Comment on amt-2022-113

Abstract

The determination of the wind profile of the lower atmospheric boundary layer is an important aspect of meteorology and wind energy science. A suitable tool to capture the wind profile is the usage of small unmanned aircraft systems (UAS). This study describes an easily repeatable type of calibration process in order to obtain an estimation of the horizontal wind vector using a rotary-wing UAS in hovering conditions. This procedure works without using wind tunnels or meteorological masts: it requires only the data from the flight control unit and a particular set of calibration flights. A modified DJI S900 hexacopter has been used for this study. The UAS body has been encased in a styrofoam sphere, leaving only the rotors and the landing gear outside, in order to grant a higher level of isotropy with respect to the incoming wind flow. A model based on the characterization of the UAS drag coefficient is proposed for the estimation of the relative horizontal wind vector. Validation flights have been performed at the German Weather Service MOL-RAO observatory in Falkenberg, Brandenburg. By hovering aside of a 99 m high meteorological mast with ultrasonic anemometers, it was possible to prove the wind prediction capability and assess the accuracy of the model. The analysis of the power spectral density highlights how the system resolves atmospheric eddies up to 0.1 Hz frequency. The overall root mean square error is less than 0.7 ms-1 for the wind speed while less than 8° for the wind direction.