Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 – 23 September 2022
Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 September – 23 September 2022
EPSC Abstracts
Vol. 16, EPSC2022-981, 2022
Europlanet Science Congress 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Turbulence in Titan's Planetary Boundary Layer explored by Large-Eddy Simulations with realistic physics

Aymeric Spiga1, Maxence Lefèvre2, and Sébastien Lebonnois1
Aymeric Spiga et al.
  • 1Sorbonne Université - Campus Pierre et Marie Curie, Laboratoire de Météorologie Dynamique BC 99, Paris, France (
  • 2AOPP, Oxford University

Titan, the largest satellite of Saturn, is known to host a rich and active meteorology, by all standards more dynamic than previously thought before the Cassini-Huygens mission. One key element of the dynamic Titan's atmosphere is the Planetary Boundary Layer (PBL), defined as the lowermost part of the atmosphere directly influenced by the presence of a surface below it. Turbulence in the PBL is a controlling factor for exchanges of momentum, heat, chemical species and aerosols between surface and atmosphere.

Following observations by the Cassini-Huygens mission, a debate has arisen on the vertical extent of the PBL mixing on Titan in daytime conditions. Radio-occultations by Voyager and Cassini, as well as insights from dune spacing, indicate that a mixed layer, following the dry adiabatic lapse rate, extends 2 to 4 km above the surface. Conversely, in situ mid-morning measurements on board the equatorial Huygens descent probe suggests a more complex structure, with a clear-cut mixed layer only found to extend 300 m from the surface of Titan, with slope breaks between 2 and 4 km in the vertical temperature profile being related to PBL processes by some studies but not by others.

The turbulent dynamics of Titan's PBL have been studied thus far either by Global Climate Models where mixing dynamics is parameterized rather than resolved, or by idealized Large-Eddy Simulations not coupled to realistic Titan physics and limited to the first hundreds meters above the surface. Here, to broaden the knowledge of Titan PBL processes, we present turbulent-resolving Large Eddy Simulations coupled with a realistic Titan radiative transfer and soil model, extended several kilometers above the surface and ran for the full daytime cycle of Titan environmental conditions. Using those new simulations, we are able to reconcile all existing observations in a single scenario of Titan PBL growth in daytime, from a couple hundreds of meters in mid-morning conditions to a 3 km fully-developed mixing layer in early afternoon conditions. We also explored turbulent statistics for Titan's PBL: sensible heat flux, updraft and downdraft intensity, wind gustiness. We also note the spontaneous occurrence of convective vortices (dustless devils) in our Titan Large-Eddy Simulations.

Our new simulations for Titan PBL bears the potential to help rethink Titan weather processes close to the surface -- and their link to the aerosol / volatile cycles. Furthermore, basic knowledge on PBL turbulence on Titan is needed in the perspective of the Dragonfly spacecraft which will be directly flying within Titan's PBL, thereby experiencing its turbulent dynamics and carrying out in situ measurements of this turbulence.

How to cite: Spiga, A., Lefèvre, M., and Lebonnois, S.: Turbulence in Titan's Planetary Boundary Layer explored by Large-Eddy Simulations with realistic physics, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-981,, 2022.


We are sorry, but the discussion is only available for users who registered for the conference. Thank you.