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1. chinaXiv:201910.00056 [pdf]

Wind regime for long-ridge yardangs in the Qaidam Basin, Northwest China

GAO Xuemin; DONG Zhibao; DUAN Zhenghu; LIU Min; CUI Xujia; LI Jiyan
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

Yardangs are typical aeolian erosion landforms, which are attracting more and more attention of geomorphologists and geologists for their various morphology and enigmatic formation mechanisms. In order to clarify the aeolian environments that influence the development of long-ridge yardangs in the northwestern Qaidam Basin of China, the present research investigated the winds by installing wind observation tower in the field. We found that the sand-driving winds mainly blow from the north-northwest, northwest and north, and occur the most frequent in summer, because the high temperature increases atmospheric instability and leads to downward momentum transfer and active local convection during these months. The annual drift potential and the ratio of resultant drift potential indicate that the study area pertains to a high-energy wind environment and a narrow unimodal wind regime. The wind energy decreases from northwest to southeast in the Qaidam Basin, with the northerly winds in the northwestern basin changing to more westerly in the southeastern basin. The strong and unidirectional wind regime for the long-ridge yardangs in the northwestern Qaidam Basin results from the combined effects of topographic obstacles such as the Altun Mountains and of the interaction between the air stream and the yardang bodies. Present study suggests that yardang evolution needs such strong and unidirectional winds in high- or intermediate-energy wind environments. This differs from sandy deserts or sandy lands, which usually develop at low- or intermediate-energy wind environments. Present study clarifies the wind regime corresponding to the long-ridge yardangs' development, and lays firm foundation to put forward the formation mechanisms for yardangs in the Qaidam Basin.

submitted time 2019-10-26 From cooperative journals:《Journal of Arid Land》 Hits2072Downloads491 Comment 0

2. chinaXiv:201910.00058 [pdf]

Influence of salinity and moisture on the threshold shear velocity of saline sand in the Qarhan Desert, Qaidam Basin of China: A wind tunnel experiment

LI Chao; DONG Zhibao; YIN Shuyan; CHEN Guoxiang; YANG Junhuai
Subjects: Environmental Sciences, Resource Sciences >> Basic Disciplines of Environmental Science and Technology

Determination of the threshold shear velocity is essential for predicting sand transport, dust release and desertification. In this study, a wind tunnel experiment was conducted to evaluate the influence of salinity and moisture on the threshold shear velocity of saline sand. Saline sand samples (mean particle size of 164.50–186.08 μm and the total silt, clay and salt content of 0.80%–8.25%) were collected from three saline sand dunes (one barchan dune and two linear dunes) in the Qarhan Desert, Qaidam Basin of China. Original saline sand samples were placed in two experimental trays for wet and dry processing to simulate deliquescence and desiccation, respectively. Surface moisture content ranging from 0.30% to 1.90% was generated by the steam method so that the saline sand can absorb water in a saturated water vapor environment. The motion of sand particles was determined by the observers with a solid laser. The laser sheet (0.80 cm thick), which was emitted by the solid laser, horizontally covered the sand surface and was bound to the sand. Results show that the cohesion of saline sand results from a combination of salt and water. The threshold shear velocity increases exponentially with the increase in crust thickness for the linear sand dunes. There is a positive linear correlation between the original moisture content and relative threshold shear velocity. The threshold shear velocity of dewatered sand is greater than that of wet sand with the same original moisture content. Our results will provide valuable information about the sand transport of highly saline soil in the desert.

submitted time 2019-10-26 From cooperative journals:《Journal of Arid Land》 Hits1980Downloads384 Comment 0

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