iii) continually enhance and enforce the flux measurement guidelines, iv)
develop and disseminate the current suite of roving standards to assist sites in maintaining internal QA/QC protocols, v) report findings to
the AmeriFlux Science Chair and Steering Committee, vi) lead and develop synthesis activities across the network, vii) serve as a resource for
measurement strategies among the network and other ad hoc, coordinated QA/QC activities, and viii) handle logistics of the annual AmeriFlux
In addition, we continued to address four specific recommendations made in the AmeriFlux internal evaluation report 2005 (and supported by the
AmeriFlux steering committee and the TCCRP final report, Running et al. 2005): i) Provided additional roving temperature standards to each
research group for calibrating their systems (High Priority); ii) provided a photosynthetic photon flux density (PPFD) sensor to each research
group as a standard that is kept in the site lab, maintained annually by the AmeriFlux QA/QC lab, and maintain all calibration records in a our
repository (High Priority); iii) provide all research groups not currently using the World Meteorological Organization-NOAA Global Monitoring
division (WMO-GMD, formally CMDL) standards with (2) Ďarchivalí CO2 standards approximately 10 ppm apart in concentration within the range of
ambient concentrations, and with an ensemble uncertainty of +/- 0.12 ppm, (High Priority), and iv) explored an appropriate means to automate
H2O calibrations for all IRGAs (High Priority).
Our primary activity was comparison of data from the AmeriFlux portable EC system (PECS) and individual AmeriFlux/NACP sites to achieve the QA/QC
goals. We prioritized selection of sites we would visit each year by i) existing sites that had not been evaluated for more than three years; ii)
sites located in the mid-continental US in support of the NACP mid-continent intensive; iii) recently established sites that were initiated as part
of the NACP, iv) sites where more than three years have passed since the last comparison. We made the NACP regional projects a high priority to
ensure coherency of flux site data quality within each region and reduce uncertainty in the synthesis of flux and meteorological data within each region.
Our instruments were calibrated in our QA lab between the site visits. We derived our own IRGA polynomials rather than use those provided by
Li-Cor, which helped us to achieve higher accuracy and precision (see Ocheltree 2007 for a detailed description). To ensure rapid turnaround
of each comparison report, we informed PIs that we will only visit sites that agree a priori to provide data within two weeks of the site visit.
We also encouraged the PIs to provide processed data while the site visit was underway to allow us to perform preliminary analyses. This improved
the quality and amount of data we had available for analysis after the site visit.
We communicate directly with individual site PIs through the process of evaluating their data quality, and iterate until we feel they address
issues we found with their measurements or data processing. General communication with AmeriFlux investigators is conducted through the
AmeriFlux list server, conferences and development of web-based materials for the AmeriFlux web site at Oak Ridge National Lab.