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Impacts of Heterogeneous Chemistry on Vertical Profiles of Martian Ozone
  • +7
  • Megan A J Brown,
  • Manish R Patel,
  • Stephen Lewis,
  • James Andrew Holmes,
  • Paul Michael Streeter,
  • Graham Sellers,
  • Amel Bennaceur,
  • Giuliano Liuzzi,
  • Geronimo Luis Villanueva,
  • Ann Carine Vandaele
Megan A J Brown
The Open University

Corresponding Author:megan.brown@open.ac.uk

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Manish R Patel
The Open University
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Stephen Lewis
Open University
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James Andrew Holmes
Open University
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Paul Michael Streeter
Open University
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Graham Sellers
The Open University
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Amel Bennaceur
The Open University
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Giuliano Liuzzi
NASA Goddard Space Flight Center
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Geronimo Luis Villanueva
NASA Goddard Space Flight Center
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Ann Carine Vandaele
Royal Belgian Institute for Space Aeronomy
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Abstract

We show a positive vertical correlation between ozone and water ice using a vertical cross-correlation analysis with observations from the ExoMars Trace Gas Orbiter’s NOMAD instrument. We find this is particularly apparent during the first half of Mars Year 35 (LS=0-180) at high southern latitudes, when the water vapour abundance is low. This contradicts the current understanding that ozone and water are, in general, anti-correlated. However, our simulations with gas-phase-only chemistry using a 1-D model show that ozone concentration is not influenced by water ice. Heterogeneous chemistry has been proposed as a mechanism to explain the underprediction of ozone in global climate models (GCMs) through the removal of HOX. We find improving the heterogeneous chemical scheme causes ozone abundance to increase when water ice is present, better matching observed trends. When water vapour abundance is high, there is no consistent vertical correlation between observed ozone and water ice and, in simulated scenarios, the heterogeneous chemistry does not have a large influence on ozone. HOX, which are by-products of water vapour, dominate ozone abundance and mask the effects of heterogeneous chemistry on ozone.
This is consistent with gas-phase-only modelled ozone, showing good agreement with observations when water vapour is abundant. High water vapour abundance masks the effect of heterogeneous reactions on ozone abundance and makes adsorption of HOX have a negligible impact on ozone. Overall, the inclusion of heterogeneous chemistry improves the ozone vertical structure in regions of low water vapour abundance, which may partially explain GCM ozone deficits.