Advection fog occurs when moist air is cooled over a cooler surface, such as water or snow. It is commonly seen over seas and is also called sea fog. Advection fog is found in many areas around the world, including Great Britain, Newfoundland, and Antarctica. Coastal advection fog is seen when cold water moves parallel to subtropical continents. The fog stays put if the wind is less than 30 knots, otherwise, it forms stratus clouds.
Advection fog is fog that occurs when moist air is moved over a surface that is cooler than the air. It is most commonly seen over seas or other bodies of water, but is also possible over snow-covered or frozen land masses. As the air temperature drops to the dew point, changes begin to occur. First, saturation occurs. Then, fog.
In areas where sea air is cooled by water, advection fog is more common. Consequently, this fog is also called sea fog. This fog is usually seen during certain seasons, particularly the spring and early summer months. At that time, the sea water surface temperature is either at its lowest or recovering from a winter season in which it was already at its lowest.
There are many examples of advection fog around the world. Great Britain is surrounded by seas and sea air almost always approaches the country from the southwest. Consequently, advection is quite common in that part of the country. Throughout Great Britain, there are regional names for the same event. For example, the ‘fret’ is common along the Northumbrian coast and the ‘haar’ is seen in the southeastern part of Scotland.
Some areas seem more of this fog than others. For example, in Newfoundland, it is typical for four days out of ten, particularly in the month of July. This is because there is a cold current called the Labrador Current in the sea which creates fog when warmer air hits it.
Other areas where advection fog is common include the waters of Oya Shio and Kamchatka in the Pacific Ocean. Additionally, there are areas of higher latitudes where it is found above pack ice and in open ocean waters, even in the summer months. These areas include Antarctica, the Canadian archipelagos and sections of the Arctic Ocean.
Coastal advection fog is seen when extremely cold water moves parallel to subtropical continents. The Canary Current near northwest Africa, the Benguela Current near southwest Africa, and the Humbolt Current near Chile are among the best known freshwater currents that work to cool low-lying air. As a result, these areas often have advection fog.
If the wind in these areas is less than 30 knots, the fog stays put. Alternatively, if the wind is stronger, the fog lifts. As a result, it forms stratus clouds.
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