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Communication Dans Un Congrès Année : 2019

A warm layer in the summer night side mesosphere of Mars

Résumé

The Mars mesosphere and thermosphere (up to ~100 - 200 km) is well known as an intermediate atmospheric region strongly impacted by coupling with the lower-middle atmosphere, exosphere, and the Sun. This intermediate region is still poorly known due to its highly variable nature and a lack of measurements. We report the detection of an extensive layer of warm air at 70 - 90 km altitudes on the night side in the summer hemisphere on Mars by stellar occultations of MAVEN/IUVS. Our result suggests the relatively permanent peaks of atmospheric temperature around 80 km exist over the northern summer night at Ls = 0 - 180 degree. Mars Climate Database does not reproduce a warm layer around 80 km altitude, gradually declining along the height. The predicted temperature by MCD underestimates the quantities of temperature by 10 to 90 K. The longitudinal distribution of atmospheric temperature suggests a mode wave-3 structure that have been potentially interpreted as signatures of thermal tides or stationary planetary waves. Such distinct layer was also found in the dusty southern summer at Ls = 249 degree, that implies 20 km-higher peaks. Warm air at this altitude range can attribute to preserve the water vapor more than hundreds ppmv as the possible maximum in the mesospheric atmosphere and prevent the water vapor condensation falling in the lower atmosphere. Our result highlighted the dynamical mesospheric thermal structure and upsurge of aerosol plays some role not fully considered in the current model, and further study of discrepancies between the model and observations offer opportunities to improve our understanding of transport processes, and thermal structure which has an interdependence with waves.
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Dates et versions

insu-04481055 , version 1 (27-02-2024)

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Hiromu Nakagawa, Sonal K. Jain, Nicholas M. Schneider, Franck Montmessin, Roger V. Yelle, et al.. A warm layer in the summer night side mesosphere of Mars. American Geophysical Union, Fall Meeting 2019, Dec 2019, San Francisco, United States. pp.abstract #P43A-07. ⟨insu-04481055⟩
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