A reanalysis of ozone on Mars from assimilation of SPICAM observations

James A. Holmes (1) , Stephen R. Lewis (1) , Manish R. Patel (1, 2) , Franck Lefèvre (3)

1 School of Physical Sciences [Milton Keynes]
2 RAL Space - Space Science and Technology Department [Didcot]
3 PLANETO - LATMOS

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 L_S= 135–180° and at northern polar (60°N–90°N) latitudes during northern fall (L_S= 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 L_S= 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.

Mots clés: chemistry; Atmospheres; data assimilation; Mars; Atmospheres; Mars data assimilation; Mars atmosphere; atmosphere; Mars; chemistry

Domaines: Planète et Univers [physics]

James A. Holmes, Stephen R. Lewis, Manish R. Patel, Franck Lefèvre. A reanalysis of ozone on Mars from assimilation of SPICAM observations. Icarus, 2018, 302, pp.308-318. ⟨10.1016/j.icarus.2017.11.026⟩. ⟨insu-01646783⟩