Toheli_Co_YYYY_dark_cleaned.csv files contain spatial averages of CO2 fluxes from 2 (2016-19) or 3 (2009-2015, 2020) automated ToHeLi soil chambers located at SMEAR II mini-catchment.

These files contain only fluxes measured at night or with dark chamber. Fluxes were further filtered based on min/max CO2 mixing ratio in open chamber and the precision of CO2 flux (residual std deviation around line fitted to CO2 records during chamber closing). Known periods of bad data from 1 or more chambers were also excluded.

The fluxes were calculated by linear fit to outlier-filtered CO2 mixing ratios collected between 40 s and 170 s after chamber closing, and corrected for air temperature and atmospheric pressure. Wet CO2 records without H2O dilution correction were used because chamber RH measurement was occasionally missing. Therefore, the fluxes are slightly underestimated.

Columns:
TIME -- The beginning of 30 min averaging period (ISO 8601, UTC+2)
FCO2soil -- Soil CO2 efflux (µmol m-2 s-1)

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The original data can be found in Toheli_[ID]_YYYY.csv files where ID is the chamber identifier and YYYY year.

Columns:

datetime -- Chamber closing time (yyyymmddHHMMSS, UTC+2)
T_ch -- Air temperature in the chamber in the beginning of closing (deg C)
T_soil -- Soil surface temperature in the chamber in the beginning of closing (deg C) 
CO2_ch -- CO2 in the chamber in the beginning of closing (ppm)
PAR_ch -- Mean photosyntecically active radiation in the chamber during closing (µmol m-2 s-1)
RH_ch --  Relative humidity in the chamber in the beginning of closing (%)
P_tow -- Air pressure at ground level (hPa)
RH_tow -- RH, measurement height varied (%) 
T_tow -- Air temperature below the canopy, measurement height varied (deg C)
F_CO2_soil -- Soil CO2 efflux (µmol m-2 s-1)
std_CO2 -- Residual standard deviation of instantaneous CO2 records from the linear fit (ppm)
N_obs -- Number of valid (unrealistic values and outliers removed) CO2 records during the fitting time window

Tower meteorological variables were downloaded from https://smear.avaa.csc.fi,
frozen dataset available at https://doi.org/10.23729/62f7ad2c-7fe0-4f66-b0a4-8d57c80524ec.

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Contact:
pasi.kolari@helsinki.fi