What Led to the Dense Fog in Delhi-NCR? Understanding the Key Factors

New Delhi: The whole of Delhi-NCR, including cities like Ghaziabad, Noida, and Gurugram, witnessed unusually dense fog during this time of the year, with conditions peaking on Friday night and continuing into Saturday morning.

The intensity and duration of this particular fog spell in Delhi-NCR was unprecedented for many residents, with some sharing visuals on social media. The ghostly haze made even nearby objects difficult to see, adding to the eerie atmosphere.

According to the India Meteorological Department (IMD), this was the season's longest spell of fog, which caused zero visibility conditions. As a result, dozens of flights and trains were affected.

Key Factors Causing Dense Fog in Delhi-NCR:

• Drop in Temperature: During winter, especially in the early morning, temperatures in the Delhi-NCR region drop significantly. This drop in surface temperature causes the ground air to cool, leading to the condensation of moisture and the formation of fog.
• Low wind speeds: Winds usually help disperse fog, but with calm winds or light breezes, the fog lingers for longer. The lack of wind in Delhi-NCR allowed the dense fog to persist, worsening the Air Quality Index (AQI).
• Increase in Humidity: The moisture content in the air was a key factor in fog formation. After recent rains and the influx of moisture from the Arabian Sea or Bay of Bengal, high humidity levels in the region contributed to the dense fog.
• Western Disturbance: Delhi and its surrounding areas experienced recent rainfall due to the impact of a western disturbance. These disturbances bring moisture to the region, which can lead to fog when combined with cold air. In this case, however, the moisture was added without clearing the fog.
• Rising Pollution: The fog situation worsened as meteorological factors combined with poor air quality in Delhi and NCR. Dropping temperatures, calm winds, high humidity, and pollution from vehicle emissions and construction activities trapped pollutants near the ground, intensifying the conditions.

The Indo-Gangetic plains, including Delhi, are particularly susceptible to dense fog due to the region's flat, low-lying topography. This geography hampers air circulation, allowing fog to remain trapped for extended periods.

The Indo-Gangetic Plains (IGP) span five states: Punjab, Haryana, Uttar Pradesh, Bihar, and West Bengal. The northwestern portion of the IGP, known as the Trans-Gangetic Plains (TGP), encompasses Delhi, Chandigarh, Punjab, and Haryana.

A thick layer of fog covered several areas of Delhi for the third consecutive morning on Sunday, disrupting flight, train, and road traffic. The Met office reported zero visibility at Palam from 4 am to 7:30 am, while on Saturday, Palam had experienced a nine-hour period of zero visibility.

(with agency inputs)