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Fog is a visible aerosol consisting of tiny water droplets or ice crystals suspended in the air at or near the Earth's surface. [1] [2] 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.
Small-scale, tornado-like circulations can occur over or near any intense surface heat source, which would have significant instability in its vicinity. Those that occur near intense wildfires are called fire whirls, which can spread a fire beyond its previous bounds. [16] A steam devil is a rotating updraft that involves steam or smoke.
With sufficient humidity in the cooler layer, fog is typically present below the inversion cap. An inversion is also produced whenever radiation from the surface of the earth exceeds the amount of radiation received from the sun, which commonly occurs at night, or during the winter when the sun is very low in the sky.
Disturbed and unstable weather due to these differences often arises along the boundary. For instance, cold fronts can bring bands of thunderstorms and cumulonimbus precipitation or be preceded by squall lines, while warm fronts are usually preceded by stratiform precipitation and fog.
Cloud condensation nuclei are necessary for cloud droplets formation because of the Kelvin effect, which describes the change in saturation vapor pressure due to a curved surface. At small radii, the amount of supersaturation needed for condensation to occur is so large, that it does not happen naturally.
Fog is commonly considered a surface-based cloud layer. [21] The fog may form at surface level in clear air or it may be the result of a very low stratus cloud subsiding to ground or sea level. Conversely, low stratiform clouds result when advection fog is lifted above surface level during breezy conditions.
Climate experts warn San Francisco's iconic fog is disappearing... and fast. U.C. Berkeley professor explains why this is happening and what can be done to stop it.
Mist is a phenomenon caused by small droplets of water suspended in the cold air, usually by condensation. Physically, it is an example of a dispersion . It is most commonly seen where water vapor in warm, moist air meets sudden cooling, such as in exhaled air in the winter, or when throwing water onto the hot stove of a sauna .