Application of a tunable diode laser to the measurement of CH 4 and N 2O fluxes from field to landscape scale using several micrometeorological techniques

Abstract

Methane and nitrous oxide fluxes were measured at the field to landscape scale by combining tunable diode laser (TDL) technology with micrometeorological techniques. The three following micrometeorological measurement platform were used: (1) tower-based eddy covariance and flux-gradient techniques for measuring methane fluxes over the Canadian boreal forest and nitrous oxide over agricultural fields; (2) blimp-based nocturnal boundary layer (NBL) budget technique over agricultural areas for measuring nitrous oxide fluxes and (3) the NRC Twin Otter aircraft-based relaxed eddy accumulation (REA) to measure methane fluxes over the Canadian boreal forest. The techniques were applied using the TDL in situ (field applications) as well as in the laboratory (environmentally controlled conditions for very high resolution). The latter is accomplished by decoupling in situ air sample collection using PTFE bags from the actual air sample analysis using the TGA100. The application of the TDL to REA and NBL flux measurement is unique. Its versatility is illustrated using results obtained from experiments carried out at scales varying from field to farms to landscape. The results of these experiments clearly demonstrate the importance of knowing the variability of fluxes temporally and spatially to broach issues of scaling up to obtain fluxes representative of large areas.