How does wind speed affect the size of sand grains that can be moved?

Wind speed is a critical factor in the movement of sand, as the ability of wind to transport particles depends on both the velocity of the air and the size of the grains. Near the surface, wind velocity must exceed a specific threshold to initiate movement, and this threshold value increases with the size of the sand grains. For instance, a wind speed of 12 km per hour (measured at a height of 10 metres) is required to move grains 0.02 cm in diameter, while a 21-km-per-hour wind is necessary to move 0.06-cm grains.1

Once movement is initiated, it can be maintained by lower wind speeds. Furthermore, the total volume of sand transported is a power function of wind speed, meaning that stronger winds move significantly larger quantities of material. Because a wind of a particular velocity moves fewer larger grains than smaller ones, only intense, strong winds are capable of moving coarse sands, which often results in the formation of specific features like sand sheet undulations.1