Abstract:

The Taklimakan Desert is one of the important dust sources in the world. Using the ERA-Interim reanalysis data from 2000 to 2013, we analyzed the wind profile over the Taklimakan Desert and found a wind speed maximum center within the boundary layer under a mean stage. This indicates that a low-level jet (LLJ) may widely exist there all year long. In order to further analyze the seasonal variation of this LLJ that may exist in this region, we defined a criterion to identify the low-level jet by considering the height of maximum wind speed, temperature inversion and wind shear. The results show that there’s a easterly LLJ persistently appearing over this region, which had a high occurring frequency with the maximum (68.4%) in August and the minimum (54.5%) in December. Both the LLJ core height and maximum wind speed had a significant seasonal variation, in summer the height of LLJ was maximum with a mean value of 339.6 m above ground level, while in winter it was lowest with a mean value of 237.7 m and in spring and autumn, it was approximately situated at 294.0 and 280.1 m, respectively. The strongest LLJ core wind speed appeared in spring and summer with a value larger than 7.5 m/s, in autumn it decreased to 6.3 m/s, and it had a minimum value about 5 m/s in winter. Furthermore，the analysis shows a relationship between the core wind speed and height, the core wind speed increased with the height firstly, but then decreased after reaching a certain height range.

Key words: Taklimakan, low-level jet, inertial oscillation

摘要：

利用2000~2013年ERA-Interim再分析资料对塔克拉玛干地区风速廓线进行分析，发现在多年平均状态下边界层内存在风速极大值中心，表明该地区可能长时间、广泛存在低空急流。为进一步判定、分析可能存在的低空急流及其季节变化特征，本文从最大风速发生高度、逆温以及风切变3个方面考虑，给出了低空急流的具体判定条件。通过客观判定表明，塔克拉玛干地区常年存在偏东方向低空急流，具有较高的发生频率，最大频率出现在8月份达68.4%，最小频率在12月份，为54.5%。急流中心高度和最大风速均存在显著的季节变化：夏季低空急流发展最高，平均高度位于地面以上339.6 m，冬季高度最低，平均高度237.7 m ，春、秋季高度相近约为290 m左右；急流最大风速春、夏季最强，平均值高于7.5 m/s，秋季风速减弱为6.3 m/s，冬季达到最小值5.0 m/s。此外，分析还发现急流最大风速先随高度上升而增加，达到地面以上某一高度范围后，又随高度增加而减小。

关键词: 塔克拉玛干, 低空急流, 惯性震荡