Most cities and towns in northwest India recorded “very poor” to “severe” air quality on Wednesday due to a drop in wind speed which has slowed the dispersion of pollutants.
The air quality index (AQI) of Baghpat, Bulandshahr, Delhi, Faridabad, Ghaziabad, Greater Noida, Meerut, Noida is in “severe” category with a reading of above 400.
According to the Air Quality Early Warning System for Delhi under ministry of earth sciences (MoES), “Surface winds are likely to remain light and ventilation will be poor resulting in deterioration in air quality.” The ventilation index on Wednesday is likely to be only 2,500 m2/s on Wednesday and 3,000 m2/s on Thursday. The ventilation index is a function of the mixing height and the wind speed and defines the ability of the atmosphere to disperse contaminants. A ventilation index below 2,350 sq metres/second is considered poor. Mixing height is the height at which pollutants mix in the air.
There was respite from the biting cold for a couple of days but minimum temperatures are again likely to fall by 1 to 3 degrees Celsius over northwest India and central India during the next three days.
India Meteorological Department (IMD) in its bulletin said “cold wave” conditions are likely to set in over Punjab, Haryana, Chandigarh, Delhi, West Uttar Pradesh on December 22 with “cold wave to severe cold wave” conditions predicted over the same region on December 23 and 24.
“Cold wave to severe cold wave” conditions are also likely over some pockets of Odisha, east Uttar Pradesh, Gangetic West Bengal, Chhattisgarh and Telangana on December 22 and 23; over Himachal Pradesh, Uttarakhand and Bihar on December 22.
“Cold day” conditions are likely over some pockets of Bihar during the next three days and over east Uttar Pradesh during the next two days. Moderate to dense fog is likely in the morning hours at isolated pockets over Punjab and Haryana, Chandigarh and Delhi on December 23, and dense to very dense fog in the morning hours at isolated pockets over the same region during December 24 to 26.
Dense fog is also likely over northern parts of Uttar Pradesh, Bihar and Assam and Meghalaya during the next three days and over Sub-Himalayan West Bengal and Sikkim during the next two days. Ground frost conditions are very likely over some pockets of Jammu, Kashmir, Ladakh, Gilgit-Baltistan and Muzaffarabad, Himachal Pradesh, Uttarakhand and Punjab during the next three days and over Haryana, Chandigarh, Delhi, East Uttar Pradesh and Rajasthan during the next two days.
“The cloud cover has moved away and the western disturbance has also passed. There are clear skies now so there will be radiational cooling. The minimum temperature is likely to be around 4 degrees Celsius in Delhi for the next two days. A mild western disturbance will affect the western Himalayas around December 24 but will have no impact in the plains. Another WD around December 26 is likely to bring light rain to Delhi on December 27. We are also expecting moderate to dense fog in Delhi and other parts of N-W India for next two days,” said Kuldeep Shrivastava, head, regional weather forecasting centre. The minimum temperature in Delhi on Tuesday was 5.3 degrees Celsius, three degree below normal.