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Global investigation of the martian D/H cycle through data assimilation

Presentation #318.06 in the session Mars’s Story as Told and Influenced by Dust and Water (Oral Presentation)

Published onOct 23, 2023
Global investigation of the martian D/H cycle through data assimilation

Accurately constraining the water and HDO cycle on Mars is critical to investigating the global D/H ratio in the study of the past amount, and fate, of water on Mars. Vertical profiles of water vapour and HDO can be retrieved from the Nadir and Occultation for MArs Discovery (NOMAD) and Atmospheric Chemistry Suite (ACS) instruments on the ExoMars Trace Gas Orbiter (TGO) with unprecedented spatiotemporal coverage. To help understand and interpret the increasing number of sparse observations made with the solar occultation technique, 4-D Global Circulation Models that simulate the global atmosphere are a critical step.

We investigate the global D/H cycle using data assimilation i.e. combining retrievals with a GCM utilising a statistically optimal approach from the start of the ExoMars TGO science observations in mid- Mars Year 34 until the end of Mars Year 35. The data include observations of water vapour and HDO from NOMAD and ACS, temperature profiles from ACS and the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter spacecraft, and dust column from MCS, which are combined with the Mars Planetary Climate Model (UK Spectral variant). This method provides a robust constraint on the chemical and dynamical structure of the atmosphere, especially through the multi-spacecraft approach combining water vapour/HDO retrievals with additional atmospheric properties (temperature and dust) that strongly influence the evolving global water distribution.

Preliminary results from the D/H assimilation dataset, that uses the latest HDO model incorporating microphysical processes of water ice clouds and supersaturation, will be discussed.

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