Voigt's line profile refers to the shape of a spectral line resulting from the "pressure" and Doppler broadening. Pressure broadening is much more important in atmosphere as far as pressure increases (heigths lower than 20 km) . Observing Earth's atmosphere in a spectral region sufficiently far from the central (unperturbed/monochromatic) absorption spectral line (off-line bands), Doppler broadening can be neglected in comparison with the pressure one. More and more off-line are the chosen spectral bands, more and more lower in atmosphere will be the atmospheric layers mostly contributing to the measured spectral radiances.
Such a relation is at the base of the inversion methods for atmospheric vertical sounding based on multi-spectral satellite observations.