Assessment of NO2 Satellite data from Sentinel 5P-TROPOMI for period of 11th March – 24th March & 25th March – 7th April for 2019 and 2020
Lauri Myllyvirta and Sunil Dahiya
After a call and test implementation of Janta Curfew (National Lock-down) for a day on 22nd March 2020, India enforced complete national lock-down for three weeks starting from 24th March 2020 to curtail the spread of coronavirus pandemic.
In our initial assessment of the continuous ambient air quality monitoring data by CPCB (Central Pollution Control Board) for operational stations across India between 2017 to present, we tried to understand the impacts of one day lock-down on 22nd March 2020 on air pollution levels and found that the curfew resulted in lowest one-day NO2 levels since 2017.
In our current analysis we tried to look at the key cities and geographical regions in India using an eye from the sky as well as ground monitoring data to find-out decrease in NO2 levels in two weeks under the national lockdown against levels two weeks before the lock-down. Sentinel-5P TROPOMI satellite data along with CAAQMS (Continuous Ambient Air Quality Monitoring System) data was used for this analysis.
The Analysis showed us drastic and clear reductions in pollution levels, which are a resultant of decreasing fossil fuel consumption in transportation, industries and energy sector.
Hot-spots over major cities as well as major industrial/coal combustion dominated areas have reduced significantly as shown in following maps depicting falling pollution levels. The reduction in this harmful pollutant which is responsible for an estimated 350,000 new cases of child asthma and 16,000 premature deaths per year in India. NO2 is also a key contributor to PM2.5 formation as it plays a significant role in secondary particulate formation.
The following maps show the extent of reduction in NO2 pollution before and after the lock-down over major cities in India when two week average NO2 level maps are compared.
Main drivers of reduction in NO2 levels
- Reduction of consumption of diesel/petrol and other petroleum products in the transportation sector within cities. I.e., consumption of HSD (Diesel) decreased by 24% in march 2020 compared to march 2019, with most of the fall seen post the lock-down. Overall consumption of petroleum products in India decreased by 18% during the same period.
- Reduction of consumption of petroleum products and coal by industries in regions within and around cities. All coal based power plants in 300 km radius of Delhi (Haryana, Punjab and Uttar Pradesh) except two units at Dadri Power Plant have been shut down due to low demand.
- Reduction in overall power demand and associated coal consumption by the power generation facilities across the country. I.e., 19 % overall reduction in power generation in India in two week after 24th March compared to power generation during two weeks before that. Coal based power generation reduced by 26% during the same period.
The reduction seen in air pollution levels across the country and globe are only temporary due to lock-down measures of various degrees, such drastic steps of shutting down the economy to be the way to clean the air are not sustainable. To avoid pollution levels bouncing back as the economy turns a corner and the coronavirus crisis passes, There are time tested methods to achieve better air quality without putting people into hardships.
- Shift from the current highly fossil fuel dependent economy to clean energy based systems has to be adopted. More comprehensive solutions such as transitioning to clean transport and energy sources. We need to
- Ensure that we invest heavily in renewable energy and other clean energy solutions.
- Transform our transportation systems towards more intensive public transportation systems along with making our cities conducive to movement of people rather than just vehicles by building better infrastructure for walking and cycling friendly cities.
- Strengthen emission standards for polluting industries and enforce full implementation with time bound targets.
The current crisis has shown us that clear skies and breathable air can be achieved very fast if concrete actions towards reducing burning of fossil fuels are taken and we feel that this could be the turning point for India towards securing the right to breathe and life for citizens of the country.