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Contributions of the troposphere and stratosphere to CH4 model biases

Wang, Zhiting ; Warneke, Thorsten ; Deutscher, Nicholas M. ; Notholt, Justus ; Karstens, Ute LU orcid ; Saunois, Marielle ; Schneider, Matthias ; Sussmann, Ralf ; Sembhi, Harjinder and Griffith, David W.T. , et al. (2017) In Atmospheric Chemistry and Physics 17(21). p.13283-13295
Abstract

Inverse modelling is a useful tool for retrieving CH4 fluxes; however, evaluation of the applied chemical transport model is an important step before using the inverted emissions. For inversions using column data one concern is how well the model represents stratospheric and tropospheric CH4 when assimilating total column measurements. In this study atmospheric CH4 from three inverse models is compared to FTS (Fourier transform spectrometry), satellite and in situ measurements. Using the FTS measurements the model biases are separated into stratospheric and tropospheric contributions. When averaged over all FTS sites the model bias amplitudes (absolute model to FTS differences) are 7.4 ± 5.1, 6.7 ± 4.8,... (More)

Inverse modelling is a useful tool for retrieving CH4 fluxes; however, evaluation of the applied chemical transport model is an important step before using the inverted emissions. For inversions using column data one concern is how well the model represents stratospheric and tropospheric CH4 when assimilating total column measurements. In this study atmospheric CH4 from three inverse models is compared to FTS (Fourier transform spectrometry), satellite and in situ measurements. Using the FTS measurements the model biases are separated into stratospheric and tropospheric contributions. When averaged over all FTS sites the model bias amplitudes (absolute model to FTS differences) are 7.4 ± 5.1, 6.7 ± 4.8, and 8.1 ± 5.5 ppb in the tropospheric partial column (the column from the surface to the tropopause) for the models TM3, TM5-4DVAR, and LMDz-PYVAR, respectively, and 4.3 ± 9.9, 4.7 ± 9.9, and 6.2 ± 11.2 ppb in the stratospheric partial column (the column from the tropopause to the top of the atmosphere). The model biases in the tropospheric partial column show a latitudinal gradient for all models; however there are no clear latitudinal dependencies for the model biases in the stratospheric partial column visible except with the LMDz-PYVAR model. Comparing modelled and FTS-measured tropospheric column-averaged mole fractions reveals a similar latitudinal gradient in the model biases but comparison with in situ measured mole fractions in the troposphere does not show a latitudinal gradient, which is attributed to the different longitudinal coverage of FTS and in situ measurements. Similarly, a latitudinal pattern exists in model biases in vertical CH4 gradients in the troposphere, which indicates that vertical transport of tropospheric CH4 is not represented correctly in the models.

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publishing date
type
Contribution to journal
publication status
published
subject
in
Atmospheric Chemistry and Physics
volume
17
issue
21
pages
13 pages
publisher
Copernicus GmbH
external identifiers
  • scopus:85034035958
ISSN
1680-7316
DOI
10.5194/acp-17-13283-2017
language
English
LU publication?
no
id
1a4218af-e808-47fd-a2d9-25ecd26ee830
date added to LUP
2018-02-09 08:46:17
date last changed
2022-04-25 05:33:30
@article{1a4218af-e808-47fd-a2d9-25ecd26ee830,
  abstract     = {{<p>Inverse modelling is a useful tool for retrieving CH<sub>4</sub> fluxes; however, evaluation of the applied chemical transport model is an important step before using the inverted emissions. For inversions using column data one concern is how well the model represents stratospheric and tropospheric CH<sub>4</sub> when assimilating total column measurements. In this study atmospheric CH<sub>4</sub> from three inverse models is compared to FTS (Fourier transform spectrometry), satellite and in situ measurements. Using the FTS measurements the model biases are separated into stratospheric and tropospheric contributions. When averaged over all FTS sites the model bias amplitudes (absolute model to FTS differences) are 7.4 ± 5.1, 6.7 ± 4.8, and 8.1 ± 5.5 ppb in the tropospheric partial column (the column from the surface to the tropopause) for the models TM3, TM5-4DVAR, and LMDz-PYVAR, respectively, and 4.3 ± 9.9, 4.7 ± 9.9, and 6.2 ± 11.2 ppb in the stratospheric partial column (the column from the tropopause to the top of the atmosphere). The model biases in the tropospheric partial column show a latitudinal gradient for all models; however there are no clear latitudinal dependencies for the model biases in the stratospheric partial column visible except with the LMDz-PYVAR model. Comparing modelled and FTS-measured tropospheric column-averaged mole fractions reveals a similar latitudinal gradient in the model biases but comparison with in situ measured mole fractions in the troposphere does not show a latitudinal gradient, which is attributed to the different longitudinal coverage of FTS and in situ measurements. Similarly, a latitudinal pattern exists in model biases in vertical CH<sub>4</sub> gradients in the troposphere, which indicates that vertical transport of tropospheric CH<sub>4</sub> is not represented correctly in the models.</p>}},
  author       = {{Wang, Zhiting and Warneke, Thorsten and Deutscher, Nicholas M. and Notholt, Justus and Karstens, Ute and Saunois, Marielle and Schneider, Matthias and Sussmann, Ralf and Sembhi, Harjinder and Griffith, David W.T. and Pollard, Dave F. and Kivi, Rigel and Petri, Christof and Velazco, Voltaire A. and Ramonet, Michel and Chen, Huilin}},
  issn         = {{1680-7316}},
  language     = {{eng}},
  month        = {{11}},
  number       = {{21}},
  pages        = {{13283--13295}},
  publisher    = {{Copernicus GmbH}},
  series       = {{Atmospheric Chemistry and Physics}},
  title        = {{Contributions of the troposphere and stratosphere to CH<sub>4</sub> model biases}},
  url          = {{http://dx.doi.org/10.5194/acp-17-13283-2017}},
  doi          = {{10.5194/acp-17-13283-2017}},
  volume       = {{17}},
  year         = {{2017}},
}