23 September 2019
The QCECOR VAP is designed to improve the surface turbulence fluxes from the Eddy Correlation Flux (ECOR) measurements. The applied corrections and quality control (QC) procedures include: 1) Eddy correlation corrections (Cook et al. 2008), 2) Determination of the quality-controlled energy fluxes from the corrected ECOR fluxes, 3) Stringent QC checks, and 4) Flagging possible incorrect fluxes due to hydrometeor impacts using the collocated surface energy balance system (SEBS) wetness measurements.
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Two variables, surface latent heat flux (LH) and sensible heat flux (SH), are included in QCECOR, together with their QC flags. Currently, the QCECOR data with 30-min time resolution are available at the Southern Great Plains (SGP) atmospheric observatory and multiple AMF sites including PYE (Point Reyes, 2005), NIM (Niamey, Niger, 2006), FKB (Black Forest, Germany, 2007), HFE (Shouxian, China, 2008), GRW (Azores, 2009 to 2010), and MAO (Manacapuru, Brazil, 2014-2015).
In recent years, ARM has significantly enhanced its ECOR systems and made them available at all its primary research observatories and mobile facilities. However, the original ECOR data were not corrected through common eddy correlation corrections and still contain suspicious data due to instrument and measurement uncertainties. By applying multiple QC procedures, the surface turbulence flux from the ECOR measurements are largely improved in the QCECOR VAP. Users are recommended to use QCECOR instead of ECOR data when available. The algorithm is now in the process of moving to production mode. After that, QCECOR will run automatically for all available ARM sites.
Besides ECOR, there is another type of instrument, the Energy Balance Bowen Ratio System (EBBR), installed at the broad ARM SGP region, with a VAP available as the Bulk Aerodynamic Technique EBBR (BAEBBR). At the SGP Central Facility, for example, the two instruments are within a few hundred meters apart. However, the turbulence fluxes measured from ECOR and EBBR are found to have significant differences, mainly due to the various surface vegetation types the instruments are representing. Users need to be careful about the surface type representation when using the turbulent flux measurements from ECOR and EBBR. More information about the comparison of ECOR and EBBR at SGP can be found in Tang et al. (2019).