ozone

Risksv0

Responsible:Niccolò Calandri

Ozone — Sentinel-5P TROPOMI O3

Overview

The Ozone (O₃) layer measures the total atmospheric column of ozone using the TROPOMI instrument aboard Sentinel-5P. Ozone plays a dual role in the atmosphere:

Stratospheric ozone (~90 % of total): forms the protective ozone layer that shields Earth's surface from harmful UV-B and UV-C radiation. Depletion of this layer (the "ozone hole") increases skin cancer risk and damages ecosystems.
Tropospheric ozone (~10 % of total): a secondary pollutant formed by photochemical reactions involving NOₓ and VOCs in the presence of sunlight. It is harmful to human health (respiratory damage) and vegetation (reduced crop yields).

Total column ozone is typically expressed in Dobson Units (DU), where 1 DU = 2.687 × 10¹⁶ molecules/cm². Global average: ~300 DU. The native resolution is ~1113 m, with output at 100 m.

Calculation Methodology

Retrieval algorithm:

Total column ozone is retrieved using the DOAS technique in the UV Hartley-Huggins bands (325–335 nm):

Spectral fitting of O₃ absorption cross-sections in the UV range
Air mass factor computation accounting for Rayleigh scattering, surface albedo, and cloud effects
Iterative correction for Ring effect (rotational Raman scattering)
Quality filtering based on cloud fraction, solar zenith angle, and fit residuals

Typical total column ozone values:

Region/Condition	O₃ (DU)
Antarctic ozone hole	< 220
Tropical average	250–280
Mid-latitude average	290–350
Arctic spring maximum	350–450

Data Sources

Code	Name	Provider	Type	Coverage	Resolution	Availability
`COPERNICUS/S5P/OFFL/L3_O3`	Sentinel-5P TROPOMI O3 L3	ESA/Copernicus	Atmospheric column	Global	~1113 m	2018-06 — present

Documentation: GEE S5P O3

Technical Notes

Total column ozone is dominated by the stratospheric contribution (~90 %); tropospheric ozone cannot be directly separated from this product
Ozone shows strong latitudinal and seasonal variations (highest at high latitudes in spring)
The "ozone hole" over Antarctica occurs annually in September-November
Cloud contamination affects retrieval accuracy but less severely than for SWIR-based products
Conversion: 1 DU corresponds to a layer of pure ozone 0.01 mm thick at STP

References

Veefkind, J.P. et al. (2012). "TROPOMI on the ESA Sentinel-5 Precursor: A GMES mission for global observations". Remote Sensing of Environment, 120, pp. 70–83.
Garane, K., Koukouli, M.E., Verhoelst, T. et al. (2019). "TROPOMI/S5P total ozone column data: global ground-based validation". Atmos. Meas. Tech., 12, pp. 5263–5287.
WMO (2022). "Scientific Assessment of Ozone Depletion: 2022". Global Ozone Research and Monitoring Project, Report No. 278.

Data Sources & References

Sources

WRD_S5O3X_99

Methodology

L'ozono (O3) viene mappato utilizzando i dati Sentinel-5P TROPOMI, prodotto OFFL L3_O3 disponibile su Google Earth Engine, con risoluzione nativa di circa 1113 metri. L'ozono ha un duplice ruolo nell'atmosfera: nella stratosfera (15-35 km, circa 90% del totale) lo strato di ozono protegge la biosfera dalla pericolosa radiazione ultravioletta UV-B e UV-C; nella troposfera (circa 10%) l'ozono è un inquinante secondario formato da reazioni fotochimiche tra ossidi di azoto (NOx) e composti organici volatili (VOC), dannoso per la salute umana e la vegetazione. L'ozono è anche un importante gas serra (GWP ~1000 su 20 anni). La banda utilizzata è 'O3_column_number_density', che misura la densità colonnare totale di ozono in mol/m². I valori sono convertibili in Dobson Units (DU) moltiplicando per 2.1415×10⁹. L'elaborazione è analoga agli altri prodotti S5P.