Parallel Session: Environment, Contributed Talk (15min)

Foreign water vapor continuum in the far infrared (50-500 cm-1)

A. Koroleva1,3, T. Odintsova1, M. Tretyakov1, O. Pirali2,4, A. Campargue3
1Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia, 2Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, Orsay, France, 3Univ. Grenoble Alpes, CNRS, LIPhy, Grenoble, France , 4SOLEIL Synchrotron, L’Orme des Merisiers, Saint-Aubin, Gif-Sur-Yvette, France

The foreign-continuum absorption of water vapour diluted in nitrogen, oxygen and air has been measured in the range of H2O pure rotational band (50-500 cm-1). This work is a continuation of our works [1-3], where the self-continuum component was determined in the same region. Spectra recordings were performed at room temperature with a Fourier transform spectrometer associated to a 151-m multipass gas cell located at the AILES beamline of the SOLEIL synchrotron. The HITRAN2016 line list and self-continuum data from [1] were used to extract the foreign-continuum from the experimental spectra. Tests of the baseline stability which is crucial for the continuum determination, were performed. The spectra were recorded for a series of pressure values. The expected linear pressure dependences of the foreign-continuum were checked for all gas mixtures under consideration. Consistency between retrieved H2O-N2, H2O-O2, and H2O-air foreign-continuum cross-sections was shown.
The study includes the first laboratory measurements in the wide 90-330 cm-1 spectral interval. Retrieved foreign-continuum cross-sections are found in good agreement with literature values available in the lower and upper parts of the studied frequency range (see figure). The reported results validate the MT_CKD [4], widely implemented in radiation transfer codes used for the atmosphere and underlying surface remote sensing, even if some overestimation of the MT_CKD values is noted in the centre of the band where experimental data were absent.
This work is partially supported by RFBR project 18-55-16006.

[1] Tatyana Odintsova et al, J Mol Struct, 2020, 1210, 128046.

[2] Tatyana Odintsova et al, J Quant Spectrosc Radiat Transfer, 2019, 227, 190–200.

[3] Tatyana Odintsova et al, J Quant Spectrosc Radiat Transfer, 2017, 187, 116–23.

[4] Eli Mlawer et al, Phil Trans R Soc 2012, 370, 2520–56.