Showing papers by "Philip W. Rosenkranz published in 2021"
TL;DR: In this paper, the authors measured the speed-dependent collisional broadening and shifting of the water vapor line at 183 GHz over the temperature range of 219-358 k using a spectrometer with radioacoustic detection of absorption, providing a signal-to-noise ratio of up to 8000.
Abstract: The water vapor line at 183 GHz was studied over the temperature range of 219–358 K using a spectrometer with radioacoustic detection of absorption, providing a signal-to-noise ratio of up to 8000. The study includes the first measurement of speed-dependent collisional broadening and shifting of this line for both self- and air-broadening, and their temperature dependences. The sign of self-shifting changes at about 280 K. Line-shape parameters are obtained for Voigt and quadratic speed-dependent Voigt shape factors. Temperature dependences of the line parameters are analyzed using empirical models from the literature. Theoretical Modified Complex Robert–Bonamy calculations of the line shape parameters, their temperature and speed-dependence are made over the temperature range of 200–3000 K. The measurements and calculations show very good agreement, although with some discrepancies for line shift parameters. The impact of the newly-measured line parameters on atmospheric water-vapor estimation from ground-based and satellite instruments is evaluated by simulation of downwelling and upwelling brightness temperatures and retrieved water-vapor mixing ratio, for atmospheric conditions typical of six climate zones. For the case of ground-based or limb-scanning radiometry with a background of cold space, the impact of speed-dependence is comparable to or exceeds that of measurement error and will introduce systematic errors if neglected. Therefore, consideration of speed-dependence is necessary for accurate estimation of water vapor with this line. The impact on upwelling brightness temperature is smaller.
7 citations
TL;DR: In this article, the impact of introducing speed-dependent line mixing and broadening coefficients into a model for the atmospheric oxygen 60-GHz band is shown to be smaller than the influence of either first or second-order speed-independent line mixing.
Abstract: Pressure broadening of the molecular oxygen fine-structure lines near 60 GHz was experimentally reexamined in the range of rotational quantum numbers up to N =39, in the pure gas at room temperature The analysis of a representative set of individual line profiles with N varying from 1 to 21 included the speed dependence of collisional relaxation, which affects absorption by 025–05% of maximum at low pressures The ratio of the two speed-dependence parameters γ 0 and γ 2 exhibits no notable variation with N Obtained data are compared with similar parameters of other oxygen bands in the near-infrared and visible spectral ranges Assuming similar speed dependence in air as for pure oxygen, we find that at 1-atm pressure, the impact of introducing speed-dependent line mixing and broadening coefficients into a model for the atmospheric oxygen 60-GHz band is 005–01% of maximum absorption, much smaller than the influence of either first- or second-order speed-independent line mixing
5 citations