FLUXNET Requirements for Data Sharing
Overview of required data and data format for files uploaded to EFDC / FLUXNET for post-processing and subsequent data sharing.
Guideline on the EFDC homepage:
Which data do we upload to FLUXNET / EFDC?
- We upload the adjusted
*_fluxnet_*output file from EddyPro (Level-1 flux calculations, for an overview of the different flux levels see here: Flux Processing Chain). The EddyPro
*_fluxnet_*file still has to be adjusted following the EFDC guidelines (note the required timestamp and variable names with _1_1_1, also only upload most relevant flux variables from this file, not all of them).
- Despite its name, the EddyPro
*_fluxnet_*file cannot directly be uploaded for sharing in FLUXNET.
- In some cases, it might be necessary to remove some clearly wrong data in the uploaded file before upload, e.g. when we are sure that a sensor was clearly defective but still produced data and erroneous fluxes were calculated. In this case, file is adjusted before upload (erroneous fluxes set to
- Important: FLUXNET needs fluxes that are not oulier-removed and not u*-filtered and not gap-filled and not partitioned because they apply their scripts to perform all of these steps! Only when data are clearly wrong it is recommended to set the data to
-9999in the data files before upload.
- In FLUXNET / EFDC, the understand the uploaded data as Level-2 data. In our case, we can directly upload our Level-1 data in most cases.
- If the Level-1 data contains erroneous fluxes that need to be removed, those fluxes are set to -9999 before sharing with FLUXNET.
- Keep in mind that we upload our Level-1 data, although FLUXNET / EFDC always understands uploaded data as (their) Level-2:
Level-2 data are original data submitted by the PI and checked/filtered only for out-of-range values or clearly wrong data. The variables available are listed in the table here below and are provided as ASCII file with missing values reported as -9999 and timestamp indicating the end of the averaging period. The file produced has in the first line the variables codes.
– Source: EFDC
- the site FluxID in the form CC-SSS (two character country code, three character site identifier within country) – e.g., CH-Dav
- the latitude and longitude for the site in the WGS 84 decimal format with at least four decimal points resolution – e.g., 42.5378 / -72.1715
- timezone of the site (time series, if timezone changed; timestamps are all local standard time, no daylight savings) – e.g., UTC-5
- height of the gas analyser – e.g., 30.0 m
- CSV file
- Missing values or error code:
- FLUXNET/EFDC now needs two timestamps in the file:
- Timestamp in the format: YYYYMMDDhhmm
- Yearly range needed: one file for each year.
TIMESTAMP_STARTin the respective file for e.g. 2020 is
TIMESTAMP_ENDin the respective file for e.g. 2020 is
- Time resolution: 30min (60min also accepted)
- Variable names need suffix, e.g.
from the EddyPro *full_output* file, renamed according to EFDC / FLUXNET variable codes
- FC (µmolCO2 m-2 s-1): Carbon Dioxide (CO2) turbulent flux (without storage component)
- FC_SSITC_TEST (adimensional): Quality check – CO2 flux – * see the note
- SC (µmolCO2 m-2 s-1): Carbon Dioxide (CO2) storage flux measured with a vertical profile system, optional if tower shorter than 3 m
- CO2 (µmolCO2 mol-1): Carbon Dioxide (CO2) mole fraction in moist air
- LE (W m-2): latent heat turbulent flux, without storage correction
- LE_SSITC_TEST (adimensional): Quality check – latent heat flux – * see the note
- SLE (W m-2): Latent heat storage below flux measurement level
- H2O (ppt: mmolH2O mol-1): Water (H2O) vapor mole fraction
- H (W m-2): sensible heat turbulent flux, without storage correction
- H_SSITC_TEST (adimensional): Quality check – sensible heat flux – * see the note
- SH (W m-2): Heat storage in air below flux measurement level
Wind & Footprint
- USTAR (m s-1): friction velocity
- WD (°): wind direction
- WS (m s-1): horizontal wind speed
- FETCH_70 (m): Fetch at which footprint cumulated probability is 70%
- FETCH_90 (m): Fetch at which footprint cumulated probability is 90%
- FETCH_MAX (m): Fetch at which footprint cumulated probability is maximum
* note: for the quality flag definition please refer to this document: Quality Flags Definition
from meteo data files, renamed according to EFDC / FLUXNET variable codes
- TA (°C): air temperature
- RH (%): relative humidity (range 0–100%)
- PA (kPa): atmospheric pressure
- SW_IN (W m-2): incoming shortwave radiation
- G (W m-2): ground heat flux, not mandatory, but needed for the energy balance closure calculations
- NETRAD (W m-2): net radiation, not mandatory, but needed for the energy balance closure calculations
- TS (°C): soil temperature
- PPFD_IN (µmolPhotons m-2 s-1): incoming photosynthetic photon flux density
- P (mm): precipitation total of each 30 or 60 minute period
- LW_IN (W m-2): incoming (down-welling) longwave radiation
- SWC (%): soil water content (volumetric), range 0–100%
Example: FLUXNET Processing Steps
The processing steps in FLUXNET are approximately like this:
- Level-1 fluxes are uploaded by PI
- Level-3 produced by FLUXNET
- calculation of NEE (storage correction, gives NEE, Papale et al., 2006)
- extension of QC flags, quality checks (spikes, u* filtering flags to filter for low-turbulence conditions, creates additional data gaps)
- Level-4 produced by FLUXNET
- application of QC flags, e.g. spike removal (Papale et al., 2006)
- partitioning (using NEE: Gross Primary Production, GPP; Terrestrial Ecosystem Respiration, TER)
- aggregation to different time resolutions