Vertical Distribution of Aeolian Sand Mass Flux based on Field Observation at Southern Rim of the Taklimakan Desert

Sand transport flux,wind speed and wind direction were observed simultaneously on bare sand surface at the southern rim of the Taklimakan Desert from April to June in 2010.Vertical distribution of sand transport flux was studied with the 28 groups of observed data.Results showed that total transport rate increased slowly when wind velocity ranged from 4.5 m·s-1 to 8 m·s-1 and increased sharply when wind velocity was higher than 8.0 m·s-1.The percentage of transport rate varied unnoticeably at lower wind velocities at the four examined layers(1 cm,3 cm,9 cm and 19 cm),but when wind velocity was higher than 6.6 m·s-1,the percentage of transport rate decreased at the lowest layer(1 cm) while increased at the highest layer(19 cm),yet it still remained unnoticeable variety at the other two layers(3 cm and 9 cm).The processes of surface erosion and sediment deposition had effect on vertical distribution of sand flux,and average saltation height reflected characteristics of these aeolian processes to some extent.Of the four frequently used models that described vertical distribution of sand flux,Zingg's modified power model produced the best fitness but the least message related to sand flow in its fitting parameters;the basic exponential model possessed the most message related to sand flow but the worst fitness;the exponential model took on a relatively good performance on both fitness and physical significance of parameters while Fryrear's modified power model was reverse.At the fine sand dominated south margin of the Taklimakan Desert,the exponential model presented better fitness than the basic power model,and validated and enriched the conclusion that was drawn from wind tunnel experiment.Based on comprehensive comparison,the exponential model was considered to be the best one to describe vertical distribution of sand flux at the southern rim of the Taklimakan Desert.