Air improves, Grap 4 ends

Stage 4 of the Graded Response Action Plan (Grap) was revoked on Thursday as a spell of light rainfall from late Wednesday to Thursday morning—caused due to a western disturbance—and strong surface winds dramatically improved the air quality in Delhi and NCR cities.

- Jasjeev Gandhiok

NEW DELHI: Stage 4 of the Graded Response Action Plan (Grap) was revoked on Thursday as a spell of light rainfall from late Wednesday to Thursday morning—caused due to a western disturbance—and strong surface winds dramatically improved the air quality in Delhi and NCR cities. The move comes a day after the Commission for Air Quality Management (CAQM) in NCR and adjoining areas imposed stages 3 and 4 of Grap due to a sudden decline in air quality due to meteorological factors.

On Thursday, Delhi's air quality index (AQI) improved to 302 ("very poor") at 4 pm from 386 ("very poor") recorded at the same time a day before. The AQI had crossed the 400 ("severe") mark by 8 pm on Wednesday, but rainfall and winds in the intervening night dispersed pollutants. At 8 pm on Thursday, the AQI improved to 288 ("poor").

According to the Central Pollution Control Board (CPCB), an AQI between 0 and 50 is considered "good," 51–100 "satisfactory," 101–200 "moderate," 201–300 "poor," 301–400 "very poor," 401–450 "severe," and above 450 "severe plus."

The Safdarjung weather station—considered representative of Delhi weather—recorded 3.9 mm of rainfall in the 24 hours preceding 8:30 am on Thursday. The highest rainfall, 10.1 mm, was recorded at the Palam station, followed by 9.7 mm at the north Ridge station.

In Gurugram, the average air quality index improved on Thursday after light to moderate rain in the city and neighboring areas in the morning.