Delhi woke up to the cleanest air it has breathed in 51 days on Wednesday after light rain as well as hail in some parts of the national capital region (NCR), helped disperse pollutants. The air quality is expected to improve further to ‘satisfactory’ on Thursday, said government agencies.
The overall average air quality index (AQI), as calculated by the Central Pollution Control Board’s (CPCB) 4 pm bulletin, was 134, as against 270 on Tuesday. The last time Delhi witnessed AQI in the moderate category was on October 8, when the air quality was recorded at 112.
On October 9, city’s air quality was 173. Between August 1 and October 9 this year, Delhi’s air quality fluctuated between ‘moderate’ and ‘satisfactory’ levels. On October 10, the air quality plunged to ‘poor’ with an AQI reading of 211.
After this, there was only one ‘moderate’ day on October 19, when the AQI was 161. In November itself, Delhi has witnessed two peak pollution episodes. On November 3, the city saw its worst air day since 2016. Then, another spell of ‘severe’ air was seen between November 12 and 15.
“It was the light rainfall and constant winds that helped improve air quality significantly. Air quality may improve further on Thursday for the impact of rain in the whole of NCR. On November 28-29, it may plunge slightly but will remain in poor zone,” said a senior CPCB official.
Pollution levels started improving from Tuesday around 8pm onwards, when there was a dip seen in the levels of particulate matter (PM), said CPCB officials.
On Wednesday, the average PM 2.5 (fine particulate matter with diameter less than 2.5 micrometres) levels at 8 pm was 59 ug/m3, well within the prescribed safe limit of 60ug/m3. The levels had come down from 118ug/m3 at 8pm on Tuesday to 75ug/m3 at 8am on Wednesday.
The levels of PM 10 (coarse particles) too came down to 122ug/m3 at 8pm on Wednesday from 230ug/m3 at the same time, the previous day. The safe limit of PM 10 is 100ug/m3.
According to the weatherman, while Safdarjung Observatory, representative of Delhi’s weather received only ‘traces’ of rain, other weather stations — such as Jafarpur — received 7mm rainfall and Delhi Ridge got 0.8mm rain.
Scientists at the India Meteorological Department (IMD) said the air quality may improve further, as many neighbouring regions, including Haryana, were still getting rainfall, which in turn is helping clean the air of accumulated pollutants.
“It might drizzle in parts of NCR on Thursday as well, which will continue to have its impact on Delhi-NCR. However, there may be a slight dip in air quality on November 29-30 with an expected drop in temperature and occurrence of fog,” said Kuldeep Srivastava, head, IMD’s regional weather forecasting centre.
The minimum temperature is expected to fall to 12 degrees Celsius on November 30 and further to 10 degrees Celsius on December 1. On Wednesday, the minimum temperature was 14.5 degrees Celsius, five notches above normal while maximum settled at 27.4 degrees Celsius, two notches above normal.
The System of Air Quality and Weather Forecasting and Research (SAFAR), ministry of earth science’s weather and air quality monitoring wing, too has forecast that air quality will further improve to ‘satisfactory’ from Wednesday evening itself.
“Rain has helped remove particles suspended in the air. The air quality may deteriorate marginally on November 29,” said a senior SAFAR scientist.
On Wednesday, the share of crop stubble burning in the neighbouring states of Punjab and Haryana contributed to 2% to overall pollution in Delhi, the SAFAR forecast said.
