腾格里沙漠东南缘沙丘迎风坡风速变化的初步研究

对腾格里沙漠东南缘格状沙丘表面气流的观测结果表明，迎风坡风速的增加程度因坡成形态和原始气流的方向，强度而不同。迎风坡风速放大率介于１．０６～１．９１之间，且在格状沙丘主梁，主要与坡形系数和高度有关；在副梁随原始风入射角，坡形系数而变化，风速放大率对沙丘形态的影响主一要增加丘顶区域的输沙率和活动性，且因区域气流的方向和强度而不同，在横向气流条件下，其迎风坡随区域气流强度和增加而变缓，变长，在双向（斜

A PRELIMINARY STUDY ON WIND VELOCITY VARIATION ON WINDWARD SLOPS OF DUNES IN SOUTHEASTERN TENGGER DESERT

Field measurement of surface air flow and sediment transport rates was made on stoss slop of network dunes in southeastern Tengger Desert to understand the dune morphology and controlling factors. The results show that the wind velocities increasing upon windward slops of the dunes vary with both slop morphology and primary wind direction related to dune crest line. The velocity amplification factors range1 from 1. 06 to 1. 91. The factors influencing velocity amplification are very complex. According to analysis of single dune variation, the most important factor is an incident angle of primary wind direction and the slop's aspect ratios. The effect of dune height and windward basal velocity becomes less significance unless the primary winds direction normal to the dune orientation. With respect to a regional wind regime, the dominant winds direction transversely to main ridges and oblique to secondary ridges of network dune. For the main ridges of this dune, the wind velocity amplifi- cation increases with adding of dune height and basal velocity. For the secondary one, it varies with incident angles of primary wind. The main effect of velocity amplification on dune morphology is to increase crestal sand transport rate and activity. The ratio of sand transport rates between crest and toe range from 3. 17 to 15. 67. It also varies with basal wind velocity and height of dunes when it vertical to primary wind direction. In this condition, the transport rates from base to crest of dunes increases exponentially in low wind velocity of dunetoes but linearly when the wind velocity became higher. Therefore, the windward slops of dunes decreases with increasing regional wind magnitude in transverse flow conditions, where it becomes short with steeper slops in hi-oblique flow conditions.