Satellite-Based Monitoring of Sulfur Dioxide Emissions

Satellite instruments have transformed our understanding of atmospheric sulfur dioxide (SO₂) emissions by providing global, systematic measurements of SO₂ column densities above the Earth’s surface. Through ultraviolet and visible spectral retrieval techniques, spaceborne sensors such as the Ozone Monitoring Instrument (OMI), Ozone Mapping and Profiler Suite (OMPS) and TROPOMI continuously map SO₂ distributions over industrial regions, volcanic sites and oil and gas operations. These observations underpin global emission inventories, reveal long-term trends and help disentangle anthropogenic and volcanic contributions. Recent advances in spatial resolution, retrieval algorithms and geostationary platforms have improved the detection threshold for weak sources and enabled near-real-time monitoring. Integration of satellite data with ground-based measurements and atmospheric transport models has enhanced the quantification of emission rates, guided regulatory policies and supported hazard mitigation efforts. Ongoing developments aim to refine vertical sensitivity and temporal sampling, laying the groundwork for comprehensive assessments of SO₂ impacts on air quality, ecosystem health and climate forcing.

Research from Nature Portfolio

Global volcanic SO₂ degassing has been characterised with unprecedented detail following the deployment of TROPOMI aboard Sentinel-5 Precursor. The improved spatial resolution and sensitivity of the TROPOMI instrument enable detection of lower-tropospheric plumes and daily monitoring of volcanic emissions worldwide. Analyses demonstrate a four-fold improvement in detection limits compared with earlier sensors, capturing previously unseen weak degassing signals and permitting the retrieval of high-frequency SO₂ fluxes under varying meteorological conditions. These capabilities have opened new avenues for real-time hazard assessment and advance our understanding of volcanic processes and their environmental impacts.

Space-based observations have revealed divergent trajectories of anthropogenic SO₂ emissions in India and China over the past decade. Satellite retrievals indicate a 75 % decline in SO₂ emissions from Chinese power plants and industry since 2007, attributable to stringent desulfurisation controls, while India’s emissions have risen by some 50 % over the same period. This contrast underscores the effectiveness of targeted regulatory measures and highlights the emerging challenge of rapidly growing SO₂ pollution in South Asia, with implications for public health and regional air quality management.

Satellite-Based Monitoring of Sulfur Dioxide Emissions publication trend

The graph below shows the total number of articles in satellite-based monitoring of sulfur dioxide emissions across all publications each year (not limited to Nature Index journals).

Technical terms

Vertical Column Density (VCD): The total amount of a trace gas molecule (such as SO₂) in a column of the atmosphere above a unit area, expressed in molecules per square centimetre.

Air Mass Factor (AMF): A dimensionless coefficient that relates the slant column density measured by a satellite instrument to the vertical column density, accounting for viewing geometry and atmospheric scattering.

Differential Optical Absorption Spectroscopy (DOAS): A retrieval technique that quantifies trace gas concentrations by analysing the wavelength-dependent absorption features in scattered sunlight spectra.

Ozone Monitoring Instrument (OMI): A nadir-viewing ultraviolet–visible spectrometer onboard NASA’s Aura satellite that measures global distributions of atmospheric ozone and pollutant gases, including SO₂.

TROPOspheric Monitoring Instrument (TROPOMI): A high-resolution ultraviolet–visible spectrometer on ESA’s Sentinel-5 Precursor satellite designed to monitor atmospheric composition with enhanced sensitivity to lower-tropospheric pollutants.

References

1. Version 2 of the global catalogue of large anthropogenic and volcanic SO2 sources and emissions derived from satellite measurements. Earth System Science Data (2023).
2. Comprehensive Evaluation of Spatial Distribution and Temporal Trend of NO2, SO2 and AOD Using Satellite Observations over South and East Asia from 2011 to 2021. Remote Sensing (2023).
3. India Is Overtaking China as the World’s Largest Emitter of Anthropogenic Sulfur Dioxide. Scientific Reports (2017).
4. Global monitoring of volcanic SO2 degassing with unprecedented resolution from TROPOMI onboard Sentinel-5 Precursor. Scientific Reports (2019).