Variable wind ripple migration at Great Sand Dunes National Park and Preserve, observed by timelapse imaging

Granule ripples at Great Sand Dunes National Park and Preserve (GSDNPP) were observed using inexpensive digital timelapse cameras over a 70-day period in winter 2010–2011. The ripples migrated during a handful of discrete events — visible ripple movement occurred on only 11 days during the observation period. The movement conditions are documented with hourly and 15-minute records from two nearby weather stations, and by a cup anemometer at the site itself. During the most prominent movement episode, when local winds averaged ~ 10 m/s, ripples of several sizes were observed simultaneously and a reciprocal relationship of ripple size and propagation speed was seen, with small (~ 10 cm) ripples moving at ~ 1.4 cm/min, and larger (~ 80 cm) ripples at ~ 0.15 cm/min. Ripple sizes and morphologies evolve throughout the observation period.