Characterization of the Martian Surface Layer

Abstract

We have estimated the diurnal evolution of Monin- Obukhov length, friction velocity, temperature scale, surface heat flux, eddy-transfer coefficients for momentum and heat, and turbulent viscous dissipation rate on the Martian surface layer for a complete Sol belonging to the Pathfinder mission. All these magnitudes have been derived from in situ wind and temperature measurements at around 1.3 m height, and simulated ground temperature (from 6 a.m. Sol 25 to 6 a.m. Sol 26). Up to the moment, neither values of turbulent viscous dissipation rate and eddy-transfer coefficients from in situ measurements for the Martian surface layer, nor diurnal evolutions of all the previous mentioned turbulent parameters for the Pathfinder had been obtained. Monin-Obukhov similarity theory for stratified surface layers has been applied to obtain the results. The values assigned to the surface roughness, and the applied parameterization of the interfacial sublayer will be discussed in detail due to the sensibility of the results on them. We have found similarities concerning the order of magnitude and qualitative behaviour of Monin- Obukhov length, friction velocity and turbulent vis-cous dissipation rate on Earth and on Mars. However, magnitudes directly related to the lower Martian atmospheric density and thermal inertia, like temperature scale and hence surface heat flux, show different order of magnitude. Finally, turbulent exchanges in the first meters have been found to be just two orders of magnitude higher than the molecular ones, while on Earth around five orders of magnitude separate both mechanisms.