04 February 2011
WFTV Severe Weather Center 9
Do you ever walk outside in the early mornings and your vision is hazed by fog? Do you ever wonder what exactly fog is? Well, fog is simply a cloud that is in contact with the ground. There are numerous types of fog, but they all have one fact in common: they form when the relative humidity reaches 100% and the dew point drops below the dew point. Here are descriptions of different types of fog as described by World of Earth Science:
Radiation or ground fog is formed after sunset when there is a cooling of the land caused by thermal radiation in calm weather conditions. When the cool ground reaches its dew point, it then produces moisture in the air, which forms into condensation or fog droplets. The fog sometimes boils over to the next morning before the sun has come up to cool ground.
Advection fog forms when warm, moist air horizontally movesover a cold surface, which cools the air to its dew point. It is common along coastlines where moist air moves from over the water to over the land, or when an air mass moves over a cold surface (e.g., snow), and the moisture in the air condenses into fog as the surface cools it..
Evaporation fog forms by the mixing of two unsaturated air masses. This can occur when cold, dry air moves over warmer water. The air, quickly saturated by evaporation and condensation, creating a steam like fog. This most commonly takes place over bodies of waters and can be known as sea smoke.
Precipitation or frontal fog forms as precipitation falls into cool, almost saturated air. This can take place with warm, cold, or stationary fronts
No matter what type of fog is drifting in the air, it is important to always take extra caution when driving. Fog reduces visibility and can be very dangerous, so make sure that you’re light are on and know when the sun come out, there will be a clear day ahead!