Measuring Surface Wind Velocity Changes

Abstract

Abstract. Agricultural spray drift is affected by many factors ranging from current weather conditions and the topography of the surrounding area, to the properties at the nozzle and the height at which the spray is released. Wind direction, speed, and solar radiation during the late spring/summer spray season of 2014 was measured at 10 Hz. Instrumentation was placed one meter off the ground to simulate conditions of a sprayer. Data was used to measure wind changes as it moved from one sensor to another, and to evaluate under what conditions wind may be most likely to have a significant direction or speed change. The data suggests that little to no linear correlation exists between an upwind and downwind sensors when measured in one minute segments, after adjusting for lag between the two sensors. The linear correlation values for wind direction and speed were 0.28 and 0.20 respectively. The downwind sensor measured a wind direction greater than 20 degrees different from the upwind sensors 16% of the time. The downwind sensor measured 1 m/s different wind speed from the upwind sensor 40% of the time. Histograms of wind big change events, where the difference in wind direction 30 seconds in the future and the current wind direction was greater than a set tolerance, were created for tolerances of 5, 25, and 45 degrees. For all tolerances, lower wind speeds (