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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ftccsdartic:oai:HAL:hal-00301413v1 2023-05-15T15:11:40+02:00 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 2004-09-07 https://hal.archives-ouvertes.fr/hal-00301413 https://hal.archives-ouvertes.fr/hal-00301413/document https://hal.archives-ouvertes.fr/hal-00301413/file/acpd-4-5075-2004.pdf en eng HAL CCSD European Geosciences Union hal-00301413 https://hal.archives-ouvertes.fr/hal-00301413 https://hal.archives-ouvertes.fr/hal-00301413/document https://hal.archives-ouvertes.fr/hal-00301413/file/acpd-4-5075-2004.pdf info:eu-repo/semantics/OpenAccess ISSN: 1680-7367 EISSN: 1680-7375 Atmospheric Chemistry and Physics Discussions https://hal.archives-ouvertes.fr/hal-00301413 Atmospheric Chemistry and Physics Discussions, European Geosciences Union, 2004, 4 (5), pp.5075-5102 [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere info:eu-repo/semantics/article Journal articles 2004 ftccsdartic 2021-12-19T04:10:59Z 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 was used to re-evaluate the magnitude and temperature dependence of the equilibrium constant. A fit of the JPL format for equilibrium constants yields K EQ =4.06×10 ?23 exp(6201/ T ), but to reconcile the observations made at low temperatures with the existing laboratory studies at room temperature, a modified equation, K EQ =2.31×10 ?13 ( T /300) ?34.9 exp( ?1118/ 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. The effects of Cl 2 O 2 isomerism are not studied in detail, but the presence of isomers other than ClOOCl would be expected to lead to reduced ozone loss. Article in Journal/Newspaper Arctic Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) Arctic |
institution |
Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
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ftccsdartic |
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 was used to re-evaluate the magnitude and temperature dependence of the equilibrium constant. A fit of the JPL format for equilibrium constants yields K EQ =4.06×10 ?23 exp(6201/ T ), but to reconcile the observations made at low temperatures with the existing laboratory studies at room temperature, a modified equation, K EQ =2.31×10 ?13 ( T /300) ?34.9 exp( ?1118/ 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. The effects of Cl 2 O 2 isomerism are not studied in detail, but the presence of isomers other than ClOOCl would be expected to lead to reduced ozone loss. |
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 |
2004 |
url |
https://hal.archives-ouvertes.fr/hal-00301413 https://hal.archives-ouvertes.fr/hal-00301413/document https://hal.archives-ouvertes.fr/hal-00301413/file/acpd-4-5075-2004.pdf |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic |
genre_facet |
Arctic |
op_source |
ISSN: 1680-7367 EISSN: 1680-7375 Atmospheric Chemistry and Physics Discussions https://hal.archives-ouvertes.fr/hal-00301413 Atmospheric Chemistry and Physics Discussions, European Geosciences Union, 2004, 4 (5), pp.5075-5102 |
op_relation |
hal-00301413 https://hal.archives-ouvertes.fr/hal-00301413 https://hal.archives-ouvertes.fr/hal-00301413/document https://hal.archives-ouvertes.fr/hal-00301413/file/acpd-4-5075-2004.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1766342490186579968 |