This typically occurs with a warm front passing through in the winter. This happens as the air is cooled to saturation by cold from the ground cooling the air above. At this point you start to see fog developing. Then you need warm, moist air moving over the cold ground.
First thing you need for this type of fog is cold ground. Clouds deflect the blowing wind to ground level.FARMERSBURG, Ind.The Earth’s surface would have a low temperature on cloudy nights.Clouds reflect back the Earth’s radiation.Clouds absorb the radiation released from the Earth’s surface.Q.2) Why are dewdrops not formed on a cloudy night? (2019) Which of the statements given above is/are correct? (2022) Low clouds have a high absorption of infrared radiation emanating from the Earth’s surface and thus cause warming effect.High clouds primarily reflect solar radiation and cool the surface of the Earth.Advection fog episodes last longer and secondary particulate formation then begins leading to rapid build-up of pollutants.Recently, Delhi recorded a spike in pollution levels with AQI in the ‘severe’ category.This results in fog formation and particulate matter hangs on the boundary layer, increasing pollution levels.The inversion layer comes down and vertical mixing reduces. As temperature declines, local wind speed also falls.According to the India Meteorological Department (IMD), Delhi being more polluted, records more fog days compared to others.In the absence of western disturbances, local moisture sources like water vapor from rivers and soil moisture can also cause fog.This can result in increased moisture levels over the region.Western disturbances, which are storms that originate in the Mediterranean Sea, bring moisture-bearing winds to northwest India.The fall in temperature along with moisture and light winds over the Indo Gangetic Plain has resulted in dense fog over the region.Cold wave conditions, in which the minimum temperature is significantly lower than normal, have been recorded recently over Punjab, Haryana, and parts of Rajasthan.Recently, Delhi recorded the lowest minimum temperature of the season so far - 6 degrees Celsius.Temperatures have begun to dip over north-western India.They are not found in Indo Gangetic Plain.Ĭonditions Favouring Fog over North-western India.It occurs at Cloud-covered mountaintops.Freezing fog is result of liquid droplets freezing on solid surfaces.Fog gets trapped at bottom of valley which lasts for several days.Valley fog is formed due to mountains preventing dense air from escaping.If wind blows in right direction, sea fog is transported over coastal land areas.It occurs where warm tropical air meets cool ocean water.It forms when warm, moist air passes over a cool surface, causing water vapour to condense.Advection fog is larger in scale for both area covered and duration.The Indo Gangetic Plain is most vulnerable to fog occurrences, with major, weeks-long spells of dense fog in the months of December and January.Areas near water bodies, for instance, may see denser fog because of the higher humidity.Fog can have “high spatial variability”, and its intensity can depend on factors like humidity, wind, and temperature.The presence of moisture and a fall in the temperature are key factors for the formation of fog.Fog begins to form in the early hours of the morning, when the temperature is at its lowest.Since cooler air cannot hold as much moisture as warm air, the water vapour in the air condenses to form fog.With the land surface cooling down at night, the air close to the surface also cools down.Context: Recently, dense fog has enveloped north-western India, including Delhi, Punjab, Haryana, parts of Uttar Pradesh, and parts of Rajasthan.
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