Severe to moderate in two days: Winds clean Delhi air
Central Pollution Control Board (CPCB) data shows that Delhi’s overall AQI on Friday was 137, considered to be in the moderate zone.
With strong winds and stubble fires in Punjab and Haryana coming to a close, Delhi’s improved drastically on Friday, falling from the severe zone to the moderate zone in just two days.
In fact, the air quality in at least eight stations improved to satisfactory on Friday, a rarity for the city during this time of year.
Central Pollution Control Board (CPCB) data shows that Delhi’s overall AQI on Friday was 137, considered to be in the moderate zone. From Wednesday, when the AQI was in the severe category, at 413, it improved to 302 (very poor) on Thursday, according to CPCB recording.
An AQI in the range of 0-50 is considered ‘good’, 51-100 ‘satisfactory’, 101-200 ‘moderate’, 201-300 ‘poor’, 301-400 ‘very poor’ and 401-500 ‘severe’.
In Lodhi Road, Aya Nagar, Pusa, Shadipur, Alipur, North Campus (Delhi University) and Indira Gandhi International Airport monitoring stations, the AQI scale turned light green, denoting satisfactory air quality, at different hours of the day.
The level of PM2.5 (ultrafine particulate matter with diameter less than 2.5 micrometres) at 6pm was 62ug/m3, just two notches above the acceptable standard. The levels of PM10 (particulate matter with diameter less than 10 micrometres) also fell to 122.3ug/m3 at 6pm on Friday. In India, the safe standard for PM 10 is 100ug/m3.
IMD scientists said that even though the wind direction continued to be north-westerly, travelling from Punjab and Haryana, the impact of stubble fires were next to negligible on Friday on Delhi’s air, said VK Soni, head of IMD’s environment monitoring research centre. He added that high wind speeds from Thursday night, which continued through Friday, helped improve the city’s air significantly.
Union ministry of earth sciences’ air quality monitoring centre, System of Air Quality and Weather Forecasting and Research (Safar), data shows that on Friday 136 fires were spotted over Punjab and Haryana, and its contribution on the Capital’s PM2.5 levels was around 2%.
“The average wind speed recorded on Thursday night was also around 8kmph, which is rare because winds tend to slow down at night. During the day too, the winds have been favourable for the dispersion of pollutants,” Soni said.
Soni also said the air quality is expected to remain between moderate and poor range till November 30, after which it is forecast to deteriorate.
Kuldeep Srivastava, head of IMD’s regional weather forecasting centre, said the wind speed on Friday had reached 15kmph and wind speeds are expected to be high on Saturday too.
“From November 30, the wind speed is likely to slow down. Now, because a western disturbance is passing the winds have picked up speed, but it will slow down again,” he said.
Srivastava said the temperature in Delhi and NCR is also expected to fall in the coming days because of the continuing snowfall in the regions of Jammu and Kashmir, Himachal Pradesh, Ladakh and parts of Uttarakhand.
On Friday, the minimum temperature recorded at the Safdarjung observatory, which is considered the official recording for the city, was 10.2 degree Celsius. The maximum temperature was 27 degree Celsius.
“From Saturday, the minimum temperature will start reducing by one or two degrees and reach around 7 degree Celsius by November 30,” Srivastava said.
