Turbulent Fluxes and Evaporation/Sublimation Rates on Earth, Mars, Titan, and Exoplanets

Turbulent fluxes of heat, momentum, and humidity in the atmospheric boundary layer are pivotal to the evolution of geology, weather and climate, and the possibility of life. Here we extend recent advances in calculating these near-surface turbulent fluxes in the Earth's atmospheric boundary layer to any terrestrial planetary body with an atmosphere. These improvements include: (a) incorporating Monin-Obukhov similarity functions that encompass the entire range of atmospheric stability expected on terrestrial planetary bodies, (b) accounting for the additional shear associated with buoyant plumes under unstable conditions, (c) using surface renewal theory to calculate transfer rates within the interfacial layer adjacent to the surface, and (d) explicitly accounting for key humidity effects that become especially important when a volatile is more buoyant than the ambient gas (e.g., on Mars where H2O is lighter than CO2). We tested and validated our model using in situ data collected on Earth, Mars, and Titan under a wide range of atmospheric stability, pressure, and surface roughness conditions. The model shows up to 71% better agreement with measurements compared to methods commonly used on Mars for evaporation/sublimation. Compared to previous estimates for H2O ice on Mars, our model predicts up to 1.5-190x lower latent heat fluxes under stable atmospheric conditions (depending on the wind speed) and 1.78x higher latent heat fluxes under unstable conditions. Our results provide improved constraints on the stability of ice on Mars and will help determine whether ice can melt under present-day conditions. As air flows over a surface, the resulting turbulent eddies cause the air to mix. The intensity of turbulence generated dictates the rate at which energy is given to, or taken away from the surface. If there are volatiles such as liquid water at the surface, then the magnitude of the turbulent fluxes determines how long the volatiles will remain stable before evaporating or freezing. We applied recent advances made on Earth to develop a model for predicting turbulent fluxes and evaporation rates on any planetary body with an atmosphere. To check whether our simulations are accurate, we compared them with measurements made on Earth, Mars and Titan. We found that our simulations agreed up to 71% better with measurements compared to previously developed models used for Mars evaporation. Our simulations predict significantly higher or lower rates of evaporation when compared to previous estimates, depending on atmospheric conditions. These results provide improved constraints on the stability of ice on Mars and will help determine whether ice can melt under present-day conditions. We present an improved model to predict atmospheric turbulent fluxes and evaporation/sublimation rates on any terrestrial planetary body The model shows up to 71% better agreement with measurements compared to methods commonly used on Mars for evaporation and sublimation Our results provide improved constraints on the stability of Martian ice and will help determine whether ice can melt on Mars at present