Enhanced Eddy Correlation Flux Product Available

Published: 26 February 2025

Time series of surface sensible heat fluxes (top), latent heat fluxes (middle), and carbon dioxide fluxes (bottom) are shown from the ECOR and QCECOR value-added product at the Eastern North Atlantic atmospheric observatory on April 18, 2024. The gray line is original ECOR data. The black line represents corrected QCECOR data, and red x’s indicate bad data and are set as missing. Black circles indicate corrected QCECOR data in earlier versions, which removed many nonsuspicious data points for surface latent heat fluxes with the usage of surface energy balance system wetness. Image is from Cheng Tao, Lawrence Livermore National Laboratory.

An enhanced version of the Quality-Controlled Eddy Correlation Flux Measurement value-added product (QCECOR VAP) has been developed for the Atmospheric Radiation Measurement (ARM) User Facility. New and reprocessed data are now available from this version of the VAP.

QCECOR is designed to improve the surface turbulence fluxes from eddy correlation flux measurement systems (ECORs) by applying eddy correlation corrections, determining quality-controlled energy fluxes from the corrected ECOR fluxes, and performing stringent quality control (QC) checks.

In earlier versions of QCECOR, a wetness QC flag from the co-located surface energy balance system (SEBS) measurements was applied to flag possible incorrect fluxes due to hydrometeor impacts. However, the usage of this SEBS wetness QC flag resulted in the removal of too many nonsuspicious data points, especially during night. In this version, wetness from SEBS data is included for users’ reference but will not be applied for any QC procedures.

Another enhancement in this version of QCECOR is the addition of corrected carbon dioxide fluxes, one of the primary ECOR measurements.

It is suggested that scientists use the corrected surface turbulent fluxes of sensible heat, latent heat, and carbon dioxide. Based on initial analysis, these corrections generally increase the latent heat flux by 10% to 30% and the sensible heat flux by 10% from the original data, especially during the day, while a much smaller increase is noticed at night.

The corrected carbon dioxide flux is consistent with the community-vetted code EddyPro. The magnitude of the corrected carbon dioxide flux is generally 0% to 50% of the original measured flux with the application of the Webb-Pearman-Leuning correction, which corrects for density fluctuations caused by heat and water vapor transfer (Webb et al. 1980). Additional corrections applied in QCECOR can result in the magnitude of the total carbon dioxide flux correction being larger than 50%, which is also consistent with EddyPro.

The uncorrected surface turbulent fluxes of sensible heat, latent heat, and carbon dioxide are included as well for the user’s convenience.

More information on QCECOR, including its technical report, is available on the VAP web page.

New data from the enhanced QCECOR VAP are now available for the following ARM Mobile Facility deployments and date ranges:

Gothic, Colorado, during the Surface Atmosphere Integrated Field Laboratory (SAIL) campaign from September 1, 2021, to June 15, 2023
La Jolla, California, during the Eastern Pacific Cloud Aerosol Precipitation Experiment (EPCAPE) from February 15 to November 6, 2023
La Porte, Texas, during the TRacking Aerosol Convection interactions ExpeRiment (TRACER) from October 1, 2021, to October 1, 2022.

In addition, all previously released QCECOR data for the following sites and date ranges have been reprocessed:

the Eastern North Atlantic atmospheric observatory on Graciosa Island in the Azores from July 3, 2014, to July 9, 2024
North Slope of Alaska extended facility E10 at Utqiaġvik (formerly Barrow) from November 7, 2011, to July 9, 2024
Southern Great Plains extended facility E14 near Lamont, Oklahoma, from September 12, 2003, to October 22, 2019
the SAIL supplemental facility 3 (S3) at Kettle Ponds from September 17, 2021, to June 16, 2023.

The QCECOR data have a time resolution of 30 minutes and are available in netCDF format.

Scientists can use the new and reprocessed QCECOR data now. Remaining historical data at other ARM sites are expected to be reprocessed and made available in early fiscal year 2025.

Access the enhanced QCECOR data in the ARM Data Center. (To download the data, first create an ARM account.)

To ask questions, provide feedback, or report data issues, please contact ARM VAP developer Cheng Tao or ARM translator Shaocheng Xie.

To cite the QCECOR data, please use doi:10.5439/1097546.

Reference: Webb EK, GI Pearman, and R Leuning. 1980. “Correction of flux measurements for density effects due to heat and water vapor transfer.” Quarterly Journal of the Royal Meteorological Society 106(447):85-100, https://doi.org/10.1002/qj.49710644707

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ARM is a DOE Office of Science user facility operated by nine DOE national laboratories.