Difference between Advection Fog & Radiation Fog?

Also called land fog because it forms only over land, not over sea. During the night, land gives off its heat very quickly. On clear nights, the radiation of heat from the land surface into space is quicker as it is unobstructed by clouds. The air in contact with the ground thus gets cooled and if cooled below its dew point, a large quantity of dew is deposited. If, however, a light breeze is blowing, turbulence causes the cold from the land surface to be communicated to the air a couple of metres above the ground and shallow fog called ‘ground fog’ results.

Radiation fog reaches its maximum about half hour after sunrise because air temperature is at its lowest at that time. It generally dissipates after the sun has shone for a few hours and the land surface has warmed up.

Conditions favourable for radiation fog are:

1) Large moisture content in the lower layers of air.

2) Little or no cloud at night.

3) Light breeze at the surface.

4) Cold wet surface of land,

Also called sea fog because it is mostly found over sea. It can, however, form over land also. It is formed when a moist wind blows over a relatively cold surface of sea or land. When the most air is cooled below its dew point, the excess water vapour condenses into small droplets of water on dust or minute particles of salt, resulting in advection fog.

Wind causes advection fog to form and also to spread. If the wind is quite strong, turbulence causes advection fog to form to considerable depth.

We can expect to experience advection fog at about 1400 hrs.