Validation Summary
The S5P L2_O3 NRTI and OFFL total ozone column data are in good overall agreement with correlative ground-based measurements from the GAW and NDACC Brewer and Dobson networks, the PGN Pandora network, and the NDACC ZSL-DOAS/SAOZ network, and with the Metop-B GOME-2, Aura OMI, and Suomi-NPP OMPS-nadir satellite instruments. Across the networks the mean bias over the entire mission lifetime is about +0.3 % (NRTI) and +1.2 % (OFFL). This bias and the standard deviation of the relative difference both comply with mission requirements, that is, a bias lower than 5 % and an uncertainty due to random errors (dispersion) better than ±2.5 %. The instrumental switch to smaller (along-track) ground pixels on the 6th of August 2019 did not affect the agreement with the ground-based reference data. An analysis of the long-term stability of the RPRO+OFFL and NRTI records against the ground-based data reveals small negative drifts of -1% to -1.5% per decade, in particular against several Brewer and Pandora instruments at low and middle latitudes, though this drift seems to resolve around mid-2025. This drift is most pronounced in the NRTI product, which implies that both products start to diverge around the 2022 mark, though again, this seems to resolve by mid-2025.
The comparison of S5P TROPOMI total ozone column data between processors (NRTI versus OFFL) and with other nadir UV satellite data sets (GOME-2B and GOME-2C, OMI, OMPS) shows in general agreement within 2-3 % at all but the highest latitudes, where retrievals are most difficult because of both high solar zenith angles and strong surface albedo gradients. The comparisons to GOME-2B and OMI do not confirm a common negative drift in both TROPOMI ozone column products as suggested by some ground-based comparisons. In fact, OFFL TROPOMI columns and operational NASA OMI columns (collection 3) appear highly consistent except for a stable long-term offset of about 1.5 %, in line with the slight overall TROPOMI OFFL positive bias w.r.t. ground-based data.
| Product ID | Stream | Version | Bias | Dispersion | Special features |
|---|---|---|---|---|---|
| L2_O3 | NRTI |
02.04.01 |
0.3% | 2% | Some increase in (negative) bias at the highest surface albedo. Increased dispersion in the comparisons to ground-based measurements at SZA > 70°. Potentially a negative drift since approx. 2022, in particular at low and middle latitudes (-2 %/decade), albeit with indications that this drift resolves around mid-2025. |
| OFFL/RPRO |
02.04.01 |
1.2% | 2% | Some increase in dispersion in the comparisons to ground-based measurements at SZA > 70°. Potentially a small negative drift since approx. 2022 at low and middle latitudes (-1 %/decade), although not confirmed by comparisons to OMI and GOME-2B. |
The graphs below summarize the up-to-date estimates of TROPOMI total O3 data quality obtained from comparisons to ground-based direct-sun and zenith-sky measurements. Shown is the meridian dependence of the median (the circular markers) and spread (±1 sigma, the error bars) of the percent relative difference between S5p and ground-based ozone column data, represented at individual stations from the Antarctic to the Arctic and per measurement type (Brewer, Dobson, Pandora and ZSL-DOAS). The values in the legend correspond to the median and spread of all median (per station) differences. For clarity, sunrise and sunset ZSL-DOAS results are represented separately (offset by -0.5˚ and +0.5˚ in latitude).
A detailed description of the method and a comprehensive discussion of validation results can be found in the Quarterly Validation Report #29: April 2018 - November 2025.
