Global impacts from high-latitude storms on Titan

ABSTRACT: One of the first large cloud systems ever observed on Titan was a stationary event at the southern pole that lasted almost two full Titan days. Its stationary nature and large extent are puzzling given that low-level winds should transport clouds eastward, pointing to a mechanism such as atmospheric waves propagating against the mean flow. We use a composite of 47 large convective events across 15 Titan years of simulations from the Titan Atmospheric Model to show that Rossby waves trigger polar convection—which halts the waves and produces stationary precipitation—and then communicate its impact globally. In the aftermath of the convection, forced waves undergo a complicated evolution, including cross-equatorial propagation and tropical-extratropical interaction. The resulting global impact from convection implies its detectability anywhere on Titan, both via surface measurements of pressure and temperature and through remote observation of the outgoing longwave radiation, which increases by ~0.5% globally. Plain Language Summary Saturn’s moon Titan hosts a methane hydrologic cycle with occasional large cloud events that are sometimes stationary and last for up to 30 days at a time. These events have previously been speculated to be caused by convective thunderstorms, but for the first time, we show that their formation is reliant on the interaction between a particular type of high-latitude atmospheric wave, a Rossby wave, and instability caused by increased surface heating during the summer. Convectively forced growth of the Rossby wave accounts for the lack of movement as waves in the summer hemisphere interact with waves that have been forced in the winter hemisphere. The resulting global impact from the forced convection may be detected both from Earth as changes in outgoing longwave radiation and on the surface, which may have relevance for the Dragonfly mission.

SUBMITTER: Battalio J 

PROVIDER: S-EPMC8588012 | biostudies-literature |

REPOSITORIES: biostudies-literature