Anomalous Absorption by Atmospheric Water Vapor and Stabilized Water Fogs in the Infrared and CM-Wave Regions.

摘要

Measurements of anomalous or excessive absorption by atmospheric water vapor, i.e., absorption in excess of water monomer absorption and droplet scattering predictions, are analyzed for the infrared and 5-17/cm regions. Both fair weather and fog data are considered. It is found that observations in both spectral regions can be explained by clustering (hydrogen bonding) of approx. .001 of vapor molecules. The development leads to several tentative conclusions: 1) equilibrium cluster populations (and maximum absorption) are only attained for vapor in contact with liquid water; 2) the clusters are formed by evaporation, are large, and cannot be modeled by Boltzmann statistics; 3) cluster modes can account for unexplained spectral features at 5-17/cm; 4) excessive absorption both in the infrared and 5-17/cm regions probably can be explained by the same cluster species. In the appendix, the visible and infrared optical properties of evaporation stabilized water fogs also are considered. Evaporation of artificial water fogs can be retarded by the application of coatings of long-chain fatty alcohols to the droplets during generation. Measurements are described, and droplet diameters and mass extinction coefficients are reported for water fogs coated with cetyl alcohol (1-hexadecanol) from a commercial generator. (aw)