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Communication Dans Un Congrès Année : 2021

Improved ultraviolet dust aerosol properties derived from MAVEN/IUVS measurements of the Mars year 34 global dust storm

Résumé

The Imaging Ultraviolet Spectrograph (IUVS) instrument on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft takes mid-UV spectral images of the Martian surface and atmosphere. From these apoapse images, information about dust aerosols can be retrieved and comprise the only MAVEN observations of airborne dust. Measuring local time variability of large-scale recurring features is made possible with MAVENs nearly-global imaging combined with its ~4.5-hour elliptical orbit, something not possible with sun-synchronous orbits. The Mars year 34 (2018) global dust storm provided a unique opportunity to improve measurements of aerosol properties. The presence of a thick layer of dust allowed us to sample the single scattering albedo (SSA) at a range of UV wavelengths unmeasured by previous missions. Having an optically thick atmosphere in the UV minimizes retrieval errors due to imprecise knowledge of surface reflectance properties and reduced sensitivity of some radiative parameters. To do this we employed the DIScrete Ordinates Radiative Transfer (DISORT) code to derive a wavelength-dependent SSA from the measured reflectance spectra given atmospheric parameters obtained from a general circulation model. The SSA was converted into an imaginary index of refraction using a T-matrix-based set of optical properties (with the real part of the index of refraction calculated using a subtractive Kramers-Kronig analysis.) With the new refractive indices, the scattering properties for the SSA retrievals were recalculated and the SSA was retrieved again until convergence was reached. Our analysis should be particularly valuable at shorter mid-UV wavelengths (200250 nm) where the SSA has not been well-characterized, and thus beneficial for IUVS retrievals during lower dust-loading conditions. It may also be of particular benefit to retrievals from EMM/EXI. We discuss our retrieved SSA and show its implications for future IUVS retrievals of dust.
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Dates et versions

insu-04436358 , version 1 (03-02-2024)

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Citer

Kyle Connour, Michael Wolff, Nicholas Schneider, Justin Deighan, Franck Lefèvre. Improved ultraviolet dust aerosol properties derived from MAVEN/IUVS measurements of the Mars year 34 global dust storm. AGU Fall Meeting 2021, Dec 2021, New Orleans, United States. pp.id. P35F-2197. ⟨insu-04436358⟩
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