Early air quality warning system deployed for Mumbai

Residents of the Mumbai Metropolitan Region (MMR) can now access real-time and forecasted data on air pollution levels through the Air Quality Early Warning System (AQEWS). Developed by the Indian Institute of Tropical Meteorology (IITM), the system provides hourly data on PM2.5 and PM10 pollutant levels across the city. The AQEWS relies on weather forecasts, satellite data, and on-ground data from 24 air quality monitoring stations. The tool can provide actionable forecasts for the near future, allowing citizens to minimise their exposure to unhealthy levels of pollution.

Mumbai: After concerns around air pollution in the city reached a fever pitch during the previous winter season, residents of the Mumbai Metropolitan Region (MMR) will now be able to minimise their exposure to unhealthy levels of ambient pollution using the Air Quality Early Warning System (AQEWS).

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This has been developed by the Indian Institute of Tropical Meteorology (IITM), Pune, to capture, monitor, and disseminate real-time and forecasted data on both PM2.5 and PM10 pollutant levels across the city at hourly scales.

At present, citizens have three official channels to gauge the city’s air quality index. These are the Central Pollution Control Board’s daily AQI bulletin issued at 4pm every day, which uses data from around 22 stations to provide an average of pollution levels over the past 24-hrs. Moreover, the live air quality index of the CPCB shows hourly data on a variety of pollutants from each of these monitors but does not provide any actionable forecasts for the near future.

The IITM’s System of Air Quality Forecasting and Research (SAFAR), the third available tool, provides a similar 24-hr assessment of the city’s AQI, but relies only on nine monitoring stations, resulting in a less comprehensive picture. As with the CPCB’s tools, SAFAR does not provide hourly data or forecasts.

The EWS tool on the other hand relies on weather forecasts, satellite data, as well as on-ground data from 24 air quality monitoring stations in Mumbai, Mahape, Vasai, Nerul and Kalyan. The tool can provide AQI forecasts similar to weather warnings, which Mumbaikars have not previously been able to access.

Mumbai’s AQEWS tool is available at the following URL: ews.tropmet.res.in/mumbai/index.php.

As of Saturday, August 26, Mumbai reflected favourable pollution levels, with a ‘good’ air quality index (AQI) of 34 at 5pm. The AQI forecast for Sunday is given every hour, and ranges between 23 to 29, also indicating ‘good’ air.

The forecasts are also expressed in anticipated hourly levels of PM2.5 and PM10, up to August 30. An accompanying map provides users with a spatial and temporal distribution of air pollution across the larger MMR area over the next few days, showing how wind speed and direction play a crucial role in the quantity and spread of airborne pollutants.

The AQEWS for Mumbai was rolled out during the ongoing India Clean Air Summit (ICAS), 2023, organised by the Centre for Air Pollution Studies (CAPS) at the Center for Study of Science, Technology and Policy (CSTEP), Bangalore. This comes with successful deployments in Delhi and Pune, with Bengaluru, Kolkata and Mumbai now following suit.

Sachin Ghude, Scientist, at IITM said, “Capturing PM2.5 levels of such magnitude is a global rarity, and we faced considerable challenges in collecting such exceptional data from the city. Our AQEWS relies on pinpoint accuracy, starting with precise weather forecasts as a foundation.”

IITM has integrated satellite data on Aerosol Optical Depth (AOD) -- which is a measure of the hazy effect that aerosols create in polluted air -- along with historical data from a network of 420 air quality monitoring stations across India for such early warning systems, which are likely to be rolled out in other non-attainment cities, where ambient air pollution levels surpass hazardous thresholds prescribed in the National Ambient Air Quality Standards.

“This innovative system holds immense potential as a decision support tool for effective air quality management, for citizens and for administrations,” added Ghude, while clarifying that the performance of these AQEWS can be enhanced with Low-Cost Sensor (LCS) devices, which are often used domestically by citizens. This can provide an even more granular picture of air pollution and support hyperlocal mitigation measures within short time frames.

Pratima Singh, a senior research scientist at CSTEP, said, “More such sensors are required to monitor every neighbourhood. Citizen science can play a crucial role here. Housing societies can take the initiative to install such devices which can be integrated into the AQEWS later.”

Within the Greater Mumbai area, the EWS tool uses 20 air quality monitoring stations, including ones at Navy Nagar, Malad West, Borivali East, Deonar, Powai, Mulund West, Bandra Kurla Complex and Chakala.