Star dunes such as this one from Namibia and the lower one from Great
Sand Dunes National Monument form in areas with bi-modal wind directions.
Top Image courtesy of NASA .Bottom image from Great Sand Dunes National Monument.
Wind Regime: As the wind direction
rose diagram indicates, these dunes occur in wind environments with a large amount of directional variability.
Sand rose illustrates the annual wind regime for Star dunes in Libya.