The ATC Data Unit

The ATC Data Unit is part of the Atmospheric Thematic Center of ICOS. It is hosted by the Laboratoire des Sciences du Climat et de l'Environnement at Gif -sur-Yvette (France).

The main tasks of the ATC Data Unit are:

  • to ensure that data are traceable to the international primary standard for GHG, maintained in NOAA CMDL, Boulder, Colorado, USA,
  • the supervision, from the raw measurement to the L2 validated product delivered to Carbon Portal, of the whole processing chain,
  • to ensure communication with ICOS Carbon Portal for metadata and data,
  • to process atmospheric data in NRT mode (24h),
  • to develop and maintain all instrument processing chain from instruments in ICOS stations,
  • to develop and maintain in house software to centrally process and quality control the data from the atmospheric ICOS networks,
  • to distribute via ATC website NRT monitoring products for PIs data and instrumental check,
  • to be the European training centre for ICOS atmospheric measurements, quality control and quality assessment.

For all requests about data products or support, or any question relating to your data and their processing, please contact the Data Unit at

ICOS Atmospheric Final Fully Quality Controlled Observational Data (Level 2)

ICOS ATC Data unit is responsible for the ICOS Atmosphere Release of Level 2 Greenhouse Gas Mole Fractions. This data collection contains the final quality controlled hourly averaged data for the mole fractions of CO2, CH4, N2O, CO and meteorological observations measured at the relevant vertical levels of the measurement stations, and where available 14C in CO2 in two-weekly integrated samples. All stations follow the ICOS Atmospheric Station specification V2.0 (doi:10.18160/GK28-2188) and are certified as ICOS atmospheric stations Class I or II.

Data processing has been performed as described in [Hazan et al., 2016] (doi:10.5194/amt-9-4719-2016).

ICOS Near Real Time Observational Data (Level 1)

ICOS ATC Data unit is also responsible  for the production of the Near Real-Time (NRT) growing time series containing data from the atmospheric network of ICOS Research Infrastructure. This collection contains the NRT hourly averaged data for the mole fractions of CO2, CO and CH4 as well as the meteorological data, measured at the relevant vertical levels of the measurement stations, starting right after the latest date of final released Level 2 data. The ICOS atmosphere NRT data is, for example, used by Copernicus Atmosphere (see, for example of evaluation of global forecasts using ICOS NRT data) on a regular basis. The data processing at ATC has implemented an alert management system to ensure fast reactivity and thus high level of data delivery success rate.

Left panel: View of L2 data (violet) and NRT data (yellow) for ICOS Saclay station, at 100m measurement level, as it is accessible on panelboard’s station on ATC website.

ATCQc, a software developed especially for data monitoring and quality control

ATCQc is a graphical application to quality controlled the measurements made within the ICOS atmospheric network. The data are either greenhouse gases measurements like carbon dioxide, methane, nitrous oxide, radon or meteorological measurements. This application is intended for the Principal Investigators (PIs) who run the instruments in  the network .
The application is connected to the ATC relational database and all QC action modifications are saved back to the database and trigger the needed reprocessing of the data.
The different aggregation data are available from high frequency data to hourly means, for in-situ measurements as well as for quality tanks. A lot of ancillary data and metadata are made available to the PIs to help them qualify their data. Results of data analysis are also available like uncertainties and detected spikes.

Right panel: Example of timeseries of CO2 measurement for 3 levels, at Trainou ICOS station as available for data monitoring and quality control in ATCQc software.

Calibration Scale Traceability

ICOS ATC ensures that data are traceable to the international WMO primary standard for GHG, maintained in NOAA CMDL, Boulder, Colorado, USA. When a new WMO in air scale is in place (e.g. WMO CO2 X2019, [Hall et al., 2021] (doi: 10.5194/amt-14-3015-2021)) the ICOS/CAL first revises the values of all tanks used within the ICOS network. The  ATC  then propagates the new scale to the ambient air and target gases measurements through the reprocessing of the calibration data and the determination of new calibration equations.

Training Sessions at ICOS ATC

ATC organizes one or two training sessions a year. The trainings are given in priority to needing station staff that are in an advanced stage of the station labelling process. Once station PIs have been trained on the ATC software tools (ATCConfig and ATCQc) and the data quality control procedures, the training focuses more on the instrumentation and associated sampling system.

ATC also maintains the hotline for expert support to the ICOS network, and support cover all aspects from station design to data processing through data collection.

Data Products

The Data unit is in charge of computing NRT atmosphere data products. Those products facilitate station management and allows getting a fast feedback on the data; they improve reactivity in case of disruption in the data flow and thus limits data gaps. Data products are daily computed, usually in the morning. It is more than a thousand plots that are automatically generated for all the atmospherics stations of ICOS measurement network.

All data products are accessible here, or on the ICOS station panel board, for a specific station.


Right panel: Example of target concentration evolution for tank D337347 as observed at Helgoland ICOS station, on GHG analyser 489, for CO2 species