Concept:Barchan dunes are crescent-shaped sand dunes that migrate with the wind.Explanation:A barchan dune has its curved horns pointing downwind.Sand is blown up the gentle windward slope and deposited on the steep leeward slope.This continuous erosion and deposition causes the whole dune to shift forward.Therefore, barchan dunes move in the same direction as the prevailing wind.Answer:In the same direction as the prevailing winds.