||Our goal is to continue quality assurance and enhance precision and accuracy for the AmeriFlux
network of tower flux sites, which will support the AmeriFlux goal of building a cohesive network of research sites to quantify and understand carbon sources and sinks and the response of terrestrial ecosystems to climate and disturbance. We will continue to build consistency in the measurements made by AmeriFlux that addresses objectives stated in the AmeriFlux strategic plan and self evaluation, the North American Carbon Program, and the US Carbon Cycle Science Program.
The approach is to 1) Conduct ~10-20 robust site comparisons each year; 2) improve site intercomparisons by identifying uncertainties associated with instrumentation and software routines through the use of ‘Gold-Files’; 3) enhance flux measurement guidelines that are posted on the AmeriFlux web site; 4) distribute roving standards to
sites so they can maintain their internal QA/QC protocols; 5) report findings to the AmeriFlux leadership; 6) lead and participate in network-wide synthesis activities; 7)
serve as a resource for measurement strategies of the network and other ad-hoc QA/QC activities (e.g. beta-testing instruments); 8) improve AmeriFlux protocols for
intercomparisons as the science and technology evolves.
The quality control and assurance (QA/QC) for AmeriFlux estimates rely on direct comparison between a portable (standard) eddy covariance system and in-house systems,
and through the comparison of different processing software by estimating fluxes using a standard raw data file (Gold-file). In addition to QA/QC at ~10-20 sites/year, the QA/QC
role addresses introduction of new instrumentation and software routines that need to be evaluated. The repeated site visits help maintain continuity of data quality with the frequent turnover of personnel at the sites.
We continue to address 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): 1) provide additional roving temperature standards (High Priority); 2) provide 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); 3) provide all AmeriFlux research groups not currently using the World Meteorological Organization-NOAA Global Monitoring division standards (WMO-GMD) with two
‘archival’ CO2 standards ~ 10 ppm apart in concentration within the range of ambient concentrations, and with an ensemble uncertainty of ±0.12 ppm, (High Priority); and 4)
explore an appropriate means to automate H2O calibrations for all IRGAs (High Priority). With six published papers, and others in press or review, we continue to lead and
participate in AmeriFlux synthesis activities.