Keywords: tracer experiments, SF&, lt, SUB align=, right&, gt, 6, sulphur hexafluoride concentrations, dispersion modelling, forest canopy, analytic model, canopy turbulence, wind profile, turbulence statistics, surface layer, air pollution, air quality, trace gas concentrations
Traceflux: a small-scale tracer experiment at a forested site
Results from four successful tracer experiments carried out in a dense forest canopy are presented. For each experiment, sulphur hexafluoride SF6 was released from a point source in trunk space and air samples were collected at 19 horizontally distributed locations in the canopy. Meteorological measurements include fast-response turbulence data recorded at several locations in and above the forest. Measured mean concentrations of SF6 are compared against concentrations calculated by an analytical solution to the equation of diffusion. For near neutral and weak unstable conditions the model performs surprisingly well, even though the wind profile and turbulence statistics deviate substantially from surface layer characteristics. Still if more than an estimate of the concentration field is needed a more sophisticated model should be applied.