Interactive comment on “Uncertainty analysis of gross primary production partitioned from net
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of net ecosystem exchange (NEE). They use a Bayesian approach, moving from the regression analysis of rectangular hyperbola fitting daytime data. The argument treated is within the scope of Biogeosciences and the computational instrument they developed is promising. Nevertheless, at this current stage the study suffer from several limitations, not only in the presentational form but also in the substance. In fact, several sources of uncertainty exist in the partitioning the GPP from eddy covariance data. GPP is not directly measured and must be extrapolated from available NEE. Both extrapolation approaches, from night-time or daytime data, can suffer from systematic errors. At least, the authors should acknowledge that a) day respiration can be significantly different from night respiration in reason of the different processes occurring at leaf level (photorespiration or dark respiration). Lower respiration values are expected during the day, see Sun et al. (2015), although compensatory effect could occur (Reichstein et al, 2005); b) the shape of the light response curve measured by eddy covariance can be significantly biased by an inadequate quantification of the storage contribution of the NEE flux, particularly if measurements are taken above high canopies like in the present study. I’m unsure that the authors can quantify these potential sources of bias using the data they have, but at least they should clearly state that they analysed only a component of the possible uncertainty sources. Overall, the approach used by Beer et al., 2010, still seems more solid.
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Interactive comment on “Uncertainty analysis of gross primary production partitioned from net
AR 1: We do not fully agree with the referee that the residual term in equation 6 is not the uncertainty in measured NEE. The residual term contains the model representation error and the random measurement error. Richardson et al. (2008) showed that the uncertainty estimates inferred from the model residuals of the tuned empirical models, which are fitted to NEE data, are comparable to the tot...
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تاریخ انتشار 2015