Seasonal Changes in Boundary-Layer Flow Over a Forested Escarpment Measured by an Uncrewed Aircraft System

The uncrewed airborne measurement platform MASC-3 (Multi-Purpose Airborne Sensor Carrier) is used to measure the influence of a forested escarpment with differing leaf area indices ( LAI ) onto the wind field. Data from flight legs between 30 and 200 m above ground with uphill (westerly) wind during summer (July–September) and winter (October–March) seasons between 2018 and 2021 are analyzed. Compared with a low value of LAI , it is found that the mean wind speed acceleration is stronger for a high values of LAI , and the turbulence is enhanced in the lee of the trees in the lowest 20–60 m above ground. During summer with a high LAI , the inclination angle is more clearly defined into an upward motion above the slope and downward motion above the plateau. The results of the airborne dataset fits well into the theoretical and analytical models established in the 1970s and 1980s.