Fog is a visible aerosol consisting of tiny water droplets or ice crystals suspended in the air at or near the Earth's surface. Fog can be considered a type of low-lying cloud, usually resembling stratus, and is heavily influenced by nearby bodies of water, topography, and wind conditions. In turn, fog has affected many human activities, such as shipping, travel, and warfare.
The term "fog" is typically distinguished from the more generic term "cloud" in that fog is low-lying, and the moisture in the fog is often generated locally (such as from a nearby body of water, like a lake or the ocean, or from nearby moist ground or marshes).
For aviation purposes in the UK, a visibility of less than 5 kilometres (3.1 mi) but greater than 999 metres (3,278 ft) is considered to be mist if the relative humidity is 95% or greater; below 95%, haze is reported.
Fog begins to form when water vapor condenses into tiny liquid water droplets that are suspended in the air. Six examples of ways that water vapor is added to the air are by wind convergence into areas of upward motion; precipitation or virga falling from above; daytime heating evaporating water from the surface of oceans, water bodies, or wet land; transpiration from plants; cool or dry air moving over warmer water; and lifting air over mountains. Water vapor normally begins to condense on condensation nuclei such as dust, ice, and salt in order to form clouds. Fog, like its elevated cousin stratus, is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass.
Fog normally occurs at a relative humidity near 100%. This occurs from either added moisture in the air, or falling ambient air temperature. However, fog can form at lower humidities, and can sometimes fail to form with relative humidity at 100%. At 100% relative humidity, the air cannot hold additional moisture, thus, the air will become supersaturated if additional moisture is added.
Fog commonly produces precipitation in the form of drizzle or very light snow. Drizzle occurs when the humidity of fog attains 100% and the minute cloud droplets begin to coalesce into larger droplets. This can occur when the fog layer is lifted and cooled sufficiently, or when it is forcibly compressed from above by descending air. Drizzle becomes freezing drizzle when the temperature at the surface drops below the freezing point.
The thickness of a fog layer is largely determined by the altitude of the inversion boundary, which in coastal or oceanic locales is also the top of the marine layer, above which the air mass is warmer and drier. The inversion boundary varies its altitude primarily in response to the weight of the air above it, which is measured in terms of atmospheric pressure. The marine layer, and any fogbank it may contain, will be "squashed" when the pressure is high, and conversely, may expand upwards when the pressure above it is lowering.
Fog can form in a number of ways, depending on how the cooling that caused the condensation occurred.
Radiation fog is formed by the cooling of land after sunset by infrared thermal radiation in calm conditions with a clear sky. The cooling ground then cools adjacent air by conduction, causing the air temperature to fall and reach the dew point, forming fog. In perfect calm, the fog layer can be less than a meter thick, but turbulence can promote a thicker layer. Radiation fog occurs at night, and usually does not last long after sunrise, but it can persist all day in the winter months, especially in areas bounded by high ground. Radiation fog is most common in autumn and early winter. Examples of this phenomenon include the Tule fog.
Ground fog is fog that obscures less than 60% of the sky and does not extend to the base of any overhead clouds. However, the term is usually a synonym for shallow radiation fog; in some cases the depth of the fog is on the order of tens of centimeters over certain kinds of terrain with the absence of wind.
Advection fog occurs when moist air passes over a cool surface by advection (wind) and is cooled. It is common as a warm front passes over an area with significant snow-pack. It is most common at sea when moist air encounters cooler waters, including areas of cold water upwelling, such as along the California coast (see San Francisco fog). A strong enough temperature difference over water or bare ground can also cause advection fog.
Although strong winds often mix the air and can disperse, fragment, or prevent many kinds of fog, markedly warmer and humid air blowing over a snowpack can continue to generate advection fog at elevated velocities up to 80 km/h (50 mph) or more – this fog will be in a turbulent, rapidly moving, and comparatively shallow layer, observed as a few centimeters/inches in depth over flat farm fields, flat urban terrain and the like, and/or form more complex forms where the terrain is different such as rotating areas in the lee of hills or large buildings and so on.
Fog formed by advection along the California coastline is propelled onto land by one of several processes. A cold front can push the marine layer coast-ward, an occurrence most typical in the spring or late fall. During the summer months, a low pressure trough produced by intense heating inland creates a strong pressure gradient, drawing in the dense marine layer. Also during the summer, strong high pressure aloft over the desert southwest, usually in connection with the summer monsoon, produces a south to southeasterly flow which can drive the offshore marine layer up the coastline; a phenomenon known as a "southerly surge", typically following a coastal heat spell. However, if the monsoonal flow is sufficiently turbulent, it might instead break up the marine layer and any fog it may contain. Moderate turbulence will typically transform a fog bank, lifting it and breaking it up into shallow convective clouds called stratocumulus.
Evaporation fog or steam fog forms over bodies of water overlain by much colder air; this situation can also lead to the formation of steam devils, which look like dust counterparts. Lake effect fog is of this type, sometimes in combination with other causes like radiation fog. It tends to differ from most advective fog formed over land in that it is, like lake-effect snow, a convective phenomenon, resulting in fog that can be very dense and deep and looks fluffy from above.
Frontal fog forms in much the same way as stratus cloud near a front when raindrops, falling from relatively warm air above a frontal surface, evaporate into cooler air close to the Earth's surface and cause it to become saturated. This type of fog can be the result of a very low frontal stratus cloud subsiding to surface level in the absence of any lifting agent after the front passes.
Ice fog forms in very low temperatures and can be the result of other mechanisms mentioned here, as well as the exhalation of moist warm air by herds of animals. It can be associated with the diamond dust form of precipitation, in which very small crystals of ice form and slowly fall. This often occurs during blue sky conditions, which can cause many types of halos and other results of refraction of sunlight by the airborne crystals.
Precipitation fog (or frontal fog) forms as precipitation falls into drier air below the cloud, the liquid droplets evaporate into water vapor. The water vapor cools and at the dewpoint it condenses and fog forms.
Hail fog sometimes occurs in the vicinity of significant hail accumulations due to decreased temperature and increased moisture leading to saturation in a very shallow layer near the surface. It most often occurs when there is a warm, humid layer atop the hail and when wind is light. This ground fog tends to be localized but can be extremely dense and abrupt. It may form shortly after the hail falls; when the hail has had time to cool the air and as it absorbs heat when melting and evaporating.
Upslope fog forms when moist air is going up the slope of a mountain or hill (orographic lifting) which condenses into fog on account of adiabatic cooling, and to a lesser extent the drop in pressure with altitude.
Freezing fog occurs when liquid fog droplets freeze to surfaces, forming white soft or hard rime. This is very common on mountain tops which are exposed to low clouds. It is equivalent to freezing rain, and essentially the same as the ice that forms inside a freezer which is not of the "frostless" or "frost-free" type. The term "freezing fog" may also refer to fog where water vapor is super-cooled, filling the air with small ice crystals similar to very light snow. It seems to make the fog "tangible", as if one could "grab a handful".
In the western United States, freezing fog may be referred to as pogonip. It occurs commonly during cold winter spells, usually in deep mountain valleys. The word pogonip is derived from the Shoshone word paγi̵nappi̵h, which means "cloud". In The Old Farmer's Almanac, in the calendar for December, the phrase "Beware the Pogonip" regularly appears. In his anthology Smoke Bellew, Jack London described a pogonip which surrounded the main characters, killing one of them.
The phenomenon is also extremely common in the inland areas of the Pacific Northwest, with temperatures in the 10 to 30 °F (−12 to −1 °C) range. The Columbia Plateau experiences this phenomenon most years due to temperature inversions, sometimes lasting for as long as three weeks. The fog typically begins forming around the area of the Columbia River and expands, sometimes covering the land to distances as far away as LaPine, Oregon, almost 150 miles (240 km) due south of the river and into south central Washington.
Frozen fog (also known as ice fog) is any kind of fog where the droplets have frozen into extremely tiny crystals of ice in midair. Generally this requires temperatures at or below −35 °C (−31 °F), making it common only in and near the Arctic and Antarctic regions. It is most often seen in urban areas where it is created by the freezing of water vapor present in automobile exhaust and combustion products from heating and power generation. Urban ice fog can become extremely dense and will persist day and night until the temperature rises. Extremely small amounts of ice fog falling from the sky form a type of precipitation called ice crystals, often reported in Utqiagvik, Alaska. Ice fog often leads to the visual phenomenon of light pillars.
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 essentially a radiation fog confined by local topography, and can last for several days in calm conditions. In California's Central Valley, valley fog is often referred to as tule fog.
Sea fog (also known as haar or fret) is heavily influenced by the presence of sea spray and microscopic airborne salt crystals. Clouds of all types require minute hygroscopic particles upon which water vapor can condense. Over the ocean surface, the most common particles are salt from salt spray produced by breaking waves. Except in areas of storminess, the most common areas of breaking waves are located near coastlines, hence the greatest densities of airborne salt particles are there.
Condensation on salt particles has been observed to occur at humidities as low as 70%, thus fog can occur even in relatively dry air in suitable locations such as the California coast. Typically, such lower humidity fog is preceded by a transparent mistiness along the coastline as condensation competes with evaporation, a phenomenon that is typically noticeable by beachgoers in the afternoon. Another recently discovered source of condensation nuclei for coastal fog is kelp seaweed. Researchers have found that under stress (intense sunlight, strong evaporation, etc.), kelp releases particles of iodine which in turn become nuclei for condensation of water vapor, causing fog that diffuses direct sunlight.
Sea smoke, also called steam fog or evaporation fog, is the most localized form and is created by cold air passing over warmer water or moist land. It often causes freezing fog, or sometimes hoar frost.
Arctic sea smoke is similar to sea smoke, but occurs when the air is very cold. Instead of condensing into water droplets, columns of freezing, rising, and condensing water vapor is formed. The water vapor produces the sea smoke fog, and is usually misty and smoke-like.
Garúa fog near the coast of Chile and Peru, occurs when typical fog produced by the sea travels inland, but suddenly meets an area of hot air. This causes the water particles of fog to shrink by evaporation, producing a "transparent mist". Garua fog is nearly invisible, yet it still forces drivers to use windshield wipers because of deposition of liquid water on hard surfaces.
Depending on the concentration of the droplets, visibility in fog can range from the appearance of haze, to almost zero visibility. Many lives are lost each year worldwide from accidents involving fog conditions on the highways, including multiple-vehicle collisions.
The aviation travel industry is affected by the severity of fog conditions. Even though modern auto-landing computers can put an aircraft down without the aid of a pilot, personnel manning an airport control tower must be able to see if aircraft are sitting on the runway awaiting takeoff. Safe operations are difficult in thick fog, and civilian airports may forbid takeoffs and landings until conditions improve.
A solution for landing returning military aircraft developed in World War II was called Fog Investigation and Dispersal Operation (FIDO). It involved burning enormous amounts of fuel alongside runways to evaporate fog, allowing returning fighter and bomber pilots sufficient visual cues to safely land their aircraft. The high energy demands of this method discourage its use for routine operations.
Shadows are cast through fog in three dimensions. The fog is dense enough to be illuminated by light that passes through gaps in a structure or tree, but thin enough to let a large quantity of that light pass through to illuminate points further on. As a result, object shadows appear as "beams" oriented in a direction parallel to the light source. These voluminous shadows are created the same way as crepuscular rays, which are the shadows of clouds. In fog, it is solid objects that cast shadows.
Sound typically travels fastest and farthest through solids, then liquids, then gases such as the atmosphere. Sound is affected during fog conditions due to the small distances between water droplets, and air temperature differences.
Molecular effect: Though fog is essentially liquid water, the many droplets are separated by small air gaps. High-pitched sounds have a high frequency, which in turn means they have a short wavelength. To transmit a high frequency wave, air must move back and forth very quickly. Short-wavelength high-pitched sound waves are reflected and refracted by many separated water droplets, partially cancelling and dissipating their energy (a process called "damping"). In contrast, low pitched notes, with a low frequency and a long wavelength, move the air less rapidly and less often, and lose less energy to interactions with small water droplets. Low-pitched notes are less affected by fog and travel further, which is why foghorns use a low-pitched tone.
Temperature effect: A fog can be caused by a temperature inversion where cold air is pooled at the surface which helped to create the fog, while warmer air sits above it. The inverted boundary between cold air and warm air reflects sound waves back toward the ground, allowing sound that would normally radiate out escaping into the upper atmosphere to instead bounce back and travel near the surface. A temperature inversion increases the distance that lower frequency sounds can travel, by reflecting the sound between the ground and the inversion layer.
The foggiest place in the world is Hamilton, New Zealand, followed closely by the Grand Banks off the coast of Newfoundland (the meeting place of the cold Labrador Current from the north and the much warmer Gulf Stream from the south). Some of the foggiest land areas in the world include Argentia (Newfoundland) and Point Reyes (California), each with over 200 foggy days per year. Even in generally warmer southern Europe, thick fog and localized fog are often found in lowlands and valleys, such as the lower part of the Po Valley and the Arno and Tiber valleys in Italy; Ebro Valley in northeastern Spain; as well as on the Swiss plateau, especially in the Seeland area, in late autumn and winter. Other notably foggy areas include coastal Chile (in the south); coastal Namibia; Nord, Greenland; and the Severnaya Zemlya islands.
Redwood forests in California receive approximately 30–40% of their moisture from coastal fog by way of fog drip. Change in climate patterns could result in relative drought in these areas. Some animals, including insects, depend on wet fog as a principal source of water, particularly in otherwise desert climes, as along many African coastal areas. Some coastal communities use fog nets to extract moisture from the atmosphere where groundwater pumping and rainwater collection are insufficient.
Artificial fog is man-made fog that is usually created by vaporizing a water- and glycol-based or glycerine-based fluid. The fluid is injected into a heated metal block, and evaporates quickly. The resulting pressure forces the vapor out of a vent. Upon coming into contact with cool outside air, the vapor condenses in microscopic droplets and appears as fog. Such fog machines are primarily used for entertainment applications.
The presence of fog has often played a key role in historical events, such as strategic battles. One example is the Battle of Long Island (August 27, 1776), when American general George Washington and his command were able to evade imminent capture by the British Army, using fog to conceal their escape. Another example is D-Day (June 6, 1944) during World War II, when the Allies landed on the beaches of Normandy, France during fog conditions. Both positive and negative results were reported from both sides during that battle, due to impaired visibility.
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Actually use the following link- http://www.ofcm.gov/publications/fmh/FMH1/FMH1.pdf and proceed to Chapter 8, etc.
The Arabian Peninsula coastal fog desert on the southern coasts of the Arabian Peninsula is an ecoregion which experiences thick fogs where visibility may be reduced to 33 feet (10 m). It is classed as an Afrotropic fog desertAround the World with Willy Fog
Around the World with Willy Fog (Spanish: La vuelta al mundo de Willy Fog, Japanese: アニメ80日間世界一周) is a Spanish-Japanese animated adaptation of Around the World in Eighty Days by Jules Verne produced by Spanish studio BRB Internacional and Televisión Española, United States studio Intersound, Inc. In 1985, with animation by Japanese studio Nippon Animation, that was first broadcast on ANTENNE 2 in 1983 and TVE1 in 1984.
In the same vein as BRB's Dogtanian and the Three Muskehounds, the characters are anthropomorphisms of various animals as the species depicted are of much greater variety than in that series. The core trio are all felines being pursued by three canine foes. Willy Fog (Phileas Fogg in the original book) is depicted as a lion, while Rigodon (Passepartout) is a cat, and Romy (Aouda) is a panther.An English dub of the series was directed by Tom Wyner, which featured artists such as Cam Clarke (as Rigodon), Gregory Snegoff (Inspector Dix), Steve Kramer (as Constable Bully) and Mike Reynolds. While the series never achieved popularity in the United States, the English version found fame when it was broadcast on Children's BBC in the United Kingdom. The series was initially screened in 1984 in the UK (and has been repeated many times since) and then on RTÉ in Ireland, while other dubs gained the series fanbases in several other countries. The series was also dubbed into Japanese and aired on Japan's TV Asahi in 1987, where it was titled Anime Around the World in 80 Days (アニメ80日間世界一周, Anime Hachijūnichikan Sekai Isshū).
With all of the international versions, the height of popularity remains in Spain, where a sequel series, Willy Fog 2, was produced in 1993 which has the characters in adaptations of Verne's science fiction novels, Journey to the Center of the Earth and 20,000 Leagues Under the Sea. Furthermore in 2008, the series spawned a live-action theatrical musical show in celebration of its 25th anniversary.Automotive lighting
The lighting system of a motor vehicle consists of lighting and signalling devices mounted or integrated to the front, rear, sides, and in some cases the top of a motor vehicle. This lights the roadway for the driver and increases the visibility of the vehicle, allowing other drivers and pedestrians to see a vehicle's presence, position, size, direction of travel, and the driver's intentions regarding direction and speed of travel. Emergency vehicles usually carry distinctive lighting equipment to warn drivers and indicate priority of movement in traffic.Cloud forest
A cloud forest, also called a water forest and primas forest, is a generally tropical or subtropical, evergreen, montane, moist forest characterized by a persistent, frequent or seasonal low-level cloud cover, usually at the canopy level, formally described in the International Cloud Atlas (2017) as silvagenitus. Cloud forests often exhibit an abundance of mosses covering the ground and vegetation, in which case they are also referred to as mossy forests. Mossy forests usually develop on the saddles of mountains, where moisture introduced by settling clouds is more effectively retained.Fog Bowl (American football)
In American football, the Fog Bowl was the December 31, 1988 National Football League (NFL) playoff game between the Philadelphia Eagles and Chicago Bears. A dense fog rolled over Chicago's Soldier Field during the 2nd quarter, cutting visibility to about 15–20 yards for the rest of the game. Philadelphia moved the ball effectively all day and Eagles quarterback Randall Cunningham had 407 passing yards despite the low visibility; but they could not get the ball into the end zone. Many players complained that they could not see the sidelines or first-down markers. The Bears ended up winning 20–12. The game eventually was named #3 on NFL Top 10's Weather Games.The game was also notable in that it involved head coaches who had been previously worked on the same staff of a Super Bowl winning team. Eagles coach Buddy Ryan had been the defensive coordinator for Mike Ditka on the Bears when the team won Super Bowl XX. An NFL Network special on the game highlighted how unusual the conditions were: the fog was caused by a very rare late-December mix of cold and hot air in the atmosphere, and the fog itself covered a very small part of Chicago (less than 15 city blocks) for a very short amount of time (less than three hours). If the game had been played in the late afternoon or at night, there would have been no fog during the game at all.Fog of war
The fog of war (German: Nebel des Krieges) is the uncertainty in situational awareness experienced by participants in military operations. The term seeks to capture the uncertainty regarding one's own capability, adversary capability, and adversary intent during an engagement, operation, or campaign. Military forces try to reduce the fog of war through military intelligence and friendly force tracking systems. The term is also used to define uncertainty mechanics in wargames.Fog shrew
The fog shrew (Sorex sonomae) is a species of mammal in the family Soricidae. It is endemic to northern California and Oregon in the United States.Foghorn
A foghorn or fog signal is a device that uses sound to warn vehicles of navigational hazards like rocky coastlines, or boats of the presence of other vessels, in foggy conditions. The term is most often used in relation to marine transport. When visual navigation aids such as lighthouses are obscured, foghorns provide an audible warning of rock outcrops, shoals, headlands, or other dangers to shipping.Great Smog of London
The Great Smog of London, or Great Smog of 1952, was a severe air-pollution event that affected the British capital of London in early December 1952. A period of cold weather, combined with an anticyclone and windless conditions, collected airborne pollutants—mostly arising from the use of coal—to form a thick layer of smog over the city. It lasted from Friday, 5 December, to Tuesday, 9 December 1952, and then dispersed quickly when the weather changed.
It caused major disruption by reducing visibility and even penetrating indoor areas, far more severe than previous smog events experienced in the past, called "pea-soupers". Government medical reports in the following weeks, however, estimated that up until 8 December, 4,000 people had died as a direct result of the smog and 100,000 more were made ill by the smog's effects on the human respiratory tract. More recent research suggests that the total number of fatalities may have been considerably greater, one paper suggested about 6,000 more died in the following months as a result of the event.London had suffered since the 13th century from poor air quality, which worsened in the 1600s, but the Great Smog is known to be the worst air-pollution event in the history of the United Kingdom, and the most significant in terms of its effect on environmental research, government regulation, and public awareness of the relationship between air quality and health. It led to several changes in practices and regulations, including the Clean Air Act 1956.Interstellar medium
In astronomy, the interstellar medium (ISM) is the matter and radiation that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space. The energy that occupies the same volume, in the form of electromagnetic radiation, is the interstellar radiation field.
The interstellar medium is composed of multiple phases, distinguished by whether matter is ionic, atomic, or molecular, and the temperature and density of the matter. The interstellar medium is composed primarily of hydrogen followed by helium with trace amounts of carbon, oxygen, and nitrogen comparatively to hydrogen. The thermal pressures of these phases are in rough equilibrium with one another. Magnetic fields and turbulent motions also provide pressure in the ISM, and are typically more important dynamically than the thermal pressure is.
In all phases, the interstellar medium is extremely tenuous by terrestrial standards. In cool, dense regions of the ISM, matter is primarily in molecular form, and reaches number densities of 106 molecules per cm3 (1 million molecules per cm3). In hot, diffuse regions of the ISM, matter is primarily ionized, and the density may be as low as 10−4 ions per cm3. Compare this with a number density of roughly 1019 molecules per cm3 for air at sea level, and 1010 molecules per cm3 (10 billion molecules per cm3) for a laboratory high-vacuum chamber. By mass, 99% of the ISM is gas in any form, and 1% is dust. Of the gas in the ISM, by number 91% of atoms are hydrogen and 8.9% are helium, with 0.1% being atoms of elements heavier than hydrogen or helium, known as "metals" in astronomical parlance. By mass this amounts to 70% hydrogen, 28% helium, and 1.5% heavier elements. The hydrogen and helium are primarily a result of primordial nucleosynthesis, while the heavier elements in the ISM are mostly a result of enrichment in the process of stellar evolution.
The ISM plays a crucial role in astrophysics precisely because of its intermediate role between stellar and galactic scales. Stars form within the densest regions of the ISM, which ultimately contributes to molecular clouds and replenishes the ISM with matter and energy through planetary nebulae, stellar winds, and supernovae. This interplay between stars and the ISM helps determine the rate at which a galaxy depletes its gaseous content, and therefore its lifespan of active star formation.
Voyager 1 reached the ISM on August 25, 2012, making it the first artificial object from Earth to do so. Interstellar plasma and dust will be studied until the mission's end in 2025. Its twin, Voyager 2 entered the ISM in November 2018.Mel Tormé
Melvin Howard Tormé (September 13, 1925 – June 5, 1999), best known as Mel Tormé and nicknamed The Velvet Fog, was an American musician, a singer of jazz standards. He was also a jazz composer and arranger, drummer, an actor in radio, film, and television, and the author of five books. He composed the music for "The Christmas Song" ("Chestnuts Roasting on an Open Fire") and co-wrote the lyrics with Bob Wells.Mist
Mist is a phenomenon caused by small droplets of water suspended in air. Physically, it is an example of a dispersion. It is most commonly seen where warm, moist air meets sudden cooling, such as in exhaled air in the winter, or when throwing water onto the hot stove of a sauna. It can be created artificially with aerosol canisters if the humidity and temperature conditions are right. It can also occur as part of natural weather, when humid air cools rapidly, for example when the air comes into contact with surfaces that are much cooler than the air.
The formation of mist, as of other suspensions, is greatly aided by the presence of nucleation sites on which the suspended water phase can congeal. Thus even such unusual sources as small particulates from volcanic eruptions, releases of strongly polar gases, and even the magnetospheric ions associated with polar lights can in right conditions trigger the formation of mist and can make mirrors appear foggy. Mist on mirrors should not be mistaken for condensation as they are very different. Mist is a collection of water droplets but condensation is the water droplets in a different form.
Mist is commonly mistaken for fog. These two things are very different, however they do have some things in common. Fog and mist are both formed the same way. Fog is denser and generally lasts for longer but mist is thinner and you can see more clearly through it.Smog
Smog is a type of severe air pollution. The word "smog" was coined in the early 20th century as a blending of the words smoke and fog to refer to smoky fog, its opacity, and odor. The word was then intended to refer to what was sometimes known as pea soup fog, a familiar and serious problem in Australia from the 19th century to the mid-20th century. This kind of visible air pollution is composed of nitrogen oxides, sulphur oxides, ozone, smoke and other particulates. Man-made smog is derived from coal combustion emissions, vehicular emissions, industrial emissions, forest and agricultural fires and photochemical reactions of these emissions.
Smog is often categorized as being either summer smog or winter smog. Summer smog is primarily associated with the photochemical formation of ozone. During the summer season when the temperatures are warmer and there is more sunlight present, photochemical smog is the dominant type of smog formation. During the winter months when the temperatures are colder, and atmospheric inversions are common, there is an increase in coal and other fossil fuel usage to heat homes and buildings. These combustion emissions, together with the lack of pollutant dispersion under inversions, characterize winter smog formation. While photochemical smog is the main smog formation mechanism during summer months, winter smog episodes are still common. Smog formation in general relies on both primary and secondary pollutants. Primary pollutants are emitted directly from a source, such as emissions of sulfur dioxide from coal combustion. Secondary pollutants, such as ozone, are formed when primary pollutants undergo chemical reactions in the atmosphere.
Photochemical smog, as found for example in Los Angeles, is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes. These pollutants react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog. In certain other cities, such as Delhi, smog severity is often aggravated by stubble burning in neighboring agricultural areas. The atmospheric pollution levels of Los Angeles, Beijing, Delhi, Lahore, Mexico City, Tehran and other cities are often increased by an inversion that traps pollution close to the ground. The developing smog is usually toxic to humans and can cause severe sickness, a shortened life span, or premature death.Stratus cloud
Stratus clouds are low-level clouds characterized by horizontal layering with a uniform base, as opposed to convective or cumuliform clouds that are formed by rising thermals. More specifically, the term stratus is used to describe flat, hazy, featureless clouds of low altitude varying in color from dark gray to nearly white. The word "stratus" comes from the Latin prefix "strato-", meaning "layer". Stratus clouds may produce a light drizzle or a small amount of snow. These clouds are essentially above-ground fog formed either through the lifting of morning fog or through cold air moving at low altitudes over a region. Some call these clouds "high fog" for the fog-like cloud. While light rain may fall, this cloud does not indicate much meteorological activity.The Fog
The Fog is a 1980 American supernatural horror film directed by John Carpenter, who also co-wrote the screenplay and created the music for the film. It stars Adrienne Barbeau, Jamie Lee Curtis, Tom Atkins, Janet Leigh and Hal Holbrook. It tells the story of a strange, glowing fog that sweeps over a small coastal town in California, bringing with it the vengeful ghosts of mariners who were killed in a shipwreck there 100 years before.
The Fog received mixed reviews upon release but did well at the box-office, making over $21 million domestically on a $1.1 million budget. Since release, it has received more positive retrospective reviews and has become a cult classic. A remake of the film was made in 2005 to very negative reviews.The Fog of War
The Fog of War: Eleven Lessons from the Life of Robert S. McNamara is a 2003 American documentary film about the life and times of former U.S. Secretary of Defense Robert S. McNamara illustrating his observations of the nature of modern warfare. The film was directed by Errol Morris and features an original score by Philip Glass. The title derives from the military concept of the "fog of war" depicting the difficulty of making decisions in the midst of conflict.
The film won the 2003 Academy Award for Best Documentary Feature and Independent Spirit Award for Best Documentary Feature. It was non-competitively screened at the Cannes Film Festival.Utility fog
Utility fog (coined by Dr. John Storrs Hall in 1993) is a hypothetical collection of tiny robots that can replicate a physical structure. As such, it is a form of self-reconfiguring modular robotics.Whiteout (weather)
Whiteout is a weather condition in which visibility and contrast are severely reduced by snow, fog, or sand. The horizon disappears from view while the sky and landscape appear featureless, leaving no points of visual reference by which to navigate. Whiteout has been defined as: "A condition of diffuse light when no shadows are cast, due to a continuous white cloud layer appearing to merge with the white snow surface. No surface irregularities of the snow are visible, but a dark object may be clearly seen. There is no visible horizon."A whiteout may be due simply to extremely heavy snowfall rates as seen in lake effect conditions, or to other factors such as diffuse lighting from overcast clouds, mist or fog, or a background of snow. A person traveling in a true whiteout is at significant risk of becoming completely disoriented and losing their way, even in familiar surroundings. Motorists typically have to stop their cars where they are, as the road is impossible to see. Normal snowfalls and blizzards, where snow is falling at 1 or 2 inches per hour (2.5 or 5.1 cm/h), or where the relief visibility is not clear yet having a clear field of view for over 30 feet (9 meters), are often incorrectly called whiteouts.
Meteorological data and variables