On the use of the post-closure methods uncertainty band to evaluate the performance of land surface models against eddy covariance flux data

[摘要] The energy balance of eddy covariance (EC) flux data is normally not closed.Therefore,at least if used for modelling, EC flux data are usually post-closed, i.e.the measuredturbulent fluxes are adjusted so as to close the energy balance. At thecurrent state ofknowledge, however, it is not clear how to partition the missing energy inthe right way.Eddy flux data therefore contain some uncertainty due to the unknown natureof theenergy balance gap, which should be considered in model evaluation and theinterpretation of simulation results. We propose to construct thepost-closure methodsuncertainty band (PUB), which essentially designates the differences betweennon-adjusted flux data and flux data adjusted with the three post-closuremethods (Bowen ratio, latent heat flux (LE) and sensible heat flux (H)method). To demonstrate this approach, simulations with the NOAH-MP landsurface model were evaluated based on EC measurements conducted at a winterwheat stand in southwest Germany in 2011, and the performance of the Jarvisand Ball–Berry stomatal resistance scheme was compared. The width of the PUBof the LE was up to 110 W m⁻² (21% of net radiation). Our studyshows that it is crucial to account for the uncertainty in EC flux dataoriginating from lacking energy balance closure. Working with only a singlepost-closing method might result in severe misinterpretations in model–datacomparisons.

[学科分类] 地球化学与岩石