Setting up an eddy covariance system to measure N2O fluxes exchanged by a production crop - First steps

In order to study N2O exchanges by a Belgian production crop, we installed an eddy covariance system at the Terrestrial Observatory of Lonzée (Belgium), using a H2O and N2O quantum cascade laser analyzer and a sonic anemometer. We obtained three days of measurements and were able to investigate data preprocessing and flux calculation. We observed a drifting time-lag between the analyzer and the anemometers time series, presumably caused by an internal clock drift. Time-lag determination (using the covariance function maximum method) was more difficult for N2O than H2O, suggesting that this routine should be adapted to gas characterized by low fluxes. We investigated high frequency loss and found a system cut-off frequency of 0.5Hz for H2O, comparing its cospectrum to sensible heat cospectrum. We were not able to retrieve a neat cospectrum for N2O because of low fluxes during turbulent conditions. Further work and more data will be needed in order to bring answers to pending questions.