Data supporting the manuscript "14C-based separation of fossil and non-fossil CO2 fluxes in cities using relaxed eddy accumulation: results from tall-tower measurements in Zurich, Paris, and Munich"

Flags for relaxed eddy accumulation (REA) measurements conducted on three tall towers in Zurich (CH-Har), Paris (FR-Rmv), and Munich (DE-Opd) within the ICOS Cities project (https://www.icos-cp.eu/projects/icos-cities). The measurements and flagging criteria are described in the following manuscript: Kunz, A.-K., Hammer, S, Aigner, P., Bignotti, La., Borchardt, L., Chen, J., Della Coletta, J., Emmenegger, L., Eritt, M., Gutiérrez, X., Hashemi, J., Hilland, R., Holst, C., Jordan, A., Kljun, N., Kneissl, R., Lan, C., Legendre, V., Levin, I., Loubet, B., Mauder, M., Molinier, B., Preunkert, S., Ramonet, M., Stagakis, S., and Christen, A.: 14C-based separation of fossil and non-fossil CO2 fluxes in cities using relaxed eddy accumulation: results from tall-tower measurements in Zurich, Paris, and Munich. Information on the start and end times, as well as flask concentrations and flux estimates, for all REA measurements can be found on the ICOS Cities data portal: https://citydata.icos-cp.eu/portal/ . Data are provided in CSV files for each measurement site. Each file contains the following columns: Column name Description REA_ID Unique, consecutively assigned identification number for the REA measurements. Comment Comment on whether the high-frequency CO2 measurements from an open-path gas analyzer (IRGASON, Campbell Scientific, Inc., Logan, UT, USA) or closed-path gas analyzer (MGA7, MIRO Analytical AG, Wallisellen, Switzerland) were used to calculate eddy covariance CO2 fluxes during the REA sampling period; whether the flask samples were successfully analyzed for 14CO2; whether the measurement was potentially influenced by identified point-source emissions. flag_FCO2qc Whether the maximum quality control flag for stationarity and well-developed turbulence (Mauder and Foken, 2004) for the 30 min EC CO2 fluxes is < 2 (1) or 2 (0). flag_betaCO2 Whether the beta coefficient, calculated from CO2, is between 0.1 and 1 (1) or not (0). flag_SNR Whether the signal-to-noise ratio, defined as the minimum of the relative fossil and non-fossil CO2 flux uncertainties, is ≥ 100 % (1) or < 100 % (0). flag_ustar_min Whether the minimum of the friction velocities of the 30 min EC averaging periods is ≥ 0.2 m/s (1) or < 0.2 m/s (0). flag_Fstrg_max Whether the maximum of the absolute storage flux estimates of the 30 min EC averaging periods is ≤ 20 µmol/m^2/s (1) or > 20 µmol/m^2/s (0). flag_FffCO2 Whether there is ffCO2 flux data (i.e., an eddy covariance-based CO2 flux estimate and 14CO2 flask measurements) available (1) or not (0). flag_WellMixed Whether flag_FffCO2, flag_FCO2qc, flag_betaCO2, flag_SNR, flag_ustar_min, and flag_Fstrg_max are 1 (1) or not (0). flag_LowTurb Whether flag_FffCO2, flag_FCO2qc, flag_betaCO2, flag_SNR, and flag_Fstrg_max are 1, and flag_ustar_min is 0 (1) or not (0). flag_Storage Whether flag_FffCO2, flag_FCO2qc, flag_betaCO2, flag_SNR, and flag_ustar_min are 1, and flag_Fstrg_max is 0 (1) or not (0). flag_NotConsidered Whether flag_FffCO2 is 1 and at least one of the flags flag_FCO2qc, flag_betaCO2, or flag_SNR is 0 (1) or not (0).