\int}_{{\mathrm{\lambda}}_{1}}^{{\mathrm{\lambda}}_{2}}\frac{{D}_{S\mathrm{\lambda}}}{{K}_{\mathrm{\lambda}}}d\mathrm{\lambda},$$
(4)
$$\begin{array}{l}{\mathrm{\Sigma}}_{S}({\mathrm{\lambda}}_{1},{\mathrm{\lambda}}_{2})={\int}_{0}^{\pi /2}{R}_{S}({\mathrm{\lambda}}_{1},{\mathrm{\lambda}}_{2})2\pi \hspace{0.17em}\text{sin}Z\hspace{0.17em}\text{cos}ZdZ;\\ {\mathrm{\Sigma}}_{S}({\mathrm{\lambda}}_{1},{\mathrm{\lambda}}_{2})={\int}_{0}^{\pi /2}\pi {R}_{S}({\mathrm{\lambda}}_{1},{\mathrm{\lambda}}_{2})\hspace{0.17em}\text{sin}2ZdZ.\end{array}$$