Satellite data provides near real-time, air quality monitoring
On the evening of March 7, 2026, a series of explosions and fires occurred at multiple oil storage and refining facilities in Tehran, Iran. A research team has utilized a constellation of satellites to investigate and quantify this sulfur dioxide (SO₂) pollution event.
The results of their study are published in the journal Advances in Atmospheric Sciences on May 26.
There is a lack of high quality, real-time ground-based atmospheric monitoring in the Middle East. This leaves a “data vacuum” when industrial disasters occur. “We aimed to demonstrate that satellite remote sensing can fill this gap by providing wide spatial coverage and frequent observations to monitor atmospheric pollutants over large areas,” said Professor Peng Zhang, Meteorological Observation Centre, China Meteorological Administration.
When the March 7 explosions and fires occurred, the Fardis, Shahran, and Aghdasieh depots, as well as the Tehran Oil Refinery were devastated. The Shahran Oil Depot was particularly hard-hit, with burning oil entering the city’s sewer system and igniting urban green belts, creating a major source of toxic smoke. Local residents reported immediate health impacts, such as respiratory distress, skin irritation, and a “bitter taste” in the mouth. Scientists are particularly concerned with SO₂ pollution because of its strong irritant and corrosive properties. The combustion of petroleum products mixed with local rainfall also produced “black rain,” a corrosive mixture of oil droplets and soot. As a major precursor of acid rain, it poses a substantial threat to the regional atmospheric environment and public health.
To assess the environmental damage, the researchers used satellites, including the Chinese Fengyun-3 (FY-3F and FY-3E) and the European Sentinel-5P. These tools allowed them to rapidly quantify SO2, a primary pollutant from refinery fires. Their study confirmed that SO2 concentrations rose from a regional mean of 0.8 DU to 2.0 DU during the event, with total emissions estimated at 2.98×104 tons. The Dobson unit (DU) is the basic measure of the amount of a trace gas in a vertical column of air from Earth’s surface to space.
The team was able to quantify emissions, determining the total mass of SO2 released and its peak concentrations. They also mapped the plume dynamics to better understand how the SO2 moved. Their observations showed the plume was transported northeastward and reaching East Asian after two-day transport, which is consistent with forward trajectories by model. A significant part of the study involved comparing the Ozone Monitoring Suite-Nadir on FY=3F with the TROMPOMI instrument on the Sentinel-5P. They established that these different sensors show consistent spatial patterns, which is crucial for global environmental monitoring.
Even a short-lived fire of one to two days can release a massive volume of pollutants that affects an area of approximately 3.0×105 km². This highlights the necessity of satellite-based tracking to inform public health warnings and environmental mitigation strategies in real-time.
The FY-3 satellite series proved their operational readiness for rapid environmental emergency assessment. While individual satellites have limitations, their combined use provides researchers with a comprehensive “time-lapse” of a disaster.
“The immediate next step is the operationalization of the Hyperspectral Infrared Atmospheric Sounder (HIRAS-II) SO2 index,” said Zhang. Currently, HIRAS-II provides a qualitative Hyperspectral Range Index, but it is not yet an official operational product. “We aim to refine these algorithms to provide precise, quantitative mass concentrations of various trace gases under diverse atmospheric conditions,” said Zhang.
“Our ultimate goal is to build a fully integrated global monitoring system using dawn-dusk, mid-morning, and afternoon sun-synchronous orbits,” said Zhang. This would ensure that no matter when a “sudden pollution event” occurs, a satellite is overhead to record the data, allowing for a seamless transition from disaster detection to environmental impact recovery.
