ECOR SmartFlux: Upgrading the ARM Eddy Correlation Flux Measurement Systems

 
Poster PDF

Authors

Ryan Sullivan — Argonne National Laboratory
David R. Cook — Argonne National Laboratory

Category

Boundary layer structure, including land-atmosphere interactions and turbulence

Description

Scatterplots of momentum (τ), sensible (H) and latent (LE) heat, and CO2 fluxes from the new ECOR with SmartFlux (ECORSF) and collocated AmeriFlux. The AmeriFlux system was designed and operated by the former instrument mentor (Cook), and has the same components and specifications as the current ECOR systems. Color scale indicates the hour of the measurement in local standard time.
ARM has been measuring near-surface turbulent fluxes since 1992 using the Energy Balance Bowen Ratio (EBBR) systems, and since 2003 using the Eddy Correlation Flux Measurement (ECOR) systems. The Gill sonic anemometers and LI-COR H2O/CO2 gas analyzers used in the ECOR are no longer manufactured, can no longer be repaired, and ARM is running out of spares, necessitating upgrading of the system. In addition to upgrading the anemometer and gas analyzer, the new ECOR systems will differ from the current ECOR systems in that they will use EddyPro processing software from within a SmartFlux box (containing a microcomputer) to produce both raw and fully corrected fluxes as outputs to be ingested into the ARM archive. The advantage of using EddyPro for processing ECOR data is that it is a fully supported commercial product and the data will not have to be corrected in a VAP as in the current system (QCECOR). In 2018, a prototype system was proposed, purchased, and built at ANL. The prototype ECOR system (ECOR with SmartFlux; “ECORSF”) was collocated with the Fermi Prairie AmeriFlux site (hereafter “AmeriFlux”) July-Aug 2018 for intercomparison. The AmeriFlux system was designed and operated by the former instrument mentor (Cook), and has the same components and specifications as the current ECOR systems. The site is located in the middle of a restored prairie, with adequate fetch in all directions (except for ENE-ESE winds). The two collocated flux systems exhibit considerable agreement in measurements of momentum, sensible and latent heat (LE), and CO2 (Fc) fluxes (r^2 = 89 – 95%). However, the magnitude of the daytime LE and Fc are slightly larger (more positive/upward and more negative/downward for LE and Fc, respectively) from ECORSF than from AmeriFlux, due to increased H2O and CO2 sensitivity of the newer LI-7500DS gas analyzer c.f. the older LI-7500 model. As the new ECOR prototype design meets the instrument mentor expectations and measurements compare well to those from a system with the same design specifications as the current ECOR system, it was recommended to replace all of the ARM SGP ECOR systems with the new system design. The remaining systems have been purchased, and following assembly at ANL, it is anticipated that installations will be completed in summer 2019.