Delhi’s air quality in March was the cleanest on record in the last five years. Experts said this was achieved through favourable meteorological conditions, including an all-time record high rainfall, unseen since the count began in 1901, along with the absence of major emission sources as a result of the coronavirus lockdown.
“What we are seeing is extraordinary. This is the baseline of what Delhi’s air quality should be after factoring in only
limited emissions from very few sources,” said an official from the Delhi environment department.
Emissions over the past 10 days have reduced, the official said, due to restrictions imposed on movement of private vehicles, public transport, commercial flights and trains, and closure of all non-essential services.
Data from the Central Pollution Control Board (CPCB), analysed by The Indian Express, shows the average monthly air quality index (AQI) this March was 128, significantly lower than average AQIs of the same month since 2016 when records began.
There were 10 ‘satisfactory’ air quality days this March, where the AQI is between 51 and 100, and one ‘good’ air quality day, where the index ranges from 0 to 50 — an AQI of this measure was not achieved in this period since 2016, as per the CPCB data.
In the previous four years in March, only ‘moderate’, ‘poor’ and ‘very poor’ air quality was seen in the capital. This year, the number of ‘poor’ air days, where the AQI is between 201 and 300, was only two, while the remaining days saw ‘good’, ‘satisfactory’ and ‘moderate’ air quality.
Kuldeep Srivastava, head of IMD’s regional forecasting centre in Delhi, said the total rainfall recorded in the city in March was 109.6mm — an all-time high for the month since counting began in 1901. The record for the second highest rainfall in March is 97.4 mm in 2015.
Six Western Disturbances that affected the city in March and brought on strong winds and rainfall. The average wind speed recorded was 15-20 kmph, said Srivastava, adding, “Due to rainfall, suspension of dust remained low and pollutants in the air kept being pushed out by the winds.”
Air quality kept improving after the ‘Janata Curfew’ on March 22. In the last week since March 25, it largely remained in the ‘satisfactory’ range and further improved to ‘good’ on Saturday.
An assessment done by the Centre’s System of Air Quality and Weather Forecasting and Research (SAFAR), of the lockdown period between March 24 and 31, showed 63% reduction in nitrogen oxide (NOx) and 49% reduction in PM2.5 presence in Delhi’s air — as compared to the same period in 2019 and 2018.
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