Abstract:

The structure of near-surface wind-blown sand flow over dry playa represents the macroscopic characteristics of micro-wind-blown sand movement at such locations. It is important to study such sand flow in order to understand the processes of wind-blown sand movement and dust emissions in dry playa. In this study, a dry playa at the end of a typical alluvial fan around North Mountain of the Ejin Banner was selected for analysis and field observations were conducted on its near-surface wind-blown sand flow structure. The results revealed an exponential wind speed profile over the dry playa surface and the aerodynamic roughness z₀ was 0.058 mm, which is smaller than those of sand and gobi surfaces. The sand flux of mixed-particle-size sand decreased exponentially with height over the dry playa surface. The average saltation height z_q of sand particles in the desert-crossing wind-sand flow was 15 cm, and 90% of the transport sand was concentrated within the height of 0-34 cm. The vertical profile curve of the sand flux in the fine-sand-particle-size group was similar to that of the mixed-particle-size sand. With increasing particle size, the sand flux in the dry playa changed with height, and the “elephant nose” curve transitioned to an “oblique Z” curve for coarse sand. Thus, this work proposes the mode of sand movement on the dry playa bed.

Key words: dry playa, wind-blown sand structure, wind velocity profile, saltation