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Numerical simulations of convective storm activity observed on Saturn by the Voyager and Cassini missions

Presentation #201.05 in the session “Giant Planets 3: Saturn”.

Published onOct 26, 2020
Numerical simulations of convective storm activity observed on Saturn by the Voyager and Cassini missions

Convective storms of different scales develop in Saturn’s atmosphere. The most energetic ones, known as Great White Spots (Sánchez-Lavega & Battaner 1987) are large outbursts of convective activity observed with an approximate periodicity of 30 years. They release as much energy as the planet radiates in one year (Dyudina et al. 2013). Much smaller scale convective storms are more frequent and were discovered during the Voyager flybys on Saturn’s northern hemisphere (Smith et al., 1981), with new storms observed by the Cassini mission on the southern hemisphere (Dyudina et al. 2007). These storms concentrate on latitude bands symmetrically located about the equator at ~ ±40° and contain multiple vortices with interactions among each other and the storms. The convective phenomena also convey electrical activity (Fischer et al. 2007) and visible lightning (Dyudina et al. 2010). Numerical simulations have shown that GWS’s planetary scale dynamics, although very complex, are mainly driven by the interaction of the storms with the zonal winds (García-Melendo & Sánchez-Lavega, 2017). Smaller storms are irregular with a complex and fast evolving morphology. The particular details of the convection, such as the strength of the divergent updrafts, turbulent flow, background vortices, etc, must be as important or even more than the storm interaction with the zonal flow. Here we present shallow water simulations of the large scale dynamics of the Storm Alley storms, and their counterparts in the northern hemisphere observed by the Voyager spacecraft. Simulations were performed with a parallelized version of the code Shallow Worlds 2 (Sánchez-Lavega et al. 2020) on the Mare Nostrum 4 supercomputer at the Barcelona Supercomputer Center. The computational domain was seeded with instabilities to produce turbulence, vortices and convective storms at the observed latitudes. Results indicate that part of the observed dynamics is due to the presence of background turbulence, as hypothesized by Sromovsky et al. (1983), and interactions with background vortices. Convective activity can also originate small vortices, as observed during the Cassini mission (Dyudina et al. 2007).

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