[P-PS01] Outer Solar System Exploration Today, and Tomorrow

[PPS01-02] Eulerian Mean Framework to Understand the Internal Structure and Circulation of Giant Planet Atmospheric Vortices

*Kunio M. Sayanagi¹, Justin Garland¹, David M. Salazar², Shawn R. Brueshaber³, Tianshu Liu², John W.C. McNabb¹ (1.Hampton University, 2.Western Michigan University, 3.Jet Propulsion Lab / Caltech)

Keywords:Planetary Atmospheres, Atmospheric Dynamics, Giant Planets

We present a theoretical framework to understand the internal structure and circulation of atmospheric vortices on giant planets. Past and ongoing observations from Earth-based telescopes as well as visiting missions including Juno have revealed key characteristics that hint at the three-dimensional structure and circulation within those vortices. Characteristics of large anticyclonic vortices like Jupiter’s Great Red Spot and Oval BA include a cyclonic ring at their outer rim from where relatively thin tropospheric thin allows thermal emissions from depth to escape to space (e.g. de Pater et al. 2010). In addition, the dark spots on Uranus and Neptune are sometimes accompany by overhanging bright clouds that may be analogous to orographic clouds on Earth (e.g. Stratman et al. 2001). Juno JIRAM mapped thermal emission patterns in and around cyclonic vortices on Jupiter; at their centers, some of the vortices seem to harbor have thick cloud while others have thin clouds (Adriani et al. 2020). In these observations, areas of thin and thick clouds are interpreted to be associated with subsidence and upwelling branches of internal circulation, respectively. Cassini observations of Saturn’s polar cyclonic vortices also have interesting dynamical characteristics which are reminiscent of terrestrial hurricanes with a central eye-like structure.

To understand these structures, we apply an Eulerian mean (EM) formulation in cylindrical coordinates. While the EM formulation is more often employed to understand zonal mean flows like atmospheric jets, we show that the formulation is applicable to any axially symmetric flow, and, when derived in the cylindrical coordinates, it can be used to represent circular vortices. I use our EM formulation in the cylindrical coordinate to test internal flow structures that have been proposed to explain observed vortex characteristics such as those by Wong et al. (2011) and Marcus et al. (2013).

This work has been supported by NASA grants CDAP 80NSSC19K0894 and SSW 80NSSC21K0166.

References:
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