Diurnal Variations in the Aphelion Cloud Belt as Observed by the Emirates Exploration Imager (EXI)

Michael J. Wolff , Anton Fernando , Michael D. Smith , François Forget (1) , Ehouarn Millour (1) , Samuel A. Atwood , Andrew R. Jones , Mikki M. Osterloo , Ralph Shuping , Mariam Al Shamsi , Christian Jeppesen , Charles Fisher

1 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)

Observations by the Emirates eXploration Imager (EXI) on-board the Emirates Mars Mission are used to characterize the diurnal, seasonal, and spatial behavior of aphelion cloud belt during Mars Year 36 L_S ∼ 30°-190°. Building from previous work with the Mars Color Imager (MARCI) onboard the Mars Reconnaissance Orbiter, we retrieve water ice extinction optical depth (τ_ice) with an uncertainty ±0.0232 (excluding particle size effects). We connect EXI and MARCI using radiance and τ_ice. Zonal and meridional diurnal trends are analyzed over 6-18 hr Local True Solar Time. The retrievals show large morning-evening asymmetries about a minimum near 12 hr. The latitudinal distributions in early morning are extensive and particularly striking near mid-summer. Comparisons to the Mars Planetary Climate Model show reasonable agreement with basic diurnal behavior, but noticeable departures include too much water ice in early morning, the general latitudinal extent, and behavior at smaller scales like the volcanoes and other topographically distinct features.

Mots clés: Mars atmosphere aerosol ultraviolet EXI EMM

Domaines: Planète et Univers [physics]

Michael J. Wolff, Anton Fernando, Michael D. Smith, François Forget, Ehouarn Millour, et al.. Diurnal Variations in the Aphelion Cloud Belt as Observed by the Emirates Exploration Imager (EXI). Geophysical Research Letters, 2022, 49, ⟨10.1029/2022GL100477⟩. ⟨insu-03847100⟩