Measurement of regional CH4 emissions in the UK using boundary layer budget methods

Emission fluxes of CH4 averaged over large tracts of the UK countryside (104 km2) using measurements in the atmospheric boundary layer have been made using tethered balloons and aircraft The methods include simple mass budget studies in the nocturnal boundary layer to provide estimates of CH4 emission at the 'field' scale from which the results are generally consistent with direct measurements using eddy co-variance techniques with fluxes are typically 40 μmol CH4 m-2 h-1. At the larger scale, measurements in the daytime boundary layer upwind and downwind of regions of the UK have provided estimates of CH4 emission along land trajectories of 120 km to 267 km. The fluxes obtained in summer over peatlands are typically 60-100 μmol CH4 m-2 h-1 and in the autumn 50 μmol CH4 m-2 h-1. For trajectories which include substantial urban and industrial areas, mean emission fluxes range from 220 to 375 μmol CH4 m-2 h-1, almost an order of magnitude larger than the wetland CH4 fluxes and demonstrating the importance of industrial and other anthropogenic sources.