Intermittent aeolian saltation over a gobi surface
Synchronous high-frequency measurement of the two time series of 3-D wind speed (25Hz) and saltating particle count rate (1Hz) over a gobi surface (39°8.062´N, 88°59.967´E). Wind velocity was measured by two RM Young 81000 Ultrasonic anemometers, situated at respective heights of 0.7 and 2 m above the gobi surface at a time interval of 0.05 s, recorded by a Campbell CR 1000 datalogger. The profile of saltating grain number was measured by a vertical array of five piezoelectric impact sensors (H11-LIN, Sensit) at heights of 0.05, 0.12, 0.38, 0.8 and 1.38 m (geometric mean) above the gobi surface with a measurement frequency of 1 Hz, also recorded by a Campbell CR 1000 datalogger. The piezoelectric impact sensors at heights of 0.12, 0.8 and 1.38 m were in a vertical profile, while due to the bulk limitation sensors, the piezoelectric impact sensors at heights of 0.05 and 0.38 m were 0.34 m and 0.24 m horizontally apart, respectively, from the vertical array of the other three sensors. The vertical array of the piezoelectric impact sensors was located 0.53 m in the spanwise direction from the anemometer to minimize their influence on airflow. Aeolian saltation flux profiles over gobi were measured by a vertical array of BSNE sand traps deployed at heights of 0.025, 0.175, 0.285, 0.585, 1.155, 1.785 and 3.000 m (midpoints of the trap inlet) . A sand trap at the height of 0.275 m was separated 1.22 m horizontally from the left array to decrease the bulk effect of the sand traps from each other as rotating, while the sand trap at 0.025 m was put between the 0.275-m high sand trap and the vertical array and set flush with the gobi surface to measure the saltation flux on the surface, yet it could not rotate.