The impact of averaging period on eddy fluxes observed at ChinaFLUX sites

In this paper, the ‘ensemble block’ time average procedure and the Ogive function are applied to three ChinaFLUX sites to determine the low-frequency contribution to eddy fluxes. It is found that both methods give similar results. They show that 30 min flux-averaging periods are sufficient to capture all flux scales over a wheat field, but 60 min or longer is necessary over forests. Our results show that the optimal averaging period is a site-specific parameter. According to this analysis, for some ChinaFLUX sites at least, an averaging period that captures the low-frequency transport may improve the energy balance problem.