Variable Wind Ripple Migration at Great Sand Dunes National Park , 3 Observed by Timelapse Imagery 4 5 Ralph

18 Granule ripples at Great Sand Dunes National Park and Preserve (GSDNPP) were observed with 19 inexpensive digital timelapse cameras over a 70-day period in winter 2010-2011. The ripples migrated 20 during a handful of discrete events visible ripple movement occurred on only 11 days during the 21 observation period. The movement conditions are documented with hourly and 15-minute records 22 from two nearby weather stations, and by a cup anemometers at the site itself. During the most 23 prominent movement episode when local winds averaged ~10m/s, ripples of several sizes were 24 observed simultaneously and a reciprocal relationship of ripple size and propagation speed was seen, 25 with small (~10cm) ripples moving at ~1.4 cm/min, and larger (~80cm) ripples at ~0.15 cm/min . Ripple 26 sizes and morphologies evolve throughout the observation. 27