Investigating the yield of H2O and H2 from methane oxidation in the stratosphere
An important driver of climate change is stratospheric water vapor (SWV), which in turn is influenced by the oxidation of atmospheric methane (CH4). In order to parameterize the production of water vapor (H2O) from CH4 oxidation, it is often assumed that the oxidation of one CH4 molecule yields exac...
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ftdlr:oai:elib.dlr.de:120968 2023-05-15T18:02:19+02:00 Investigating the yield of H2O and H2 from methane oxidation in the stratosphere Frank, Franziska Jöckel, Patrick Gromov, Sergey Dameris, Martin Grooß, Jens-Uwe 2018-07-13 application/pdf https://elib.dlr.de/120968/ https://elib.dlr.de/120968/1/acp-18-9955-2018.pdf https://www.atmos-chem-phys.net/18/9955/2018/ en eng Copernicus Publications https://elib.dlr.de/120968/1/acp-18-9955-2018.pdf Frank, Franziska und Jöckel, Patrick und Gromov, Sergey und Dameris, Martin (2018) Investigating the yield of H2O and H2 from methane oxidation in the stratosphere. Atmospheric Chemistry and Physics (ACP), 18 (13), Seiten 9955-9973. Copernicus Publications. DOI:10.5194/acp-18-9955-2018 <https://doi.org/10.5194/acp-18-9955-2018> ISSN 1680-7316 cc_by CC-BY Erdsystem-Modellierung Zeitschriftenbeitrag PeerReviewed 2018 ftdlr https://doi.org/10.5194/acp-18-9955-2018 2019-05-05T22:53:05Z An important driver of climate change is stratospheric water vapor (SWV), which in turn is influenced by the oxidation of atmospheric methane (CH4). In order to parameterize the production of water vapor (H2O) from CH4 oxidation, it is often assumed that the oxidation of one CH4 molecule yields exactly two molecules of H2O. However, this assumption is based on an early study, which also gives evidence that this is not true at all altitudes. In the current study, we re-evaluate this assumption with a comprehensive systematic analysis using a state-of-the-art chemistry-climate model (CCM), namely the ECHAM/MESSy Atmospheric Chemistry (EMAC) model, and present three approaches to investigate the yield of H2O and hydrogen gas (H2) from CH4 oxidation. We thereby make use of the Module Efficiently Calculating the Chemistry of the Atmosphere (MECCA) in a box model and global model configuration. Furthermore, we use the kinetic chemistry tagging technique (MECCA-TAG) to investigate the chemical pathways between CH4, H2O and H2, by being able to distinguish hydrogen atoms produced by CH4 from H2 from other sources. We apply three approaches, which all agree that assuming a yield of 2 overestimates the production of H2O in the lower stratosphere (calculated as 1.5-1.7). Additionally, transport and subsequent photochemical processing of longer-lived intermediates (mostly H2) raise the local yield values in the upper stratosphere and lower mesosphere above 2 (maximum > 2.2). In the middle and upper mesosphere, the influence of loss and recycling of H2O increases, making it a crucial factor in the parameterization of the yield of H2O from CH4 oxidation. An additional sensitivity study with the Chemistry As A Boxmodel Application (CAABA) shows a dependence of the yield on the hydroxyl radical (OH) abundance. No significant temperature dependence is found. We focus representatively on the tropical zone between 23°S and 23°N. It is found in the global approach that presented results are mostly valid for midlatitudes as well. During the polar night, the method is not applicable. Our conclusions question the use of a constant yield of H2O from CH4 oxidation in climate modeling and encourage to apply comprehensive parameterizations that follow the vertical profiles of the H2O yield derived here and take the chemical H2O loss into account. Other Non-Article Part of Journal/Newspaper polar night German Aerospace Center: elib - DLR electronic library Atmospheric Chemistry and Physics 18 13 9955 9973 |
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German Aerospace Center: elib - DLR electronic library |
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English |
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Erdsystem-Modellierung |
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Erdsystem-Modellierung Frank, Franziska Jöckel, Patrick Gromov, Sergey Dameris, Martin Investigating the yield of H2O and H2 from methane oxidation in the stratosphere |
topic_facet |
Erdsystem-Modellierung |
description |
An important driver of climate change is stratospheric water vapor (SWV), which in turn is influenced by the oxidation of atmospheric methane (CH4). In order to parameterize the production of water vapor (H2O) from CH4 oxidation, it is often assumed that the oxidation of one CH4 molecule yields exactly two molecules of H2O. However, this assumption is based on an early study, which also gives evidence that this is not true at all altitudes. In the current study, we re-evaluate this assumption with a comprehensive systematic analysis using a state-of-the-art chemistry-climate model (CCM), namely the ECHAM/MESSy Atmospheric Chemistry (EMAC) model, and present three approaches to investigate the yield of H2O and hydrogen gas (H2) from CH4 oxidation. We thereby make use of the Module Efficiently Calculating the Chemistry of the Atmosphere (MECCA) in a box model and global model configuration. Furthermore, we use the kinetic chemistry tagging technique (MECCA-TAG) to investigate the chemical pathways between CH4, H2O and H2, by being able to distinguish hydrogen atoms produced by CH4 from H2 from other sources. We apply three approaches, which all agree that assuming a yield of 2 overestimates the production of H2O in the lower stratosphere (calculated as 1.5-1.7). Additionally, transport and subsequent photochemical processing of longer-lived intermediates (mostly H2) raise the local yield values in the upper stratosphere and lower mesosphere above 2 (maximum > 2.2). In the middle and upper mesosphere, the influence of loss and recycling of H2O increases, making it a crucial factor in the parameterization of the yield of H2O from CH4 oxidation. An additional sensitivity study with the Chemistry As A Boxmodel Application (CAABA) shows a dependence of the yield on the hydroxyl radical (OH) abundance. No significant temperature dependence is found. We focus representatively on the tropical zone between 23°S and 23°N. It is found in the global approach that presented results are mostly valid for midlatitudes as well. During the polar night, the method is not applicable. Our conclusions question the use of a constant yield of H2O from CH4 oxidation in climate modeling and encourage to apply comprehensive parameterizations that follow the vertical profiles of the H2O yield derived here and take the chemical H2O loss into account. |
author2 |
Grooß, Jens-Uwe |
format |
Other Non-Article Part of Journal/Newspaper |
author |
Frank, Franziska Jöckel, Patrick Gromov, Sergey Dameris, Martin |
author_facet |
Frank, Franziska Jöckel, Patrick Gromov, Sergey Dameris, Martin |
author_sort |
Frank, Franziska |
title |
Investigating the yield of H2O and H2 from methane oxidation in the stratosphere |
title_short |
Investigating the yield of H2O and H2 from methane oxidation in the stratosphere |
title_full |
Investigating the yield of H2O and H2 from methane oxidation in the stratosphere |
title_fullStr |
Investigating the yield of H2O and H2 from methane oxidation in the stratosphere |
title_full_unstemmed |
Investigating the yield of H2O and H2 from methane oxidation in the stratosphere |
title_sort |
investigating the yield of h2o and h2 from methane oxidation in the stratosphere |
publisher |
Copernicus Publications |
publishDate |
2018 |
url |
https://elib.dlr.de/120968/ https://elib.dlr.de/120968/1/acp-18-9955-2018.pdf https://www.atmos-chem-phys.net/18/9955/2018/ |
genre |
polar night |
genre_facet |
polar night |
op_relation |
https://elib.dlr.de/120968/1/acp-18-9955-2018.pdf Frank, Franziska und Jöckel, Patrick und Gromov, Sergey und Dameris, Martin (2018) Investigating the yield of H2O and H2 from methane oxidation in the stratosphere. Atmospheric Chemistry and Physics (ACP), 18 (13), Seiten 9955-9973. Copernicus Publications. DOI:10.5194/acp-18-9955-2018 <https://doi.org/10.5194/acp-18-9955-2018> ISSN 1680-7316 |
op_rights |
cc_by |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.5194/acp-18-9955-2018 |
container_title |
Atmospheric Chemistry and Physics |
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18 |
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13 |
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9955 |
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9973 |
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1766172126904057856 |