风向对半固定沙垄表面风速影响——以古尔班通古特沙漠为例

 利用DETI可移动测风系统对古尔班通古特沙漠半固定沙垄表面风速进行实地观测，获取了主要风季不同风向条件下沙垄表面7个典型部位距离地表20 cm、40 cm、60 cm、100 cm和200 cm 5个高度的风速系列数据，系统研究风向对半固定沙垄表面坡面风速及风速廓线的影响。结果表明，迎风坡的气流加速和背风坡的风速降低现象在实际观测中得到证实，但受风向的影响甚大。垄顶风速放大率随入射角的增大呈指数关系递增，而背风坡风速占垄顶风速的比率则随入射角的增大呈线性关系递减。大角度入射气流速度变化主要受控于沙垄形态，小角度入射气流速度变化主要受控于地表植被状况。无论气流以何种角度入射，距沙垄表面20 cm高度气流的加速均较其他高度缓和。沙垄底部和坡中下部的风速廓线变化趋势基本一致,且呈较好的对数拟合关系；两坡中上部和垄顶部的对数拟合方程相关系数偏小；受回旋涡流的影响，风速廓线在背风坡上部有明显偏折，初步断定涡流中心在距地表40 cm左右的高度。

Airflow Velocity over Semi-fixed Longitudinal Dune in Different Wind Directions: A case study of Gurbantunggut Desert

Field measurement of airflow velocity under different wind directions at five heights (0.2 m, 0.4 m, 0.6 m, 1 m and 2 m) over semi-fixed longitudinal dune was made in Gurbantunggut Desert. It was found that the airflow velocity increased over the windward slope and decreased over the lee slope, and both processes were deeply affected by wind direction. There exists a strong linear relationship between wind velocity and wind incidence angle. The magnification of wind velocity over the dune crest rises up with the incidence angles increase, while the proportions of wind velocity at 2 m high over lee slope to wind velocity at 2 m high over the dune crest reduce with the incidence angle's increase. The variation of airflow velocity was mainly controlled by the shape of dune when incidence angles were big, and that is mainly controlled by character of vegetation when incidence angles were small. No matter what direction the airflow come from, the variation amplitude of airflow velocity at 0.2 m high over dune surface was smaller than that at the other 4 heights. The wind speed profile in inter-dune was same with that over lower slope and both of them have a strong logarithm relationship with height, while the relationship does not exist over the upper slope and the dune crest. According to the wind speed profile over the upper of lee slope, a primarily conclusion is drew that the center of the whirlpool is at 0.4 m high from the sand surface.