Effects of Averaging Period on Energy Fluxes and the Energy-Balance Ratio as Measured with an Eddy-Covariance System

The eddy-covariance method is an important technique for investigating the exchange of energy and substances between the atmosphere and an ecosystem. However, an inappropriate averaging period leads to inaccurate fluxes and a low energy-balance ratio (EBR). The effects of various averaging periods on fluxes and the EBR are analyzed using flux data from the entire growth stage of maize measured with an eddy-covariance system in northern China. We find that the relative error of the flux between an averaging period of 10–60 min and the commonly used averaging period of 30 min is within 3%. When the averaging period is between 10 and 60 min, the magnitudes of fluxes increase with the length of the averaging period at various growth stages. For averaging periods exceeding 60 min, the magnitudes of fluxes vary significantly, particularly for periods longer than 120 min. In general, \({ EBR} > 0.8\) in the maize field, tending to increase within periods of 10–60 min, but decreasing rapidly at various growth stages for averaging periods longer than 120 min. Ogive functions indicate an optimal averaging period of the seedling–shooting and shooting–heading stages is approximately 10–30 min, and that of the heading–filling and filling–maturity stages is 30–60 min.