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Up-slope fog or hill fog forms when winds blow air up a slope (called orographic lift), adiabatically cooling it as it rises and causing the moisture in it to condense. This often causes freezing fog on mountaintops, where the cloud ceiling would not otherwise be low enough. Valley fog forms in mountain valleys, often during winter. It is ...
Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain. [ 1 ] : 162 As the air mass gains altitude it quickly cools down adiabatically , which can raise the relative humidity to 100% and create clouds and, under the right conditions, precipitation .
Sea of fog riding the coastal marine layer through the Golden Gate Bridge at San Francisco, California Afternoon smog within a coastal marine layer in West Los Angeles. A marine layer is an air mass that develops over the surface of a large body of water, such as an ocean or large lake, in the presence of a temperature inversion.
As this layer moves over progressively warmer waters, however, turbulence within the marine layer can gradually lift the inversion layer to higher altitudes, and eventually even pierce it, producing thunderstorms, and under the right circumstances, tropical cyclones. The accumulated smog and dust under the inversion quickly taints the sky ...
What causes fog? Fog is essentially "a cloud at the ground," Boxell said. For fog to form, the air needs to be saturated, meaning it's holding the maximum amount of moisture possible, so ...
Stratus clouds form when weak vertical currents lift a layer of air off the ground and it depressurizes, following the lapse rate. This causes the relative humidity to increase due to the adiabatic cooling. [4] This occurs in environments where atmospheric stability is abundant. [5]
Dynamic instability is produced through the horizontal movement of air and the physical forces it is subjected to such as the Coriolis force and pressure gradient force; resulting dynamic lifting and mixing produces cloud, precipitation and storms often on a synoptic scale.
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.