Temperature dependence of atmospheric absorption in the wavelength range 8–14 µm

THE Earth's atmosphere has relatively high transparency to wavelengths between 8 and 14 µm, which makes them particularly important for communications and remote sensing. A reliable model of molecular absorption in this range is of particular value1 as it may be used to relate atmospheric temperatures to radiant flux measurements made by artificial satellites—it seems that even in conditions when particle scattering can be neglected, absorption losses can be greater than is expected from present models. To study the remaining loss, or anomalous absorption, we have made new measurements in which particular attention was given to the temperature dependence of the anomalous component. The motivation for this was to test the hypothesis2 that anomalous absorption could be ascribed to an equilibrium concentration of water dimers in the atmosphere. We find that this explanation cannot account for anomalous absorption in all conditions.