Experts call for more efficient methods of tracking farm fires; say current count may be an underestimation

Experts question satellite-based tracking of farm fires in Punjab, suggesting under-reporting of fires impacting air quality in Delhi.

With air quality in Delhi plummeting to hazardous levels, despite a five-year decline in the instances of stubble burning in Punjab, experts suggest that the current approach to satellite-based tracking of farm fires by government agencies may be leading to under-reporting the number of fires.

Hiren Jethva, a researcher who studies air flow in particulate matter and the role of farm fires at the Morgan State University in the U.S., has been saying in a series of posts on X since mid-October that the drop in instances of fires from Punjab may be an illusion.

The data on fire counts are from a heat-sensing instrument on two American satellites — Suomi-NPP and NOAA-20 polar-orbiting satellites. Instruments on polar-orbiting satellites typically observe a wildfire at a given location a few times a day as they orbit the Earth, pole to pole. They pass over India from 1 p.m. to 2 p.m.

The instrument on them, called the Visible Infrared Imaging Radiometer Suite (VIIRS) can sense aerosols, smoke, heat and is considered the most accurate to track wildfires across the globe. While the satellites map any particular location twice in 24 hours, they can miss fires that are set and extinguished outside of the period of tracking. Data on fire counts reported by the Punjab government and other agencies around the world are reliant on these polar-orbiting satellites.

Mr. Jethva said that data from another satellite, the GEO-KOMSAT 2A, a Korean satellite that, unlike the polar satellites, tracked the same swathe of Earth continuously, seemed to suggest that there was a spike in smoke and fires in the late afternoon in both Punjab province in Pakistan and Punjab in India. However, he hasn’t furnished the actual fire count data from the KOMSAT.

Moreover, the quantity of aerosols, or airborne pollutants, in the atmosphere hadn’t shown any measurable change despite a decline in fire counts, he posted. “(There is a) drastic downward trend in fire detection in north-west India since 2022. However, aerosol loading in atmosphere has increased or is near stable, raises suspicion that farm fires are ignited after satellite overpass time. No blame on farmers but lack of policy implementation,” he posted on October 28.

As of November 17 this year, there have been 42,314 fires reported since September 15. This is the lowest since such data was made publicly available in 2012. In 2016, 1,33,442 fires were reported during a comparable period — an all-time high, according to bulletins by the Indian Agricultural Research Institute.