Circadian Rhythm of Dune‐Field Activity.

Wind‐blown sand dunes are both a consequence and a driver of climate dynamics; they arise under persistently dry and windy conditions, and are sometimes a source for airborne dust. Dune fields experience extreme daily changes in temperature, yet the role of atmospheric stability in driving sand transport and dust emission has not been established. Here, we report on an unprecedented multiscale field experiment at the White Sands Dune Field (New Mexico, USA), where by measuring wind, humidity and temperature profiles in the atmosphere concurrently with sediment transport, we demonstrate that a daily rhythm of sand and dust transport arises from nonequilibrium atmospheric boundary layer convection. A global analysis of 45 dune fields confirms the connection found in situ between surface wind speed and diurnal temperature cycles, revealing an unrecognized climate feedback that may contribute to the growth of deserts on Earth and dune activity on Mars. Plain Language Summary: As the bottom of the atmosphere heats and cools throughout the day, the winds near the land surface pick up and slow down, respectively, all else equal. This happens because it is easier to "mix" the fast winds high up in the atmosphere down to the surface when the surface air is convecting. We find that this wind effect is pronounced over dune fields, expansive patches of sand that are extreme in their daily heat cycles, and that the knock‐on effect is for those fast daytime winds to move sand and dust (the process that must occur for dune fields to grow). This is interesting because often the effect of heat on the near‐surface winds is ignored when considering sediment movement, and also because over geologic timescales this process might contribute to the growth of dune fields. Key Points: Winds that move sand and dust at White Sands Dune Field are strongly tied to boundary layer convectionThe typical equilibrium assumption for atmospheric boundary layer theory fails in White Sands' extreme daily cycleThe above key points likely scale with dune field size and contribute to dune field growth [ABSTRACT FROM AUTHOR]