Footprint Application to Long-term CO2 Flux Observations

Flux footprint functions are used to estimate location and relative importance of passive scalar sources influencing flux measurements. In this contribution, we present an extension of the footprint parameterisation of Kljun et al. (2004) taking into account cross-wind dispersion. The parameterisation is further improved for footprints in stable stratifications. It is then evaluated using footprint estimates of the Lagrangian stochastic particle footprint model LPDM-B for varying boundary layer stratifications, receptor heights and roughness lengths.

The new footprint parameterisation is used to derive a footprint climatology for a flux station in the southern boreal forest in Saskatchewan, Canada (Old Jack Pine, Canadian Carbon Program). We show that by overlaying the footprint results with high spatial resolution, three-dimensional scanning LIDAR data, structure of vegetation and small changes in elevation impact the net carbon dioxide flux at this site.

Reference: Kljun, N., P. Calanca, M.W. Rotach, H.P. Schmid: 2004, 'A Simple Parameterisation for Flux Footprint Predictions', Boundary-Layer Meteorology, 112, 503-523.