State Regional Budgetary Special (Correctional) Educational Institution for Students, Pupils with Disabilities "Special (Correctional) General Education Boarding School for Blind and Visually Impaired Children" Fog as a natural phenomenon The work of a 7th grade student Ivan Noskov head teacher of physics Gosteva Marina Alekseevna
Perm, 2015 Contents: Introduction 3 p. 1. Description of fog in fiction and popular science literature 4 p. 2. Fog from the point of view of physics p. 5 a) occurrence of fog p 5. b) types of fog p. ) fog and color p. 9 d) smog p. 10 3. Geographers about fog p. 11 a) what fog is made of p. 12 b) what fogs are p. 13 c) meteorological visibility p. 16 d) artificial scattering fog – p. 18 4. Application of fogging plants in agriculture p. 19 5. Proverbs and sayings p. 20 Conclusion p. 23 Glossary p. 24 Literature p. 26 6. Applications – p. 27
INTRODUCTION The night is turning pale... The veil of fogs In the hollows and meadows becomes whiter, The forest is louder, the moon is lifeless And the silver dew on the glasses is colder. IA Bunin Why I chose this topic With fog, we usually associate something obscure, mysterious, imperceptibly enveloping. Forests, mountains, villages, city streets, all surrounding objects seem to dissolve in a weightless and intangible environment, becoming invisible. Compared to other meteorological phenomena such as a hurricane, thunderstorm, hail, snow, downpour, fog, it seems that you can’t call it a formidable force of nature. This is a very simple and common phenomenon (see Fig. 1). And, nevertheless, it has a significant impact on the physical and chemical phenomena occurring in nature, production processes, and finally, on the operation of transport and the well-being of people. A huge number of pages in the ship's books and logbooks of sailors and navigators, in the diaries of meteorologists and researchers' reports are devoted to the description of fogs. Fogs are interested in poets and artists. But what is fog anyway? Purpose: to study in more detail such a natural phenomenon as fog. Tasks: find out what fogs are; understand how fog is formed, what it consists of, what color it is; determine the benefits and harms of fog for human life.
Description of fogs in fiction and popular science literature Quite often the description of fog is found in literary works. For example, Charles Dickens' novel Bleak House opens with a depressingly gloomy picture: “Fog is everywhere. Fog on the upper Thames, where it floats over green islets and meadows; the mist on the lower Thames, where, having lost its purity, curls between the forest of masts and the riverside dregs of the big (and dirty) city. Fog in the Essex Marshes, fog in the Kentish Highlands. Fog creeps into the galleys of the coal-brigs; fog lies on the yards and floats through the rigging of the great ships; fog settles on the sides of barges and boats. The fog dazzles the eyes and clogs the throats of the elderly Greenwich pensioners wheezing by the fires in the house of care; the mist has penetrated the stem and head of the pipe that the angry skipper smokes after dinner, sitting in his cramped cabin; the fog cruelly pinches the fingers and toes of his little cabin boy, trembling on the deck. On the bridges, some people, leaning over the railing, look into the foggy underworld and, surrounded by fog themselves, feel like in a balloon hanging among the clouds. In many scenes of the novels of Balzac, Zola, Dickens, Dostoevsky, there is a description of the fog. And at the same time, the classics did not spare epithets (see Fig. 2). The canvases of famous artists Turner, Monet, Pissarro are shrouded in a soft, damp, translucent haze.
Fog in terms of physics Fog is an accumulation of small water droplets or ice crystals, or both, in the surface layer of the atmosphere (sometimes to a height of several hundred meters), reducing horizontal visibility to 1 km or less. The occurrence of fog The occurrence of fog is the phenomenon of dew falling, and what is essential, not on the surface of the earth or water, not on the surfaces of leaves or blades of grass, but in the volume of air. Under certain conditions, water vapor in the air partially condenses, resulting in water droplets of fog. It is known that only a very small part of the mass of water vapor is converted into water contained in the fog droplets. Dew falls at temperatures close to 20 °C, when the total mass of saturated vapor in a cubic meter of air is 20 g. At the same time, the water content of the fog usually does not exceed 0.1 g/m3. This means that approximately no more than 1% of the mass of water vapor condenses into the water of the fog drops. It is known that the air contains water vapor, in our latitudes it is approximately 0.32.5% of its mass. Each temperature has its own limit of humidity, saturation. The warmer the air, the more water vapor it can hold. For example, at a temperature of "40 ° C" one cubic meter of air can contain 0.2 g of moisture, and at "+ 40 ° C" almost 250 times more! For the occurrence of fog, two conditions must be met: the content of a sufficiently large number of so-called condensation nuclei of centers on which vapor condensation occurs. Along with individual molecules of air or vapor, as well as randomly formed clusters of molecules, the role of condensation nuclei is played by ions, water droplets, dust particles, soot particles, and in general all kinds of small contaminants that, for one reason or another, may appear in the air. In urban air, due to its relatively strong pollution, the density of condensation nuclei is 10100 times greater than in the air of rural, marine, mountainous areas. That is why urban fogs are more dense and stable;
the presence of supersaturated steam; its density should be several times greater than the density of saturated vapor. It is clear that if the temperature drops, then part of the saturated steam should condense, stand out in the form of water. The fog is easy to see. It is enough to wait until the kettle boils, or on a frosty day to slightly open the window from the warm room to the street, and you can observe the process of fog formation. The amount of water released in this case (puffs of steam) is the difference in humidity at room temperature and at air temperature outside. The colder the day, the denser the fog. At home, the mechanism of fog formation can be understood by performing a series of simple experiments while studying the condensation process. Equipment: glass cup, ice, cold water, hot water, bowl. 1) If you pour a little boiling water into a bowl, then steam rises above the bowl (see Fig. 3). 2) Pour into a glass cold water and put some ice cubes in it. Put the glass in a warm place. After a while, water droplets appear on the outside of the glass (see Fig. 4). The physical mechanism of fog formation is described above only in the most general terms. In reality, it is much more difficult. The supersaturation of vapor required for the formation of fog depends on the density and nature of the condensation nuclei, as well as on temperature. Both quantities can vary both in time and from one point in space to another; this leads to corresponding changes in time and space in the density of the fog. As a result, the fog swirls, worries, creeps. During the formation of fog, the relative humidity of the air decreases. This is due to several reasons: some decrease in absolute humidity due to partial condensation of vapor, an increase in the density of saturated vapor above the convex surface (above the surface of the drop); an increase in the density of saturated steam as a result of an increase in temperature due to the release of heat of vaporization during steam condensation. Therefore, the process of fog formation, having begun, then develops by no means like an avalanche, but rather quickly stops. Not without reason, no more than 1% of the mass of vapor condenses into water drops of fog. The resulting fog droplets do not remain unchanged. Colliding with each other, they merge, increase in size, under the influence of gravity they quickly settle down, dew is formed. If the steam is not saturated enough, the droplets evaporate and the fog dissipates.
Different types of fogs can be divided into two groups: cooling fogs and evaporation fogs. Types of fog Fogs Evaporation fogs Cooling fogs Evaporation of an additional amount of steam from the surface of the water cooled morning air. c Transfer of heat from the heated layer of near-surface air to the rapidly cooling ground. Cooling of the risen warm layers of air enriched with moisture over heated water. Movement of layers of cold air from ice to open water surface (Arctic). Enrichment with moisture, then cooling over a snow-covered shore or over sea water of warm air, heated in winter over river water, or in summer over the shore. In this regard, five specific examples of fogs are distinguished.
First example. The cooled morning air adjacent to the water has a lower temperature than water. Therefore, an additional amount of steam evaporates from the warm water surface into the cold air. The result is an evaporation mist (see Fig. 5). Most often it is morning fog, which is very unstable. At sunrise, he disappears without a trace. Wanting to emphasize the transience of youth and young dreams, A. S. Pushkin mentions the morning mist for a reason. Here are his lines from the poem "To Chaadaev": Love, hope, quiet glory The deceit did not live long for us, Young amusements disappeared, Like a dream, like a morning mist. Second example. Evaporation of additional vapor into relatively cold air (which is above the ice surface) from a relatively warm surface, such as open water. As in the previous example, this fog is evaporation fog. Third example. Warm air, heated in the first case (in winter) over river water, and in the second case (in summer) over the shore, is enriched with moisture, and then cools over a snow-covered shore or over sea water. In both cases, a cooling mist occurs. Such are the winter fogs characteristic of St. Petersburg. Another case is also possible: a layer of air, having warmed up above the shore, moves towards the sea and there it gives off heat to cold sea water. These fogs form summer evenings on the sea near the shore. A. S. Pushkin has the following lines: The day light went out, The blue evening mist fell on the sea. Fourth example. Warm layers of air, enriched with moisture, rise up and are strongly cooled. A cooling fog develops, which then descends down the mountainside back to the sea. It was this situation that I. A. Bunin described in his poem “Twilight”: Everything is exactly half asleep. Above the gray water The mist, cold and thick, is creeping down from the mountains, The surf is buzzing under it, growing ominously, And the coastal wall of dark bare rocks, Immersed in the smoking mist, Smokes lazily, getting lost in the mist. Fifth example. Due to the transfer of heat from the heated layer of near-surface air to the rapidly cooled ground, cooling occurs.
air and a typical cooling fog appears, described by M. Yu. Lermontov: And the day disappeared; swirling, the mists clothed the dark glades with a wide white veil. Let us pay attention to the property of fog to swirl, noticed by Lermontov. But the fog doesn't necessarily swirl. More often he "creeps, spreads." Fog creeps over the grass. The division of fogs into evaporation and cooling fogs is rather arbitrary; Typically, the fogging process involves both cooling the air and evaporating more vapor into it. For example, morning fog over a shallow bay refers to evaporation fogs from the surface of warm water, an additional mass of vapor evaporates into the cooled air. However, we must not forget that, before cooling down, the layer of air adjacent to the water was warm and therefore was enriched with moisture. So fog began to form already during the cooling of the air, and at this stage the fog should be considered as a cooling fog. Fog and color What color is the fog? Light misty haze over the sea has a bluish color. The well-known poem by M. Yu. Lermontov “Sail” begins like this: A lonely sail turns white In the blue fog of the sea ... The color of the fog is determined by light waves, which, scattering on water droplets, fall into the observer's eye. Droplets with a diameter much larger than a micrometer scatter light almost equally in the entire range of wavelengths perceived by the eye. This explains the milky white and whitish color of dense fogs. Small droplets, the diameter of which is less than 1 μm, scatter predominantly shorter light waves(blue rays). Therefore, fogs that are not too dense, and even more so foggy haze, are painted in bluish and bluish tones. The sun, moon, lanterns, observed through the fog, appear reddish. So, the fog itself is white or bluish, and the light sources observed through it have red tints. But in nature, quite unexpected situations sometimes occur. For example, a painting by Claude Monet, in which the artist depicted Westminster Abbey in London (see Fig. 6). We see Westminster Abbey through a dense fog, which in the picture is painted in red and even crimson tones. This initially caused
no small surprise among the audience, who believed that the fog could not be red. However, the artist turned out to be right: he painted evening fog, and such fog can indeed be painted in red tones. This is due to the scattering of large drops of fog of red rays coming to us from the setting sun. As already noted, city fogs often have yellowish tints, look gray, dirty. This is due to the strong air pollution in many large cities, the presence of dust and soot particles in it. It must also be borne in mind that chemical compounds, poisoning the air of cities, dissolving in drops of fog, can paint them in various color tones, including yellowish ones. The color of the famous London fogs changes from black to yellow. The particles on which vapors condense here are mainly products of combustion: smoke, acids, salts. Depending on the predominance of certain particles, the color changes. So, early morning the city is usually shrouded in a lighter fog, but then emissions from millions of fireplaces and chimneys from hundreds of businesses settle on droplets of fog, giving it an almost black color. This is especially noticeable on winter days when the air is saturated with water vapor. This kind of fog is called smog. Smog Smog is the scourge of large industrial cities. In the form of a yellow-gray veil consisting of smoke, fog and dust, it hangs over megacities with developed industry and, as a result, with significant atmospheric emissions of harmful substances and suffocates all life. Significantly impairs visibility on the roads The word "smog" comes from a combination of the English "smoke" smoke and "fog": fog. This is a very accurate name, as it fully corresponds to the nature of the phenomenon. A “cap” of moisture droplets, water vapor and smoke hangs in the air, these are automobile exhaust gases, and combustion products of foundries emitted into the air through pipes, and gas waste from countless boiler houses and thermal power plants. Solar ultraviolet radiation causes smog components to react with each other. As a result, substances that cause respiratory diseases are formed. People suddenly begin to choke with a cough, there are pains in the throat, tears involuntarily flow from the eyes. Toxic smog compounds stop the work of chlorophyll in plants. That is why the trees in large cities seem to be faded, yellowish.
They are just sick. Agricultural crops near cities also suffer. Poisoned by smog, they do not ripen. Smog is most dangerous in calm weather, when nothing can dispel it. Fixed smog is typical for cities located near large and warm bodies of water. The hot air that came from them, as it were, covers the colder surface layers, preventing the veil of smog from dissipating. On such days, doctors do not recommend going out unnecessarily, and everyone else is advised to use protective breathing masks. However, it does little to help sick people. So, in 1962, the London smog sent 2,000 citizens to the next world! Geographers about fog In everyday life, fog is usually called air, in which a very large number of tiny droplets of water is suspended. At the same time, meteorologists add that we are talking only about the surface layer of air, where the transition of water vapor to a liquid state is observed, as a result of which the transparency of the air decreases and the visibility of ground objects worsens. The “earthiness” of fog is not emphasized by chance, because the veil of low clouds covering the tops of trees and hills is no longer considered fog, but a stratus cloud. From this it is clear how conditional their division is. For example, in a mountainous area, each cloud that envelops the observer appears to him as fog, and from the bottom of the valley this fog may look like a stratus cloud (see Fig. 7). Fog is a cloud lying on the ground. Therefore, there are no fundamental differences between fog and cloud. And this is very figuratively and amazingly accurately conveyed by S. Yesenin: "A month in a cloudy fog plays a game with clouds."
What fog consists of The answer to this question is given by the placed microphysical picture of the fog. A glass plate lubricated with petroleum jelly was held in atmospheric fog and photographed under a microscope. The settled water droplets, water mist, are clearly visible on the plate (see Fig. 8). The size of the mist droplets varies within a fairly wide range from 0.1 to 100 micrometers. Most often, fogs consist of medium-sized droplets. It is known that drops of light rain are about 5 times larger, moderate ones are 10 times larger, and heavy ones are 15 times larger. If the fog is dominated by dwarf droplets (with a radius of less than 1 micrometer), then they say that this is not fog, but haze. If they are so large that they are visible to the naked eye, then this is a drizzle. Fog can contain very small and very large droplets at the same time. Some more, others less. An interesting relationship has been established. The predominance of large or small droplets in the fog depends on the air temperature: the higher it is, the more large droplets. With positive
temperatures, droplets with a radius of 712 µm predominate, at negative 25 µm. Warm mist consists of thicker droplets, cold mist consists of thinner ones. Not only the size of the droplets determine the water content of the fogs, but also how tightly they are “packed”. In one cubic centimeter in a weak fog, there are 50,100 droplets, and in a thick one, 500,600, that is, almost ten times more. In addition to water fogs, there are also ice ones. They are made up of tiny ice crystals that are shaped like columns. The number of crystals per cubic centimeter of ice fog is usually less than 100. Therefore, ice fogs are usually not very thick. During moderate frosts, drop-liquid supercooled fogs are usually formed. At temperatures below minus 20 °C, ice fogs prevail. They are well known to the inhabitants of Siberia and Alaska. What are fogs At first glance, all fogs are the same. However, meteorologists do not think so. There are different classifications of fogs, all of them are based on differences in the synoptic processes that lead to the formation of fogs. Meteorologists distinguish, first of all, cooling fogs (the most frequent), evaporation fogs, and frontal fogs. radiation cooling fogs; advective evaporation fogs FOGs frontal fogs prefrontal; frontal; postfrontal various advectively radiative; mists of slopes;
fumes; frosty ice fogs or cooling fogs are divided into radiation fogs, formed as a result of radiative cooling of the earth's surface, and from it the air, and advective fogs, associated with the transfer of air masses. Radiation fog. The main reason for the occurrence of radiation fog is the strong cooling of the Earth's surface on clear nights, with a slight wind. The decrease in temperature is transferred from the soil to the adjacent layer of air. The cooled air is supersaturated with moisture, and water vapor begins to be released in the form of tiny droplets. Usually, with the rising of the Sun, radiation fogs quickly dissipate and rise. Then from Earth they appear to be a stratus cloud. For example, as in Lermontov: “A golden cloud spent the night on the chest of a giant cliff ...”? In the cold season, with prolonged cooling of the soil, when there is no wind and high relative humidity, especially strong radiation fogs are formed that do not disappear for several days. Sometimes they reach 300500 meters in height and are denser at the top than on the surface of the soil. Mists are probably most associated with autumn, when the soil evaporates a lot of moisture and the nights get longer and colder. Yesenin says this about it: The fields are compressed, the groves are bare, Fog and dampness from water ... In lowlands, logs, ravines, marshy areas, where cold dense air flows and where it is always humid, fogs form especially often. For example, it has been recorded that in the North-West of the European part of Russia in many settlements located in depressions near shallow water bodies (Valdai, Krestsy, Vinnitsa, etc.) there are 3050 radiation fogs a year. In neighboring villages located on the hills, there are two to three times less of them. Another pattern has also been noticed: radiation fogs rarely occur on the shores of large lakes. So, in Gdov, Novaya Ladoga, Lisy Nos, only 614 fogs are observed per year. The reason is breeze winds and the insignificance of night cooling. By the way, the same (small amplitude of daily temperatures) can also explain the fact that radiation fogs are rare in large cities. So in St. Petersburg there are only about 10 such foggy days during the summer. But in cold weather, fogs in coastal cities occur much more often due to the abundance of incoming moisture.
S. Yesenin also drew attention to the phenomenon, which in the language of meteorologists is called ground radiation fog: Spicy wind. Dawns go out. Fog creeps over the grass. It “creeps” because the ground fog is low, often below human height, and is densest at the very surface of the earth. These mists are unstable. In the morning, when the sun warms the soil and the adjacent layer of air, the wind intensifies and the fog breaks. Some of its shreds are scattered in the warmed air. Advective fog (from Latin advectio - “delivery”) is typical for border areas: land, sea, warm cold current, sea ice border, snow cover border. Advective fog, unlike radiation fog, occurs at higher wind speeds near the Earth's surface, which are most often 48 m/s, but it can also form at more strong wind reaching 1215 m/s. A feature of advective fog is also an increase in density with height. At the same time, visibility near the Earth's surface can be quite satisfactory, but as soon as you climb a few tens of meters (3050 m), the horizontal visibility completely disappears. Such conditions are more common in the northern hemisphere. There are areas that can be considered "fog poles". So, at the junction of the warm Gulf Stream and the cold Labrador Current in the Newfoundland region (Canada), there are 120 foggy days per year, especially in summer, with an average of 22 foggy days per month. This area is considered one of the most dangerous for navigation. The well-known "Petersburg fogs" are caused by the horizontal transfer of air masses under conditions of temperature contrast. Warm, moist air moves over colder land or sea surfaces. At the same time, the temperature of warm air decreases, water vapor condenses, and fog forms. Often such fogs occur in winter when warm winds come. Therefore, the most foggy months in St. Petersburg are December, February, March, they account for almost 40% of all foggy days per year. Fogs are frequent on Vaigach Island 19 days in the summer month, on the Kola Peninsula 50100 foggy days a year, they are slightly less common on the coasts of the Barents, North and Baltic Seas, in the areas of Florida, California, in the Sea of Okhotsk and the Sea of Japan. It is interesting that advective fogs in the coastal zone in the cold half of the year are formed mainly over land, in the warm half of the year over the adjacent part of the sea. In the cold months, masses of relatively warm moist air move from the sea to land, and in the warm season from land to the sea.
The greater the temperature difference, the more intense the fog. Over the cold surface of the sea, the conditions for the formation of fog are especially favorable: high humidity and a large constancy of the temperature of the water surface. Advective fogs usually form during cloudy weather, in warm sectors of the cyclone. Outwardly, advective fog looks like a large stratus cloud that touches the Earth's surface and covers a vast area, sometimes thousands of kilometers. These mists are very stable and can last for weeks. This is often observed, for example, in the regions of the North Caucasus. Advective fogs almost never occur during severe frosts, and they form very rarely during snow. Evaporation fogs arise as a result of the influx of water vapor due to evaporation from the water surface into the air moving above it, the temperature of which is 810 ° C or more lower than the temperature of the water. Such fogs are formed in the polar regions when cold air moves from the snowy surface to open water (open water, ice-free bay, open sea). Similarly, evaporation fogs form over rivers and lakes in autumn. Frontal fogs are fogs that occur on atmospheric fronts. There are three types: prefrontal, frontal, and postfrontal. Pre-frontal fog is formed due to the saturation of cold air under the frontal surface with moisture. The most favorable conditions for the formation of pre-frontal fog are when the temperature of the falling rain is much higher than the temperature of the cold air located near the Earth's surface. Frontal fog occurs directly when the front passes. Such a fog is a frontal cloud system that propagates to the Earth's surface; it is especially often observed when fronts pass over hills. Afrontal fog forms immediately after the passage of a warm front or warm occlusion. The formation of a frontal fog is practically no different from the conditions for the formation of an advective fog. In addition to the above main most common types of fog, others are also observed, such as: advective-radiation; mists of slopes; fumes; frosty or icy fogs.
The names of such varieties of fogs as coastal, frontal fogs of mountain slopes and valleys, urban, frosty (Siberian) already speak about the features of their formation. For example, Siberian fogs are associated with very low temperatures and a complete lull in the air. Sometimes you can watch; how a stopped person is gradually enveloped in a cloud of fog formed from his breath and evaporation from his clothes. This is explained by the fact that frosty air can hold only a very small amount of water vapor. Almost all of the moisture released is immediately converted into mist.
Meteorological range of visibility Fog is a phenomenon when water droplets or ice crystals suspended in the air reduce the visibility range to 1 km or less. Fog noticeably disturbs orientation in space. Objects lose their usual outlines, so it becomes difficult to assess their true dimensions and determine true distances (see Fig. 9). Navigators must take all measures to obtain reports and weather forecasts for the navigation area. In cases where the received forecasts are of a background nature, observation from a ship of local weather signs can be of significant help in refining the forecast. At the same time, it should be remembered: one cannot completely trust any one sign, it is necessary to evaluate all the observed phenomena in the aggregate. Observations should be systematic and continuous, especially when changing rapidly. weather conditions. It is necessary to take into account those signs that contradict big picture and find the reason for them. For meteorologists main characteristic hazy visibility in it. Not without reason, when they want to emphasize the density of the fog, they say: "Nothing is visible at arm's length." In essence, the meteorological visibility range (as it is called scientifically) is a characteristic of the intensity of fogs. If it is 500–1000 m, the fog is weak, 50–500 m is moderate, up to 50 m is strong. meteorological visibility range, m 500–1000 50–500 up to 50 fog intensity characteristic number of drops per cm3 weak moderate strong, dense 50100 100500 500 600 Deterioration of visibility of objects in fog is mainly due to light scattering. In its own way physical nature fog is like a cloud. Often one phenomenon leads to another. For example, when the fog rises, it transforms into low stratus clouds. Therefore, the optical properties of fogs are similar to those of clouds. Sunlight is well reflected from the layer of fog. Approximately 80% of the light can be reflected. But when the Sun rises higher, the reflectivity of the fog sharply
falls, it begins to warm up and dissipate. That is why fogs do not disappear at sunrise, but somewhat later. Interestingly, the mists absorb more solar radiation than clouds, which is associated with greater pollution of the receiving air layer. Around a bright light source in fog, optical phenomena associated with a special form of light scattering - diffraction can be observed. So, rainbow crowns are often observed around street lamps. Ice mists form circles around the sun and moon. To take into account the visibility of objects in the fog, it is necessary to know the signs of its approach. Here is some of them. Signs of approaching fog and its intensification: a gradual increase in absolute humidity with a simultaneous increase in relative humidity and a decrease in air temperature; high relative humidity with a slight diurnal variation and moderate air temperature without a tendency to increase continuously in the presence of fog; low atmospheric pressure, which is maintained and changes little during the day in the presence of fog; decrease in air temperature during fog; the decrease in water temperature as the ship moves through fog.
Artificial fog dissipation Fog, low overcast (see Fig. 10). Both pilots and passengers know that aircraft delays, unscheduled landings in other ports, lost time, hundreds of thousands of rubles in losses are associated with this. Is it possible to fight fogs? Scientists have proposed the following ways to deal with fogs. The artificial dissipation of fog, at least temporarily and over a limited area, has a long history. A particularly difficult nut to crack in the history of artificial scattering turned out to be warm fogs that form at temperatures above zero. For example, in England during the Second World War, oil burners were installed at six airfields along the runways. During their work, the air temperature increased, and the fog layer of several tens of meters evaporated. Horizontal visibility increased from 90-120 meters to 1200 meters. It seemed to be a success! But ... during this operation, the fuel consumption was about a thousand gallons (4,540 liters) per minute. Economically, the experiment did not justify itself and was terminated. And according to other indicators, this method is inefficient: during the combustion of fuel, water vapor is released and condensed in a large amount, and the heating system “works” to a greater extent against itself. But they learned to deal with supercooled fogs. So, at the French Orly airport, liquid propane has been affecting fogs for half a century. Of course, they are not completely scattered, but the visibility conditions are noticeably improved, which makes it easier to take off and land. They have not yet learned how to artificially “destroy” Siberian ice fogs.
The use of fogging plants in agriculture Fog also brings benefits. In the agricultural sectors, fogging installations are used, which allow you to create high-quality fog. Fog in the English interpretation is a wet wind from the sea, saturated with an aerosol of water, turning into a tangible state. The hand feels, but remains dry. Particle size 515 microns (no more). The proportion of fog should be 9095% of the total mass of water that turns into an aerosol, and it is these requirements that formed the basis for the creation of fogging installations. High-quality fog has always been and will be a product produced by high-tech equipment. The main use of fog is to create the necessary conditions for high humidity during green cuttings. Using the installation, you do not have to spend a lot of time in the greenhouse standing with a hose and constantly monitoring the humidity. Everything is done by automation, pumps and nozzles. The uniform distribution of fog over the irrigation area determines the quality of the coverage. The main indicators of the quality of the coating are the absence of large drops, which, not holding on to the plant, tend to roll off it. Fog - indispensable assistant in the accelerated production of planting material, any seedlings, growing oyster mushrooms and for many other purposes. Fogs are desirable for bath crops, for the production of seedlings of vegetables (when picking into cubes). In hot weather, poultices are desirable, followed by ventilation. The poultice effect (a one-time rise in temperature at absolute humidity) has a detrimental effect on pathogens, powdery mildew, bud and spider mites, showing a healing effect.
Together with the fog, you can pump: fertilizers, chemical protection, phytohormones, protein nutrition, growth regulators, etc. The fog is also indispensable in nursery farming. Forcing stone fruit grafts in a fog environment increases the percentage of survival (especially sweet cherries). With the reproduction of breeding achievements, the multiplication factor increases many times due to the forcing of a large biomass of propagated plants. The main consumers of fog: nursery growers, mushroom growers, vegetable growers, flower growers. Additional possibilities of application are for fire-fighting purposes, cleaning the air from dust in workshops, creating a water wall in “hot” industries for personnel, emergency use of fog in poultry houses (for indoor air cooling). Proverbs and sayings It has always been important for a person to know what the weather will be like, because it affects his activity and well-being. Observing nature in bad weather, on a sunny day, at dusk, at night, people noted the characteristic signs that precede certain changes in the weather. So there were numerous signs - witnesses of folk wisdom. Quite a lot of them are associated with the fall of fog. For example, fog spreads over the water in the morning - to good weather. This sign is interpreted as follows. In the absence of clouds at night, the earth cools more due to thermal radiation than in cloudy weather. This causes the condensation of atmospheric water vapor and, as a result, dew, the appearance of fog. Often the same physical phenomenon several proverbs and sayings of different peoples are given. Fogs also provide a basis for predicting rain or dew or fair weather. Below is only a small part of them, grouped according to various criteria. Pretty correct definitions of the essence of fog are made in Russia: Fog, the earth is vapor (Khark. Gubernia). The fog is leaving the ground. There are falling or rising fogs, morning or evening fogs, fogs in the mountains or lowlands, etc. (see Fig. 11, 12) From the fog, either dew or rain. The fog falls to the bucket; rises to disaster. The fog descended into dew. The fog lifted into a cloud.
God bless the fogs (fogs) with silence, after the fogs there are sometimes storms. The heavy dews following the fog are always considered a sign of a clear bucket day. Especially interesting for observations are fogs that creep in the early fresh morning over water or above the ground: Fog creeps in the morning along the water to good weather; rises from the water up to the rain. If in the morning the fog from the water rises in pillars, it will rain (Chuvash.). The fog that disappears after sunrise portends good weather. If fog spreads over the earth, then this portends rain the next day (mingr.). Fog, descending to the ground in winter, portends an odlyga (thaw), high above the ground, good weather (malor., Kharkov. Gub.). If the fog falls down (disappears in place) there will be a bucket (Chuvash.). As for the fog rising up or falling down, the observations of all peoples are the same and agree with the above Russians: If the fog rises, this is a sign of rain, if it settles, a sign of good weather (fr.). Fog that does not settle well moistens the earth (fr.). Fog high water low (Spanish). The banks in the fog will rain (Serb.). If fog gathers over the banks, so that from a distance it seems as if they were smoking, and if the fog lies for a long time, then, spreading, falls down, then it will rain; but if the fog, spreading, rises up, then there will be good weather (Serb.). The next series of signs concerns morning and evening fogs, fog on the mountains, in the lowlands, over the sea, over swamps, rivers, etc. The mountains brew fogs, and the plains must drink them (German). We have the following observations: if there is fog over the forest, it will rain (Podol. lips.). If, after a little rain, fog spreads over the earth, there will be more rain (Podil. Lip.). If in the summertime, after hot days, there are fresh mornings, then usually: Fogs spread along the bottoms. There are fogs on the bottoms, they don’t let you mow until the sun. Very numerous, very interesting, and quite consistent with our signs of fog among foreigners who watch the fogs that shroud the mountains or creep over the seas.
Morning fog does not portend bad weather, does not stop the traveler, but can bring a thunderstorm. Morning fog does not stop the traveler (fr.). Morning mist will definitely be a thunderstorm (Eng.). After a foggy morning, there is often a clear day (Italian). Fog at the beginning of the day for good weather (German). When the morning fog hangs over the earth, there will be fine weather, and when it rises, bad weather (German). In the mountainous regions of Siberia, there are two signs about fog: If the fog is patchy on the mountains, then there will be bad weather. If the fog from the mountains rises, then there will be a bucket. In Germany, they notice that if in the summer, after sunset, thick fog falls on rivers, streams and neighboring meadows, good weather will be established for a long time. If shortly before the full moon before sunrise it is foggy on the mountains and in the valleys, then the next day the weather will be fine and warm. Fogs are also associated with the phases of the moon: Fogs with a young and old moon promise good weather (fr.). Fog under a young moon will be good weather; fog on the damage of the moon rain in the next three days (fr.). Fogs on the young and on the old moon to the bucket, fogs on the damage (immediately after the full moon) will bring rain in three days. Until then, the fogs hold on until the sun lifts them up; sometimes it’s time for them to end; and a little mist can ruin a good day. The Germans consider thick fogs dangerous, they even increase mortality: As long as the fogs stay above the ground, until the sun lifts them up. And it's time for the fog to come down from the blue of the sea. A little mist ruins a beautiful day. In very dense fog, even the strongest light fades. Dense fog brings death and the coffin. In Italy, on the contrary, a beneficial effect is attributed to fogs: Fog clears the weather. The Italians notice that three fogs provide water. The Germans have the same sign: Three fogs are followed by one rain. According to the Serbian sign: If there is a lot of fog in autumn, then in winter there will be a lot of snow. According to the observations of the British, large fogs in winter foreshadow frost, and black fog shows the approach of rain. As has been said above, when the fog descends, dew usually appears in greater or lesser abundance. But even without fogs, there are dews in the evening and in the morning, which predict a clear day. The absence of dew is regarded as a harbinger of rain. In this regard, there is generally
he will receive a lot, and, moreover, quite agreeing among themselves, but not always justifying themselves in practice: Dew wets at dawn (rain over the pores). Rain drop by drop, dew drop by drop. God's dew sprinkles God's earth. It should be noted that one sign cannot make a reliable conclusion about the upcoming weather. All signs are approximate, due to the complexity of the processes occurring in the atmosphere. The more signs match, the more accurate the weather forecast will be. In sayings, a private judgment, expressed by a hint or a half-hint, becomes complete, generalizing if they use artistic definitions - epithets. For example: Fog in my eyes, I see everything in a fog (cloudy, dark, unclear, like in smoke). Let fog, set fog (splurge, fool). He has a fog in his head (thoughts are unclear, confused). The fog dissipates - the wolf does not like it (the possibility of deception disappears). Conclusion Perhaps, fogs are of particular concern today to airport controllers, workers of sea and river ports, pilots, ship captains, car drivers and, of course, a huge army of meteorologists and weather forecasters. "Attention! Visibility on the roads is up to 1 km,” the weather service warns us on the radio. This means that light fog is expected. With moderate fog, visibility decreases to hundreds of meters, and with heavy fog, up to several tens of meters. And then airfields are temporarily closed, ships anchor, lighthouse sirens turn on. I learned a lot about fogs and answered all my questions. The fog is awesome natural phenomenon with which one has to reckon. Despite the time spent, I really enjoyed working on this essay. The study of this topic personally helped me to plunge deeper into interesting world nature.
The issues of using fogs have not yet been fully studied and, therefore, the research of scientists in this area is quite a promising occupation. Glossary Advective fog fog resulting from the cooling of warm, moist air over colder land or water surfaces when the temperature of the air mass falls below the dew point. The water content of the fog is the total mass of all water droplets per unit volume of fog. Dynamic equilibrium is a state in which the number of molecules emitted from the surface of the liquid per unit time is equal to the number of molecules returning back. Haze is a slight turbidity of the air near the earth's surface, caused by the scattering of light on the smallest droplets (their diameter is less than 1 micron) of water or ice crystals; rudimentary cloud layer.
An ion is an atom with an excess or deficiency of electrons. Evaporation is the formation of vapor from the free surface of a liquid. Condensation is the process of the transition of a substance from a liquid state to a gaseous state. Haze cloudiness of the air of the lower layers of the atmosphere due to the presence of suspended aerosol particles of dust, smoke, burning, etc. in it. In heavy darkness, the visibility range drops, as with fog. Meteorological elements characterizing the state of air and atmospheric processes: temperature, pressure, air humidity, wind, cloudiness and precipitation, visibility range, fogs, thunderstorms, etc.; as well as the duration of sunshine, temperature and condition of the soil, height and condition of the snow cover, etc. Observations of meteorological elements are carried out at meteorological stations. Drizzle – fog drops are relatively large, about 100 µm in diameter. Saturated steam is steam that is in a state of dynamic equilibrium. Sea soaring fog over the surface of the sea, river or lake, appearing in the cold season, when the water temperature is higher than the air temperature. Supersaturated steam is a state of steam in which the intensity of the condensation process prevails over the intensity of evaporation. A proverb is a short saying, widespread among the people, figuratively defining an object and phenomenon according to their characteristic features. A proverb is a judgment that contains a complete thought, arises from observations verified by life. Density - physical quantity, showing what is the mass per unit volume. Radiation fog is fog that results from the radiative cooling of the earth's surface and a mass of moist ground air to the dew point. Smog is an extreme form of radiation fog that occurs in industrial areas. The dew point is the temperature at which water vapor reaches saturation. Fog is the accumulation in the surface layer of the atmosphere of the smallest drops of water or ice crystals suspended in the air, which are formed as a result of: condensation of water vapor when the air cools below the dew point (cooling fogs); or evaporation with a warmer evaporating
surfaces into cold air over water bodies and wet land areas (evaporation fogs). Condensation nuclei are individual molecules (clusters of molecules), ions, water droplets, dust particles, soot particles, and in general all kinds of small contaminants that are in the air for one reason or another. LV Tarasov Physics in nature: a book for students. - M.: "VerbumM", Literature 2002 V. I. Elkin Original lessons in physics and teaching methods / Comp. E. M. Bravermann. – M.: ShkolaPress, 2001
LD Landau, AI Kitaygorodsky Physics for all: Molecules. - 6th ed., erased. M.: Science. The main edition of physical and mathematical literature, 1984 My first scientific experiments on the publication of My Book of Science Experiments, "Publishing Group" Content "with the assistance of CJSC" Publishing House Christina - new Age”, 2003 SA Tikhomirova Physics in proverbs and sayings, poetry and prose, fairy tales and anecdotes. A guide for the teacher. M.: Novaya shkola, 2002 AP Usoltsev Problems in physics based on literary subjects. - Ekaterinburg: UFaktoriya, 2003 I. G. Kirillova Book for reading in physics: Proc. allowance for students 67 cells. avg. school / Comp. I. G. Kirillova, M .: "Enlightenment", 1986 S.V. Gromov, N.A. Homeland Physics: Proc. For 8 cells. general education institutions. - M.: Enlightenment, 1999 L.S. Khizhnyakova, A.A. Sinyavina Physics: Mechanics. Thermodynamics and molecular physics: Proc. For 8 cells. general education institutions. - M .: Vita Press, 2000 A.E. Gurevich Physics. The structure of matter. Grade 7: Proc. For general education educational institutions. - M .: Bustard, 2000 V.I. Dal Dictionary Russian language. Modern version. M .: Izdvo EKSMOPress, 2001 Polar truth No. 21 dated 02/17/2006
Fog. The reasonsoccurrence
The work was done by a student of the 2nd
course
Anokhina Yana Fog - atmospheric
event, accumulation
water in the air when
the smallest
condensation products
water vapor (at
air temperature
above −10° -
tiny droplets
water, at −10..−15° -
mixture of water droplets and
ice crystals,
temperatures below −15°
- ice crystals
sparkling in the sun
beams or in the light of the moon and
lanterns). General information
Relative humidity
in fogs it is usually close to 100
% (at least exceeds
85-90%). However, in strong
frosts (−30° and below) in
settlements, on the
railway stations and
airfields, fogs can
be observed at any
relative humidity
(even less than 50%) - due to
water vapor condensation
formed during combustion
fuel (in engines, furnaces, etc.)
etc.) and thrown into
atmosphere through the exhaust
pipes and chimneys.
continuous duration
fog is usually from
several hours (and sometimes
half an hour to an hour) up to several days,
especially during the cold season
of the year. The fogs obstruct
normal operation of all
modes of transport
(especially aviation),
so fog forecast
has a large national economic
value.artificial
creating fogs
used in scientific
research, in
chemical
industry,
heat engineering, anti-
plant pests and
other areas. Varieties of fog
The following types of fog are noted at weather stations:
Translucent
fog
continuous fog
underground fog ground mist
Ground mist - mist, low
creeping over the earth
surface (or body of water)
continuous thin layer or
the form of separate shreds, so that in
fog layer horizontal
visibility is less than 1000
m, and at the level of 2 m - exceeds
1000 m (usually as
in haze, from 1 to 9 km, and sometimes
10 km or more). It is observed as
usually in the evening, night and
morning hours. Separately
marked ground ice
fog - observed at
air temperature below
−10..−15° and consisting of
ice crystals sparkling in
sunshine or moonlight
and lanterns. translucent fog
translucent fog - mist with
level visibility
2 m less than 1000 m (usually it
is several hundred meters, and
in some cases even reduced to
several tens of meters), weakly
it is possible to determine the state of the sky
(number and shape of clouds). More often
observed in the evening, at night and in the morning,
but can also be seen during the day
especially during the cold season
rise in air temperature.
Translucent
ice fog - observed at
air temperature below −10..−15° and
sparkling in the sun or
the light of the moon and lanterns. continuous fog
Fog - continuous fog with
horizontal visibility to
2 m level less than 1000 m (usually
it is several hundred
meters, and in some cases
reduced even to a few
tens of meters), enough
developed vertically, so that
impossible to determine
sky condition (number and
cloud shape). More often
observed in the evening, at night and
in the morning, but can be observed and
during the day, especially when it's cold
half a year with an increase
air temperature. Separately
icy fog is noted -
observed at temperature
air below −10..−15° and
made up of ice crystals
sparkling in the sun
or in the light of the moon and lanterns. Fog classification
By way
occurrence of fog
are divided into two types:
Cooling fogs -
are formed due to
water condensation
steam on cooling
air below the point
dew. dew
Mists of evaporation -
are vapors from
warmer
evaporating
surfaces in cold
air over water and
wet areas
sushi. In addition, fog
differ in
synoptic
conditions
education:
Intramass -
emerging in
homogeneous
air masses.
Frontal -
formed on
borders
atmospheric
fronts. Inside the massive fogs
sea mist
Radiation fogs
Advective fogs Radiation fogs
fogs that appear in
radiation
cooling of the earth's surface
and masses of wet ground
air to the dew point. Usually
radiation mist arises
at night in anticyclone conditions
in clear weather and
light breeze. Often
radiation mist arises
under conditions of temperature
inversion preventing
rise in air mass.
After sunrise
radiation fogs are usually
quickly dissipate. However, in
cold season in
stable anticyclones they
can persist during the day, sometimes
many days in a row. AT
industrial areas can
an extreme form
radiation fog - smog. Advective fogs
formed as a result of cooling
warm moist air
moving over colder
land or water surface. Them
intensity depends on the difference
temperature between air and
underlying surface and
air moisture content. These
fogs can develop as over
by sea and over land and cover
huge spaces, in separate
cases up to hundreds of thousands of km².
Advective fogs are usually
occur on cloudy days and
most often in warm sectors
cyclones. Advective fogs
more stable than
radiation, and often not
scattered during the day. sea fogs
advective fog,
emerging from the sea
during the transfer
cold air on
warm water. This
fog is
evaporation mist.
Fogs of this type
frequent, for example,
Arctic when the air
comes from the ice
cover for open
sea surface. Frontal and dry fogs
Frontal fogs
EditFrontal fogs form near
atmospheric fronts and move with them.
Air is saturated with water vapor due to
evaporation of precipitation falling in the front zone. some
plays a role in strengthening the fog in front of the fronts
the drop in atmospheric pressure observed here,
which creates a slight adiabatic depression
air temperature.
Dry fogs
EditTo the mists in colloquial speech and in
fiction is sometimes referred to as the so-called
dry fogs (haze, haze) - significant deterioration
visibility due to the smoke of forest, peat or steppe
fires, or due to loess dust or part of the sand,
lifted and carried by the wind, sometimes to considerable
distance, as well as due to industrial emissions
enterprises. Not rare is the transitional stage between dry and
wet fogs - such fogs consist of water
particles together with sufficiently large masses of dust, smoke and
soot. These are the so-called dirty, city fogs,
resulting from the presence in the air of large
cities masses of particulate matter emitted during combustion
smoke, and even more - factory
pipes. Why does fog appear?
Many would be interested
find out why it appears
fog, and what is he like
represents. mist
called
meteorological phenomenon,
during which in the air
there is a high
water vapor concentration. AT
warm weather fog
represents
accumulation of small drops
water, and in the cold to them
small
ice crystals that
in sunlight may
shine. Fog formation mechanism
The formation of fog occurs at those moments
when cold air meets warm air
humidity over 85%. In towns this
The phenomenon can also occur when relatively
little humidity. This happens in
as a result of the condensation of water vapor,
arising from the combustion of various types
fuel. It should be noted that the origin
fog is not always natural, it can
be artificial. Such mists wear
the name of the radiation. They are formed due to
air cooling under the influence of radiation.
Natural fogs have a denser
consistency than artificial ones, but
duration they can be from several
hours to several days. In fact, the fog
call it a cloud that forms over
ground or water surface. Most often fog
appears in lowlands and over reservoirs early
in the morning or at night. Why is it happening
exactly? This is because when it's cold
air comes into contact with warm soil or water,
moisture begins to condense and
drops of water just hangs in the atmosphere. In
the place where fog occurs, the relative
humidity approaches 100%. The structure of fog is directly dependent on temperature.
air. At temperatures above -10 degrees cloud
consists of very small drops of water, from -10 to -15
degrees is a mixture of water and the smallest
ice crystals, if the temperature is below -15
degrees, then the cloud will consist entirely of
ice crystals. As for the inhabitants
points, then the fog will be denser there due to
condensation of steam from exhaust gases. By level
visibility fogs can be divided into several
types: haze, ground, translucent and
solid. A very faint cloud is called haze.
Ground fog is the one that spreads along
surface of water or land with a thin continuous
layer and has little effect on visibility. Visibility
with translucent fog, it ranges from tens
up to hundreds of meters, but through it you can see
clouds, sky, moon and stars. As for the continuous
fog, then it is a whitish cloud,
through which it is almost impossible to see
even large objects at a distance of tens
meters. Being in it, one can feel very tangibly
dampness, as well as almost impossible to see
clouds, sky and sun. This phenomenon makes it difficult
movement of many modes of transport, in particular
aircraft.
Research topic: "Fog" 1st grade student Daria Sergeevna Mavritseva Supervisor: Petoshina O.S. MOU "Average comprehensive school#4 with in-depth study objects of the artistic and aesthetic cycle "Murom district of the Vladimir region
Know what is fog? Explain the causes of different types of fog. Conduct a practical study: the formation of fog at home.
Worked with reference literature; Turned to Internet resources; Conducted experiments on the creation of fog at home.
This is an atmospheric phenomenon that makes the air less transparent, cloudy, and objects become hard to see. In other words, it is a cloud at the surface of the earth. Fog is the accumulation in the surface layer of the atmosphere of the smallest drops of water or ice crystals suspended in the air, which are formed as a result of: - condensation of water vapor when the air cools below the dew point (cooling fogs); or - Evaporation from a warmer evaporating surface into cold air over bodies of water and wet land areas (evaporative fogs).
S. Yesenin: The fields are compressed, the groves are bare, Fog and dampness from the water ... A spicy wind. Dawns go out. Fog creeps over the grass. A.S. Pushkin: "The light of the day went out, On the blue evening fog fell."
First example. The cooled morning air adjacent to the water has a lower temperature than water. Therefore, from the warm water surface, cold air evaporates an additional amount of steam. The result is an evaporation mist.
Second example. Here, additional steam is evaporated into relatively cold air (which is above the surface of the ice) from a relatively warm surface, which is in this case open water surface. As in the previous example, we are dealing here with evaporative fog.
Third example. Warm air, heated in winter over river water, is enriched with moisture, and then cools over a snow-covered shore or over sea water. In both cases, a cooling mist occurs.
Fourth example. Warm layers of air, enriched with moisture, rise up and are strongly cooled. A cooling fog develops, which then descends down the mountainside back to the sea.
Fifth example. Due to the transfer of heat from the heated layer of near-surface air to the rapidly cooling ground, the air cools and a typical cooling fog occurs.
I will need: An empty bottle with a narrow neck Hot water A few drops of alcohol Ice cubes Dropper
To make fog, I first filled the decanter by a third hot water. Dropped a few drops of alcohol into the decanter with a pipette. She took an ice cube and held it over the neck of the decanter. A mist formed in the decanter.
Fog is formed when cold air and warm earth. As a result of such a collision, the water that evaporates on contact with the warm earth rises again into the cold air, slows down and condenses. Fog comes in several forms. Learned how to create fog at home
1 of 15
Presentation on the topic: How does fog form?
slide number 1
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slide number 3
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slide number 4
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What is fog? Fog is a form of condensation of water vapor in the form of microscopic drops or ice crystals, which, gathering in the surface layer of the atmosphere (sometimes up to several hundred meters), make the air less transparent. Fog formation begins with the condensation or sublimation of water vapor on condensation nuclei - liquid or solid particles suspended in the atmosphere. Water droplets are observed mainly at air temperatures above -20 °C, but can occur even at temperatures below -40 °C. At temperatures below -20 °C, ice fogs predominate. The largest number of foggy days at sea level - an average of more than 120 per year - is observed on the Canadian island of Newfoundland in Atlantic Ocean. Fogs in populated areas are more common than far from them. This is facilitated by the increased content of hydroscopic condensation nuclei (for example, combustion products) in the urban air. Fogs impede the normal operation of all modes of transport, so fog forecasts are of great national economic importance. Artificial fogging is used in scientific research, in the chemical industry, heat engineering and other areas.
slide number 5
Description of the slide:
What causes fogs? Any fog, as a rule, arises under the influence of several factors. On this basis, a genetic classification of fogs is built. A decrease in air temperature is one of the main causes of water vapor condensation both near the earth's surface and in the free atmosphere. Due to the decrease in temperature, the most intense fogs are formed. Depending on the type of process leading to cooling, there are: radiative and advective fogs and orographic fogs. Radiation fogs are formed as a result of the cooling of the earth's surface and the adjacent air layer under the influence of radiation and turbulent mixing. It is usually believed that during the formation of radiation fogs, the proportion of water vapor remains almost constant when the air is cooled to the dew point. A decrease in temperature below the dew point is accompanied by condensation of water vapor, which leads to a decrease in the proportion and pressure of water vapor. For fog to form, a certain amount of water vapor must condense. Favorable conditions for the formation of radiation fogs are: the absence of clouds or the presence of clouds only in the upper tier. An increase in the number of clouds and a decrease in their height leads to an increase in the counter-radiation of the atmosphere and a decrease in the effective radiation of the earth's surface, which does not contribute to the cooling of the latter; high relative humidity at the initial moment. The higher the relative humidity, the less cooling is required to achieve saturation and fog formation.
slide number 6
Description of the slide:
Artificial fog. The artificial creation of fogs is used in scientific research, in the chemical industry, heat engineering and other fields. How Artificial Fog Helps agriculture? Most efficient technology growing plants is a method of green cuttings, which can propagate many plants - roses, chrysanthemums, grapes, many fruit and berry crops, even tomatoes. In order for the plant to take root, the air humidity must be close to 100%, because. green cuttings with leaves do not have their own root system and moisture, as well as nutrition, can only be obtained through the leaves. Therefore, seedlings are grown in greenhouses, where from time to time water is sprayed, supplied under pressure of several tens of atmospheres, forming a fog consisting of droplets no larger than 30 microns in size. Fog from larger droplets quickly settles. Fog in a greenhouse not only saturates the air with moisture, but can also lower the temperature in it by several tens of degrees, taking away the heat necessary for evaporation, which makes it possible to use greenhouses in hot climates. In outdoor cultivation, the creation of artificial fog during night frosts directs the heat radiated from the Earth to warm the plants. This is due to the fact that water vapor intensely absorbs infrared radiation.
slide number 7
Description of the slide:
1) Types of fogs. According to the method of occurrence, fogs are divided into two types: Cooling fogs - are formed due to the condensation of water vapor when the air is cooled below the dew point. Evaporation fogs are evaporation from a warmer evaporating surface into cold air over water bodies and wet land areas. In addition, fogs differ in synoptic conditions of formation: Intramass - formed in homogeneous air masses. Frontal - formed at the boundaries of atmospheric fronts.
slide number 8
Finding yourself in the middle of a white continuous cloud, so dense that it is almost impossible to distinguish anything at arm's length, you often ask yourself the question: why such a dense fog formed, why is it white and you start to think about how long this phenomenon usually lasts, and also why any fog dissipates.
Fogs form when droplets or ice crystals accumulate in the air in the lower layers of the atmosphere, which causes a cloud-like veil to form along the earth's surface, limiting visibility so much that space is not visible beyond one kilometer, and in some cases objects become difficult to distinguish even at a distance several meters.
If the temperature environment exceeds -10°С, the vapor veil consists only of droplets. If the temperature fluctuates from -10 to -15 ° C - from water droplets and ice crystals, and when it is -15 ° C outside - the fog consists of small ice crystals shimmering in the light of night lights.
Why this phenomenon is formed is not difficult to answer: it owes its appearance either to the evaporation of water from a warm surface into cold air, or to the cooling of warm air streams saturated with moisture. For example, the formation of terrestrial clouds can often be observed in the evening or in the morning after the temperature of the soil and vegetation (grass) drops, the lower layers of the atmosphere cool so much that they begin to release excess moisture in the form of water droplets.
Another example, this time in winter, is fog over a river, lake or other body of water, on the ice of which an ice hole has formed: in frosts, there is always a veil over it, spreading over the water surface. This happens because the temperature of the water during frosts is warmer than the surrounding ice and the air in contact with it (because of this, the air above the water is always warmer than the rest, and there is almost always fog over the river in the area of the hole).
After the warm air mixes with cold air currents, it begins to cool, releasing steam and forming a cloud at the very surface of the Earth. Therefore, the fog over the river and other bodies of water is usually stable and long-lasting: cold and warm air currents and currents are constantly mixed here.
A striking example of this phenomenon is the Canadian island of Newfoundland located in the Atlantic Ocean. Due to the fact that two currents collide with each other here - the warm Gulf Stream and the cold Labrador, locals forced to spend among the haze about one hundred and twenty foggy days a year.
Formation of terrestrial clouds
When water-saturated air cools or mixes with colder air currents, droplets begin to form in the atmosphere. After that, if there is earth's surface the smallest particles of dust, they begin to stick to them, layering on each other and forming drops more large sizes(the more dust in the air, the faster the cloud forms, so big cities almost always shrouded in a faint, almost imperceptible veil).
In the warm season, the size of such a drop varies from 5 to 15 microns, during frosts - from 2 to 5 microns, so winter cold fog is not as thick as summer. As soon as the drops reach the required volumes, the objects turn out to be vague and difficult to distinguish: the air becomes whitish with a strong fog and bluish with a weak one.
The answer to the question why this phenomenon comes in different colors is simple: smaller drops scatter short blue rays better, while in dense terrestrial clouds, larger drops and light waves scatter all rays equally, regardless of their length.
The water content of such clouds usually does not exceed 0.5 g/m3, but sometimes thick fog can contain up to 1.5 g/m3 (this water is enough for plants to get the necessary moisture, this is especially important for the vegetation of arid regions of the planet). How impenetrable the shroud will be depends largely on the humidity of the air, which during the formation of terrestrial clouds usually ranges from 85 to 100%:
- if visibility does not exceed 50 meters, dense fog is observed, and the number of drops is 1200 per cubic centimeter;
- if the space is viewed at a distance of 50 to 500 meters - moderate (water drops in this case from 100 to 600);
- if visibility is a kilometer - weak (drops - from 50 to 100).
Fogs are also frequent during frosts, and the phenomenon can be seen even when the humidity does not exceed fifty percent. They are commonly seen in cities, especially at train and bus stations, where the veil is formed by the steam generated during fuel combustion and released into the air through chimneys and exhaust pipes.
Kinds
Terrestrial clouds do not always owe their origin only to nature: big number fogs arise in cities, and therefore they consist not only of drops and dust, but also of smoke, soot, which are emitted by factory or chimneys, or arise after or during fires when forest, peat or steppe burns. By origin, meteorologists divide fogs into dry (smoke, soot, etc. are to blame for their formation) and wet (only water and dust are involved), while often the second form flows into the first.
In turn, wet fogs, the formation of which was directly influenced by nature, are evening, night or morning fog (this is the period that is optimal for the appearance of clouds creeping along the ground), meteorologists are also divided into groups:
- Underground. Evening or morning fog that hangs low over the earth's surface or a body of water (for example, fog over a river). The veil can be continuous, or it can go in separate shreds, and visibility will not exceed a kilometer.
- translucent. Despite the fact that visibility along the surface is low and in some cases does not exceed a few meters, it is quite possible to distinguish clouds in the sky. This type includes night, evening, and morning fog.
- Solid. The visibility of the dense fog is very limited and often does not exceed fifty meters. The sky is almost invisible, so the clouds are almost impossible to distinguish. This is mainly evening, night and morning fog, and during cold weather, with an increase in temperature, cold fog can be seen during the day.
Why do fogs disappear
The duration of this phenomenon is different and can range from half an hour to several days (especially during cold weather or when warm and cold air and water flows collide, for example, fog over a river). The main reason why any fog dissipates is the heating of the air. Since the veil forms near the surface, after the sun's rays warm it up, the air also heats up, as a result of which the droplets evaporate and turn into steam.
The higher above the earth's surface, the weaker the fog dissipates, as in the upper layers of the atmosphere the air temperature begins to drop again, the vapor is converted into water droplets and forms clouds.
