Sentence:  Of extreme importance in the <WSD>saltation</WSD> phenomenon is the vertical distribution of particles, as well as total flux, as functions of the wind speed. The formations of all scales of bed formations, from centimeter-size ripples to kilometer-size dunes, are all due to the <WSD>saltation</WSD> process. 
Meaning of the word marked with <WSD> tags:  The transport of loose particles by a fluid (such as wind or flowing water).