Observations of wind ripple migration on an Egyptian seif dune using an inexpensive digital timelapse camera

I report experiments on the observation of sand ripples on the Quattani dunes in Egypt using an inexpensive ($150) digital timelapse camera. Simple ripples in the fine sand had a wavelength of 10 cm and propagated downwind (windspeed ∼10 m/s) at a speed of ∼3 cm/min, and Y-junction defects moved one wavelength forward in the propagating ripple pattern over ∼6 min. This defect propagation speed of ∼0.5 times the ripple speed is rather slower than suggested in idealized models. Compound ripples at a nearby site were also observed – the megaripples moved at ∼0.2 cm/min while smaller superposed normal ripples moved ∼3–4× faster: the small ripples did not propagate through the larger ones. Experimental technique and some aspects of the design of a windsock/gnomon for use in further studies are discussed. A similar experimental setup should be able to observe fast-moving barchans.