Measuring trace gas fluxes on a regional scale using airborne relaxed eddy accumulation

The relaxed eddy accumulation (REA) technique was used successfully to measure fluxes of a range of trace gases including agrochemicals, volatile organic compounds (VOC's) and N2O. The REA sampling system was mounted on the National Research Council Twin Otter research aircraft and flown above forest and agricultural land, providing trace gas fluxes at the regional scale (>100 km2). Various collection devices and analyzers were required depending on the chemical nature of the different gases, but the underlying sampling methodology remained unchanged. In order to evaluate the performance of the REA technique, CO2 fluxes were measured simultaneously by both REA and eddy covariance, which showed very good agreement. The flux results clearly demonstrated that the aircraft-based relaxed eddy accumulation technique is a promising approach for quantifying the atmosphere-surface exchange of a wide range of trace gases at a regional scale.