The third Cabauw Intercomparison of UV-visible DOAS instruments

2023-2024
In May-June 2024, BIRA-IASB participated in the third “Cabauw Intercomparison of UV-visible DOAS Instruments” (CINDI-3). The main purpose of this campaign was to intercompare various remote-sensing instruments measuring pollutants such as NO2 and ozone, and contribute to further develop the reference systems needed for satellite validation.

Together with the 100 persons from 18 countries involved in the deployments, BIRA-IASB scientists operated several instruments and were strongly involved in the coordination of field activities.

A wide range of instruments for studying air quality in Cabauw

The third “Cabauw Intercomparison of UV-Vis DOAS Instruments” (CINDI-3) took place from May 21st to the 24th of June 2024 at the Cabauw station, a semi-rural facility part of the Dutch Ruisdael Observatory close to the cities of Rotterdam and Utrecht.

Its main objective was to intercompare a large number of UV-visible remote-sensing instruments measuring air quality gases and aerosols, with the aim to assess their performance under a range of observational conditions, and to progress towards a better understanding of the measurement technique through community effort.

To support the interpretation of the data, a comprehensive set of ancillary measurements (sondes, lidars, long-path DOAS systems, in-situ sensors, etc) was operated.

Furthermore, mobile instruments were deployed in the same area using cars and a small research aircraft operated by the Royal Belgian Institute of Natural Sciences (RBINS), to provide a more complete picture of the distribution of pollutants in the surroundings of Rotterdam.

BIRA-IASB scientists at work in the field

In close collaboration with the Dutch Royal Meteorological Institute (KNMI), BIRA-IASB contributed to the scientific coordination of the campaign and supported the refereeing of UV-visible measurements. It also provided an important contribution to field measurements, with the deployment of

Together with other measuring devices, a complete picture of the distribution of pollutants in the industrial and urban areas around the Rotterdam-Utrecht axis could be compiled. The NO2 distribution over Antwerp was also mapped from the aircraft as part of the same campaign. All flights were carried out in synchronisation with the Copernicus Sentinel-5 Precursor platform, which carries the TROPOMI instrument.

International context

The CINDI-3 campaign was organized under the auspices of the Network for the Detection of Changes in Atmospheric Composition (NDACC) and the ACTRIS Center for Remote Sensing of Reactive Gases (CREGARS), with additional support from ESA and NASA.

In total, more than 100 researchers from 18 countries participated in the deployments. This was a major international event that will contribute significantly to strengthening the scientific community active in air quality remote sensing.

Cindi 3 logo
Measuring instruments, NO2 camera visible in foreground.
Measuring instruments installed at Cabauw. BIRA-IASB’s NO2 camera is visible in the foreground. Credits: Michel Van Roozendael (BIRA-IASB)
Aerial surveillance aircraft passing over Observatory
Belgian aerial surveillance aircraft passing over the Cabauw Observatory on June 7th, 2024. Credits: Arnoud Apituley (KNMI)
NO2 vertical column distribution over the Rotterdam
NO2 vertical column distribution over the Rotterdam city and surrounding industrial area, as measured from the Belgian aerial surveillance aircraft on June 5th, 2024. The white dots indicate the main NOx emission sources, derived from the E-PRTR emission inventory. Credits: Frederik Tack and Alexis Merlaud (BIRA-IASB)