Fog is a visible aerosol consisting of tiny water droplets or ice crystals suspended in the air at or near the Earth's surface. Fog can be considered a type of low-lying cloud, usually resembling stratus, and is heavily influenced by nearby bodies of water, topography, and wind conditions. In turn, fog has affected many human activities, such as shipping, travel, and warfare.
Fog is a natural weather conditions that can cause visibility to become zero. It can cause accidents on normally safe roads and is such a serious weather condition that schools delay the start of the day until the sun burns it off. So how does fog form? First it is important to understand that fog is basically a cloud on the ground. This means like clouds it is a collection of tiny water droplets formed when evaporated water is cooled. The way it is cooled determines how fog is formed.
1. Radiation fog: formed by the cooling of land after sunset by infrared thermal radiation in calm conditions with a clear sky.
2. Ground fog: obscures less than 60% of the sky and does not extend to the base of any overhead clouds
3. Advection fog: occurs when moist air passes over a cool surface by advection (wind) and is cooled.
4. Evaporation fog or steam fog: forms over bodies of water overlain by much colder air; this situation can also lead to the formation of steam devils, which look like dust counterparts.
5. Ice fog: forms in very low temperatures and can be the result of other mechanisms mentioned here, as well as the exhalation of moist warm air by herds of animals.
6. Freezing fog: which deposits rime, is composed of droplets of supercooled water that freeze to surfaces on contact.
7.Precipitation fog (or frontal fog): forms as precipitation falls into drier air below the cloud, the liquid droplets evaporate into water vapor.
8. Hail fog: sometimes occurs in the vicinity of significant hail accumulations due to decreased temperature and increased moisture leading to saturation in a very shallow layer near the surface.
9. Upslope fog: forms when moist air is going up the slope of a mountain or hill (orographic lifting) which condenses into fog on account of adiabatic cooling, and to a lesser extent the drop in pressure with altitude.
