| Eddy covariance technique is widely used to estimate heat, water, and CO2 exchange, as well as other trace gases. In order to investigate the uncertainty of eddy covariance measurement, we performed a 9 week, side-by-side experiment of three eddy covariance stations on a small airfield in Mainz-Finthen/Germany (49.969° N, 8.148° E, 227 m a.s.l.) in late summer/autumn 2011. Turbulent fluctuations of CO2, H2O have been measured by three open path Li-7500 CO2/H2O analyzers (Li-COR Biosciences) and, turbulent fluctuations of ozone concentration have been measured by three gas-phase chemiluminescence analyzers (enviscope GmbH/ Germany). Three 3D sonic anemometers (model USA-1, METEK/Germany; model CSAT3, Campbell Scientific/U.K.) have been applied to obtain fluctuations of 3D wind vectors and temperature. All the turbulent fluctuations have been measured at 20Hz. All fast response sensors were mounted at 3 m above ground, the three flux stations have been aligned in cross-wind direction in a distance of about 5.5 m to each other. TK3 algorithm (Department of Micrometeorology, University Bayreuth, Germany) is applied to calculate the fluxes of CO2, sensible heat, latent heat and momentum from time series. We will present results of different sensor combinations of elucidate the impact of instrumental variability (among fast-response analyzers, as well as among 3D ultrasonic anemometers) on the evaluation of fluxes. |
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