The Sentinel-5p TROPOMI L2_O3 data (both NRTI and OFFL) are in good overall agreement with correlative ground-based measurements from the Brewer, Dobson and NDACC ZSL-DOAS/SAOZ monitoring networks, and also with the MetOp-B GOME-2, Aura OMI, and Suomi-NPP OMPS-nadir satellite instruments. Across the monitoring networks the median bias of about +0.8% (NRTI) and +0.3% (OFFL) and the standard deviation of the relative difference meet mission requirements, that is, a bias lower than 3.5% 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 does not alter the agreement with the ground-based reference data. The upgrade of the UPAS processor to version 02.01.03 on 16 July 2020 (NRTI) and 13 July 2020 (OFFL) improves the agreement to ground-based data for the NRTI product over complex snow/ice scenes.
|Product ID||Stream||Version||Orbits||Bias||Dispersion||Special features|
|L2_O3||NRTI||02.01.03||14285-||0.5%||2.4%||Improved performance over snow/ice w.r.t. v01.xx.xx|
|0.8%||2.4%||Larger dispersion over snow/ice due to coarse surface albedo climatology (up to v02.01.03)|
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, for the UPASv2 processor in operation since 16 July 2020 (NRTI, upper panel) and 13 July 2020 (OFFL, lower panel). 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, 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 #9: April 2018 – December 2020.