Absorption Of Infrared Radiation By Atmospheric Water Vapor In The Region 4.3-5.5 Micron - Preliminary Measurements

Experimental measurements of infra-red transmittance are reported, which show that the computer code LOWTRAN-4 predicts too high a transmittance in the region 4.3-5.5 micron, and that the discrepancy is dependent on the water vapor content. We have carried out experiments at various ranges up to 45 km in order to vary the precipitable water amount over a wide range, and from the results we have deduced that the anomalous transmittance results from an incorrect estimate of the continuous absorption, while the spectral component is substantially correct.