A UAV-Based Eddy Covariance System for Measurement of Mass and Energy Exchange of the Ecosystem: Preliminary Results

Abstract

Airborne eddy covariance (EC) measurement is one of the most effective methods to directly measure the surface mass and energy fluxes at the regional scale. It offers the possibility to bridge the scale gap between local- and global-scale measurements by ground-based sites and remote-sensing instrumentations, and to validate the surface fluxes estimated by satellite products or process-based models. In this study, we developed an unmanned aerial vehicle (UAV)-based EC system that can be operated to measure the turbulent fluxes in carbon dioxides, momentum, latent and sensible heat, as well as net radiation and photosynthetically active radiation. Flight tests of the developed UAV-based EC system over land were conducted in October 2020 in Inner Mongolia, China. The in-flight calibration was firstly conducted to correct the mounting error. Then, three flight comparison tests were performed, and we compared the measurement with those from a ground tower. The results, along with power spectral comparison and consideration of the differing measurement strategies indicate that the system can resolve the turbulent fluxes in the encountered measurement condition. Lastly, the challenges of the UAV-based EC method were discussed, and potential improvements with further development were explored. The results of this paper reveal the considerable potential of the UAV-based EC method for land surface process studies.

Evaluation of the quality of a UAV-based eddy covariance system for measurements of wind and turbulent flux

“…Inspired by these studies, Sun et al (2021a) used a high-performance fuel-powered vertical take-off and landing (VTOL), fixed-wing platform to integrate the scientific payloads for EC and radiation measurements to obtain a comprehensive measurement of turbulent and radiation flux using an UAV. This UAV-based EC system measured turbulent fluxes including sensible heat, latent heat, and CO 2 , as well as radiation including net radiation and upward-and downward-looking photosynthetically active radiation (PAR).…”

“…fuselage size (Reineman et al, 2013). More importantly, the advancements in small, fast, and powerful sensors and microprocessors make it possible to use of UAVs for comprehensive atmospheric measurements (Sun et al, 2021a). Several UAVs with different turbulence measurement objectives have been developed and deployed, ranging from small payload capacity (e.g., 140 g SUMO) to medium (e.g., 1.5 kg M 2 AV, 1.0 kg MASC) and large (e.g., 6.8 kg Manta, 5.6 kg ScanEagle) (Reuder et al, 2016;Bå serud et al, 2016;Van Den Kroonenberg et al, 2012;Reineman et al, 2013).…”

“…Several UAVs with different turbulence measurement objectives have been developed and deployed, ranging from small payload capacity (e.g., 140 g SUMO) to medium (e.g., 1.5 kg M 2 AV, 1.0 kg MASC) and large (e.g., 6.8 kg Manta, 5.6 kg ScanEagle) (Reuder et al, 2016;Bå serud et al, 2016;Van Den Kroonenberg et al, 2012;Reineman et al, 2013). A comprehensive overview of the use of these UAVs for turbulence sampling can be found in Elston et al (2015) and Sun et al (2021a). For turbulence measurements, the UAVs were equipped with a commercial or custom multi-hole (5-or 9-hole) probe paired with an integrated navigation system to obtain the wind vector.…”

“…For turbulence measurements, the UAVs were equipped with a commercial or custom multi-hole (5-or 9-hole) probe paired with an integrated navigation system to obtain the wind vector. Small and medium UAVs typically could only measure fast 3D wind vector and air temperature fluctuations for measurements of momentum and sensible heat flux, whereas, large UAVs were equipped with more types (e.g., radiation, image, or gas concentration) and more accurate sensors for measurement of a larger range of meteorological properties including sensible and latent heat fluxes, radiation fluxes as well as surface properties (Reineman et al, 2013;Sun et al, 2021a). UAVs equipped with scientific instruments can be deployed in a variety of application environments and conditions.…”

Unmanned aerial vehicle “Tsimlyanin” for studying turbulent structure of atmospheric boundary layer

“…It has several advantages over the multi-rotor platforms, such as a longer endurance and a smaller distortion of the air flow. Recently, the vertical take-off and landing (VTOL) scheme have started to be used on such UAVs [6,7]. It allows for a safer landing and provides more universality with respect to take-off and landing conditions.…”