methane

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Responsible:Niccolò Calandri

Methane — Sentinel-5P TROPOMI CH4

Overview

The Methane (CH₄) layer measures the column-averaged dry-air mixing ratio of methane using the TROPOMI instrument aboard Sentinel-5P. Methane is the second most important anthropogenic greenhouse gas after CO₂, with a global warming potential (GWP) of 28–34 over a 100-year horizon.

Major methane sources and their approximate contributions:

Source	Contribution	Examples
Agriculture	~40 %	Enteric fermentation (livestock), rice paddies, manure management
Fossil fuels	~35 %	Natural gas leaks, coal mining, oil extraction
Waste	~15 %	Landfills, wastewater treatment
Biomass burning	~10 %	Wildfires, agricultural burning

Methane has an atmospheric lifetime of approximately 12 years and is responsible for roughly 30 % of the global warming observed since the pre-industrial era. Monitoring CH₄ concentrations is critical for climate policy compliance, fugitive emission detection, and agricultural emission inventories.

Native resolution is approximately 1113 m, with output at 100 m.

Calculation Methodology

Retrieval algorithm:

The CH₄ column-averaged mixing ratio (XCH₄) is retrieved from the shortwave infrared (SWIR) spectral range around 2.3 µm:

Full-physics retrieval — Simultaneous fitting of CH₄ and H₂O absorption features, atmospheric scattering, and surface reflectivity
Proxy method — CH₄/CO ratio method to reduce sensitivity to systematic errors
Quality filtering — Strict criteria on cloud fraction (< 0.03), surface albedo, and aerosol loading
Bias correction — Empirical corrections based on validation against TCCON ground stations

Typical atmospheric concentrations:

Environment	XCH₄ (ppb)
Global background	~1900
Northern Hemisphere average	~1920
Agricultural regions	1920–1960
Fossil fuel extraction areas	1950–2050
Major point sources (plumes)	> 2100

Data Sources

Code	Name	Provider	Type	Coverage	Resolution	Availability
`COPERNICUS/S5P/OFFL/L3_CH4`	Sentinel-5P TROPOMI CH4 L3	ESA/Copernicus	Atmospheric column	Global (land only)	~1113 m	2018-06 — present

Documentation: GEE S5P CH4

Technical Notes

CH₄ retrievals are available only over land surfaces (no ocean retrievals) due to the SWIR approach
Very strict cloud filtering means data coverage is sparse in persistently cloudy regions
The column-averaged mixing ratio represents the entire atmospheric column, not surface-level concentrations
Point source detection requires high-resolution plume modeling beyond the current product capabilities
Seasonal variations are driven by wetland emissions (summer peaks in boreal regions) and biomass burning

References

Veefkind, J.P. et al. (2012). "TROPOMI on the ESA Sentinel-5 Precursor". Remote Sensing of Environment, 120, pp. 70–83.
Hasekamp, O., Lorber, A., Hu, H. et al. (2021). "Analysis of polarimetric satellite measurements suggests stronger cooling due to aerosol-cloud interactions". Nature Communications, 12, 6095.
Saunois, M. et al. (2020). "The Global Methane Budget 2000–2017". Earth Syst. Sci. Data, 12, pp. 1561–1623.

Data Sources & References

Sources

WRD_S5CH4_992d

Methodology

Il metano (CH4) viene mappato utilizzando i dati Sentinel-5P TROPOMI, prodotto OFFL L3_CH4 disponibile su Google Earth Engine, con risoluzione nativa di circa 1113 metri (~7 km x 7 km per pixel). Il metano è il secondo gas serra più importante dopo la CO2 per il contributo antropogenico all'effetto serra, con un potenziale di riscaldamento globale (GWP) di 28-34 su 100 anni. Circa il 60% delle emissioni sono di origine antropica: agricoltura (40% - risaie, fermentazione enterica del bestiame), combustibili fossili (35% - estrazione e distribuzione di gas naturale, petrolio, carbone), discariche (15% - decomposizione anaerobica dei rifiuti), incendi (10%). La banda utilizzata è 'CH4_column_volume_mixing_ratio_dry_air', che misura il rapporto di mescolanza medio in colonna in ppb (parti per miliardo). L'elaborazione è analoga agli altri prodotti S5P: ricampionamento bilineare a 100m e composizione media.

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