Article Index

Validation Method

Sentinel-5p TROPOMI ozone column data are compared to correlative ground-based measurements collected from several monitoring networks contributing to WMO's Global Atmosphere Watch: direct-Sun observations from Brewer and Dobson UV spectrophotometers, and zenith-sky observations from NDACC DOAS UV-Visible spectrometers (ZSL-DOAS).

Co-locations between TROPOMI and direct-Sun measurements are defined as “pixel contains station”, with a maximum time difference of 3 hours. Note that direct-sun measurements obtained through the NDACC and WOUDC data archives are usually daily means of the individual measurements.

To reduce co-location mismatch errors due to the significant difference in horizontal smoothing between TROPOMI and ZSL-DOAS measurements, TROPOMI ozone column values (from afternoon ground pixels at high resolution) are averaged over the footprint of the larger air mass to which the ground-based twilight zenith-sky measurement is sensitive. For more details about the validation methodology, read Lambert et al. (1997, 1999), Balis et al. (2007), Koukouli et al. (2015), Verhoelst et al. (2015), and Garane et al. (2019).

TROPOMI ozone column data processed with the NRTI and OFFL processors are regularly intercompared.

TROPOMI ozone column data are also compared to alternative retrievals, and to corresponding satellite data from the MetOp-B GOME-2, Aura OMI, and Suomi-NPP OMPS-nadir satellite instruments.



  • Koukouli, M. E., Lerot, C., Granville, J., Goutail, F., Lambert, J.-C., et al. Evaluating a new homogeneous total ozone climate data record from GOME/ERS-2, SCIAMACHY/Envisat, and GOME-2/MetOp-A J. Geophys. Res. Atmos., Wiley-Blackwell, 2015, 120, 12,296-12,312
  • Garane, K., Koukouli, M.-E., Verhoelst, T., Fioletov, V., Lerot, C., Heue, K.-P., Bais, A., Balis, D., Bazureau, A., Dehn, A., Goutail, F., Granville, J., Griffin, D., Hubert, D., Keppens, A., Lambert, J.-C., Loyola, D., McLinden, C., Pazmino, A., Pommereau, J.-P., Redondas, A., Romahn, F., Valks, P., Van Roozendael, M., Xu, J., Zehner, C., Zerefos, C., and
    Zimmer, W.: TROPOMI/S5ptotal ozone column data: global ground-based validation and consistency with other satellite missions, Atmos. Meas. Tech.,, 2019.
  • Verhoelst, T., Granville, J., Hendrick, F., Köhler, U., Lerot, C., Pommereau, J.-P., Redondas, A., Van Roozendael, M., and Lambert, J.-C.: Metrology of ground-based satellite validation: co-location mismatch and smoothing issues of total ozone comparisons, Atmos. Meas. Tech., 8, 5039-5062,, 2015. 
  • Balis, D., Lambert, J.-C., Van Roozendael, M., Spurr, R., Loyola, D., et al. Ten years of GOME/ERS2 total ozone data: The new GOME data processor (GDP) version 4: 2. Ground-based validation and comparisons with TOMS V7/V8 J. Geophys. Res., Wiley-Blackwell, 2007, 112, n/a-n/a
  • Lambert, J.-C., M. Van Roozendael, M. De Mazière, P.C. Simon, J.-P. Pommereau, F. Goutail, A. Sarkissian, and J.F. Gleason, Investigation of pole-to-pole performances of spaceborne atmospheric chemistry sensors with the NDSC, Journal of the Atmospheric Sciences, Vol. 56, pp. 176-193,<0176:IOPTPP>2.0.CO;2 , 1999.
  • Lambert, J.-C., M. Van Roozendael, J. Granville, P. Gerard, P. Peeters, P.C. Simon, H. Claude and J. Staehelin, Comparison of the GOME ozone and NO2 total amounts at mid-latitude with ground-based zenith-sky measurements, in Atmospheric Ozone - 18th Quad. Ozone Symp., L’Aquila, Italy, 1996, R. Bojkov and G. Visconti (Eds.), Vol. I, pp. 301-304, 1997.