NEW DELHI: The season’s first fog and change in wind direction majorly contributed to the already high pollution levels post-Diwali. The fog cover allowing pollutants to remain trapped in the air enveloped the city in a thick layer of haze on Friday morning. Shallow to moderate fog is likely to occur on Saturday as well, but strong surface winds are likely to help improve air quality marginally, said officials in the India Meteorological Department (IMD).
Delhi on Friday saw the worst air pollution spike since 2016 with an AQI reading of 462. However, IMD scientists said that wind speed picked up during the day, which may allow dispersion of pollutants. Also, the absence of sunlight contributed to the settling of pollutants in the atmosphere, close to the earth’s surface.
According to IMD officials, the season’s first fog on November 4 reduced the visibility to 500 metres in the early hours. “Fog conditions intensified on November 5, with moderate fog reducing visibility to 200-500 metres from 5.30 am to 8 am. Foggy conditions make the air heavier, which allows higher concentration of pollutants. While fog cover is expected on Saturday as well, strong wind of 20-25kmph and sunlight can improve air quality and take it back to ‘very poor’ zone,” said RK Jenamani, Head of Indira Gandhi International (IGI) airport’s MeT dept.
Delhi had reported calm or light winds from westerly to northwesterly direction on November 4, after the season’s first fog. “So far southeasterly winds were blowing over Delhi. The wind direction changed from the night of November 4 to northwesterly, where stubble burning activity is at its peak. Whenever there is a transition in wind direction, it results in calm wind conditions, which means atmosphere is still. This does not allow pollutants hanging in the air to disperse and hence result in a spike in pollution levels. Just like one would feel suffocated in a room with a low roof and no ventilation,” said a senior IMD official, who did not wish to be named.