Articles | Volume 11, issue 4
Atmos. Meas. Tech., 11, 2159–2171, 2018
https://doi.org/10.5194/amt-11-2159-2018
Atmos. Meas. Tech., 11, 2159–2171, 2018
https://doi.org/10.5194/amt-11-2159-2018

Research article 16 Apr 2018

Research article | 16 Apr 2018

The water vapour self-continuum absorption in the infrared atmospheric windows: new laser measurements near 3.3 and 2.0 µm

Loic Lechevallier1,2, Semen Vasilchenko1,3, Roberto Grilli2, Didier Mondelain1, Daniele Romanini1, and Alain Campargue1 Loic Lechevallier et al.
  • 1Univ. Grenoble Alpes, CNRS, LIPhy, 38000 Grenoble, France
  • 2Univ. Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, 38000 Grenoble, France
  • 3Laboratory of Molecular Spectroscopy, V. E. Zuev Institute of Atmospheric Optics, SB, Russian Academy of Science, 1 Akademician Zuev square, 634021 Tomsk, Russia

Abstract. The amplitude, the temperature dependence, and the physical origin of the water vapour absorption continuum are a long-standing issue in molecular spectroscopy with direct impact in atmospheric and planetary sciences. In recent years, we have determined the self-continuum absorption of water vapour at different spectral points of the atmospheric windows at 4.0, 2.1, 1.6, and 1.25 µm, by highly sensitive cavity-enhanced laser techniques. These accurate experimental constraints have been used to adjust the last version (3.2) of the semi-empirical MT_CKD model (Mlawer-Tobin_Clough-Kneizys-Davies), which is widely incorporated in atmospheric radiative-transfer codes. In the present work, the self-continuum cross-sections, CS, are newly determined at 3.3 µm (3007 cm−1) and 2.0 µm (5000 cm−1) by optical-feedback-cavity enhanced absorption spectroscopy (OFCEAS) and cavity ring-down spectroscopy (CRDS), respectively. These new data allow extending the spectral coverage of the 4.0 and 2.1 µm windows, respectively, and testing the recently released 3.2 version of the MT_CKD continuum. By considering high temperature literature data together with our data, the temperature dependence of the self-continuum is also obtained.

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Short summary
The amplitude, the temperature dependence, and the physical origin of the water vapour absorption continuum are a long standing issue in molecular spectroscopy with a direct impact in atmospheric and planetary sciences. Using highly sensitive laser spectrometers, the water self continuum has been determined with unprecedented sensitivity in infrared atmospheric transparency windows.