A theoretical framework to calculate pressure-broadened halfwidths with an uncertainty of ~ 5% for atmospherically important species will be developed. Calculations are also expected to yield pressure-induced line shifts. Two approaches to computing the halfwidth and line shift for water vapor perturbed by nitrogen or oxygen will be compared with experimental measurements, and the method that results in the best agreement will be used to generate a database for atmospherically important transitions of water vapor. Next, the calculations will be extended to methane perturbed by nitrogen or oxygen. The research is motivated by the need for increased confidence in remote sensing measurements and a better determination of the radiative forcings of greenhouse gases. This investigation will lay the foundation for further calculations of halfwidths and line shifts for other atmospheric species.
