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Why do we have Fog during winters?

At the onset of winter season , we are almost guaranteed of experiencing the dense fog. Winters bring along with them foggy days and even foggier , chilling nights. Lets find out what exactly fog is and how it is formed.

Fog is a cloud that remains on ground. Its a thick cloud of tiny water droplets that remains suspended in the atmosphere which restricts the visibility and sometimes brings it down to less than 1 kms.

How it is formed?

Before we get into the formation of fog , first lets understand the concept of Dew Point which plays a vital role in the formation of fog. Dew Point is the temperature at which air can no longer hold its water vapors and some water vapors condenses into liquid water. Usually dew point is always lower than or equal to air temperature.

The process of fog formation initiates when the atmospheric air cools down and looses its capability to hold the water vapors. As the air temperature cools to the dew point , it becomes fully saturated with water vapors and this vapor condenses around tiny microscopic particles like dust which finally forms water droplets.

Types of Fog During Winters

Fog types

Depending upon how the air cools down there are a variety of fog.

  • Radiation Fog -> One of the most common type of fog is the radiation fog which is usually formed due to the difference in temperature during the day time and night hours. During day time, the ground absorbs solar radiations which makes the air warm and moist. During night, when temperature drops this warm air collides with the cooler air which causes the water vapors in the air to condense and hence the fog is formed.
  • Advection Fog -> Another kind of fog is the Advection Fog which is formed due to wind. When the warm air moves across the cooler surface it gets condensed and results into formation of fog. It needs to surface that is already cool. Unlike Radiation fog which forms only on the land , advection fog can also form over the sea too. This form of form usually affects the flights as they cross the oceans.
  • Freezing Fog -> In this type of fog the water droplets in air are cooled to freezing point. Super cooled water droplets remain in the liquid state until they come into contact with a surface upon which they can freeze.
  • Sea Fog or Steam Fog -> These are very similar as they are formed when very cool air moves over warmer water.

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