The energy balance experiment EBEX-2000. Part II: Intercomparison of eddy-covariance sensors and post-field data processing methods

Abstract

The eddy-covariance method is the primary way of measuring turbulent fluxes directly. Many investigators have found that these flux measurements oftenThe National Center for Atmospheric Research is supported by the National Science Foundation. do not satisfy a fundamental criterion-closure of the surface energy balance. This study investigates to what extent the eddy-covariance measurement technology can be made responsible for this deficiency, in particular the effects of instrumentation or of the post-field data processing. Therefore, current eddy-covariance sensors and several post-field data processing methods were compared. The differences in methodology resulted in deviations of 10% for the sensible heat flux and of 15% for the latent heat flux for an averaging time of 30 min. These disparities were mostly due to different sensor separation corrections and a linear detrending of the data. The impact of different instrumentation on the resulting heat flux estimates was significantly higher. Large deviations from the reference system of up to 50% were found for some sensor combinations. However, very good measurement quality was found for a CSAT3 sonic together with a KH20 krypton hygrometer and also for a UW sonic together with a KH20. If these systems are well calibrated and maintained, an accuracy of better than 5% can be achieved for 30-min values of sensible and latent heat flux measurements. The results from the sonic anemometers Gill Solent-HS, ATI-K, Metek USA-1, and R.M. Young 81000 showed more or less larger deviations from the reference system. The LI-COR LI-7500 open-path H 2 O/CO 2 gas analyser in the test was one of the first serial numbers of this sensor type and had technical problems regarding direct solar radiation sensitivity and signal delay. These problems are known by the manufacturer and improvements of the sensor have since been made.

Quality control of CarboEurope flux data – Part 1: Coupling footprint analyses with flux data quality assessment to evaluate sites in forest ecosystems

“…Site names and main characteristics are listed in Table 1. Flux data processing for all participating sites followed the concept proposed by Aubinet et al (2000), which has been further refined by Mauder et al (2006Mauder et al ( , 2007. Original flow fields were rotated according to the planar fit method (Wilczak et al, 2001), and subsequently the Moore- (Moore, 1986), Schotanus- (Liu et al, 2001), and WPL-corrections (Webb et al, 1980) were performed.…”

“…Therefore, to ensure provision of high quality data for the growing community of flux data users, sophisticated protocols for the processing of eddy-covariance measurements (e.g. Mauder et al, 2006;Papale et al, 2006; Correspondence to: M. Göckede (mathias.goeckede@oregonstate.edu) Mauder et al, 2007) as well as for quality assessment and quality control (QA/QC, e.g. have been established.…”

Intercomparison and assessment of turbulent and physiological exchange parameters of grassland

“…They also report an uncertainty of 15% or less than 30 W m −2 in their latent heat flux estimates. Mauder et al (2007) compared the performance of different analysis packages/methodologies applied to the same data and concluded that methodological differences resulted in deviations of 10% and 15% for sensible and latent heat fluxes, respectively. In the same study data from nine different anemometers and six different fast-response water vapour sensors were also processed with a common analysis program, obtaining regressions that are in the same range as the results obtained here.…”

Available energy and energy balance closure at four coniferous forest sites across Europe

“…However, turbulent fluxes of latent heat and sensible heat also bear uncertainties. Mauder et al (2007b) pointed out that different post-field data processing methods and their order in post-field data processing process can cause differences up to 15% for fluxes of latent and sensible heat recorded with same system. A simple test was made and the turbulent fluxes were enlarged/reduced by 15% but this did not result in a closed energy balance.…”