Amid rising concerns over stubble burning contributing to soaring air pollution levels in North India, a NASA scientist said farmers in Haryana and Punjab are burning crops in the afternoon to avoid getting caught by satellite imaging, said an NDTV report.
While transportation remains the biggest contributor to increasing levels of pollution, farm fires due to stubble burning in Punjab and Haryana after harvesting the paddy crop in October and November have indeed become another major factor to take into account.
Citing the insights and high-definition satellite images shared by Hiren Jethva, an aerosol remote sensing scientist at NASA Goddard Space Flight Center, the NDTV report emphasized how the elevated levels of air pollution across the Indo-Gangetic Plains (IGP) have left the northern Indian states of Punjab, Haryana, Uttar Pradesh, Delhi, parts of north Rajasthan, Himachal Pradesh and Uttarakhand engulfed with thick layers of smog.
Taking it to microblogging site X, Mr. Jethva shared satellite images from October 29 captured by the GEO-KOMSAT A2 satellite including a timelapse of the crop-burning activities in northwest India.
Stubble burning: Are farmers evading NASA satellites?
While the Commission for Air Quality Management (CAQM) appreciated Punjab for making efforts to cut down stubble-burning count by nearly 71 per cent as compared to last year, the NASA satellite images, as per the report, showed increased level smoke after 4 PM when compared to 1:30 PM, suggesting late evening crop burnings by the farmers to avoid NASA satellite surveillance.
NDTV quoted the NASA scientist saying, "It is not true that farm fires in Punjab and Haryana have gone down. We use the afternoon satellite overpass time data from NASA Satellites like Suomi NPP and Aqua. They overpass the region around 1:30-2:00 pm but somehow they (farmers) have learnt that they can bypass the satellite overpass time and can burn the crop residue in the late afternoon. This is confirmed by the South Korean geostationary satellite that the majority of the crop burning happens after 2 pm once the NASA satellites overpass the region when there is no surveillance, but the fires cannot be hidden from geostationary satellites which take a picture of the region every five minutes."
"Yes, farmers can hide the crop burning from the 1:30 pm overpass time but the PM 2.5 data and the pollution load over the Indo-Gangetic plain region, the geostationary satellite data and the burnt...everything is pointing toward fire is still present. Maybe it's still increasing...Smog towers are a small fix. It won't work unless we address the issue of crop burning in the region", Mr Jethva concluded.
Further explaining the concept of 'Thermal Inversion' behind the sudden spike in pollution levels, Mr Jethva said, "The warmer air sits above the cooler air on the ground and that does not allow the vertical mixing of pollutants and whatever we emit at the surface stays for around 200 metres within the boundary layer. The stronger the thermal inversion, the more pollutants will be trapped near the surface because there is no venting place for the pollutants to go up in the vertical direction."
"In the satellite images, we can notice that smoke from crop burning is mixed with clouds or is above them and that kind of situation furthers thermal inversion because of the absorption of light-absorbing aerosols and that it further warms the upper layer and increases thermal inversion," Mr Jethva said.
