塔克拉玛干沙漠腹地贴地层风沙流结构研究

摘要

利用微梯度集沙仪在塔克拉玛干沙漠腹地塔中地区实测的2014年7—8月贴地层输沙量梯度观测资料(观测高度区间0～5 mm、5～15 mm、15～35 mm、35～85 mm),对沙尘天气过程贴地层风沙流结构进行了研究.结果表明:(1)沙尘天气(沙尘暴和扬沙)过程中,随着风速的增大,各高度层输沙量也随之增大.沙尘暴天气中,风速<7.5 m·s-1时,15～35 mm处的百分含量超过5～15 mm处的百分含量,风速>7.5 m·s-1时,15～35 mm处的百分含量达到最大,其余各高度含量变化不明显.扬沙天气中,风速<8.0 m·s-1时,百分含量最大值出现在35～85 mm高度处,占48.9％,风速>8.0 m·s-1时,大小依次为:15～35 mm(49.5％)>35～85 mm(31.7％)>0～5 mm(12.7％)>5～15 mm(9.2％).(2)两种天气过程中,沙粒的平均粒径在垂直高度上均呈现先减小后增大的趋势.粒径峰值均处在125～250 um,极细砂含量最高,细砂次之.与扬沙天气相比,沙尘暴天气过程中极细砂、细砂、中砂在各高度层上的含量略微下降,粉尘含量有所升高.%The wind-sand flow structure of surface layer was studied based on the data of aeolian sand (observed height range was 0～5 mm,5～15 mm,15～35 mm,35～85 mm)during July to August 2014, measuring with a micro-gradient sand sampler in the hinterland of the Taklamakan Desert. The results showed that:(1)During dust event, process, the amounts of aeolian sand for all layers increased with wind speed. During sandstorms, the percentage of amount of aeolian sand for layer at 15～35 mm high was larger than 5～15 mm when the wind speed was less than 7.5 m·s-1, and the percentage for layer at 15～35 mm high was the largest when wind speed was greater than 7.5 m·s-1, other layers did not change significantly. During blowing sand, the percentage of amount of aeolian sand for layer at 35～85 mm high was maximum, taking up 48.9％ when the wind speed was less than 8 m·s-1.The percentage followed the rule of 15～35 mm(49.5％)>35～85 mm(31.7％)>0～5 mm (12.7％)>5～15mm (9.2％)when the wind speed was larger than 8 m·s-1.(2)During two kinds of dust weather, the average particle size decreased with height firstly, and then increased with height. The peak value of sand particle maintained 125～250 um, and the content of very fine sand was maximum, followed by fine sand.Compared with the blowing sand, the content of dust increased for all layers.