Analysis of Saturn's Hexagon between 2012 and 2016: Dynamical and Morphological Changes
Abstract
We present analyses of Saturn's wind fields and cloud morphology in the northern Hexagon region, combining visible-light imaging from the Cassini ISS instrument with measurements of Saturn's thermal structure and zonal wind shear from the Cassini CIRS instrument and ground-based VLT/VISIR imaging. Our study focuses on temporal changes occurring in the region around 77 degree N planetocentric latitude, which has been illuminated by sunlight since 2008, and captured by ISS with good observation geometries in 2012-2013 and 2016. The goal of our analysis is to detect any change in the cloud morphology, atmospheric dynamics and thermal structure. To measure the wind field in the Hexagon region, we utilize the two-dimensional correlation imaging velocimetry (CIV) technique. We also calculate the relative vorticity and divergence from the wind field. To detect changes in the dynamics of the Hexagon, we compare measurements of the wind, relative vorticity, and divergence in 2012 with those from 2016, as well as evaluating changes in the zonal mean temperature gradient across the Hexagon boundaries. We compare cloud reflectivity between 2012 and 2016 in images that show the Hexagon under similar illumination conditions, calculating the zonal mean reflectivity as a function of latitude. Furthermore, we assess the winds and cloud reflectivity at several wavelengths in order to look for changes occurring at different altitudes, and relate this to temperature variations in the 100-700 mbar region assessed from Cassini and ground-based VLT imaging. Specifically, we focus on the CB2 continuum filter which senses thick tropospheric clouds and the MT2 and MT3 methane filters which sense the upper tropospheric and stratospheric haze layers. Our work has been supported by NASA PATM NNX14AK07G, CDAPS NNX15AD33G, NSF AAG 1212216, and NASA NESSF NNX15AQ70H.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.P31D..06B
- Keywords:
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- 5704 Atmospheres;
- PLANETARY SCIENCES: FLUID PLANETSDE: 5706 Aurorae;
- PLANETARY SCIENCES: FLUID PLANETSDE: 5724 Interiors;
- PLANETARY SCIENCES: FLUID PLANETSDE: 5737 Magnetospheres;
- PLANETARY SCIENCES: FLUID PLANETS