Line parameter variations and the profile dependence of atmospheric transmittance

The effect of variations in the parameters that characterize infrared absorption lines on the calculated profile dependence of narrow-band line-center atmospheric transmittance is assessed. It is assumed that the Galatry profile accurately describes the line shape for all absorption lines and transmission paths. The errors introduced by parameter variations under these conditions are compared to those introduced by using approximate line profiles. It is found that the temperature dependence of the collision cross section, the collision-broadened halfwidth at half-maximum under standard conditions, and the variations in two line parameters are significant. Variations in the two parameters may mask the profile dependence in a particular transmittance calculation.