Delhiites woke up to a foggy morning today as dense fog engulfed some areas of Delhi NCR. The international airport Palam recorded season’s first day of dense fog reducing visibility to zero for nearly 4 hours impacting flying operations. Zero horizontal visibility was reported between 0430 and 0830 hours and improved to 200 metres only by 1000 hours. There was a thick blanket of fog over the airport, some green pockets and water bodies.
Dense fog amounts to visibility reducing to 50 metres or less restricting the air operations. Such conditions become frequent in winter season when the winds are light, humidity is high and the temperature is low.
Dispersion of aerosols becomes likely after a few hours of sunrise because of heat and breeze. The most probable period of dense fog remains from late night till early morning.
On average, Palam records 13 days of fog (visibility < 1000 metres) in December. It peaks in January with 19 days and drops again to 10 days in February. The frequency of dense fog hitting rail, road and air operations simultaneously is about 2, 4 and 2 days respectively in these months. Palam and neighbourhood are more prone to dense fog for 4, 8 and 6 days in December, January, and February respectively.
Western disturbance presently marked over Jammu and Kashmir and adjoining parts is likely to cause rain and snow in the hills and influence the wind pattern over the plains including Delhi NCR. Accordingly, poor visibility conditions are likely for the next 48 hours over this area. Light rains are expected in some areas of Delhi NCR between 11th and 13th December. Dense fog may appear in the wake of this spell with large spread over northern plains including the national capital.