Development of a Robust CO2 Sensing Platform for Boundary Layer Measurements with UAS

Carbon dioxide (CO₂) concentrations and fluxes in the atmospheric boundary layer have been demonstrated to have strong seasonal and diurnal fluctuations that are influenced by industry, crop health, land usage, and fossil fuel consumption. These local and regional variations in CO₂ are often ignored in current climate modeling because traditional sampling methods such as aircraft, ground stations, and satellites, do not provide data with adequate vertical and horizontal resolution in the atmospheric boundary layer. Advances in unmanned aerial systems (UAS) make them an appealing option for a low-cost, rugged vehicle to probe the atmospheric boundary layer. This presentation will highlight the development and deployment of a robust CO₂ sampling system designed to be carried by small UAS. First, the response of commercially available near-infrared gas sensors (Senseair K30-FR) were thoroughly characterized to assess their capabilities and limitations. Afterward, reported CO₂ values were then validated against a non-dispersive infrared (NDIR) CO₂ gas analyzer that corrects for water vapor (LI-COR 840A) and found to have agreement within 2-5 ppm. After optimizing airflow, placement, operating parameters, and shielding, the sensing units were integrated into a fixed wing (Tuffwing UAV Mapper) and a rotocraft (University of Oklahoma CopterSonde) for field deployment. The results presented in this presentation come from observations made during weekly deployments at the Kessler Atmospheric and Ecological Research Farm (KAEFS) in Washington, Oklahoma over the course of several months to facilitate the examination of seasonal trends. This data set is supplemented by winter measurements completed during the Innovative Strategies for Observations in the Arctic Atmospheric Boundary Layer (ISOBAR) campaign in Hailuoto, Finland in February 2018. Future experiments will explore diurnal variability as well as examining the role of land usage and precipitation on CO₂.