How does fog form?

Answer 1

Fog is a cloud in contact with the ground. Fog is defined as cloud which reduces visibility to less than 1 km, where as mist is that which reduces visibility to less than 2 km.

Fog forms when water vapor in the air at the surface begins to condense into liquid water. Fog normally occurs at a relative humidity of 100%. This can be achieved by either adding moisture to the air or dropping the ambient air temperature. Fog can form at lower humidities, and fog can sometimes not form with relative humidity at 100%. A reading of 100% relative humidity does not mean that the air can not hold any more moisture, but the air will then becomes known as supersaturated. Fog formation does require all of the elements that normal cloud formation requires with the most important being condensation nuclei. When the air is saturated, additional moisture tends to condense rather than staying in the air as vapor. Condensation nuclei must be present in the form of dust, aeresols, pollutants, etc. for the water to condense upon. When there are exceptional amounts of condensation nuclei present, especially hydroscopic (water seeking such as salt) then the water vapor may condense below 100% relative humidity.

Fog can form suddenly, and can dissipate just as rapidly, depending what side of the dewpoint the temperature is on. This phenomenon is known as Flash Fog and is the inspiration for an antiburglary device that stops burglars by filling the room with artificial fog.

Another type of formation also common is sea fog (also knows as salt fog or salty Fog). This is due to the peculiar effect of salt. Clouds of all types require minute hygroscopic particles upon which water vapor can condense. Over the ocean surface, the most common particles are salt from salt spray produced by breaking waves. Except in areas of storminess, the most common areas of breaking waves are located near Coastlines, hence the greatest densities of airborne salt particles are there. Condensation on salt particles has been observed to occur at humidities as low as 70%, thus fog can occur even in relatively dry air in suitable locations such as the California coast. Typically, such lower humidity fog is preceded by a transparent mistiness along the coastline as condensation competes with evaporation, a phenomenon that is typically noticeable by beachgoers in the afternoon. Fog occasionally produces precipitation in the form of drizzle. Drizzle occurs when the humidity of fog attains 100% and the minute cloud droplets begin to coalesce into larger droplets. This can occur when the fog layer is lifted and cooled sufficiently, or when it is forcibly compressed from above. Drizzle becomes freezing drizzle when the temperature at the surface drops below the freezing point. The thickness of fog is largely determined by the altitude of the inversion boundary, which in coastal or oceanic locales is also the top of the marine layer, above which the airmass is warmer and drier. The inversion boundary varies its altitude primarily in response to the weight of the air above it which is measured in terms of atmospheric pressure. The marine layer and any fogbank it may contain will be "squashed" when the pressure is high, and conversely, may expand upwards when the pressure above it is lowering.

Answer 2

When there is warm, moist ground and cold air runs over it then the evaporating water condenses into fog.
Because sometimes the clouds are high, but other times they are much lower, and when there is fog, it is when the clouds are so low that they actually touch the ground. High clouds, like Cirrus Clouds or Cirrocumulus clouds are usually much colder, but the Cumulonimbus clouds tower from very high down to very low, I don't know why they go in hand with big storms. When its fog, the clouds are so low down that they aren't really that cold, although fog is really quite rare in the summers. I'm from Britain and in Late October and a lot of November that is the time of year when we get the most fog. Fog is thicker than mist. Mist is usually when the clouds are white and flat

Answer 3

Fog forms at the ground. Moisture laden air reaches a saturation point. The fog begins at ground, and fills in space going upward. Since this occurs between sundown and sunrise, with the first rays of sun, the warming reduces the moisture saturation. The cloud "lifts" upward into the sky, becoming just another usual cloud.

Answer 4

Fog is formed in 4 different ways.

1. radiation fog
2. advection fog
3. upslope fog
4. steam fog

Answer 5

When cold air meets warm air, and when they condense like steam in shower. Warm air meets cold air, and they condense which forms steam.

Answer 6

from water vapor

Answer 7

the ground botta bing botta boom