Point Reyes is bounded on the southeastern side by Bolinas lagoon and the northeastern side by Tomales Bay. Point Reyes can get windy and foggy during certain months, and this is the reason why the lighthouse was built below the characteristic high-fog. When foggy, visibility is usually affected, and the light is the only thing which is visible to the ships sailing through this region. Point Reyes experiences over two hundred foggy days annually. Located at the southwest corner of the state of Washington, Cape Disappointment is one of the foggiest regions in the United States.
The cape experiences over 2, hours of fog annually which is approximately foggy days. San Francisco is well known for its fog, and for good reason. The many landmarks of this northern Californian metropolis is regularly covered by low-lying fog, brought on by a combination of factors like temperature and atmospheric moisture. Fog is especially common during the summer season. However, during the winter, San Francisco is still affected by tule fog, a very dense type of fog unique to the California coast.
The fog capital of the Atlantic coast is Mistake Island in Maine. Located in the northeastern part of Bar Harbor, Mistake Island receives over 1, hours of fog annually, mostly thanks to the close proximity of the chilly Atlantic ocean.
This process is called advection , a scientific name describing the movement of fluid. In the atmosphere, the fluid is wind. When the moist , warm air makes contact with the cooler surface air, water vapor condenses to create fog.
Advection fog shows up mostly in places where warm, tropical air meets cooler ocean water. The Pacific coast of the United States, from Washington to California, is often covered in advection fog.
The cold California Current , which runs along the western coast of North America, is much cooler than the warm air along the coast. Valley fog forms in mountain valleys, usually during winter. Valley fog develops when mountains prevent the dense air from escaping. The fog is trapped in the bowl of the valley. In , vapor condensed around particles of air pollution in the Meuse Valley, Belgium. More than 60 people died as a result of this deadly valley fog.
Freezing fog happens when the liquid fog droplets freeze to solid surfaces. Mountaintops that are covered by clouds are often covered in freezing fog. As the freezing fog lifts, the ground, the trees, and even objects like spider webs, are blanketed by a layer of frost. The white landscapes of freezing fog are common in places with cold, moist climates, such as Scandinavia or Antarctica. Fog Catchers Many ancient cultures collected water from fog by placing large pots under trees and shrubs.
As the water from fog collected on these objects, the pots collected the water. This method of water collection was effective, but not as effective as collecting rainwater or other liquid water. Today, engineer s are working on more sophisticated ways to collect water from fog. As fog glides in, water droplets form around the thin screens and drip to the collection pools below.
In one day, a single screen can collect more than a hundred gallons of water. The village of Bellavista, Peru, relies on fog catchers. Bellavista is an area that has little access to liquid water—no rivers, lakes, or glaciers are nearby.
Wells dry up quickly. Water for irrigation and human consumption is threatened. Every year, however, huge fogs blow in from the Pacific Ocean. In , the community invested in a series of fog catchers outside of town. Now, the residents of Bellavista have enough water to irrigate trees and gardens, as well as provide for their own drinking and hygiene needs.
As this air cools, the fog will extend upward. The most favored areas for fog development are sheltered valleys where there is little to no wind and locations near bodies of water. Wind would disrupt the formation of radiation fog. Thicker instances of radiation fog tend to form in valleys or over calm bodies of water. Is it a humid place, commonly covered with clouds , or a drier, inland desert that commonly has clear skies?
Proximity to the ocean or other large bodies of water will clearly be a major factor in fog formation, since such water bodies can contribute abundant moisture to the air, if they are warm enough. Water also warms up and cools down more slowly than land, so it tends to help moderate any temperature swings of the adjacent land cooler days and warmer nights than land farther away from water.
Prevailing wind directions are important since they can bring moist or dry air into an area. Especially important is whether breezes along a shoreline blow onshore or offshore toward the water. Topography and elevation are clearly key factors, since they control temperatures and influence local wind directions.
Mountain slopes have upslope winds at some times and downslope winds at others. They also interact with the prevailing winds. This map shows major ocean currents and land cover. Warm ocean currents are in red and cold ocean currents are blue. On the land, green colors show abundant vegetation , tan colors show areas with less vegetation, and white areas are covered by ice and snow.
Examine this map and think about how these ocean currents and regional patterns could influence the frequency of fog. Radiation fogs are common in inland areas, which often experience clear skies and a significant drop in temperature at night. Radiation fog can persist when there is a temperature inversion to stabilize the atmosphere and hold the fog in place, low to the ground.
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