Examples of the effects of different averaging methods on carbon dioxide fluxes calculated using the eddy correlation method

Three hours of high frequency vertical windspeed and carbon dioxide concent ration data recorded over tropical forest in Brazil are presented and discu ssed in relation to various detrending techniques used in eddy correlation analysis. Running means with time constants 100, 1000 and 1875s and a 30 mi nute linear detrend, as commonly used to determine fluxes, have been calcul ated for each case study and are presented. It is shown that, for different trends in the background concentration of carbon dioxide, the different me thods can lead to the calculation of radically different fluxes over an hou rly period. The examples emphasise the need for caution when interpreting e ddy correlation derived fluxes especially for short term process studies.