Atmospheric Measurement Techniques www.atmos-meas-tech.net 1867-1381 1867-8548 3 1 2010 10.5194/amt-3-163-2010 http://www.atmos-meas-tech.net/3/163/2010/ http://www.atmos-meas-tech.net/3/163/2010/amt-3-163-2010.html http://www.atmos-meas-tech.net/3/163/2010/amt-3-163-2010.pdf 163 176 2010-02-08 Sources of uncertainty in eddy covariance ozone flux measurements made by dry chemiluminescence fast response analysers J. B. A. Muller jennifer.muller@postgrad.manchester.ac.uk C. J. Percival M. W. Gallagher D. Fowler M. Coyle E. Nemitz School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Simon Building, Brunswick Street, Manchester, M13 9PL, UK Centre for Ecology & Hydrology, Bush Estate, Penicuik, EH26 0QB, UK We present a systematic intercomparison study of eddy covariance ozone flux measurements made using two fast response dry chemiluminescence analysers. Ozone deposition was measured over a well characterised managed grassland near Edinburgh, Scotland, during August 2007. A data quality control procedure specific to these analysers is introduced. Absolute ozone fluxes were calculated based on the relative signals of the dry chemiluminescence analysers using three different methods and the results are compared for both analysers. It is shown that the error in the fitted analyser calibration parameters required for the flux calculations provides a substantial source of uncertainty in the fluxes. The choice of the calculation method itself can also constitute an uncertainty in the flux as the calculated fluxes by the three methods do not agree within error at all times. This finding highlights the need for a consistent and rigorous approach for comparable datasets, such as e.g. in flux networks. Ozone fluxes calculated by one of the methods were then used to compare the two analysers in more detail. 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