A Study On The Characteristics Of Wind Speed Pulsation In Sandy And Green Land Of The Taklimakan Desert

The wind is the direct driving force for sand movement.Due to the turbulent motion of the atmosphere,the wind speed and wind direction present the phenomenon of fluctuation with time.The characteristics of wind is explored,which is not only helpful to enhance the understanding of the characteristics of this important meteorological variable;but also can promote the understanding of the process and mechanism of the interaction between the wind and underlying surface,,which are of great significance for the study of wind and sand movement.In this paper,the observations of wind speed,wind direction,horizontal visibility,dust aerosol concentration(PM₁₀,PM_2.5)and sanding were used in the middle of the Taklimakan Desert,to systematically analyze the average wind speed,wind speed fluctuation,and wind direction fluctuation at the different altitude,under the different weather processes,natural sand and constructed green land.Further,the relationship between wind speed fluctuation and sand movement was discussed to deepen the understanding of the wind speed characteristics in arid area and its effect on sand movement.The research results are as follows below:(1)Under the different weather backgrounds,the fluctuations of the wind velocity of 0.5m,1.0m,2.0m,4.0m and 10m in the surface layer show the uniform phenomenon in time series,and with the good correlation each other.Especially,the correlation of pulsating wind speed in adjacent height is the most significant.Moreover,the range of fluctuation of the wind speed present the positive proportional to the height.In addition,the wind speed pulsation intensity is basically the same under the weather background of sandstorm and blowing sand,which show the tendency that the fluctuation increases as the increment of height,however,under the clear sky,the tendency that the fluctuation of wind speed increases first and then deceases with the increment of height.Further,under the three weather conditions,the turbulence of wind speed pulsation is relatively small,and the turbulence degree increases first and then decreases with the height and average wind speed,and finally tends to be stable.The wind pulsation of different heights is highly correlated under the same weather conditions.The variation of wind direction pulsation under different weather conditions is not significant.(2)Under the different wind speed backgrounds,the wind velocity fluctuation amplitude of the 0.5m,1.0m,2.0m,4.0m,10m,20m,32m,47m,63m and 80m heights in the near-surface layer increases with the increment of height and wind speed.However,the correlation in adjacent heights is significant,and the pulsation intensity of wind speed increases first and then decreases;Moreover,the turbulence of each layer decreases with the increment of height,and remain basically unchanged with the increase of wind speed..In spring and early summer,when the average wind speed at height of 2m for 1min is 4.3m·s^-1,the average wind speed at a height of 10m is 5.77m·s^-1 or above,and the average wind speed at a height of 2m and 10m for10min is 5.2m·s^-1 and 6.59m·s^-1 respectively,dust weather may occur.Additionally,when the average wind speed at 2m height lasting for 1min or 10min reaches more than 6m·s^-1,and the average wind speed at 10m height reaches more than 8m·s^-1,dust weather will occur.(3)The amplitude of wind speed pulsation in constructed green land and natural sand at height of 10m present uniform phenomenon in time series,and the adjacent height layer show significant correlation.However,the variation of wind speed pulsation amplitude in the each height layer in the artificial green land,Stronger than natural sand.And fluctuation intensity decreases with height reduction and wind speed decrease,especially,the constructed green land changes more obviously below 2m height.(4)The wind velocity fluctuation is inversely proportional to the horizontal visibility during the sandstorm weather,and is proportional to PM10 and PM2.5.Moreover,there is a good correspondence between the wind speed pulsation and the number of impact particles.And based on the number of impact particles and the synchronous wind speed data,the correspondence between the wind speed data with hysteresis of 1s is better than the wind speed data with lags of 2s,3s,5s and 10s.