风蚀起沙的影响因子及其变化特征

Factors Affecting on Dust Emission by Wind Erosion and Their Variational Characteristics

以敦煌地区的戈壁和绿洲为例,对地表土壤风蚀起沙的临界摩擦速度及其变化特征和风蚀起沙过程中地表土壤的粒子尺度分布及其对垂直尘粒通量的影响进行了分析研究。结果表明,地表土壤风蚀起沙的临界摩擦速度随土壤水分含量和植被覆盖度的增大而增大,随粒子尺度的变化是先减小后增大,在中间某一尺度处有一最小值;土壤的人工利用和管理对临界摩擦速度也有着相当大的影响;风蚀起沙过程中,地表土壤的粒子尺度分布随时间发生变化,瞬时的粒子尺度分布不同于平均的粒子尺度分布,利用前者计算得到的垂直尘粒通量对摩擦速度的变化更敏感,利用后者计算得到的垂直尘粒通量偏大。

With the examples of Gobi and oasis in Dunhuang, the critical friction velocity of dust emission by wind erosion and the particle size distribution of surface soil during the wind erosion were analyzed in this paper. The results indicate that the u ＊ t increased with soil moisture and vegetation cover, and the variation of u ＊ t, with diameter of particle is decreased firstly and is then increased, and there is a minimal u ＊ t at some diameter, moreover, the land management practice also plays an important role. The particle size distribution of surface soil changes with time during the wind erosion. The instant particle size distribution is different from the average particle size distribution, and the vertical dust flux confirmed by the former is more sensitive with the variation of u ＊ t, while the vertical dust flux confirmed u ＊ t by the latter is bigger.