Near-Real-Time provision of aerosol and reactive species from ACTRIS and EMEP surface observation networks

Project overview

The ACTRIS and EMEP networks provide precise data on the state of the atmosphere. For this purpose, we are developing quality assurance procedures in the ACTRIS project that will make the data even more reliable. In the CAMS2_21a project, the usability of the ACTRIS data is to be improved by making the processed data available in near-real-time as well.

CAMS2_21a consolidates the procedures for data transfer from the ACTRIS in-situ observation network and extends the scope to additional variables (NOx and VOC) and further European sites in the ACTRIS and/or EMEP network.


  • French National Center for Scientific Research (CNRS), FR
  • University of Lille, FR
  • Leibniz Institute for Tropospheric Research (TROPOS), DE
  • French National Institute for Industrial Environment and Risks (INERIS), FR
  • Institute Mines-Telecom (IMT Nord Europe), FR
  • Eidgenoessische Materialpruefungs- und Forschungsanstalt (EMPA), CH
  • Norwegian Institute for Air Research (NILU), NO
  • University of Helsinki, FI
  • University of Urbino, IT

Our tasks within the project

As a calibration centre, FZJ is responsible for the routines for processing the nitrogen oxide data measured at the stations. A central part of this is a routine developed at the FZJ, which reduces the cross-sensitivities of the measurements to ozone and humidity. This procedure is not used so far at the stations of the European Measurement Network (EAA) and the European Monitoring and Evaluation Programme (EMEP) network, which the ECMWF uses for its forecasts.

Within the framework of the project, the ACTRIS routine will be applied to existing NOx data sets from EMEP, ACTRIS and EAA to demonstrate the usefulness of the ACTRIS quality measures for EMEP and EAA.

Another quality assurance measure in the ACTRIS network is the use of photolytic converters. Nitrogen dioxide (NO2) must be converted to nitric oxide (NO) for detection. At most EMEP and EAA stations, NO2 is converted using a heated molybdenum converter. This converter is efficient, but it also converts other nitrogenous compounds besides NO2 into NO, so these measurements overestimate real NO2 concentrations. In the ACTRIS network, a photolytic converter is prescribed that works much more selectively. In the project, therefore, the importance of using a photolytic converter is to be demonstrated using a data set as an example.

Effect of interference correction on a NOx dataset, at different residence times of the sample in the inlet line (tline) in the converter (conv) or after the converter (tpos). Already at a residence time of 2s (lower panel) the NO concentration is 5% top low without interference correction. At a residence of 7s (uppermost panel) NO is already 20%-30% top low.

Project Period

November 2022-May 2026

Funded by

European Centre for Medium-Range Weather Forecasts (ECMWF).


Dr. Robert WegenerSenior Scientist Head of group "Energy Related Emissions"Building 05.2 / Room 3053+49 2461/61-6914
Benjamin WinterBuilding 05.2 / Room 3054+49 2461/61-85227

Last Modified: 20.10.2023