carbon_monoxide

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Responsible:Niccolò Calandri

Carbon Monoxide — Sentinel-5P TROPOMI CO

Overview

The Carbon Monoxide (CO) layer measures the total column density of CO in the atmosphere using the TROPOMI (TROPOspheric Monitoring Instrument) aboard ESA's Sentinel-5P satellite. Carbon monoxide is a colorless, odorless trace gas produced primarily by:

Fossil fuel combustion (~60 %): vehicles, power plants, industrial processes
Biomass burning (~25 %): wildfires, agricultural burning, deforestation
Methane oxidation (~15 %): photochemical reactions in the troposphere

CO has an atmospheric lifetime of approximately 2 months, making it an effective tracer for long-range transport of pollution plumes. It serves as a precursor to tropospheric ozone (O₃) formation and is a key indicator of air quality degradation, combustion efficiency, and fire activity.

The native resolution is approximately 1113 m (7 km × 3.5 km footprint at nadir, resampled), with output maps generated at 100 m resolution through spatial interpolation.

Calculation Methodology

Retrieval algorithm:

The CO total column is retrieved from the shortwave infrared (SWIR) spectral range around 2.3 µm, where CO has strong absorption features. The SICOR (Shortwave Infrared CO Retrieval) algorithm:

Measures radiance in the 2.3 µm CO absorption band
Corrects for atmospheric scattering using simultaneously retrieved effective cloud parameters
Accounts for surface reflectivity variations
Derives total column density in mol/m² through spectral fitting

Post-processing:

Quality filtering based on retrieval quality assurance flags (qa_value > 0.5)
Cloud fraction filtering (< 0.5)
Spatial resampling from ~7 km native to 100 m output via kriging interpolation
Temporal compositing over the requested period

Typical values:

Environment	CO Column (mol/m²)
Clean background	0.01–0.02
Rural areas	0.02–0.03
Urban areas	0.03–0.05
Fire plumes	0.05–0.15
Extreme pollution	> 0.15

Data Sources

Code	Name	Provider	Type	Coverage	Resolution	Availability
`COPERNICUS/S5P/OFFL/L3_CO`	Sentinel-5P TROPOMI CO L3	ESA/Copernicus	Atmospheric column	Global	~1113 m	2018-06 — present

Documentation: GEE S5P CO

Quality Range and Levels

Indicator	Unit	Range	Inverted
`carbon_monoxide`	mol/m²	[0, 0.02, 0.03, 0.05, 0.10, 0.20]	Yes

Inverted = Yes: a higher value indicates worse air quality.

Technical Notes

CO retrievals are most reliable over land surfaces; ocean retrievals have higher uncertainty due to low surface reflectivity in the SWIR
Cloud contamination reduces data availability, particularly in tropical regions
The ~2 month atmospheric lifetime means that CO concentrations integrate transport processes and are not purely indicative of local sources
Diurnal variations are not captured due to the sun-synchronous orbit (13:30 local overpass time)

References

Veefkind, J.P., Aben, I., McMullan, K. et al. (2012). "TROPOMI on the ESA Sentinel-5 Precursor: A GMES mission for global observations of the atmospheric composition". Remote Sensing of Environment, 120, pp. 70–83.
Landgraf, J., aan de Brugh, J., Scheepmaker, R. et al. (2016). "Carbon monoxide total column retrievals from TROPOMI shortwave infrared measurements". Atmospheric Measurement Techniques, 9, pp. 4955–4975.
Borsdorff, T., Hasber, J., Schneider, A. et al. (2018). "Mapping carbon monoxide pollution from space down to city scales with daily global coverage". Atmos. Meas. Tech., 11, pp. 5507–5518.

Data Sources & References

Sources

WRD_S5COX_992d

Methodology

Il monossido di carbonio (CO) viene mappato utilizzando i dati Sentinel-5P TROPOMI, prodotto OFFL L3_CO disponibile su Google Earth Engine, con risoluzione nativa di circa 1113 metri (~7 km x 7 km al suolo). Il CO è un gas traccia atmosferico importante per la chimica troposferica, prodotto da: combustione incompleta di combustibili fossili, incendi boschivi (biomass burning), e ossidazione atmosferica di metano e altri composti organici volatili. Con un tempo di vita di circa 2 mesi, può essere trasportato a lunga distanza, rendendolo un indicatore di inquinamento atmosferico su scala regionale e di eventi di combustione. La banda utilizzata è 'CO_column_number_density', che misura la densità colonnare verticalmente integrata di CO in mol/m². L'elaborazione è analoga a quella di NO2: filtraggio qualità, ricampionamento bilineare a 100m, composizione media temporale, e merge per aree estese.