Tolerance of eddy covariance flux measurement

Eddy covariance (EC) flux measurement is the most-used technique for observation of the fluxes of sensible heat H, latent heat lE, and carbon dioxide Fc between the land surface and the atmospheric boundary layer. Despite the availability of plentiful EC data from numerous research projects, it is difficult to make meaningful comparisons of EC at different sites, to validate the models used, and to integrate observed data with models because the uncertainties of the method are inadequately defined. We developed a method to evaluate the uncertainties of the EC method without the need to consider individual site specifications and flux characteristics. We showed that the fractional error of EC (i.e., tolerance T) can be separated into random and illegitimate components. T can be used as a scale parameter for spatiotemporal stationarity, and can be defined as a rational function. We demonstrated a practical application of T analyses for various contrasting areas, and showed that T analysis provides an appropriate and effective method to determine the uncertainties associated with EC.