Uniform error bounds for fast calculation of approximate Voigt profiles

Abstract: The broadband line-by-line analysis of radiative transfer in the atmosphere is extremely demanding with regard to computational resources. As a remedy, we present here the calculation of uniform error bounds for approximating the classical Voigt profile. A new "full" Voigt profile, which can be expressed as a combination of two Faddeeva evaluations, is also presented and included in the analysis. The uniform bounds can be used to rigorously determine the domains on which the Voigt profiles can be approximated by the corresponding Lorentz profiles to any desired accuracy. The bounds can furthermore be employed to make a fast and efficient estimate of the most significant lines to be included in a subband adaptive line selection strategy. By using a realistic numerical example of radiative transfer in the atmosphere, we demonstrate that these approximation approaches are able to reduce the computational time of the associated line-by-line analysis by several orders of magnitude with little loss of accuracy.