Quasiperiodic saltation in the windsand flux over desertified areas

Resumo

Saltation in a windsand flux over a desertified area is studied on the basis of high-speed video recording data using spectral and wavelet analysis. Features of quasiperiodic variations in the saltating sand concentration are studied. It is ascertained that narrow bands in the spectrum (“spectral lines”) of the power density of the saltating sand concentration fluctuations in the range from 100 to 200 Hz are consistent with trains (wave packets) of up to 8–9 periods in duration. It is suggested to use the duration of the trains observed as a measure of the coherence of wind speed pulsations in the surface air layer. It is shown that the trains in the quasiperiodic variability of the saltating sand concentration can be explained by the interaction of wind gusts with wave irregularities on the underlying surface of a fine ripple type. The wave packet formation of 4–5 periods in duration can be explained using the jet-pulse saltation model.