Half hourly fluxes of CO2 and CH4 were computed from the covariation of high frequency vertical wind direction and CO2 and CH4 concentration using the EddyPro software package (Version 7.0.6, LICOR, Inc., Lincoln, NE, USA), as well as latent heat exchange and friction velocity. Within software specifications, raw high frequency data were despiked and a double coordinate rotation was applied to anemometer measurements along with a flux correction for the effects of humidity on sonic air temperature, high-frequency and low-frequency spectral attenuations, and air density fluctuations coupled to instrument-related sensible heat flux in the winter. Computed fluxes were exported to .csv files. We report fluxes of carbon dioxide as net ecosystem exchange (NEE), where negative values for both NEE and CH4 indicate net uptake of gas by the land surface and positive values indicate net loss of gas to the atmosphere. We removed low quality measurements (ranked as less than or equal to 1 quality flag per EddyPro based on Mauder and Foken, 2006), measurements made during and immediately following precipitation events, and any measurement collected during site maintenance or known instrument malfunction. We also removed measurements made during low‐turbulence conditions with potential advective losses and when friction velocity, ustar, was below a site specific threshold of 0.118 meters per second calculated in the R-based software package REddyProc (Version 1.2.2, Wutzler and others 2018). Instrument malfunction caused a gap in some meteorological data from late-January through mid-April 2021 and are represented as blanks in the data. The .csv files containing the meterological data and the .csv file containing the computed fluxes were matched by datetime and merged in R.
Wutzler, T., Lucas-Moffat, A., Migliavacca, M., Knauer, J., Sickel, K., Šigut, L., Menzer, O., and Reichstein, M., 2018, Basic and extensible post-processing of eddy covariance flux data with REddyProc: Biogeosciences Discussions, February, 1–39.
https://doi.org/10.5194/bg-2018-56.
Mauder, M., and Foken, T., 2006, Impact of post-field data processing on eddy covariance flux estimates and energy balance closure: Meteorologische Zeitschrift, vol. 15, p. 597-609