Fine-Scale Simulations Of Aeolian Sediment Dispersion In A Small Area In The Northern Chihuahuan Desert

The northern Chihuahuan Desert in New Mexico contains mesquite bushes and small coppice dunes as well as open areas lacking vegetation. Sandstorms are common in this area, gradually reshaping the flat grassland into a landscape of mesquite coppice dunes and bare open patches. During storms, complex airflows entrain sediment from the open areas, depositing it around downwind bushes and dunes. Understanding and quantifying these processes could help to clarify the ongoing process of desert formation. Sand flux patterns for eight storms occurring in April 2003 and April 2004 were predicted for a (60 m by 60 m) site on the basis of 297 10-min average velocity simulations using a semiempirical mass consistent diagnostic wind field model: Quick Urban & Industrial Complex version 3.5 (QUIC) used with a sand flux parameterization. The sand flux patterns were highly heterogeneous, varying with wind direction and differing between storms. Generally, the nonvegetated areas experienced high sand fluxes, while wake areas behind dunes experienced little or no sand flux. Sediment erosion and deposition patterns were calculated by taking the divergence of the sand flux. The open areas were the sources of the sediment, while the windward sides of the mesquite bushes and dunes were the primary deposition areas. The simulated sediment erosion and deposition magnitudes were qualitatively similar to an annual average from 45 years of measurements.