Calculated tropospheric dispersion and absorption due to the 22-GHz water vapor line

To evaluate the complex transmission factor for the troposphere in the 15- to 35-GHz region, the dispersion and attenuation caused by the isolated molecular resonance of water vapor at 22.235 GHz were calculated. The spectroscopic parameters have been previously determined at low pressures (
\leq20
torr) under controlled laboratory conditions with a microwave dispersometer. The computation takes into account the gas composition, pressure, and temperature. Examples for two standard atmospheres and a vertical path model are given. Three theoretical frequency profiles appropriate for a pressure-broadened line are compared with reported measurements, and discrepancies are discussed.