Aeolian Sediment Transport over Sandy Gobi: Field Studies in the Nanhu Gobi along the Hami-Lop Nor Railway

We report the results of observations of three transport events on a sandy gobi along the Hami-Lop Nor Railway based on high-frequency saltation particle count and horizontal sediment flux measurements coupled with instantaneous wind velocity measurements.
For the observation event on 29 October 2018,the wind velocity and direction were measured by two 3-D ultrasonic anemometers (Wind Master Pro, Gill Instruments). The two anemometers were situated at heights of 1.2 and 2.8 m above the gobi surface, and wind data were recorded at a time interval of 1 s (1 Hz) by a Campbell CR 3000 datalogger. The saltating grain number profile was measured by a vertical array of five piezoelectric impact sensors (H11-LIN 10×, Sensit). The five impact sensors were deployed at heights of 0.05, 0.12, 0.38, 0.80, and 1.41 m (geometric mean) above the gobi surface with a measurement frequency of 1 Hz, and those data were also recorded by a Campbell CR 3000 datalogger. The wind velocity (direction) and saltating grains were measured synchronously over time. Aeolian saltation flux profiles over the gobi surface were measured by a vertical array of Big Spring Number Eight (BSNE) sand traps, which had a vertical sampler opening of 0.02 (width) × 0.05 m (height). Seven sand traps were deployed at inlet heights of 0.02, 0.17, 0.33, 0.74, 1.30, 1.92, and 3.15 m (geometric mean). All instruments were deployed in a spanwise direction of approximately 60° (ENE-WSW) vertical to 300° (WNW), which was the main sand-driving wind direction in the study area. The aeolian transport event was measured from 12:00 to 17:30 p.m.
For the observation events on 18 May 2019 and 23 May 2019, Wind velocity profiles were measured by three cup anemometers at heights of 0.2, 1.0, and 2.0 m, and the wind direction was measured with a wind vane set at a height of 2.0 m. Data from these instruments were recorded every 30 s by a data logger. The instantaneous sediment transport over gobi was measured by a vertical sediment trap that weighed the total collected sediment automatically with a weighing sensor connected to a data logger. This sediment trap, with a total height of 0.60 m and width of 0.02 m, has a rectangular steel box (0.35×0.35×0.30 m) on the bottom. The weighing sensor has an area of 0.30×0.30 m, and the measurement range is 0-25 kg with a precision of 1 g. The acquisition frequency ranges from 0.1 to 3600 s, and in this study, it was set as 30 s. The wind velocity, wind direction and sediment transport were measured synchronously over time. The aeolian transport events on 18 May 2019 and 23 May 2019 were measured from 05:30 to 09:30 a.m. and from 17:30 to 20:30 p.m., respectively.

本研究基于高频跃移颗粒计数、水平输沙通量观测与瞬时风速测量相结合的方法，报道了哈密-罗布泊铁路沿线沙质戈壁上3次风沙输运事件的观测结果。针对2018年10月29日的观测事件，采用两台三维超声风速仪（3-D ultrasonic anemometer，型号Wind Master Pro，Gill Instruments公司生产）测量风速与风向。两台仪器分别布设于戈壁地表上方1.2 m与2.8 m高度处，风速数据通过Campbell CR 3000数据采集器（datalogger）以1 s（1 Hz）的时间间隔记录。跃移颗粒数剖面通过垂直排布的5台压电冲击传感器（piezoelectric impact sensor，型号H11-LIN 10×，Sensit公司生产）测量，该5台传感器分别布设于戈壁地表上方0.05 m、0.12 m、0.38 m、0.80 m及1.41 m（几何平均间距）高度处，测量频率为1 Hz，数据同样由Campbell CR 3000数据采集器记录。风速（风向）与跃移颗粒数实现同步时序测量。戈壁地表上方的风沙跃移输沙通量剖面通过垂直排布的Big Spring Number Eight（BSNE）集沙仪测量，该集沙仪的垂直采样开口尺寸为0.02 m（宽度）×0.05 m（高度）。共布设7台集沙仪，其进沙口高度分别为0.02 m、0.17 m、0.33 m、0.74 m、1.30 m、1.92 m及3.15 m（几何平均间距）。所有仪器均沿垂直于研究区主要输沙风向（300°，西西北向）的展向方向布设，该方向约为60°（东东北-西西南向）。本次风沙输运事件的观测时段为当日12:00至17:30。针对2019年5月18日与2019年5月23日的观测事件，采用3台布设于0.2 m、1.0 m及2.0 m高度处的杯式风速仪（cup anemometer）测量风速廓线，并通过安装于2.0 m高度处的风向标（wind vane）测量风向。上述仪器的数据通过数据采集器以30 s的间隔记录。戈壁地表的瞬时输沙量通过垂直集沙仪测量，该集沙仪搭载称重传感器，可自动称量收集到的总沙量，并将数据传输至数据采集器。该集沙仪总高度为0.60 m，宽度为0.02 m，底部设有0.35×0.35×0.30 m的矩形钢质箱体。称重传感器的有效面积为0.30×0.30 m，测量量程为0~25 kg，精度达1 g。数据采集频率范围为0.1~3600 s，本研究中设置为30 s。风速、风向与输沙量实现同步时序测量。2019年5月18日及2019年5月23日的风沙输运事件观测时段分别为当日05:30至09:30，以及17:30至20:30。