The self- and foreign-absorption continua of water vapor by cavity ring-down spectroscopy near 2.35 μm

Mondelain, D.; Vasilchenko, S.; Čermák, P.; Kassi, S.; Campargue, A.

doi:10.1039/c5cp01238d

Cited by 32 publications

(50 citation statements)

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“…When the OF‐CEAS cell is filled with water vapor, the total absorption coefficient can be expressed as a sum of three terms:

α_{tot} ((),, ν, T) = α_{cavity} + α_{normalW normalM normalL} + α_{normalW normalC normalS}

where α cavity , α WML , and α WCS are the contributions due to the cavity, water vapor monomer local lines (WML), and water vapor self‐continuum (WCS), Rayleigh scattering contribution being negligible in the considered region [ Mondelain et al ., ]. In the following we will assume that the cavity losses, α cavity , are unaffected by the injection of water and correspond then to those of the evacuated cavity.…”

Section: Of‐ceas In the 4 µM Windowmentioning

confidence: 99%

“…In this window, the measurements were performed at spectral points around 4350 and 4520 cm −1 , intermediate between those of our previous OF‐CEAS and CRDS measurements near 4300 cm −1 and the OF‐CEAS measurements at the center of the window at 4723 cm −1 [ Mondelain et al ., ; Ventrillard et al ., ]. The 4350 and 4520 cm −1 measurements were performed with a Distributed Feedback (DFB) diode laser similar to the laser source used in Mondelain et al .…”

Section: Crds With Vecsel and Dfb Laser Diode In The 21 µM Windowmentioning

confidence: 99%

“…[] from 2050 to 2180 cm −1 and (ii) the need for a lower self‐continuum in the 2400–2600 cm −1 region due to an increase in the foreign continuum and in N 2 ‐H 2 O collision‐induced absorption motivated by the measurements of Baranov and Lafferty [] and Mondelain et al . [].…”

Section: Introductionmentioning

confidence: 99%

“…In the 2.1 µm window, room temperature measurements were performed by CRDS [ Mondelain et al ., ] and OF‐CEAS [ Ventrillard et al ., ] toward the low‐energy edge of the window (4249–4302 cm −1 ) and near the center (4723 cm −1 ). The OF‐CEAS measurements at 4302 and 4723 cm −1 were also performed at five further temperatures up to 323 K [ Ventrillard et al ., ].…”

Section: Introductionmentioning

confidence: 99%

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Accurate laboratory determination of the near‐infrared water vapor self‐continuum: A test of the MT_CKD model

et al. 2016

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The semi‐empirical MT_CKD model of the absorption continuum of water vapor is widely used in atmospheric radiative transfer codes of the atmosphere of Earth and, recently, of exoplanets but lacks of experimental validation in the atmospheric windows. Recent laboratory measurements by Fourier transform Spectroscopy led to self‐continuum cross sections much larger than the MT_CKD values in the near‐infrared transparency windows. We report on accurate measurements by Cavity Ring Down Spectroscopy (CRDS) and Optical Feedback‐Cavity‐Enhanced Absorption Spectroscopy (OF‐CEAS) at selected spectral points of the transparency windows centered around 4.0, 2.1, and 1.25 µm. The temperature dependence of the absorption continuum at 4.38 µm is measured in the 23–39°C range. The self‐continuum water vapor absorption is derived either from the baseline variation of water vapor spectra recorded for a series of pressure values over a small spectral interval or from baseline monitoring at fixed laser frequency during pressure ramps. After subtraction of the local water monomer lines contribution, self‐continuum cross sections, Cs, are determined with an accuracy better than 10% from the pressure squared dependence of the continuum absorption measured up to about 15 Torr. Together with our previous measurements in the 2.1 and 1.6 µm windows, the present results provide a unique set of water vapor cross sections for testing the MT_CKD model in four transparency windows. Although showing some important deviations of the absolute values (up to about a factor 4), our accurate measurements validate the overall frequency dependence of the most recent version (V2.8) of the MT_CKD model.

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“…When the OF‐CEAS cell is filled with water vapor, the total absorption coefficient can be expressed as a sum of three terms:

α_{tot} ((),, ν, T) = α_{cavity} + α_{normalW normalM normalL} + α_{normalW normalC normalS}

Section: Of‐ceas In the 4 µM Windowmentioning

confidence: 99%

Section: Crds With Vecsel and Dfb Laser Diode In The 21 µM Windowmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Accurate laboratory determination of the near‐infrared water vapor self‐continuum: A test of the MT_CKD model

et al. 2016

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“…Another issue is that laboratory measurements performed by different techniques have yielded too inconsistent results. For example, the magnitude of the self-continuum in NIR windows derived from laboratory FTIR spectrometry is higher by about 1 order or magnitude compared to results obtained by cavity ring-down spectroscopy (CRDS; Mondelain et al, 2013Mondelain et al, , 2015, which furthermore differ significantly from laboratory results obtained by calorimetric interferometry (Bicknell et al, 2006). Finally, a drawback of laboratory measurements is that they are typically performed at least at room temperature or even heated, in order to detect the weak continuum absorption in the limited optical path length of the cells.…”

Section: Introductionmentioning

confidence: 53%

The Zugspitze radiative closure experiment for quantifying water vapor absorption over the terrestrial and solar infrared – Part 1: Setup, uncertainty analysis, and assessment of far-infrared water vapor continuum

2016

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Abstract. Quantitative knowledge of water vapor radiative processes in the atmosphere throughout the terrestrial and solar infrared spectrum is still incomplete even though this is crucial input to the radiation codes forming the core of both remote sensing methods and climate simulations. Beside laboratory spectroscopy, ground-based remote sensing field studies in the context of so-called radiative closure experiments are a powerful approach because this is the only way to quantify water absorption under cold atmospheric conditions. For this purpose, we have set up at the Zugspitze (47.42 • N, 10.98 • E; 2964 m a.s.l.) a long-term radiative closure experiment designed to cover the infrared spectrum between 400 and 7800 cm −1 (1.28-25 µm). As a benefit for such experiments, the atmospheric states at the Zugspitze frequently comprise very low integrated water vapor (IWV; minimum = 0.1 mm, median = 2.3 mm) and very low aerosol optical depth (AOD = 0.0024-0.0032 at 7800 cm −1 at air mass 1). All instruments for radiance measurements and atmospheric-state measurements are described along with their measurement uncertainties. Based on all parameter uncertainties and the corresponding radiance Jacobians, a systematic residual radiance uncertainty budget has been set up to characterize the sensitivity of the radiative closure over the whole infrared spectral range. The dominant uncertainty contribution in the spectral windows used for far-infrared (FIR) continuum quantification is from IWV uncertainties, while T profile uncertainties dominate in the mid-infrared (MIR). Uncertainty contributions to near-infrared (NIR) radiance residuals are dominated by water vapor line parameters in the vicinity of the strong water vapor bands. The window regions in between these bands are dominated by solar Fourier transform infrared (FTIR) calibration uncertainties at low NIR wavenumbers, while uncertainties due to AOD become an increasing and dominant contribution towards higher NIR wavenumbers. Exceptions are methane or nitrous oxide bands in the NIR, where the associated line parameter uncertainties dominate the overall uncertainty.As a first demonstration of the Zugspitze closure experiment, a water vapor continuum quantification in the FIR spectral region (400-580 cm −1 ) has been performed. The resulting FIR foreign-continuum coefficients are consistent with the MT_CKD 2.5.2 continuum model and also agree with the most recent atmospheric closure study carried out in Antarctica. Results from the first determination of the NIR water vapor continuum in a field experiment are detailed in a companion paper (Reichert and Sussmann, 2016) while a novel NIR calibration scheme for the underlying FTIR measurements of incoming solar radiance is presented in another companion paper .

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2021

Collisional Effects on Molecular Spectra

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The self- and foreign-absorption continua of water vapor by cavity ring-down spectroscopy near 2.35 μm

Abstract: International audienc

Cited by 32 publications

References 30 publications

Accurate laboratory determination of the near‐infrared water vapor self‐continuum: A test of the MT_CKD model

Accurate laboratory determination of the near‐infrared water vapor self‐continuum: A test of the MT_CKD model

The Zugspitze radiative closure experiment for quantifying water vapor absorption over the terrestrial and solar infrared – Part 1: Setup, uncertainty analysis, and assessment of far-infrared water vapor continuum

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