NEW DELHI: A dense blanket of fog enveloped Delhi-NCR on Monday morning, severely reducing visibility across roads and disrupting normal movement, while the region continued to grapple with toxic air quality in the ‘severe-plus’ category. The deteriorating weather and pollution conditions also impacted air travel, prompting IndiGo Airlines to issue a travel advisory warning passengers of possible delays and urging them to plan their journeys with extra caution.
Amid changing weather conditions, IndiGo Airlines on Monday issued a travel advisory for passengers as Delhi witnessed the first signs of winter fog this season, impacting visibility at the airport.
In its advisory, the airline said visibility levels around the airport were currently reduced, and as a result, flight operations were being adjusted, with some departures likely to take longer than usual. IndiGo assured passengers that its teams remain available to provide support, acknowledging that travel plans, schedules, and connections are important.
The airline also cautioned that road traffic could be slower due to foggy conditions and advised passengers to plan their journeys accordingly and allow additional time to reach the airport. IndiGo said it is closely monitoring the situation and will keep passengers informed, adding that departures will continue as conditions improve, with safety remaining the top priority.
Similarly Air India issued a travel advisory for passengers; it said, "Poor visibility due to dense fog is impacting flight operations in Delhi and parts of Northern India. Please check your flight status at: http://airindia.com/in/en/manage/flight-status.html before heading to the airport."
Earlier on Sunday, Delhiites could literally see poison in the air. A thick layer of toxic smog enveloped the capital, turning the city into a gas chamber with air quality plunging to 'severe-plus' category for the first time this year.
AQI Severe-Plus, Delhi’s Worst In More Than 1 Yr
The city's 24-hour average air quality index stood at 461, the second-worst recorded in Dec and the worst in nearly 13 months. Since the scale began in April 2015, only once has a higher AQI been recorded in Dec - 469 on Dec 21, 2017. For any month, the last time Delhiites a suffered worst AQI was on Nov 18 last year (494).
High moisture, low temperatures and calm winds effectively trapped pollution close to the surface even as a grey smog screened out the sun for most of the day. Winds are predicted to pick up slightly post-noon on Monday, which could disperse some pollutants.
On Sunday, atmospheric ‘inversion’ made the situation worse. This occurs when cooler air near the ground gets trapped under warmer air above, stopping pollutants from dispersing. Though meteorological conditions remained unfavourable for the dispersion of pollutants, local emissions continued to remain high.
“This is a true depiction of Delhi’s local emissions because wind speeds are almost zero, meaning there is hardly any inflow or outflow of air. Vertical ventilation is confined to a column of just 600 metres, which means whatever remains in the box — Delhi — is largely its own emissions. Under these conditions, the contribution of dust is negligible. When dust is released from construction activity, it usually spreads to other areas due to wind, but with winds nearly calm, it cannot pollute places beyond the immediate site of release,” said Gufran Beig, founder of the System of Air Quality and Weather Forecasting and Research (SAFAR) and Chair Professor at the National Institute of Advanced Studies (NIAS).
Of the total 39 active air quality monitoring stations, 38 saw ‘severe’ AQI while only Shadipur was placed in the ‘very poor’ category at 375. Of these, three stations — Wazirpur, Rohini and Ashok Vihar — maxed out at 500, while several others reported AQI above 490.
This is the second spell of severe air days in Delhi this season. The city had recorded three consecutive severe days from Nov 11 to 13. In this winter season, the city has recorded five such days, when AQI surpassed 400.
After air quality started rapidly deteriorating on Saturday, the Graded Response Action Plan’s stage III was imposed in the morning. Stage IV was invoked on Saturday evening as AQI showed no sign of improvement. Currently, all stages of GRAP are in force.
Delhi’s highest-ever AQI of 497 was recorded on Nov 6, 2016. The second-worst air quality day followed on Nov 18 last year with AQI reaching 494.
Experts said since winds are likely to rise only marginally post-noon, no significant respite from toxic air quality is expected on Monday. However, the Centre’s Air Quality Early Warning System (EWS) stated that the AQI may dip to ‘very poor’ on Monday. “Delhi’s air quality is likely to be in the ‘very poor’ category from Dec 15 till 17. The outlook for the subsequent six days from Dec 18 is that AQI is likely to be in the ‘very poor’ category,” said the EWS.
The CPCB classifies AQI 050 as 'good', 51-100 as 'satisfactory', 101-200 as 'moderate', 201300 as 'poor', 301-400 as 'very poor', 401-450 as 'severe', and 451 and above as ‘severe plus.’ Meanwhile, the lowest visibility on Sunday morning was recorded at 200 metres at Safdarjung. It was 350 metres at Palam. “Safdarjung reported 300 metres at 5.30am but calm winds further reduced the visibility to 200 metres at 8am,” said a Met official.
India Meteorological Department measures fog in terms of visibility. Visibility between 500-1,000 metres is considered ‘shallow’ fog. Fog is 'moderate' when visibility is between 200-500 metres, and ‘dense’ below 200 metres.
The maximum temperature was recorded at 24 degrees Celsius, one degree above normal. The minimum stood at 8.2 degrees C. IMD has predicted shallow to moderate fog in the early hours of Monday.