The ASK-16 Motorized Glider: An Airborne Eddy Covariance Platform to measure Turbulence, Energy and Matter Fluxes

Abstract. Airborne eddy covariance measurements can bridge the gap between local (tower-based) to regional (satellite/inversion-derived) flux data, as they provide information about the spatial distribution of turbulent fluxes for larger regions. Here, we introduce an airborne eddy covariance measurement platform based on an ASK 16 touring motor glider (TMG; also referred to as a power glider, hereafter referred to as motorized glider), which is equipped to measure the three dimensional wind vector, atmospheric conditions and derive airborne turbulent fluxes for the use of measurement campaigns over European landscapes. This study describes the measurement setup of the platform, and explains the workflows that were used to calculate and calibrate the three-dimensional wind vector, turbulent fluxes and their associated source areas. The glider is equipped with an 858 AJ Rosemount five-hole probe, a Picarro G2311-f gas analyser, a Novatel FlexPak G2-V2 GNSS-INS system, Vaisala temperature and humidity sensors (HMT311), and an OMEGA CHAL-003 thermocouple temperature sensor. Measurement data is processed with PyWingpod (python) and eddy4R (R) software packages to calculate wind vectors, turbulent fluxes, and assign footprints to the calculated fluxes. To evaluate the quality of the obtained fluxes, different quality assessments have been performed, including the determination of detection limits, spectral analysis, stationarity tests, the analysis of integral turbulence characteristics, and measurement noise and error evaluation. The uncertainty of w is between 0.15 to 0.27 m/s (median = 0.23 m/s) and the uncertainty of, u and v ranges between 0.16 to 0.55 m/s (median = 0.25 m/s). Analysis of exemplary flux data from flight transects indicates that the platform is capable of producing spatially highly resolved turbulent fluxes over heterogeneous landscapes. Overall, results from our analysis suggest that the ASK-16 airborne platform can measuring turbulent fluxes with a similar quality as earlier established high quality platforms.