  As wind energy continues to expand, increased interaction between wind farms
and their surroundings can be expected. Using natural snowfall to visualize the
air flow in the wake of a utility-scale wind turbine at unprecedented
spatio-temporal resolution, we observe intermittent periods of strong
interaction between the wake and the ground surface and quantify the momentum
flux during these periods. Significantly, we identify two turbine
operational-dependent pathways that lead to these periods of increased
wake-ground interaction. Data from a nearby meteorological tower provides
further insights into the strength and persistence of the enhanced flux for
each pathway under different atmospheric conditions. These pathways allow us to
resolve discrepancies between previous conflicting studies on the impact of
wind turbines on surface fluxes. Furthermore, we use our results to generate a
map of the potential impact of wind farms on surface momentum flux throughout
the Continental United States, providing a valuable resource for wind farm
siting decisions. These findings have implications for agriculture in
particular, as crop growth is significantly affected by surface fluxes.
