Abstract:

Based on the observations from field experiments in Tazhong area that located in the hinterland of the Taklimakan Desert, the dust emission threshold wind speeds (ut) with different time steps were calculated based on the Gaussian time fraction equivalence equation established by Stout, and the influence of time step on calculating dust emission threshold wind speed was discussed. Results are as follows: (1) There was some difference for dust emission threshold wind speeds when they were calculated with different time steps. As time step was shortened, the ut became more and more detailed. The ut was a constant when time step was 28-day, the value of it was 4.85 m·s-1. The average ut was 4.63 m·s-1 when time step was one day. when time step was 12-hour, the average ut was 4.68 m·s-1 during 00:00-11:00 BST，while it was 4.58 m·s-1 during 12:00-23:00 BST. When time step was 6-hour, the average ut was 4.46 m·s-1 during 00:00-05:00 BST, and it was 4.74, 4.50, 4.36 m·s-1 during 06:00-11:00 BST, 12:00-17:00 BST, 18:00-23:00 BST, respectively. (2) The observed total horizontal dust flux was 732.9 kg·m-1, and the duration of sand moving was 7 663 minutes. (3) The estimated values of total horizontal dust flux and the duration of sand moving with the observations were compared respectively, it showed that the calculations of total horizontal dust flux were all overestimated, and the duration of sand moving based on the dust emission threshold wind speed calculated with time step of 28 days was more close to the observation.

Key words: dust emission threshold wind speed, time step, Taklimakan Desert

摘要：

利用塔克拉玛干沙漠腹地塔中地区的野外观测试验数据，通过STOUT建立的高斯时间分数等值方程计算不同时间步长所对应的临界起沙风速，探讨时间步长对计算临界起沙风速的影响，结果表明:(1)利用不同时间步长获取的临界起沙风速具有一定的差异，随着时间步长的缩小，临界起沙风速的获取越来越细化：当时间步长取28 d时，临界起沙风速ut为定值4.85 m·s-1；当时间步长取1 d时，ut平均值为4.63 m·s-1；当时间步长取12 h时，00:00—11:00（北京时，下同），ut平均值为4.68 m·s-1，12:00—23:00，ut平均值为4.58 m·s-1；当时间步长取6 h时，计算得到00:00—05:00、06:00—11:00、12:00—17:00和18:00—23:00各时间段的临界起沙风速平均值分别为4.46、4.74、4.50和4.36  m·s-1。(2)观测期间，总沙尘水平通量为732.9 kg·m-1，风沙活动持续7 663 min。（3）将不同时间步长获取的临界起沙风速所对应的总沙尘水平通量、沙尘持续时间与观测值进行对比，总沙尘水平通量的计算值均明显高于观测值，时间步长取28 d时，风沙活动持续时间与观测值最接近。

关键词: 临界起沙风速, 时间间隔, 塔克拉玛干沙漠