What is the difference between fog and marine layer

When the moist, warm air makes contact with the cooler surface air, water vapor condenses to create fog. When fog forms in temperatures that are below freezing, the tiny water droplets in the air remain as liquid. They become supercooled water droplets remaining liquid even though they are below freezing temperature. When droplets from freezing fog freeze onto surfaces, a white deposit of feathery ice crystals is formed. When the sun rises, the air and ground warm up.

This leads to the air temperature being warmer than the dew point temperature, which causes the fog droplets to evaporate. As the air cools during the longer night the relative humidity increases, which can result in to fog formation. According to the old folklore, it really can. Fog is a cloud that appears near the ground or touches the ground. Mist is a thin fog that appears near the ground.

Dew is deposit of water drops that is formed on cold surfaces by condensation of water vapors in the air. At that point, the air condenses into water droplets, which we see as fog. Many people, including television weather presenters, mistakenly interchange marine layer with clouds. Although clouds are often present in this moist layer of air, it is not a requirement. The marine layer forms when relatively dry and warm air moves atop a body of cooler water. The warmer air close to the surface of the water cools and, thanks to its proximity to the water, becomes saturated with water vapor.

This often leads to the famous low-level cloud formation. The wind then carries those clouds over land, sometimes as far inland as 80 miles or more! The marine layer is usually no more than 4, feet deep. A deeper marine layer usually results in extensive cloud coverage extending well inland, often to the foothills of the mountains. If strong high pressure moves overhead higher in the atmosphere, it can squash the marine layer depth to under 1, feet or even dissipate it altogether.

However, due to the cold water, the air temperature increases with height resulting in a temperature inversion. The air below the inversion is called the marine layer and is cooled to the point at which clouds form.

Because of its persistence in early Summer, the people in Southern California it is often refer to it as the "May Gray" or "June Gloom". This can occur near any large body of water such as the Great Lakes region when the water temperature is significantly colder than the air moving over it. The depth of the marine layer depends upon the large-scale weather patterns that pass high overhead. Sinking air, under high pressure systems, located at elevations from 15, to 30, feet 4, to 9, meters , will squash the marine layer down to the earth's surface.

The strength of the sinking air impacts the depth of the marine layer. If the downward force of air is very strong, the marine layer is very shallow with low clouds and foggy weather confined to the beaches and very warm, sunny conditions beginning just a mile or so inland.

Any decrease in downward forcing allows the marine layer to deepen and move farther inland. Near the beach, the fog lifts into a low cloud layer. The leading edge of the marine layer extends farther inland pushing the fog inland. Further lifting of the marine layer will allow cooler marine air move over the coastal mountains and spill into the interior valleys. Because of this, often the maximum daily temperatures in the San Joaquin and Sacramento Valleys of California will undergo a roller coaster effect in Summer.