A reanalysis of ozone on Mars from assimilation of SPICAM observations

• Published in: Icarus (New York, N.Y. 1962) Vol. 302; pp. 308 - 318
• Main Authors: Holmes, James A., Lewis, Stephen R., Patel, Manish R., Lefèvre, Franck
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.03.2018; Elsevier
• Subjects: Atmospheres; chemistry; Mars atmosphere; Mars data assimilation; Sciences of the Universe; chemistry; Mars atmosphere; Atmospheres; Mars data assimilation; atmosphere; Mars; data assimilation
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2017.11.026

•First photochemical assimilation of chemical species data into a Mars GCM.•Largest increments in total ozone linked to excessive transport of water vapour.•Southern polar high altitude ozone layer altered by assimilation. We have assimilated for the first time SPICAM retrievals of total ozone into a Martian global circulation model to provide a global reanalysis of the ozone cycle. Disagreement in total ozone between model prediction and assimilation is observed between 45°S–10°S from LS=135–180° and at northern polar (60°N–90°N) latitudes during northern fall (LS=150–195°). Large percentage differences in total ozone at northern fall polar latitudes identified through the assimilation process are linked with excessive northward transport of water vapour west of Tharsis and over Arabia Terra. Modelling biases in water vapour can also explain the underestimation of total ozone between 45°S–10°S from LS=135–180°. Heterogeneous uptake of odd hydrogen radicals are unable to explain the outstanding underestimation of northern polar total ozone in late northern fall. Assimilation of total ozone retrievals results in alterations of the modelled spatial distribution of ozone in the southern polar winter high altitude ozone layer. This illustrates the potential use of assimilation methods in constraining total ozone where SPICAM cannot observe, in a region where total ozone is especially important for potential investigations of the polar dynamics.