The third Cabauw INtercomparison of UV-Vis DOAS Instruments, CINDI-3, took place from 21 May to 24 June 2024 at the Cabauw Experimental Site for Atmospheric Research (CESAR), one of the main facilities of the Dutch Ruisdael Observatory (https://ruisdael-observatory.nl/) located midway in between the cities of Rotterdam and Utrecht, and managed by KNMI. CINDI-3 was organized under the umbrella of NDACC and conducted as part of the ACTRIS-CREGARS Topical Center for trace gas remote sensing with additional support from the European Space Agency and from the EU ATMO-ACCESS project (https://www.atmo-access.eu/ ). Several PGN instruments (PGN being a co-operating network of NDACC) participated in CINDI-3 and the PGN team also supported all campaign participants with their instrument calibration efforts.
CINDI-3 is the third intercomparison campaign following CINDI-2 in 2016 [1] and CINDI in 2009 [2]. Over 100 researchers from 16 countries participated in the campaign, operating 44 instruments to compare and intercalibrate measurements of air pollutants and to support the validation of satellite measurements from space-borne instruments such as Sentinel-5p/TROPOMI.
Fig 1: Picture of the two-story container setup assembled for the CINDI-3 intercomparison activities at the Cabauw campaign site. Photo credit: Gaël Dubois.
Fig 2: CINDI-3 participants on the container roof (left picture) in front of MAX-DOAS instruments (right panel). Photo credit: Arnoud Apituley.
The list of trace gases measured during CINDI-3 has grown substantially from the original CINDI campaign and includes in addition to nitrogen dioxide (NO 2 ) many other important atmospheric trace gases such as ozone, aerosols, formaldehyde, glyoxal, nitrous acid and bromine oxide. Many of these trace gases will be included in the formal NDACC semi-blind intercomparison exercise. Similar to CINDI-2, all participating instruments were setup in close proximity to each other and a comprehensive measurement protocol was used to ensure synchronisation in timing of the measurements and in viewing direction.
The stationary remote sensing UV-vis observations were complemented with a range of additional measurements from ozone and aerosol lidars, NO 2 and ozone sondes, long-path DOAS and in-situ instruments. Furthermore, mobile measurements around Cabauw, De Bilt and Rotterdam were also made during selected days with favourable weather conditions using cars and bikes as well as a small research aircraft, to provide a more complete picture of the distribution of pollutants from the industrial and urbanised area around Rotterdam.
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[2] Roscoe, H. K., Van Roozendael, M., Fayt, C., du Piesanie, A., Abuhassan, N., Adams, C., Akrami, M., Cede, A., Chong, J., Clémer, K., Friess, U., Gil Ojeda, M., Goutail, F., Graves, R., Griesfeller, A., Grossmann, K., Hemerijckx, G., Hendrick, F., Herman, J., Hermans, C., Irie, H., Johnston, P. V., Kanaya, Y., Kreher, K., Leigh, R., Merlaud, A., Mount, G. H., Navarro, M., Oetjen, H., Pazmino, A., Perez-Camacho, M., Peters, E., Pinardi, G., Puentedura, O., Richter, A., Schönhardt, A., Shaiganfar, R., Spinei, E., Strong, K., Takashima, H., Vlemmix, T., Vrekoussis, M., Wagner, T., Wittrock, F., Yela, M., Yilmaz, S., Boersma, F., Hains, J., Kroon, M., Piters, A., and Kim, Y. J.: Intercomparison of slant column measurements of NO2 and O4 by MAX-DOAS and zenith-sky UV and visible spectrometers, Atmos. Meas. Tech., 3, 1629–1646, https://doi.org/10.5194/amt-3-1629-2010, 2010.