Mesoscale Modelling of Titan's Shangri-La region: the impact of surface properties on winds

The knowledge of Titan's near-surface atmosphere is sparse. The Huygens descent probe measured winds, and the multiple dune field observations and possible dust storms suggest active near-surface dynamics. The Dragonfly rotorcraft lander will fly close to the surface in the Shangri-La region, near the Huygens landing site, where complex dune orientations were observed. This study presents the first mesoscale modelling of the near-surface dynamics in this region. However, due to a lack of high-resolution topography data, synthetic maps of surface properties were built. The surface was divided into different topographical units, such as plains, mountains, etc. The slopes and height of those units were then parametrised. Maps of thermal inertia, albedo and the aerodynamic roughness height were also built. The mesoscale model is coupled to a comprehensive radiative transfer code and forced by a global climate model. No moist processes are considered in this study. Topography has a major impact on near-surface wind amplitude and direction through slope flows and valley circulations. The majority of the winds are below 0.25 m/s. These winds induce a sensible heat flux comparable to the surface solar flux. Spatially varying thermal inertia has the biggest impact on the wind and surface temperature, with high values leading to smaller diurnal amplitude. The seasonal variability is taken into account, with stronger winds in northern summer. Predicted mesoscale near-surface winds are capable of lifting dust over dune fields, with different orientations during the year, and can therefore potentially play a role in sediment transport on Titan.