A re-evaluation of the ClO/Cl 2 O 2 equilibrium constant based on stratospheric in-situ observations
International audience In-situ measurements of ClO and its dimer carried out during the SOLVE II/VINTERSOL-EUPLEX and ENVISAT Validation campaigns in the Arctic winter 2003 suggest that the thermal equilibrium between the dimer formation and dissociation is shifted significantly towards the monomer...
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ftinsu:oai:HAL:hal-00295630v1 2024-02-11T10:01:28+01:00 A re-evaluation of the ClO/Cl 2 O 2 equilibrium constant based on stratospheric in-situ observations von Hobe, M. Grooss, J.-U. Müller, R. Hrechanyy, S. Winkler, U. Stroh, F. Institut für Chemie und Dynamik der Geosphäre - Stratosphäre (ICG-1) Forschungszentrum Jülich GmbH Helmholtz-Gemeinschaft = Helmholtz Association-Helmholtz-Gemeinschaft = Helmholtz Association 2005-03-02 https://hal.science/hal-00295630 https://hal.science/hal-00295630/document https://hal.science/hal-00295630/file/acp-5-693-2005.pdf en eng HAL CCSD European Geosciences Union hal-00295630 https://hal.science/hal-00295630 https://hal.science/hal-00295630/document https://hal.science/hal-00295630/file/acp-5-693-2005.pdf info:eu-repo/semantics/OpenAccess ISSN: 1680-7316 EISSN: 1680-7324 Atmospheric Chemistry and Physics https://hal.science/hal-00295630 Atmospheric Chemistry and Physics, 2005, 5 (3), pp.693-702 [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere info:eu-repo/semantics/article Journal articles 2005 ftinsu 2024-01-17T17:27:37Z International audience In-situ measurements of ClO and its dimer carried out during the SOLVE II/VINTERSOL-EUPLEX and ENVISAT Validation campaigns in the Arctic winter 2003 suggest that the thermal equilibrium between the dimer formation and dissociation is shifted significantly towards the monomer compared to the current JPL 2002 recommendation. Detailed analysis of observations made in thermal equilibrium allowed to re-evaluate the magnitude and temperature dependence of the equilibrium constant. A fit of the JPL format for equilibrium constants yields K EQ =3.61x10 -27 exp(8167/ T ), but to reconcile the observations made at low temperatures with the existing laboratory studies at room temperature, a modified equation, K EQ =5.47x10 -25 ( T /300) -2.29 exp(6969/ T ), is required. This format can be rationalised by a strong temperature dependence of the reaction enthalpy possibly induced by Cl 2 O 2 isomerism effects. At stratospheric temperatures, both equations are practically equivalent. Using the equilibrium constant reported here rather than the JPL 2002 recommendation in atmospheric models does not have a large impact on simulated ozone loss. Solely at large zenith angles after sunrise, a small decrease of the ozone loss rate due to the ClO dimer cycle and an increase due to the ClO-BrO cycle (attributed to the enhanced equilibrium ClO concentrations) is observed, the net effect being a slightly stronger ozone loss rate. Article in Journal/Newspaper Arctic Institut national des sciences de l'Univers: HAL-INSU Arctic |
institution |
Open Polar |
collection |
Institut national des sciences de l'Univers: HAL-INSU |
op_collection_id |
ftinsu |
language |
English |
topic |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
spellingShingle |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere von Hobe, M. Grooss, J.-U. Müller, R. Hrechanyy, S. Winkler, U. Stroh, F. A re-evaluation of the ClO/Cl 2 O 2 equilibrium constant based on stratospheric in-situ observations |
topic_facet |
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
description |
International audience In-situ measurements of ClO and its dimer carried out during the SOLVE II/VINTERSOL-EUPLEX and ENVISAT Validation campaigns in the Arctic winter 2003 suggest that the thermal equilibrium between the dimer formation and dissociation is shifted significantly towards the monomer compared to the current JPL 2002 recommendation. Detailed analysis of observations made in thermal equilibrium allowed to re-evaluate the magnitude and temperature dependence of the equilibrium constant. A fit of the JPL format for equilibrium constants yields K EQ =3.61x10 -27 exp(8167/ T ), but to reconcile the observations made at low temperatures with the existing laboratory studies at room temperature, a modified equation, K EQ =5.47x10 -25 ( T /300) -2.29 exp(6969/ T ), is required. This format can be rationalised by a strong temperature dependence of the reaction enthalpy possibly induced by Cl 2 O 2 isomerism effects. At stratospheric temperatures, both equations are practically equivalent. Using the equilibrium constant reported here rather than the JPL 2002 recommendation in atmospheric models does not have a large impact on simulated ozone loss. Solely at large zenith angles after sunrise, a small decrease of the ozone loss rate due to the ClO dimer cycle and an increase due to the ClO-BrO cycle (attributed to the enhanced equilibrium ClO concentrations) is observed, the net effect being a slightly stronger ozone loss rate. |
author2 |
Institut für Chemie und Dynamik der Geosphäre - Stratosphäre (ICG-1) Forschungszentrum Jülich GmbH Helmholtz-Gemeinschaft = Helmholtz Association-Helmholtz-Gemeinschaft = Helmholtz Association |
format |
Article in Journal/Newspaper |
author |
von Hobe, M. Grooss, J.-U. Müller, R. Hrechanyy, S. Winkler, U. Stroh, F. |
author_facet |
von Hobe, M. Grooss, J.-U. Müller, R. Hrechanyy, S. Winkler, U. Stroh, F. |
author_sort |
von Hobe, M. |
title |
A re-evaluation of the ClO/Cl 2 O 2 equilibrium constant based on stratospheric in-situ observations |
title_short |
A re-evaluation of the ClO/Cl 2 O 2 equilibrium constant based on stratospheric in-situ observations |
title_full |
A re-evaluation of the ClO/Cl 2 O 2 equilibrium constant based on stratospheric in-situ observations |
title_fullStr |
A re-evaluation of the ClO/Cl 2 O 2 equilibrium constant based on stratospheric in-situ observations |
title_full_unstemmed |
A re-evaluation of the ClO/Cl 2 O 2 equilibrium constant based on stratospheric in-situ observations |
title_sort |
re-evaluation of the clo/cl 2 o 2 equilibrium constant based on stratospheric in-situ observations |
publisher |
HAL CCSD |
publishDate |
2005 |
url |
https://hal.science/hal-00295630 https://hal.science/hal-00295630/document https://hal.science/hal-00295630/file/acp-5-693-2005.pdf |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic |
genre_facet |
Arctic |
op_source |
ISSN: 1680-7316 EISSN: 1680-7324 Atmospheric Chemistry and Physics https://hal.science/hal-00295630 Atmospheric Chemistry and Physics, 2005, 5 (3), pp.693-702 |
op_relation |
hal-00295630 https://hal.science/hal-00295630 https://hal.science/hal-00295630/document https://hal.science/hal-00295630/file/acp-5-693-2005.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1790597266699976704 |