The Water Vapor Continuum as Wings of Strong Absorption Lines

Theory of the water vapor continuum and validations

“…This formulation is still widely used because of its simplicity, but it does not reproduce the improved experimental laboratory data of Burch and co-workers (1982Burch and co-workers ( , 1984Burch and co-workers ( , 1985, nor does it model correctly the temperature dependence observed by Montgomery (1978) and by Loper et al (1983). Thomas and Nordstrom (1980, 1982a,b, 1985 sought to model the continuum absorption in terms of a modified line shape. They assumed a Lorentzian line shape near the line center matched to a statistical line shape in the far wings using a large number of adjustable parameters fit to various spectral regions at different temperatures.…”

The Water Vapour Continuum: Brief History and Recent Developments

“…More sophisticated far-wing theories were developed (e.g., Nordstrom and Thomas 1980;Thomas and Nordstrom 1985). The most widely known emerged from the quantum-mechanical approach of Fano (1963) and Rosenkranz (1985Rosenkranz ( , 1987 and its later development by Tipping (e.g., Ma andTipping 1991, 1992;Tipping and Ma 1995) based on the quasi-static approximation for the far wings.…”

Below-Room-Temperature Water-Vapor Continuum Absorption within the 8- to 12-Micrometer Atmospheric Transmission Window.

“…Collisional-broadening or water-vapor aggregate (mainly water dimer) mechanisms, or both, have been most frequently proposed to account for water continuum absorption within the 8-to 12-um window. The most thoroughly developed collisional-broadening 1 7 ' 18 and water dimer models 19 , 2 0 can predict the proper magnitude of the 8-to 12-pm continuum absorption near room temperature. These models, however, predict different dependences of the continuum absorption on temperature and water partial pressure.…”