Assessing the uncertainties in flux measurements

Abstract

Climate and environmental studies require knowledge of the exchange of carbon, water vapor, and energy between the atmosphere and terrestrial ecosystems. These exchanges are measured by tower instruments at numerous sites around the world using a technique known as eddy covariance. However, there are few studies estimating the errors in those flux tower networks by comparing their measurements with measurements from independent instruments. Schmidt et al. assessed the errors in the AmeriFlux network by comparing measurements made by the towers to measurements made using portable instruments during 84 site visits between 2002 and 2012. They found that, after statistical outliers were removed, the network had mean relative instrumental errors of less than 10% for all variables measured. The lowest errors were for meteorological variables, while the highest errors were for latent heat and carbon dioxide flux measurements. They note that many of the errors, such as calibration problems, were corrected at the sites. Overall, the authors say the study confirms the high quality and value of the AmeriFlux network data for studying fluxes between the atmosphere and the terrestrial surface. (Journal of Geophysical Research‐Biogeosciences, doi:10.1029/2012JG002100, 2012)