The India Meteorological Department (IMD) has forecast a fairly clear sky, with moderate to dense fog, in Delhi on Wednesday, with the minimum and maximum temperatures expected to be at 8 and 17 degrees Celsius, respectively.
Delhi witnessed this season’s densest fog between Monday night and Tuesday morning, as parts of the haze spread from Punjab to all the way across the Indo-Gangetic plain. Visibility dropped to 50 metres at Delhi’s Indira Gandhi International Airport from 10 pm on Monday till 4 am on Tuesday, delaying around 100 flights. Five other flights were diverted to Jaipur.
IMD’s seven-day forecast states that the city is likely to witness moderate-to-dense fog on Thursday, followed by a resurgent cold wave at isolated places on Friday and Saturday. The city is likely to get clear skies with shallow-moderate fog in the morning by Sunday next week. IMD classifies a fog as ‘shallow’ when visibility dips below 1,000 metres, ‘moderate’ when visibility is between 200 and 500 metres, ‘dense’ when it is below 200 metres, and ‘very dense’ when it’s below 50 metres.
Meanwhile, Delhi’s air quality was in the ‘very poor’ category on Wednesday morning. Data from the Central Pollution Control Board showed that the hourly air quality index (AQI) at 7 am stood at 376. On Tuesday, the average 24-hour AQI was 385, which is at the higher-end of the category. The prominent pollutants in Delhi’s air were PM2.5 particles.
An AQI between zero and 50 is considered ‘good’, 51 and 100 ‘satisfactory’, 101 and 200 ‘moderate’, 201 and 300 ‘poor’, 301 and 400 ‘very poor’, and 401 and 500 ‘severe’.
On Tuesday, the Union ministry of earth science’s air quality monitoring centre – System of Air Quality and Weather Forecasting and Research (Safar) – said, “Overall AQI indicates ‘very poor’ air quality. Fine particles (size less than 2.5 micrometer) contribute 63% to PM10. For the next three days, surface wind speed (10 to 12 km/hr) and temperature (maximum 17-19 degree Celsius to minimum 7-4 degree Celsius) are likely to worsen air quality. Mixing layer height is likely to be 1.0 km that will help in dilution of pollutants.”
“Air quality is likely to deteriorate but within ‘very poor’ for the next three days due to low temperature which helps accumulation of pollutants and moderate surface winds which enhances dispersion of pollutants. Morning fog will continue to persist due to cold wind coming from northwest region experiencing cold wave,” the Safar forecast added.
