The Role and Lifetime of Dissociative Heterogeneous Processes in Improving Simulated Ozone on Mars
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- Centre for Atmospheric Science University of Cambridge Cambridge UK, The Open University Milton Keynes UK
- The Open University Milton Keynes UK, Space Science and Technology Department Science and Technology Facilities Council Rutherford Appleton Laboratory Oxfordshire UK
- The Open University Milton Keynes UK
- LATMOS Sorbonne Université UVSQ Université Paris‐Saclay CNRS Paris France
- Department of Physics and Astronomy California State University, San Bernardino San Bernardino CA USA
Abstract Ozone simulated in Mars Global Climate Models (MGCMs) is used to assess the underlying chemistry occurring in the atmosphere. Currently, ozone total column abundance (TCA) is under‐predicted in MGCMs by up to 120%, implying missing or inaccurate chemistry in models. Heterogeneous reactions of hydroxyl radicals (HO X ) have been offered as an explanation for some of this bias, because they cause ozone to increase at locations where it's currently under‐predicted. We use four simulations to compare modeled ozone TCA with observations from the UVIS spectrometer aboard the ExoMars Trace Gas Orbiter to improve the representation of heterogeneous processes and their impact on ozone. We use a gas‐phase only run, a dissociative scheme, an adsorbed HO X retention scheme, and a hybrid scheme that combines the dissociative mechanism with the retention of HO X on water ice. We find retention of HO X is dependent on water ice sublimation, and ozone abundance increases when water ice persists for longer periods (1–20 sols). Over time, the loss of HO X causes a depletion in H 2 O 2 concentration (HO X reservoir), and thus allows ozone concentration to increase. When adsorbed HO X are desorbed and dissociate into other by‐products, HO X are not immediately available to destroy ozone. This results in larger ozone concentrations than if desorbed HO X are released directly back into their gaseous states. When using the hybrid scheme, ozone TCA is increased up to 50% where the ozone deficit is greatest, demonstrating the best agreement with observations, and implying that HO X radicals are both retained when adsorbed and dissociate.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 2396378
- Alternate ID(s):
- OSTI ID: 2396380
- Journal Information:
- Journal of Geophysical Research. Planets, Journal Name: Journal of Geophysical Research. Planets Journal Issue: 7 Vol. 129; ISSN 2169-9097
- Publisher:
- American Geophysical Union (AGU)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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