The marine layer usually causes a dense fog in areas near the sea.
A marine layer is a dense mass of cold, moist air that accumulates on the surface of large bodies of water, especially in the oceans. It is caused by a temperature inversion, which means that the air near the ground is colder than hot, while warm air above presses on it, preventing it from dissipating. This phenomenon is responsible for the haze that plagues many coastal communities and can also cause unusual phenomena such as smoke from a campfire flattening instead of rising.
People in coastal communities are familiar with the sea layer in the form of clouds that hang over the horizon, waiting for an opportunity to move to shore.
The formation of a marine layer can occur in several ways. Generally, the air becomes saturated with moisture, making it cold and dense, or cools at night and when it is cloudy. Warmer air from above will force cold air down, creating an inversion. A mass of warm air can also float on top of cooler air, trapping it so that it becomes cooler and denser as a result. If the air becomes saturated enough, it will become hazy. These cold air masses can also be quite large and extend into the atmosphere.
In some cases, the smog can get so bad that citizens are warned not to leave their homes as the air quality is extremely poor.
People in coastal communities are familiar with the sea layer in the form of ominous haze and clouds that loom on the horizon, waiting for an opportunity to move ashore. As coastal conditions cool, air moves in, saturating the coast with fog and sometimes drizzle. Inland communities can sometimes be extremely hot and sunny; in fact, this traps even more cold air, creating a bubble of warmth that surrounds you.
Many communities that experience this type of weather also struggle with smog, particulate matter that pollutes the air. Smoke can become trapped in cooler air, and the same temperature inversion that causes this phenomenon can also create a dense mass of smoke. In some cases, the smog can get so bad that citizens are warned not to leave their homes as the air quality is extremely poor. Temperature inversions can also occur in valleys or depressions deep in the earth’s surface, especially if they have large water resources, which is why Mexico City fights against pollution despite being in the middle of Mexico.
Strong winds can break up a marine layer, usually pushing it inshore for the sun to dissipate. Storms can also disperse it, as can turbulence in the air column.