# Three-dimensional modeling of the O2(1Δ) dayglow and implications for ozone in the middle atmosphere.

Mouhamadou Diouf, Franck Lefèvre, Alain Hauchecorne, Jean-Loup Bertaux

► To cite this version:

Mouhamadou Diouf, Franck Lefèvre, Alain Hauchecorne, Jean-Loup Bertaux. Three-dimensional modeling of the O2(1Δ) dayglow and implications for ozone in the middle atmosphere. EGU General Assembly 2024, Apr 2024, Vienna and Online, Austria. pp.EGU24-1897, 10.5194/egusphere-egu24-1897. insu-04501100

HAL Id: insu-04501100

https://insu.hal.science/insu-04501100

Submitted on 3 Jun 2024

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<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Three-dimensional modeling of the O2(1Δ) dayglow and implications for ozone in the middle atmosphere.

Mouhamadou Diouf, Franck Lefèvre, Alain Hauchecorne, Jean-Loup Bertaux

► To cite this version:

Mouhamadou Diouf, Franck Lefèvre, Alain Hauchecorne, Jean-Loup Bertaux. Three-dimensional modeling of the O2(1Δ) dayglow and implications for ozone in the middle atmosphere. EGU General Assembly 2024, Apr 2024, Vienna and Online, Austria. pp.EGU24-1897, 10.5194/egusphere-egu24-1897. insu-04501100

HAL Id: insu-04501100

https://insu.hal.science/insu-04501100v1

Submitted on 3 Jun 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_2.png" /></figure>

# Three-dimensional modeling of the O₂('Δ) dayglow and implications for ozone in the middle atmosphere.

Mouhamadou Diouf, Franck Lefevre, Alain Hauchecorne, and jean-loup Bertaux

LATMOS, CNRS, Sorbonne Université, Université Paris-Saclay, Paris, France (mouhamadou.diouf@latmos.ipsl.fr)

Future space missions dedicated to measuring CO₂ on a global scale can make advantageous use of the O₂ band at 1.27 µm to retrieve the air column. The 1.27 µm band is close to the CO₂ absorption bands at 1.6 and 2.0 µm, which allows a better transfer of the aerosol properties than with the usual O₂ band at 0.76 µm. However, the 1.27 µm band is polluted by the spontaneous dayglow of the excited state O₂('Δ), which must be removed from the observed signal.

We investigate here our quantitative understanding of the O₂('Δ) dayglow with a chemistry-transport model. We show that the previously reported -13% deficit in O₂('Δ) dayglow calculated with the same model is essentially due a -20 to -30% ozone deficit between 45-60 km. We find that this ozone deficit is due to excessively high temperatures (+15 K) of the meteorological analyses used to drive the model in the mesosphere.

The use of lower analyzed temperatures (ERA5), in better agreement with the observations, slows down the hydrogen-catalyzed and Chapman ozone loss cycles. This effect leads to an almost total elimination of the ozone and O₂('Δ) deficits in the lower mesosphere. Once integrated vertically to simulate a nadir measurement, the deficit in modeled O₂('Δ) brightness is reduced to -4±3%. This illustrates the need for accurate mesospheric temperatures for a priori estimations of the O₂('Δ) brightness in algorithms using the 1.27 µm band.
<figure><img src="image_2.png" /></figure>

# Three-dimensional modeling of the O₂('Δ) dayglow and implications for ozone in the middle atmosphere.

Mouhamadou Diouf, Franck Lefevre, Alain Hauchecorne, and jean-loup Bertaux

LATMOS, CNRS, Sorbonne Université, Université Paris-Saclay, Paris, France (mouhamadou.diouf@latmos.ipsl.fr)

Future space missions dedicated to measuring CO₂ on a global scale can make advantageous use of the O₂ band at 1.27 µm to retrieve the air column. The 1.27 µm band is close to the CO₂ absorption bands at 1.6 and 2.0 µm, which allows a better transfer of the aerosol properties than with the usual O₂ band at 0.76 µm. However, the 1.27 µm band is polluted by the spontaneous dayglow of the excited state O₂('Δ), which must be removed from the observed signal.

We investigate here our quantitative understanding of the O₂('Δ) dayglow with a chemistry-transport model. We show that the previously reported -13% deficit in O₂('Δ) dayglow calculated with the same model is essentially due a -20 to -30% ozone deficit between 45-60 km. We find that this ozone deficit is due to excessively high temperatures (+15 K) of the meteorological analyses used to drive the model in the mesosphere.

The use of lower analyzed temperatures (ERA5), in better agreement with the observations, slows down the hydrogen-catalyzed and Chapman ozone loss cycles. This effect leads to an almost total elimination of the ozone and O₂('Δ) deficits in the lower mesosphere. Once integrated vertically to simulate a nadir measurement, the deficit in modeled O₂('Δ) brightness is reduced to -4±3%. This illustrates the need for accurate mesospheric temperatures for a priori estimations of the O₂('Δ) brightness in algorithms using the 1.27 µm band.