Fog – the natural atmospheric phenomenon arising in close proximity to the earth's surface. It is the haze formed by a huge number of the smallest water drops. Process of emergence of fog is very similar to two others – formation of a cumulonimbus cloud and loss of dew. Sometimes it and is characterized - a cloud, at the Earth's surface. And fog differs from dew in the fact that condensation of moisture happens not on the earth, and in air.
Instruction
1. Emergence of fog is possible only in the presence of certain conditions. The first necessary factor is the content of water vapor in air. However, water vapor is always present at the atmosphere, even in the droughty hot summer or in hard winter frosts. But the oversaturated water vapors which density can significantly exceed density of saturated steam, i.e. it which is in dynamic balance with the liquid are necessary for emergence of fog.
2. The second necessary condition – existence of enough so-called kernels of condensation, i.e. the surfaces necessary for transformation of steam into water. It can be the motes lifted in air, motes, parts of soot and in general various pollution; and also water droplets which are already available in air, etc. At the same time only 1% of the water vapor which is contained in air is condensed.
3. Fogs are divided by a way of emergence – though is very conditional – on two categories: fogs of cooling and evaporation. Example of emergence of fog of cooling: from a water surface highly in air the warm, saturated with moisture air masses rise. They are strongly cooled and moisture is partially condensed. There is fog which gradually goes down to a water surface.
4. Example of emergence of fog of evaporation: the air which cooled down in a night adjoins to water. Water cools down more slowly than air and its temperature is higher. As a result of evaporation from the water surface steam which cools down at contact with cold air masses and is condensed is formed. Fog is formed.
5. Also other options are possible. These examples are a little schematical – actually harder and harder. As a rule, business is not limited only to evaporation or cooling. At some certain stage the second process is connected to the basic. Just its influence can be more short-term and not so considerable.
6. Fog – the phenomenon the most usual, also arises at all seasons of the year, mainly in the mornings. Most often it can be observed over the water surface and in lowlands where air is sated with a large amount of water vapor. In winter time it curls over not frozen rivers in which water is much warmer than air. Especially frequent and dense fogs are observed in the fall.