The foreign-continuum absorption of water vapour in the far-infrared (50–500 cm−1)

Pure rotational R(0) and R(1) lines of CO in Ar baths: experimental broadening, shifting and mixing parameters in a wide pressure range versus ab initio calculations

“…where n c is the line center frequency; n 0 is the transition frequency at zero pressure; D w is the line center pressure shift; w is for either V or 0; D V , D 0 , G V , G 0 and G 2 are conventional shift and half-width parameters for VP and qSDVP models, respectively (D 2 parameter is set to 0 in the model for all spectra); d V , d 0 , g V , g 0 and g 2 are the corresponding pressure independent line shape coefficients; G w,O R is the effective half-width parameter to take into account the effect of transition saturation by radiation power; O R is the Rabi frequency quantifying the transition saturation; 41 k = 2p/l is the wavenumber; and D 0 is the molecular diffusion coefficient, so the term k 2 D 0 /P takes into account the collisional confinement of the active molecules, known as the Dicke narrowing effect (eqn (III. 19) in Hartmann et al 1 ). The effect is assumed to influence noticeably the line shape at low pressures typical for the video spectrometer.…”

“…The absolute speed-dependent broadening parameter G(u) is a thermal average of G(u r ) over ũp , with ũ held constant. The conversion from G(u r ) to G(u) can be carried out by fitting the analytically defined function G(u) = G 0 (1 + m p /m) Àn/2 M(Àn/2;3/2; À(m p /m)z 2 ) (19) (m and m p are the masses of the optically active molecule and the perturber, respectively, and M(. .…”

“…[15][16][17][18] The solution of the problem is additionally complicated by insufficient accuracy of the resonant line parameters distorting the continuum spectrum. 19 To break through this challenge, a thorough investigation of line shape is necessary, including the range of frequency detuning from the line center where the impact approximation becomes no longer valid. The detuning should be thus comparable to or even larger than 1/2pt c , where t c is the molecular collision duration, which is about 0.1-1 ps 1,20 and, therefore, the requested detuning should be at least 1-10 cm À1 .…”

The FORUM end-to-end simulator project: architecture and results

“…The dataset aims at providing a benchmark for the validation of radiative transfer models and, with this, also for radiative routines used in climate models through the use of satellite simulators (ESA, 2019). The objectives of the L1 FORUM radiance measurements are (i) the validation and refinement of the current spectroscopic properties (such as those concerning water vapor and carbon dioxide; e.g., Mlawer et al, 2019), (ii) the evaluation of the level of accuracy of current radiative transfer codes, such as the parameterization of the water vapor continuum in an underexplored part of the spectrum (e.g., Serio et al, 2008, andKoroleva et al, 2021), and (iii) the characterization of the radiative signal in presence of high-level clouds and the enhancement of the performances of the algorithms used in cirrus cloud identification from infrared measurements only (Maestri et al, 2019b).…”

The water vapor self-continuum absorption at room temperature in the 1.25 µm window

“…This is a common situation when WM resonant lines represent a significant fraction of the measured continuum and the corresponding WM line parameters are not accurately known (see e.g. [45]). The uncertainty related to the line parameters can be evaluated by propagation of the uncertainties provided by HITRAN2020 for the different line parameters.…”