Updated: August 26, 2021 9:19:37 pm
Rising air pollution will lead to a drop in monsoon rainfall across the country, researchers have said.
“Air Pollution is likely to decrease the Southwest Monsoon rainfall by 10 per cent to 15 per cent for the entire country. Some places might even see amount of rain reduced by as much as 50 per cent. It will also impact the dynamics of monsoon, for instance delay in onset,” said Dr Dilip Ganguly, associate professor, Centre for Atmospheric Sciences, IIT-Delhi in a statement.
“Air pollution does not allow the landmass to warm up to the required levels. Due to the presence of pollutants, heating of land takes place at a slower rate. For instance, the required surface temperature is 40 degress Celsius while the presence of air pollution will result in restricting temperature up to 38 or 39 degress Celsius,” he added.
Professor S N Tripathi, head of department, civil engineering, IIT Kanpur, and steering committee member, National Clean Air Programme, MoEFCC, said, “The number might be true because there is a strong latitudinal and vertical gradient in aerosols present in the atmosphere. This will lead to suppression in convection and gradually result in reduction in Southwest Monsoon mean rainfall. The most affected places will be areas with more pollution levels. It is very non-linear as it is the result of an interplay between meteorology and aerosols. The Southwest Monsoon is driven by the difference between land temperature and ocean temperature. Large scale presence of aerosols over the Indian landmass will lead to dimming of the land surface. The entire process will weaken the dynamics of the monsoon, which might even include delay in onset of monsoon.”
According to data released by The State of Global Air 2020, India saw 980,000 deaths attributable to PM 2.5 in 2019. Pollution during summer also remained above Central Pollution Control Board’s safety limits of 40 ug/m3 for PM 2.5. Delhi’s average PM 2.5 concentration for March to May dropped from 95.6 ug/m3 in 2019 to 69 ug/m3 in 2020 when lockdown was imposed, but quickly rose to 95 ug/m3 in 2021 afterwards.
While Lucknow saw its PM 2.5 concentration in the three months decrease consistently from 2019, it still remained above permissible limits. Its average PM 2.5 concentration in 2019 for March, April and May was 103 ug/m3, which dropped to 92 ug/m3 in 2020 during lockdown and further to 79.6 ug/m3 in 2021. Similar trends can be seen for many other cities across the Indo-Gangetic plain, experts have said.