Sentinel-5p TROPOMI provides two SO₂ data products:

Sulphur dioxide total column and sulphur dioxide layer height. For both validation results in the latest ROCVR are available. On these pages the validation of SO2 total column is explained.

Validation Summary

The Sentinel-5p TROPOMI L2_SO2 (NRTI and OFFL) sulphur dioxide column data are found in general good agreement with ground-based MAX-DOAS and PGN measurements and with other satellite observations from OMI and S-NPP OMPS. The bias and dispersion with respect to validation data are typically below 0.2 DU. From these comparisons it can be concluded that over polluted regions the mission requirements are fulfilled. Over volcanic plumes the requirement on the bias is fulfilled, while the dispersion can exceed slightly the requirement on the random component of the uncertainty. Here it should be noted that detailed validation of SO2 in volcanic plumes based on ground based observations is still lacking.

In April 2023, the whole SO 2 data set was reprocessed with the new processor version 02.04.01. The reprocessed SO2 data show very good agreement with previous versions.

Sentinel-5p TROPOMI SO2 total column data is validated through comparisons to the following correlative ground-based measurements.

• Direct-sun measurements from Pandora spectrometers of the PGN network. Note that these are still in demonstration phase. Pandora direct-sun measurements (Knepp et al., 2015; Fioletov et al., 2016; McLinden et al., 2021) are sensitive to the entire column.
• Multi-axis DOAS UV-visible measurements (MAX-DOAS). MAX-DOAS measurements (e.g., Wang et al., 2017; Theys et al., 2015) are mainly sensitive to the lower tropospheric column.

References

Knepp, T. et al., Estimating surface NO2 and SO2 mixing ratios from fast-response total column observations and potential application to geostationary missions, J. Atmos. Chem., 2015, 72, 261-286, doi.org/10.1007/s10874-013-9257-6

Fioletov, V.E. et al., Sulfur dioxide (SO2) vertical column density measurements by Pandora spectrometer over the Canadian oil sands, Atmos. Meas. Tech., 2016, 9, 2961-2976, doi.org/10.5194/amt-9-2961-2016

McLinden, C.A. et al., Inconsistencies in sulfur dioxide emissions from the Canadian oil sands and potential implications, Environmental Research Letters, 2021, 16, 014012, doi.org/10.1088/1748-9326/abcbbb

Wang, Y. et al., Validation of OMI, GOME-2A and GOME-2B tropospheric NO2, SO2 and HCHO products using MAX-DOAS observations from 2011 to 2014 in Wuxi, China: investigation of the effects of priori profiles and aerosols on the satellite products, Atmos. Chem. Phys., 2017, 17, 5007-5033, doi.org/10.5194/acp-17-5007-2017

Theys, N. et al. Sulfur dioxide vertical column DOAS retrievals from the Ozone Monitoring Instrument: Global observations and comparison to ground-based and satellite data,
J. Geophys. Res. Atmos., 2015, 120, 1-22, doi.org/10.1002/2014jd022657

The Sentinel-5p Mission Performance Centre provides an operational validation service relying on the VDAF Automated Validation Server (VDAF-AVS).  This fully automated data analysis system collects correlative measurements from quality-controlled monitoring networks and compares them to Sentinel-5p data using community endorsed protocols.  It outputs a suite of traceable quality indicators enabling users to judge the fitness-for-purpose of the Sentinel-5p data.

The illustration given hereafter shows the automated comparison of Sentinel-5p TROPOMI total SO₂ column data with respect to correlative measurements aquired by a Pandora UV/Visible spectrometer of the Pandonia Global Network.  More TROPOMI SO₂ validation results are available at http://mpc-vdaf-server.tropomi.eu/so2 .

The VDAF Automated Validation Server in brief:

• hosted at BIRA-IASB and operated with s[&]t,
• provides routine validation for the ESA/Copernicus Sentinel-5p Mission Performance Centre,
• ingests correlative measurements from the ESA Atmospheric Validation Data Centre (EVDC) hosted at NILU, collected from ESA's Fiducial Reference Measurements (FRM) programme and from ground-based monitoring networks contributing to WMO's Global Atmosphere Watch,
• builds on heritage from the Multi-TASTE satellite validation system, the QA4ECV validation server (EC FP7 QA4ECV project) and the CAMS NDACC validation server (EC FP7 NORS project),
• is co-funded by ESA and the Belgian Science Policy Office (BELSPO) as a contribution to the Copernicus Space Component.

Latest Issue

Quarterly Validation Report of the Copernicus Sentinel-5 Precursor Operational Data Products #21: April 2018 - November 2023

Archive

Previous issues of the quarterly validation report are archived here.