Speed dependence of 22- And 118-GHz line shapes for tropospheric remote sensing

Line shapes are influenced by the dependence of collision cross sections on molecular speeds, with resulting effect on the absorption of up to a few percents. Speed-dependence effects on the water line at 22.23 GHz and the oxygen line at 118.75 GHz are calculated for atmospheric conditions common in midlatitudes. The effect on water vapor profiles retrieved with a ground-based microwave radiometer shows an impact (in simulations) comparable in magnitude to those of measurement errors and of uncertainties in spectroscopic parameters.