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 is about +0.5 % (NRTI) and +1.3 % (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. A first analysis of the long-term stability of the RPRO+OFFL record against the ground-based data reveals drifts below the GCOS 2022 Implementation Plan threshold of 3 %/decade at almost all stations with sufficiently well sampled time series.
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 agreement within 1-2 % at all but the highest latitudes, where retrievals are most difficult because of both low solar zenith angles and strong surface albedo gradients. Differences with GOME-2C do contain a systematic component of -2 %, but ground-based validation suggests the latter to be biased high by such an amount.
| Product ID | Stream | Version | Bias | Dispersion | Special features |
|---|---|---|---|---|---|
| L2_O3 | NRTI |
02.04.01 |
0.5% | 2% | Some increase in dispersion in the comparisons to ground-based measurements at SZA > 70°. |
| OFFL/RPRO |
02.04.01 |
1.3% | 2% | Some increase in dispersion in the comparisons to ground-based measurements at SZA > 70°. |
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 #28: April 2018 - August 2025.
