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.