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Improving atmospheric CO2 retrievals using line mixing and speed-dependence when fitting high-resolution ground-based solar spectra.

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Title: Improving atmospheric CO2 retrievals using line mixing and speed-dependence when fitting high-resolution ground-based solar spectra.
Authors: Mendonca, J.1 joseph.mendonca@utoronto.ca, Strong, K.1, Toon, G.C.2, Wunch, D.3, Sung, K.2, Deutscher, N.M.4, Griffith, D.W.T.4, Franklin, J.E.5
Source: Journal of Molecular Spectroscopy. May2016, Vol. 323, p15-27. 13p.
Subjects: Atmospheric carbon dioxide, Solar spectra, Spectral lines, Absorption coefficients, Voigt effect, Standard deviations
Abstract: A quadratic speed-dependent Voigt spectral line shape with line mixing (qSDV + LM) has been included in atmospheric trace-gas retrievals to improve the accuracy of the calculated CO 2 absorption coefficients. CO 2 laboratory spectra were used to validate absorption coefficient calculations for three bands: the strong 20013 ← 00001 band centered at 4850 cm −1 , and the weak 30013 ← 00001 and 30012 ← 00001 bands centered at 6220 cm −1 and 6340 cm −1 respectively, and referred to below as bands 1 and 2. Several different line lists were tested. Laboratory spectra were best reproduced for the strong CO 2 band when using HITRAN 2008 spectroscopic data with air-broadened widths divided by 0.985, self-broadened widths divided by 0.978, line mixing coefficients calculated using the exponential power gap (EPG) law, and a speed-dependent parameter of 0.11 used for all lines. For the weak CO 2 bands, laboratory spectra were best reproduced using spectroscopic parameters from the studies by Devi et al. in 2007 coupled with line mixing coefficients calculated using the EPG law. A total of 132,598 high-resolution ground-based solar absorption spectra were fitted using qSDV + LM to calculate CO 2 absorption coefficients and compared to fits that used the Voigt line shape. For the strong CO 2 band, the average root mean square (RMS) residual is 0.49 ± 0.22% when using qSDV + LM to calculate the absorption coefficients. This is an improvement over the results with the Voigt line shape, which had an average RMS residual of 0.60 ± 0.21%. When using the qSDV + LM to fit the two weak CO 2 bands, the average RMS residual is 0.47 ± 0.19% and 0.51 ± 0.20% for bands 1 and 2, respectively. These values are identical to those obtained with the Voigt line shape. Finally, we find that using the qSDV + LM decreases the airmass dependence of the column averaged dry air mole fraction of CO 2 retrieved from the strong and both weak CO 2 bands when compared to the retrievals obtained using the Voigt line shape. [ABSTRACT FROM AUTHOR]
Copyright of Journal of Molecular Spectroscopy is the property of Academic Press Inc. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Improving atmospheric CO2 retrievals using line mixing and speed-dependence when fitting high-resolution ground-based solar spectra.
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  Data: <searchLink fieldCode="AR" term="%22Mendonca%2C+J%2E%22">Mendonca, J.</searchLink><relatesTo>1</relatesTo><i> joseph.mendonca@utoronto.ca</i><br /><searchLink fieldCode="AR" term="%22Strong%2C+K%2E%22">Strong, K.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Toon%2C+G%2EC%2E%22">Toon, G.C.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Wunch%2C+D%2E%22">Wunch, D.</searchLink><relatesTo>3</relatesTo><br /><searchLink fieldCode="AR" term="%22Sung%2C+K%2E%22">Sung, K.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Deutscher%2C+N%2EM%2E%22">Deutscher, N.M.</searchLink><relatesTo>4</relatesTo><br /><searchLink fieldCode="AR" term="%22Griffith%2C+D%2EW%2ET%2E%22">Griffith, D.W.T.</searchLink><relatesTo>4</relatesTo><br /><searchLink fieldCode="AR" term="%22Franklin%2C+J%2EE%2E%22">Franklin, J.E.</searchLink><relatesTo>5</relatesTo>
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Molecular+Spectroscopy%22">Journal of Molecular Spectroscopy</searchLink>. May2016, Vol. 323, p15-27. 13p.
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  Data: <searchLink fieldCode="DE" term="%22Atmospheric+carbon+dioxide%22">Atmospheric carbon dioxide</searchLink><br /><searchLink fieldCode="DE" term="%22Solar+spectra%22">Solar spectra</searchLink><br /><searchLink fieldCode="DE" term="%22Spectral+lines%22">Spectral lines</searchLink><br /><searchLink fieldCode="DE" term="%22Absorption+coefficients%22">Absorption coefficients</searchLink><br /><searchLink fieldCode="DE" term="%22Voigt+effect%22">Voigt effect</searchLink><br /><searchLink fieldCode="DE" term="%22Standard+deviations%22">Standard deviations</searchLink>
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  Label: Abstract
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  Data: A quadratic speed-dependent Voigt spectral line shape with line mixing (qSDV + LM) has been included in atmospheric trace-gas retrievals to improve the accuracy of the calculated CO 2 absorption coefficients. CO 2 laboratory spectra were used to validate absorption coefficient calculations for three bands: the strong 20013 ← 00001 band centered at 4850 cm −1 , and the weak 30013 ← 00001 and 30012 ← 00001 bands centered at 6220 cm −1 and 6340 cm −1 respectively, and referred to below as bands 1 and 2. Several different line lists were tested. Laboratory spectra were best reproduced for the strong CO 2 band when using HITRAN 2008 spectroscopic data with air-broadened widths divided by 0.985, self-broadened widths divided by 0.978, line mixing coefficients calculated using the exponential power gap (EPG) law, and a speed-dependent parameter of 0.11 used for all lines. For the weak CO 2 bands, laboratory spectra were best reproduced using spectroscopic parameters from the studies by Devi et al. in 2007 coupled with line mixing coefficients calculated using the EPG law. A total of 132,598 high-resolution ground-based solar absorption spectra were fitted using qSDV + LM to calculate CO 2 absorption coefficients and compared to fits that used the Voigt line shape. For the strong CO 2 band, the average root mean square (RMS) residual is 0.49 ± 0.22% when using qSDV + LM to calculate the absorption coefficients. This is an improvement over the results with the Voigt line shape, which had an average RMS residual of 0.60 ± 0.21%. When using the qSDV + LM to fit the two weak CO 2 bands, the average RMS residual is 0.47 ± 0.19% and 0.51 ± 0.20% for bands 1 and 2, respectively. These values are identical to those obtained with the Voigt line shape. Finally, we find that using the qSDV + LM decreases the airmass dependence of the column averaged dry air mole fraction of CO 2 retrieved from the strong and both weak CO 2 bands when compared to the retrievals obtained using the Voigt line shape. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Journal of Molecular Spectroscopy is the property of Academic Press Inc. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
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      – Type: doi
        Value: 10.1016/j.jms.2016.01.007
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 13
        StartPage: 15
    Subjects:
      – SubjectFull: Atmospheric carbon dioxide
        Type: general
      – SubjectFull: Solar spectra
        Type: general
      – SubjectFull: Spectral lines
        Type: general
      – SubjectFull: Absorption coefficients
        Type: general
      – SubjectFull: Voigt effect
        Type: general
      – SubjectFull: Standard deviations
        Type: general
    Titles:
      – TitleFull: Improving atmospheric CO2 retrievals using line mixing and speed-dependence when fitting high-resolution ground-based solar spectra.
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              M: 05
              Text: May2016
              Type: published
              Y: 2016
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