These files contain data and other outputs supporting all results reported in Louge et al. Water vapor transport across an arid sand surface - non-linear thermal coupling, wind-driven pore advection, subsurface waves, and exchange with the atmospheric boundary layer. In Louge et al., we found:

Deserts inhale and exhale water vapor through their surface. Although this process affects the water balance over vast sand seas, it is poorly understood for want of sensitive instruments. We discover how it operates using a new probe that detects tiny amounts of moisture on sand grains.

Our analysis reveals that vapor infiltration is considerably slower in dry sand, and that wind flowing over a dune creates weak internal air currents contributing to the transport of moisture. Their strength depends on dune location, wind speed and direction.

When wind is strong enough to let dry sand meander over a dune, the resulting rapid variation in surface moisture sends evanescent waves of humidity downward. An analysis of these waves implies that water evaporation from individual sand grains behaves like a slow chemical reaction.

The exchange of moisture with the atmosphere is not always driven by the difference between humidity at the dune surface and in the ambient, as current models assume, and it is weaker than they predict.

In future, the new probe can be used as ground truth to calibrate satellite observations over deserts, explore extra-terrestrial environments holding scant water, and detect moisture contamination in pharmaceutical products.