Particle production and aeolian transport from a "supply-limited" source area in the Chihuahuan desert, New Mexico, United States

Wind erosion mechanisms were investigated for the "scrape site" at the Jorn ada Experimental Range near Las Cruces, New Mexico, in the Chihuahuan deser t. The scrape site was denuded of vegetation and scraped flat in 1991. We a dopted the site in 1994 because it offered an opportunity to study wind ero sion mechanisms for a large area of unprotected sandy and crusted soil in a n otherwise natural setting and over a period of several years. We installe d and operated the following instrumentation for a period of 35 months: thr ee meteorological towers, each 2 m in height, with wind speed sensors at 0. 2, 0.5, 1.0, and 2.0 m above ground; air temperature at 0.2 and 2 m height; rain gauge; seven sets of particle collectors at 0.1, 0.5, and 1.0 m heigh ts; and three fast-response particle mass flux sensors at 0.02, 0.1, 0.2, a nd 0.5 m heights; all along a transect crossing the site and parallel to th e predominant southwesterly wind direction. The minimum threshold friction velocity for the scrape site with a thin layer of loose material was 25 cm s(-1). This minimum threshold velocity increased to as high as 100 cm s(-1) depending on the degree of particle depletion and the site's status which varied between supply unlimited just after a high wind episode and supply l imited which was more typical for the rest of the time. The dominant mechan ism producing fresh sediment for transport was sandblasting of the surface crust. The measurements showed that supply and availability of loose, fine particles on the surface is a strong control of rates of erosion rather tha n wind energy alone.