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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.
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.
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.
Tule fog is a radiation fog, which condenses when there is a high relative humidity (typically after a heavy rain), calm winds, and rapid cooling during the night. The nights are longer in the winter months, which allows an extended period of ground cooling, and thereby a pronounced temperature inversion at a low altitude.
Often these stretched polar vortex events repeat themselves with time and in rare winters this can persist for the entire winter. This last happened in 2013-14 resulting in a very cold winter."
The fog season is usually based in the cooler months (late autumn, winter and early spring). An example is found in the San Joaquin Valley and Sacramento Valley areas of California's Great Central Valley, where a thick ground fog, known as Tule fog, may form, in particular in the months from November through March. [1]
The days are short and the nights are long. That can only mean one thing: The winter solstice is coming. The first day of winter for the northern hemisphere of Earth will begin on Dec. 21 at ...
"The dangerously cold wind chills as low as 35 below zero could cause frostbite on exposed skin in as little as 10 minutes," the weather service in Duluth, Minnesota, warned.