Eddy covariance method: Schematic of the turbulent boundary layer above a nitrous oxide (N₂O)–emitting surface, showing high mixing ratios in updrafts and low ratios in downdrafts (w). The emission flux is estimated from the covariance between mixing ratios and vertical wind.
Estimated nitrous oxide (N₂O) fluxes for selected flight sections: under dry conditions (14a, 26b) and shortly after rainfall (21a, 21b), which ended an unusually long dry period. Fluxes are shown at the measurement location, while the sources are located on the upwind ground.
An IPA study was highlighted in Atmospheric Measurement Techniques.
A research team from the DLR Institute of Atmospheric Physics (IPA) employed an innovative airborne measurement system to quantify emissions of two highly potent greenhouse gases, nitrous oxide (N₂O) and methane (CH₄), from agricultural landscapes.
In recent years, significant methodological advances have improved greenhouse gas (GHG) measurements. However, capturing emissions over agricultural areas remains particularly challenging due to their spatial heterogeneity and diffuse nature. While ground-based measurements can only provide limited, point-scale information, satellite observations currently do not provide reliable N₂O data and are only partially suitable for diffuse agricultural CH₄ sources. To address this gap, the IPA team developed a novel airborne eddy-covariance system, combining a high-frequency quantum cascade laser spectrometer for CH₄ and N₂O with meteorological measurements of wind, temperature, and humidity. This setup allows the determination of emissions from areal sources with high spatial and temporal resolution.
During the first deployment in June 2023 on the DLR Cessna Grand Caravan over intensively managed agricultural landscapes in Friesland, the Netherlands, the measurements revealed high temporal and spatial variability in N₂O emissions. Observed N₂O fluxes were among the highest recorded globally for agricultural regions during the spring growing season.
Cockpit footage from the DLR Cessna. The rocking motion intuitively illustrates the eddy covariance measurement principle: updrafts in the turbulent boundary layer lift the aircraft, while downdrafts push it down. The same motions affect greenhouse gases emitted from the surface. By averaging the upward and downward transport over a sufficiently long flight section, the net vertical flux—or the transfer of greenhouse gases from the surface to the atmosphere—can be determined.
Eddy in Motion
Your consent to the storage of data ('cookies') is required for the playback of this video on Quickchannel.com. You can view and change your current data storage settings at any time under privacy.
Eddy in Motion
Cockpit footage from the DLR Cessna. The rocking motion intuitively illustrates the eddy covariance measurement principle: updrafts in the turbulent boundary layer lift the aircraft, while downdrafts push it down. The same motions affect greenhouse gases emitted from the surface. By averaging the upward and downward transport over a sufficiently long flight section, the net vertical flux—or the transfer of greenhouse gases from the surface to the atmosphere—can be determined.
Comparisons with established emission inventories indicate that these underestimate N₂O emissions during the growing season and fail to capture their seasonal dynamics. These findings highlight the necessity of independent, observation-based measurements.
The results of this measurement campaign were published in Atmospheric Measurement Techniques and recognized as a Highlight Paper. This work demonstrates the advantages of the new airborne measurement system, as it enables the investigation and quantification of complex agricultural emission processes at regional scales, while simultaneously providing a means to validate modeled assumptions in emission inventories.
N₂O and CH₄ are, after CO₂, the most important anthropogenic greenhouse gases, with high global warming potential. Agricultural activities contribute substantially to their total global emissions. Reducing uncertainties in measurements and improving process-level understanding is therefore critical for accurately quantifying greenhouse gas budgets, which in turn supports prioritization, implementation, and monitoring of mitigation strategies.
This study was conducted within the framework of the DLR GHGMon project.
Text & Illustrations: Paul Waldmann
Reference: Waldmann, P., Eckl, M., Knez, L., Gottschaldt, K.-D., Fiehn, A., Mallaun, C., Gałkowski, M., Kiemle, C., Hutjes, R., Röckmann, T., Chen, H., and Roiger, A.: Quantifying agricultural N2O and CH4 emissions in the Netherlands using an airborne eddy covariance system, Atmos. Meas. Tech., 19, 185–210, https://doi.org/10.5194/amt-19-185-2026, 2026.
Kontakt
Dr. Anke Roiger
Head of Department
Institute of Atmospheric Physics
Atmospheric Trace Species
Münchener Straße 20, 82234 Oberpfaffenhofen-Wessling
