Eddies in motion: visualizing boundary-layer turbulence above an open boreal peatland using UAS thermal videos

High resolution thermal infrared (TIR) imaging is opening up new vistas in biosphere-atmosphere heat exchange studies. The rapidly developing unmanned aerial systems (UAS) and specially designed TIR cameras offer opportunities for TIR survey with increasingly high resolution, reduced noise, prolonged flight times and better gimbals. A state-of-the-art science platform is assembled using a Matrice 210 V2 drone equipped with a Zenmuse XT2 thermal camera and deployed over a pristine boreal peatland with the aim to test its performance in a heterogeneous ecosystem with short vegetation. The study utilizes the capability of the UAS platform to hover for prolonged times (about 20 min) whilst recording high-frequency (1–30 Hz) TIR videos. A methodology to derive thermal signatures of near-ground coherent turbulent structures impinging on the land surface, surface temperature spectra and heat fluxes from the retrieved videos is developed. The size, residence time and movement of the coherent structures are computed from the surface temperature maps, and their dependency on atmospheric conditions is examined. A ground-based eddy-covariance system and a collocated meteorological setup are used for reference.