3 research outputs found
Saturn's Seasonal Variability from Four Decades of Ground-Based Mid-Infrared Observations
A multi-decade record of ground-based mid-infrared (7-25 m) images of
Saturn is used to explore seasonal and non-seasonal variability in thermal
emission over more than a Saturnian year (1984-2022). Thermal emission measured
by 3-m and 8-m-class observatories compares favourably with synthetic images
based on both Cassini-derived temperature records and the predictions of
radiative climate models. 8-m class facilities are capable of resolving thermal
contrasts on the scale of Saturn's belts, zones, polar hexagon, and polar
cyclones, superimposed onto large-scale seasonal asymmetries. Seasonal changes
in brightness temperatures of K in the stratosphere and K in
the upper troposphere are observed, as the northern and southern polar
stratospheric vortices (NPSV and SPSV) form in spring and dissipate in autumn.
The timings of the first appearance of the warm polar vortices is successfully
reproduced by radiative climate models, confirming them to be radiative
phenomena, albeit entrained within sharp boundaries influenced by dynamics.
Axisymmetric thermal bands (4-5 per hemisphere) display temperature gradients
that are strongly correlated with Saturn's zonal winds, indicating winds that
decay in strength with altitude, and implying meridional circulation cells
forming the system of cool zones and warm belts. Saturn's thermal structure is
largely repeatable from year to year (via comparison of infrared images in 1989
and 2018), with the exception of low-latitudes. Here we find evidence of
inter-annual variations because the equatorial banding at 7.9 m is
inconsistent with a -year period for Saturn's equatorial stratospheric
oscillation, i.e., it is not strictly semi-annual. Finally, observations
between 2017-2022 extend the legacy of the Cassini mission, revealing the
continued warming of the NPSV during northern summer. [Abr.]Comment: 25 pages, 15 figures, accepted for publication in Icaru
A new description of Titan's aerosol optical properties from the analysis of VIMS Emission Phase Function observations
International audienceHere we present the analysis of the EPF observation performed by VIMS during the Cassini Titan flyby T88 in terms of aerosol optical properties
Radiative Transfer Modeling in Titan's Atmosphere and Surface: Application to Cassini/VIMS Data Analysis at Regional to Global Scale
International audienceWe aim at developing an accurate and fast radiative transfer model and inversion scheme for Titan in order to massively invert the Titan VIMS dataset and determine the main chemical species present on Titan’s surface and follow the atmospheric extinction evolution over time