Evaluation of a plot-scale methane emission model using eddy covariance observations and footprint modelling
- 1Earth and Climate Cluster, Faculty of Earth and Life Sciences, VU University Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, the Netherlands
- 2Institute of Evolutionary Biology and Environmental Studies, University of Zürich, Winterhurerstraße 190, 8057, Zürich, Switzerland
- 3Department of Physical Geography and Ecosystem Science, Lund University, Sölvegatan 12, 223 62, Lund, Sweden
- 4LI-COR Biosciences GmbH, Siemenstraße 25a, 61352, Bad Homburg, Germany
- 5Biogeochemical Cycles of Permafrost Ecosystems Lab, Institute for Biological Problems of Cryolithozone SB RAS, 41 Lenin ave., 678891, Yakutsk, Russia
- 6International scientific and educational center of biogeochemistry and climatology BEST (Biogeoscience Educational and Scientific Trainings), Kulakovskogo 46, 677000, Yakutsk, Russia
Abstract. Most plot-scale methane emission models – of which many have been developed in the recent past – are validated using data collected with the closed-chamber technique. This method, however, suffers from a low spatial representativeness and a poor temporal resolution. Also, during a chamber-flux measurement the air within a chamber is separated from the ambient atmosphere, which negates the influence of wind on emissions.
Additionally, some methane models are validated by upscaling fluxes based on the area-weighted averages of modelled fluxes, and by comparing those to the eddy covariance (EC) flux. This technique is rather inaccurate, as the area of upscaling might be different from the EC tower footprint, therefore introducing significant mismatch.
In this study, we present an approach to validate plot-scale methane models with EC observations using the footprint-weighted average method. Our results show that the fluxes obtained by the footprint-weighted average method are of the same magnitude as the EC flux. More importantly, the temporal dynamics of the EC flux on a daily timescale are also captured (r2 = 0.7). In contrast, using the area-weighted average method yielded a low (r2 = 0.14) correlation with the EC measurements. This shows that the footprint-weighted average method is preferable when validating methane emission models with EC fluxes for areas with a heterogeneous and irregular vegetation pattern.