The atmosphere is heterogeneous. In its composition, especially near the earth's surface, air masses can be distinguished.
Air masses are separate large volumes of air, which have certain common properties (temperature, humidity, transparency, etc.) and moving as one. However, inside this volume, winds can be different. The properties of the air mass are determined by the area of \u200b\u200bits formation. It acquires them in the process of contact with the underlying surface, above which it is formed or delayed. Air masses have different properties. For example, the air of the Arctic is low, and the air of the tropics are high temperatures in all seasons of the year, the air of the North Atlantic is significantly different from the air of the mainland Eurasia. The horizontal size of the air masses is huge, they are commensurate with the mainland and oceans or their large parts. The main (zonal) types of air masses are distinguished, forming in belts with different atmospheric pressure: arctic (antarctic), moderate (polar), tropical and equatorial. Zonal air masses are divided into marine and continental - depending on the nature of the underlying surface in the area of \u200b\u200btheir formation.
The Arctic air is formed over the Arctic Ocean, and in the winter and above the North of Eurasia and North America. Air is characterized by low temperature, low moisture content, good visibility and stability. Its invasion of moderate latitudes cause significant and sharp cooling and determine predominantly clear and cloudless weather. The Arctic air is divided into the following varieties.
Marine Arctic Air (MAV) is formed in a warmer European Arctic free from ice, with a higher temperature and large moisture content. His invasion of mainland in winter cause warming.
Continental Arctic air (KAV) is formed above the central and eastern Ice Arctic and the northern coast of the mainland (winter). Air has very low temperatures, low moisture content. The invasion of Kav on the mainland determines the strong cooling with clear weather and good visibility.
The analogue of the arctic air in the southern hemisphere is the Antarctic air, but its effects is distributed mainly on the surrounding sea surfaces, less often - on the southern tip of South America.
Moderate (polar) air. This is the air of moderate latitudes. It also distinguishes two subtypes. Continental moderate air (CU), which is formed over the extensive surfaces of the mainland. In winter, it is very cooled and stable, the weather is usually clear with strong frosts. In the summer, he strongly warms up, ascending currents arise, clouds are formed, it is often raining, thunderstorms are observed. Sea moderate air (muv) is formed in medium latitudes over the oceans, western winds and cyclones are transferred to the continent. It is characterized by high humidity and moderate temperatures. In winter, MOV brings cloudy weather, abundant precipitation and temperature increase (thaw). In the summer, he also brings more clouds, rains; The temperature drops with its invidence.
Moderate air penetrates polar, as well as subtropical and tropical latitudes.
The tropical air is formed in tropical and subtropical latitudes, and in the summer - both in the continental districts in the south of moderate latitudes. There are two subtype of tropical air. Continental tropical air (KTV) is formed above the land, characterized by high temperatures, dryness and dusting. Sea tropical air (MTV) is formed over tropical waters (tropical areas of the ocean), differs in high temperature and humidity.
Tropical air penetrates moderate and equatorial latitudes.
Equatorial air is formed in the equatorial zone from the tropical air, which arrived by the trade winds. It is characterized by high temperatures and high humidity within the course of the year. In addition, these qualities are preserved and above the land, and above the sea, therefore, equatorial air is not divided into marine and continental subtypes.
Air masses are in continuous motion. At the same time, if the air masses move into higher latitudes or on a colder surface, they are called warm, as they bring warming. Air masses moving into lower latitudes or on a warmer surface are called cold. They bring cooling.
Moving to other geographic areas, air masses gradually change their properties, primarily temperature and humidity, i.e. Transfer to the air masses of another type. The process of converting air masses from one type in another under the influence of local conditions is called transformation. For example, tropical air, penetrating the equator and moderate latitudes, is transformed accordingly into equatorial and moderate air. Sea moderate air, being in the depths of the continents, is cooled in winter, and in the summer heats up and always drags, turning into continental moderate air.
All air masses are related to each other in the process of their constant movement, in the process of total circulation of the troposphere.
Aerial masses - large air volumes at the bottom of the earth's atmosphere - a troposphere that have horizontal dimensions of many hundreds or several thousand kilometers and vertical dimensions of several kilometers, characterized by the approximate homogeneity of temperature and moisture content horizontally.
Views:Arcticor antarctic air (AV), Moderate air (HC), Tropical air (TV), Equatorial air (EV).
Air in the ventilation layers can be moved as laminar or turbulent Flood. Concept "laminar" This means that individual air flows are parallel to each other and move in the ventilation space without twist. When turbulent flow Its particles are moving not only in parallel, but also make a transverse movement. This leads to a vortex formation throughout the sequence of the ventilation channel.
The condition of the air flow in the ventilation space depends on: Air flow velocities, air temperature, ventilation channel cross-sectional area, shape and surface of building elements on the border of the ventilation channel.
In the earth's atmosphere, there are air movements of a wide variety of scales - from dozens and hundreds of meters (local winds) to hundreds and thousands of kilometers (cyclones, anticyclones, monsimes, trade winds, planetary front zones).
The air is continuously moving: it rises - ascending movement, lowered downward movement. The air movement in the horizontal direction is called the wind. The cause of the wind is an uneven distribution of air pressure on the ground surface, which is caused by an uneven temperature distribution. In this case, the air flow moves from places with a large pressure to the side, where the pressure is less.
Under the wind, the air is moving not evenly, but impulses, gust, especially at the surface of the Earth. There are many reasons that affect air movement: the friction of the air flow on the surface of the Earth, meeting with obstacles, etc. In addition, air flows under the influence of the Earth's rotation are denied in the northern hemisphere to the right, and in South - left.
Coming in areas with other thermal properties of the surface, air masses are gradually transformed. For example, sea moderate air, entering the land and moving into the mainland deep, is gradually heated and drained, turning into continental. The transformation of the air masses is especially characteristic of moderate latitudes, in which from time to time invades warm and dry air from tropical latitudes and cold and dry - from the sugar
The interaction of the ocean and the atmosphere.
27. Circulation of air masses.
© Vladimir Kalanov,
"Knowledge is power".
The movement of air masses in the atmosphere is determined by the thermal regime and a change in air pressure. A combination of major air flows over the planet is called total atmospheric circulation. Major large-scale atmospheric movements, aligning atmospheric circulation: air flow, jet flows, air flows in cyclones and anticyclones, trade winds and monsoons.
Air movement relative to the earth's surface - wind - It appears because the atmospheric pressure in various places of air mass is different. It is believed that the wind is a horizontal movement of air. In fact, the air is usually moving not parallel to the surface of the earth, but at a low angle, because Atmospheric pressure changes in horizontal and in vertical directions. Wind direction (North, South, etc.) means where the wind blows. Under the power of the wind, its speed is implied. What she is higher, the wind is stronger. Wind speed is measured on meteorological stations at an altitude of 10 meters above the earth, in meters per second. In practice, the strength of the wind is evaluated in points. Each score corresponds to the two or three meters per second. With the strength of the wind, in 9 points it is already considered a storm, and with 12 ballasts - hurricane. Comable term "storm" means any very strong wind, regardless of the number of points. The speed of strong wind, for example, in tropical hurricane, reaches huge values \u200b\u200b- up to 115 m / s or more. The wind increases on average with a height. At the surface of the earth, its speed is reduced by friction. In winter, the wind speed is generally higher than in the summer. The greatest wind speeds are observed in moderate and polar latitudes in the troposphere and the lower stratosphere.
The pattern of changing the wind speed over the continents at small heights (100-200 m) is not entirely clear. Here the wind speeds reaches the biggest values \u200b\u200bof the afternoon, and the smallest - at night. It is observed best in the summer.
Very strong winds, to storm, there are afternoon in the deserts of Central Asia, and at night there comes a full calm. But already at an altitude of 150-200 m, the opposite picture is observed: maximum speed at night and at least in the afternoon. The same picture is observed in summer, and in winter in moderate latitudes.
A lot of trouble can bring a gusty wind to pilots of airplanes and helicopters. Air jets moving in various directions, jesters, gust, then weakening, then intensifying, create a big obstacle to the movement of aircraft - a boltne appears - a dangerous violation of normal flight.
Winds, which are made from the mountain ranges of the lambed mainland towards the warm sea, are called boro.. It is a strong, cold, gusty wind that is usually in the cold season.
Many famous boron in the area of \u200b\u200bNovorossiysk, on the Black Sea. It created such natural conditions that the boards speed can reach 40 and even 60 m / s, and the air temperature decreases to minus 20 ° C. Bohr occurs most often in the period from September to March, on average 45 days a year. Sometimes it was the consequences of it: the harbor frozen, the ice covered the ships, the buildings, the embankment, the roofs were broken, the wagons were tipped off, the shores were dropped ashore. Bora is observed in other areas of Russia - on Baikal, on a new land. Known boron on the Mediterranean coast of France (there it is called Mistral) and in the Gulf of Mexico.
Sometimes in the atmosphere there are vertical vortices with rapid spiral air movement. These vortices are called tornadoes in America). Solorals are a diameter of several tens of meters, sometimes up to 100-150 m. Measure the speed of the air inside the tornado is extremely difficult. According to the nature of the damage produced by the estimates of the speed, 50-100 m / s may well be, and in particularly strong vortices - up to 200-250 m / s with a large vertical component of speed. Pressure in the center of a rising torn riser drops a few tens of millibars. Millibars for determining pressure are usually used in synoptic practice (along with millimeters of mercury pillar). To transfer bars (millibar) in mm. Mercury pillar exist special tables. In the system, the atmospheric pressure is measured in hectopascals. 1GPa \u003d 10 2 Pa \u003d 1MB \u003d 10 -3 bar.
Solorals exist for a short time - from a few minutes to several hours. But for this a short time they have time to do a lot of trouble. At the approach of the tornado (above the sludge is sometimes called tombami) to buildings the difference between pressure inside the building and in the center of Tromba leads to the fact that the buildings are exploded from the inside - the walls are destroyed, the glasses and frames are destroyed, the roofs take off, sometimes without human Victims. There are cases when people, animals, as well as various items of tornado lifts into the air and tolerates dozens, or even hundreds of meters. In its movement, the tornadoes are moving away for several tens of kilometers over the sea and even more - above the land. The destructive power of tornadow over the sea is less than above the land. In Europe, the clomes are rare, more often they arise in the Asian part of Russia. But especially frequent and destructive tornadoes in the United States. About Tornado and Tornado Read Advanced on our website in the section.
Atmospheric pressure is very changeable. It depends on the height of the air column, its density and acceleration of gravity, which varies depending on geographic latitude and height above sea level. The air density is called the mass of its volume. The density of wet and dry air is noticeably different at high temperatures and high humidity. When the temperature decreases, the density increases, with a height of the air density decreases slower than the pressure. Air density is usually not directly measured, but calculated by equations based on measured temperatures and pressure values. Indirectly air density is measured in the braking of artificial satellites of the Earth, as well as from observations of the vague of artificial clouds from sodium vapors created by meteorological missiles.
In Europe, the air density at the surface of the earth is 1.258 kg / m 3, at an altitude of 5 km - 0.735, at an altitude of 20 km - 0.087, and at an altitude of 40 km - 0.004 kg / m 3.
The shorter of the air column, i.e. The higher the place, the pressure is less. But the decrease in air density with a height complicates this dependence. The equation expresses the law of pressure changes with a height in a resting atmosphere is called the basic equation of statics. It follows from it that with an increase in height, the pressure change is negative, and when the pressure drop in the same height is the greater, the greater the more air density and the acceleration of gravity. The main role here belongs to changes in air density. From the main equation of statics, you can calculate the value of the vertical pressure gradient, showing the change in pressure when moving per unit height, i.e. decrease in pressure per unit distance vertical (MB / 100 m). The pressure gradient is a force leading to air. In addition to the power of the pressure gradient in the atmosphere, inertia (Coriolis strength and centrifugal), as well as the friction force. All air flows are considered regarding the Earth, which revolves around its axis.
The spatial distribution of atmospheric pressure is called a baric field. This is a system of surfaces of equal pressure, or isobaric surfaces.
Vertical section of isobaric surfaces over the cyclone (H) and anticyclone (B).
Surfaces were carried out at equal pressure intervals P.
Isobaric surfaces can not be parallel to each other and the earth's surface, because The temperature and pressure are constantly changing in the horizontal direction. Therefore, the isobaric surfaces have a diverse appearance - from the downstream "Kotlovin" flashed down to the extended "hills".
When crossing the horizontal plane of isobaric surfaces, curves are obtained - isobars, i.e. Lines connecting points with the same pressure values.
Maps areobar, which are built according to the results of observations at a certain point in time, are called synoptic maps. Maps of the isobar, compiled on average perennial data for the month, season, year, are called climatological.
Perennial medium cards of absolute topography of the isobaric surface 500 MB for December - February.
Heights in geopotential decamers.
On the synoptic maps between isobami, an interval was taken equal to 5 hectopascals (GPA).
On the cards of a limited area of \u200b\u200bIsobara can be broken, but on the map of the entire globe, each isobar, naturally, is closed.
But on a limited map, there are often closed isobars that limit the plots of low or high pressure. Reduced pressure in the center - this cyclones, and areas with relatively high pressure are anticyclones.
Under cyclone understand A huge vortex in the lower layer of the atmosphere, which has a low atmospheric pressure in the center and the ascending movement of the air masses. In the cyclone, the pressure increases from the center to the periphery, and the air is moving counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. The ascending movement of air leads to the formation of clouds and to precipitation. From space, cyclones look in the form of twisting cloud spirals in moderate latitudes.
Anticyclone - This is a high pressure area. It occurs simultaneously with the development of the cyclone and is a whirlwind with closed isobami and the highest pressure in the center. The winds in the anticyclone are shown clockwise in the northern hemisphere and counterclockwise - in southern. In Anticyclone, there is always a downward movement of air, which prevents the emergence of powerful cloudiness and prolonged precipitation.
Thus, large-scale atmospheric circulation in moderate latitudes is constantly reduced to education, development, movement, and then to the attenuation and disappearance of cyclones and anticyclones. Cyclones arising from the front separating warm and cold air masses move towards the poles, i.e. Put warm air into polar latitudes. On the contrary, anticyclones arising in the rear of cyclones in the cold air mass, move into subtropical latitudes, carrying cold air there.
Average 75 cyclones arise over the European territory of Russia per year. The cyclone diameter reaches 1000 km and more. In Europe, in the year, an average of 36 anticyclones, some of which have pressure in the center of more than 1050 GPa. The average pressure in the northern hemisphere at sea level is 1013.7 GPa, and in the southern hemisphere - 1011.7 GPa.
In January, low pressure areas are observed in the northern parts of the Atlantic and Pacific Ocean Icelandic and Aleutian depression. Depression, or baric minimaare characterized by minimal pressure values \u200b\u200b- an average of about 995 GPa.
At the same period of the year, high-pressure areas called Canadian and Siberian anticyclones arise over Canada and Asia. The highest pressure (1075-1085 GPa) is registered in Yakutia and the Krasnoyarsk Territory, and the minimum - in typhoons above the Pacific Ocean (880-875 GPa).
Depression is observed in areas where cyclones often arise, which, as it moves to the East and the Northeast, gradually fill and inferior to anticyclones. Asian and Canadian anticyclones arise due to the presence of Eurasia and North America's extensive continents on these latitudes. In these areas, the anticyclones prevail over cyclones.
In the summer above these continents, the scheme of the baric field and circulation is radically changing, and the zone of the formation of cyclones in the northern hemisphere is shifted to higher latitudes.
In moderate latitudes of the southern hemisphere, cyclones arising over the homogeneous surface of the oceans, moving to the southeast, meet the ice of Antarctica and here are forced, having low air pressure in their centers. In winter and summer, Antarctica is surrounded by a low pressure belt (985-990 GPa).
In subtropical latitudes, the atmosphere circulation is different over the oceans and in areas of contact continues and oceans. Above the Atlantic and Pacific Oceans in the subtropics of both hemispheres are high pressure areas: these are Azores and Southatic subtropical anticyclones (or baric minima) in the Atlantic and Hawaiian and South African subtropical anticyclones in the Pacish Ocean.
The greatest amount of solar heat is constantly received by the equatorial area. Therefore, in equatorial latitudes (up to 10 ° of the northern and southern latitude along the equator), a reduced atmospheric pressure is held during the year, and in tropical latitudes, in the strip 30-40 ° C. and Yu.Sh. - Increased, as a result of which constant air flows are formed, directed from the tropics to the equator. These air flows are called passatam. Passat winds are blowing throughout the year, changing their intensity only in minor limits. These are the most stable winds on the globe. The strength of the horizontal baric gradient directs the flow of air from the areas of increased pressure in the region of reduced pressure in the meridion direction, i.e. south and north. Note: A horizontal baric gradient is a pressure difference per unit of range of normal to isobar.
But the meridional direction of the trade winds changes under the action of the two forces of inertia - deflecting the power of the earth (Coriolis forces) and the centrifugal force, as well as under the action of air friction for the earth's surface. Coriolis strength acts on each body moving along the meridian. Let 1 kg of air in the northern hemisphere located on the latitude µ And begins to move at speeds V. Along the meridian to the north. This kilogram of air, like any body on Earth, has a linear speed of rotation U \u003d Ωr.where ω - angular speed of rotation of the Earth, and r. - Distance to the axis of rotation. By law of inertia, this kilogram of air will maintain a linear speed U.which he had on latitude µ . Moved to the north, it will turn out to be at higher latitudes, where the rotation radius is smaller and the linear speed of rotation of the Earth is less. Thus, this body will be ahead of fixed bodies located on the same meridian, but in higher latitudes.
For an observer, it will look like the deviation of this body to the right under the action of some force. This power is Coriolis. Under the same logic, the air kilogram in the southern hemisphere will be rejected to the left of the direction of movement. The horizontal component of the Coriolis force acting on 1 kg of air is equal to the SC \u003d 2WVSINY. She deviates air, acting at a right angle to the velocity vector V. In the northern hemisphere, it rejects this vector to the right, and in the southern hemisphere - to the left. It follows from the formula that the power of the Coriolis does not occur if the body is resting, i.e. It acts only when the air moves. In the atmosphere of the earth, the magnitude of the horizontal baric gradient and the power of Coriolis have one order, so sometimes they almost balance each other. In such cases, the air movement is almost straightforward, and it moves not along the pressure gradient, but along the isobar or close to it.
Air flows in the atmosphere are usually a vortex nature, so in such a movement on each unit of air mass acts centrifugal force P \u003d V / Rwhere V.- wind speed, and R. - Radius of the curvature of the trajectory of movement. In the atmosphere, this force is always less than the forces of the Baric gradient and therefore remains, so to speak, by the force of "local meaning."
As for the friction force arising between the moving air and the surface of the Earth, it slows down to a certain extent slows down the wind speed. This happens like this: the lower volumes of air, which reduce their horizontal velocity due to the irregularities of the earth's surface, is transferred from the lower levels upwards. Thus, friction about the earth surface is transmitted upwards, gradually weakening. The slowdown of the wind speed is noticeably in the so-called planetary borderline layer, Component 1.0 - 1.5 km. Above 1.5 km, the effect of friction is insignificant, so higher air layers are called free atmosphere.
In the Equatorial zone, the linear speed of rotation of the Earth is the greatest, respectively, here and the power of Coriolis is the largest. Therefore, in the tropical belt of the Northern Hemisphere, the Passats blow almost always from the northeast, and in the southern hemisphere - from the south-east.
Low pressure in the equatorial zone is observed constantly, in winter and summer. Low pressure strip covering the entire globe on the equator is called equatorial hollow.
Taking power over the oceans of both hemispheres, two transfers, moving towards each other, rushed to the center of equatorial hollow. On the low pressure line they face, forming the so-called Interopic convergence zone (Convergence means "convergence"). As a result of this "convergence" there is an upward movement of air and its outflow above the trade winds to subtropics. This process creates conditions for the existence of the convergence zone constantly, during the year. Otherwise, the convergent air flows of the trade winds would quickly fill the hollow.
The ascending movements of wet tropical air lead to the formation of a powerful layer of cucumber-rain clouds with a length of 100-200 km, of which tropical livne fell. Thus, it turns out that the intrachetic zone of convergence becomes a place where rains are poured out of a couple collected by trade winds over the oceans.
So simplistic, schematically looks like a picture of the circulation of the atmosphere in the Equatorial zone of the Earth.
Winds, changing their direction by season, are called monsoon. The Arab word "Mausin", meaning "time of year", gave the name by these sustainable air flows.
Monsons, unlike inkjet flows, arise in certain areas of land, where twice a year the prevailing winds move in opposite directions, forming summer and winter monsime. Summer monsoon is a stream of air from the ocean on the mainland, winter - from the mainland on the ocean. Known tropical and veneropic monsoons. In Northeast India and Africa, winter tropical monsions add up with the trade winds, and the summer southwester is completely destroyed by the trade winds. The most powerful tropical monsoons are observed in the northern part of the Indian Ocean and in South Asia. Wovenropic monsoshs are born in the powerful sustainable areas of increased pressure in winter and lowered over the continent in the winter.
Typical in this respect are the districts of the Russian Far East, China, Japan. For example, Vladivostok, lying on the breadth of Sochi, due to the action of the Vnetropic Monsoon in winter, colder than Archangelsk, and in the summer there are often fogs, sediments, the wet and cool air comes from the sea.
Many tropical countries of South Asia receive moisture, brought in the form of a summer tropical monsoon, brought in the form of torrential rains.
Any winds are the result of the interaction of various physical factors arising in an atmosphere over certain geographic areas. Local winds include breeze. They appear near the coastal feature of the seas and oceans and have a daily shift of the direction: they blow it from the sea to land, and at night with sushi at sea. This phenomenon explains the temperature difference over the sea and land at different times of the day. The heat capacity of sushi and the sea is different. In the afternoon, the sun's rays heats the land faster than the sea, and the pressure above the land decreases. The air begins to move toward a smaller pressure - blowing sea \u200b\u200bbreeze. In the evening, everything happens on the contrary. Sude and air over it emit heat faster than the sea, the pressure becomes higher than above the sea, and the air masses rush towards the sea - blowing coastal breeze. Breeze are especially reeks when quiet sunny weather, when they do not interfere with anything, i.e. No other air flows are superimposed, which are easily drunk breeze. The breeze rate is rarely above 5 m / s, but in the tropics, where the difference in the temperature of the sea surfaces and sushi is significant, the breeze blows sometimes at a speed of 10 m / s. In moderate latitudes, breeze penetrate the territory of 25-30 km.
Breeze, strictly speaking, the same monsoons, only on a smaller scale - they have a daily cycle and a change in the direction depends on the change of the night and the day, the monso have the annual cycle and change the direction depending on the time of year.
Ocean currents, meeting on their path of the banks of the continents, are divided into two branches, directed along the coarse continents to the north and south. In the Atlantic Ocean, the southern branch forms the Brazilian flow, the shores of South America, and the northern branch is a warm Golf Stream, turning into the North Atlantic current, and called the Nordskap the course reaching the Kola Peninsula.
Pacific Ocean Northern Equatorial Flow Branch goes into Kuro-Sivo.
Previously, we have already mentioned the seasonal warm warmth of the coast of Ecuador, Peru and Northern Chile. It usually arises in December (not every year) and causes a sharp decline in fish catch off the coast of these countries due to the fact that there are very little plankton in warm water - the main food resource for fish. A sharp increase in the temperature of coastal waters causes the development of cumulating rain clouds, of which strong rains shed.
Fishermen ironically called it a warm current of El Niño, which means "Christmas Gift" (from Isp. El Ninjo - Baby, Boy). But we want to emphasize not the emotional perception of the Chilean and Peruvian fishermen of this phenomenon, and its physical cause. The fact is that the increase in water temperature off the coast of South America is caused not only for warm current. Changes in the overall situation in the "ocean-atmosphere" system on the huge expanses of the Pacific and the atmospheric process called " Southern oscillation" This process, interacting with currents, determines all physical phenomena occurring in the tropics. All this confirms that the circulation of air masses in the atmosphere, especially above the surface of the world ocean, is a complex, multidimensional process. But with all the complexity, mobility and variability of air flows, there are still certain patterns, by virtue of which major-scale large-scale, as well as local atmospheric circulation processes are repeated in certain areas of the Earth.
In conclusion of the chapter, we present some examples of the use of wind energy. The wind energy people use from time immemorial, since they have learned to go to the sea under the sail. Then the windmills appeared, and later - wind engines - electricity sources. The wind is an eternal source of energy, the stocks of which are incommens. Unfortunately, the use of wind as a source of electricity is greater difficulty due to the variability of its speed and direction. However, with the help of windy electric motors, it became possible to quite efficiently use the wind energy. Windmill blades forcing it almost always "keep the nose" in the wind. When the wind is sufficient, the current goes directly to consumers: on lighting, refrigeration installations, devices for various purposes and charging batteries. When the wind subsides, the batteries are given to the network accumulated electricity.
In scientific stations in the Arctic and Antarctic, the electricity of wind turbines gives light and heat, ensures the operation of radio stations and other electricity consumers. Of course, each scientific station has diesel generators for which you need to have a permanent stock of fuel.
The very first navigators used the strength of the wind is spontaneously, without taking into account the system of winds and ocean currents. They just knew nothing about the existence of such a system. Knowledge of winds and currents accumulated centuries and even thousands of years.
One of the contemporaries Chinese navigator Zheng HE for 1405-1433. He headed several expeditions, which passed the so-called great monsoon through the mouth of the Yangtze River to India and the eastern shores of Africa. Save information about the scale of the first of these expeditions. It consisted of 62 ships with 27,800 participants. For the swimming expeditions, the Chinese used their knowledge of the laws of monsoon winds. From China, they went to the sea at the end of November - early December, when the northeast winter monsoon blows. The passing wind helped them reach India and East Africa. They returned to China in May - June, when the summer south-western monsoon was installed, which in the South China became southern.
Take an example from closer time to us. It will be about traveling the famous Norwegian scientist Tour Heyerdal. With the help of wind, or rather, with the help of Passats, Heyerdal was able to prove the scientific value of the two hypotheses. The first hypothesis was that Polynesia islands in the Pacific could be, according to Heyerdal, were settled once in the past, from South America, which crossed a significant part of the Pacific Ocean on their primitive plaques. These plaquinities were rafts from a balsal tree, which is noteworthy in that after a long stay in water, it does not change its density, and therefore does not sink.
Residents of Peru enjoyed such dams for millennia, even before the Empire Inca. Tour Heyerdal in 1947 tied a raft from large balsal bolstered and called it "Con-Tika", which means Sun-Tiki - the deity of the Polynesian ancestors. Taking the "aboard" of his flesh of five adventure lovers, he went on a sail from Callao (Peru) to Polynesia. At the beginning of the raft swimming, the Peruvian current and Southeastern Passat were carried, and then the Eastern Pattack of the Pacific Ocean began for work, which almost three months without a break was well to the West, and after 101 days, Kon-Tika arrived safely for one of the islands of the Tuamot archipelago ( Now French Polynesia).
The second hypothesis of Heyerdala consisted that he considered it quite possible that the culture of Olmekov, Aztecs, Maya and other Central America tribes was transferred from ancient Egypt. It was possible, according to a scientist, because sometime in antiquity people swam across the Atlantic Ocean on papyrus boats. Proving the viability of this hypothesis Heyerdal also helped the trade winds.
Together with a group of satellite-like-minded people, he made two swims on Papiral boats "RA-1" and "RA-2". The first boat ("RA-1") collapsed, without reaching the American coast of several tens of kilometers. The crew was seriously danger, but everything went well. The boat for the second navigation ("RA-2") knitted "Higher Specialists" - Indians from the central Andes. Coming out of the port of Safi (Morocco), Papiral boat "RA-2" after 56 days crossed the Atlantic Ocean and reached the island of Barbados (about 300-350 km from the coast of Venezuela), overcoming 6100 km of the road. At first, the boat was adjusted by the Northeast Passat, and starting from the middle of the ocean - East Passat.
The scientific relationship of the second hypothesis Heyerdal was proven. But the other was also proved: despite the prosperous outcome of the swimming, the boat associated from papyrus beams, reed, cane or another aquatic plant, is not suitable for swimming in the ocean. Such "shipbuilding material" should not be used, because He quickly wet and plunges into the water. Well, if there are still lovers, obsessed with the desire to twist the ocean on any exotic plaques, then let them mean that the raft from the bilt-sided tree is more reliable than a papyrus boat, as well as what a trip is always and in any case dangerous.
© Vladimir Kalanov,
"Knowledge is power"
Since childhood, invisible movements around us were fascinated: a weak breeze, circling autumn leaves in a close courtyard or a powerful winter cyclone. It turns out that these processes have completely understandable physical laws.
What strength make air masses move
Warm air is lighter than cold - this simple principle is able to explain the movement of air on the planet. It all starts at the equator. Here, the sun rays fall on the surface of the earth at a right angle, and a small part of the equatorial air gets a little more heat than the neighboring. This warm particle becomes easier than the neighboring, and hence, begins to pop up until it does not lose all heat and will not start to descend. But the movement down is already happening in the thirties latitudes of the northern or southern hemisphere.
If there were no additional forces, it would be so that air and moved from the equator to the poles. But there are not alone, but at once a few forces that force air masses to move:
- Floating power. When warm air pops up, and the cold remains downstairs.
- Coriolis strength. I will tell about it just below.
- Relief planet. Combine seas and oceans, mountains and plains.
Rejection
Meteorologists would be easier if our planet did not rotate. But she rotates! This generates deflecting the power of the Earth's rotation or the power of Coriolis. Due to the movement of the planet, the very "light" particle of the air not only displaces, say, north, but also shifted to the right. Either she is displaced to the south and deviates to the left.
So the constant winds of Western or Eastern directions are born. Perhaps you heard about the flow of western winds or about roaring forties? These constant air movements arose precisely thanks to the power of Coriolis.
Seas and oceans, mountains and plains
The final confusion makes a relief. The distribution of sushi and ocean changes classic circulation. So, in the southern hemisphere, sushi is much less than in the northern, and nothing prevents the air to move over the water stroke in the direction you need, there are neither mountains, nor major cities, while Himalayas are radically changed air circulation in their area.
Air mass movement
All the air of the Earth continuously circulates between the equator and poles. The air heated at the equator climbs up, is divided into two parts, one part begins to move to the North Pole, the other part is to the southern pole. Reaching the poles, the air is cooled. At the poles, it twists and lowers down.
Figure 1. The principle of twisting air
It turns out two huge vortices, each of which covers on a whole hemisphere, the centers of these vortices are at the poles.
Having dropped by the poles, the air begins to move back to the equator, the heated air rises upwards. Then again moves to the poles.
In the lower layers of the atmosphere, the movement is somewhat more complicated. In the lower layers of the atmosphere, the air from the equator as usually begins to move towards the poles, but the 30th parallel drops down. Its part of it returns to the equator, where it rises up, another part of it, dropping away from the 30th parallels down, continues to move towards poles.
Figure 2. The movement of the air of the northern hemisphere
Concept of wind
Wind - Air movement relative to the earth's surface (the horizontal component of this movement), sometimes speak of ascending or on the downward wind, given and its vertical component.
Wind speed
Evaluation of wind speed in points, so-called scale Beaufort, in which the entire interval of possible wind speeds is divided into 12 gradations. This scale binds wind power with various effects, such as the degree of excitement to the sea, swing branches and trees, the spread of smoke from pipes, etc. Each gradation on the Beaufort scale carries a specific name. So, zero the scale of Beaufort corresponds to the calm, i.e. Full absence of wind. The wind in 4 points, is called moderate on Beaufort and corresponds to a speed of 5-7 m / s; In 7 points - strong, at a speed of 12-15 m / s; In 9 points - storm, at a speed of 18-21 m / s; finally, the wind in 12 points on Beaufort is already a hurricane, with a speed of over 29 m / s . The earth's surface most often has to deal with winds, whose velocities are about 4-8 m / s and rarely exceed 12-15 m / s. But in the storms and hurricanes moderate latitudes of speeds may exceed 30 m / s, and in separate Gusts reach 60 m / s. In tropical hurricane wind speed reach up to 65 m / s, and individual gusts - up to 100 m / s. In small-scale vortices (tumor, thrombus) are possible velocities and more than 100 m / s. In so-called inkjet currents in the upper troposphere and in the lower stratosphere The average wind speed for a long time and on a large area can reach up to 70-100 m / s . Wind speed in the earth's surface is measured by anemometers of different designs. The wind measurement devices at ground stations are installed at an altitude of 10-15 m above the ground surface.
| Table 1. Wind power. | |||
| Beaufort scale to determine the strength of the wind | |||
| Point | Visual signs on land | Wind speed, km / h | Terms defining wind power |
| Quietly; Smoke rises vertically | Less than 1.6 | Calm | |
| The wind direction is noticeable to deviate smoke, but not on the fluger | 1,6–4,8 | Quiet | |
| The wind is felt by the skin of the face; rustle leaves; Rotate ordinary floors | 6,4–11,2 | Easy | |
| Leaves and small twigs are in constant motion; Light flags flush | 12,8–19,2 | Weak | |
| The wind raises dust and papers; Thin branches are swinging | 20,8–28,8 | Moderate | |
| Swinging trees covered with foliage; Appears ripples on sushi water bodies | 30,4–38,4 | Fresh | |
| Thick branches are swinging; The whistle is heard in the electrophores; It is difficult to hold an umbrella | 40,0–49,6 | Strong | |
| Trees trunks are swinging; hard to go against wind | 51,2–60,8 | Strong | |
| Branches of trees break; almost impossible to go against the wind | 62,4–73,6 | Very strong | |
| Minor damage; The wind breaks down the smoke caps and roofs | 75,2–86,4 | Storm | |
| There is rare on land. Trees turn with roots. Significant destruction of buildings | 88,0–100,8 | Heavy storm | |
| There is very rare on land. Accompanied by destruction on a large space | 102,4–115,2 | Cruel storm | |
| Strong destruction (scores 13-17 were added by the US Weather Bureau in 1955 and apply in USA and Great Britain) | 116,8–131,2 | Hurricane | |
| 132,8–147,2 | |||
| 148,8–164,8 | |||
| 166,4–182,4 | |||
| 184,0–200,0 | |||
| 201,6–217,6 | |||
Direction of the wind
Under the direction of the wind, they mean the direction from where it blows. You can specify this direction by calling either the point of the horizon, from where the wind blows, or an angle formed by the direction of the wind with the meridian of the place, i.e. His azimuth. In the first case, there are eight main horizon rumbes: north, northeast, east, south-east, south, south-west, west, northwest. And eight intermediate rumbes between them: North-North-East, East-Northeast, East-South-East, South-Southeast, South-South-West, West-South-West, West-North-West, North -northwest. Sixteen Rumbes, pointing the direction, from where the wind blows, have abbreviated designations:
| Table 2. Abbreviated designations of rumbes | |||||||
| FROM | N. | IN | E. | YU | S. | W. | |
| CCB. | NNE | Vüv. | ESE. | Yuyuz | SSW. | ZSZ | WNW. |
| CB. | Ne | Yow | SE | Yuz | SW. | SZ | NW. |
| BCB. | ENE. | Yuyuv. | SSE | Zuzy | WSW. | CVD | NNW. |
| N - Nord, E - Ost, S - Site, W - West |
Circulation of the atmosphere
Circulation of the atmosphere - Meteorological observations on the state of the air shell of the globe - the atmosphere - show that it is not at night at all: with the help of flugers and anemometers, we constantly observe the wind mass of air from one place to another. Studying winds in various locations of the globe showed that the movement of the atmosphere in those lower layers that are available to our observation are very different. There are areas where wind phenomena, as well as other weather features, have a very clearly pronounced nature of stability, known as the desire for constancy. In the other localities, the winds so quickly and often change their character, so abruptly and suddenly their direction and force, as if no legality in their rapid shifts would exist. With the introduction of the synoptic method for studying non-periodic weather changes, it was, however, the ability to notice some connection between the pressure distribution and the movement of air mass; Further theoretical studies of Ferrel, Guldberg and Mona, Helmholtz, Betzold, Oberbek, Sprung, Werner Siemens and other meteorologists explained, from where and how the air flow arise and how they are distributed over the earth's surface and in the mass of the atmosphere. Attentive study of meteorological maps depicting the state of the lower layer of the atmosphere - the weather at the very surface of the earth, showed that the pressure of the atmosphere is distributed quite unevenly, commonly in the form of areas with lower or higher than in the surrounding area, pressure; According to the wind system, in them arising, these areas represent real atmospheric vortices. Areas of reduced pressure are customary to be called commonly barometric minima, barometric depressions or cyclones; The field of increased pressure is called barometric maxima or anticyclones. All the weather in the area occupied by them is closely connected with these areas, sharply different for the areas of reduced pressure from weather in relatively high pressure regions. Moving along the earth's surface, the mentioned areas are transferred with themselves and characteristic, they are characteristic of the weather, and its non-periodic changes are caused by their movements. Further study of those and other areas led to the conclusion that these types of atmospheric pressure distribution may have another character in the ability to maintain their existence and change their position on the earth's surface, differ very not equally stable: there are barometric minima and maxima temporary and constant. While the first - vortices are temporary and do not detect sufficient stability and more or less quickly change their place on the earth's surface, then intensifying, then weakening and, finally, absolutely breaking down at relatively short periods of time, the area of \u200b\u200bpermanent maxima and lows have Extremely large stability and for a very long time is held, without significant changes, in the same place. Of course, the stability of the weather and the nature of air flows in the area occupied by them are also closely resistant to these areas and the nature of air flows in their area: constant maxima and minima will be configured and constant, stable weather and a certain, unchanged wind system, for months on the place of their existence; The time vortices in their fast, constant movements and changes cause extremely changeable weather and the wind system is very non-permanent for this area. Thus, in the lower layer of the atmosphere, near the earth's surface, the movement of the atmosphere is distinguished by a large variety and complexity, and besides, not always and not everywhere they have sufficient stability, especially in those areas where the vortices of a temporary nature prevail. What are the movements of air masses in a slightly higher layers of the atmosphere, the usual observations do not say anything; Only observations on the movements of the clouds allow you to think that there is some height above the surface of the Earth, all the movements of the air masses are somewhat simplified, wearing a more definite and more monotonous nature. Meanwhile, there is no shortage of facts indicating the tremendous influence of the high layers of the weather at the weather in the lower: enough, for example, to point out that the direction of movement of temporary vortices is, apparently, in direct dependence on the movement of high atmospheric layers. Therefore, before the science began to have enough facts to decide on the movements of the high layers of the atmosphere, there are already some theories that attempted to combine all individual observations on the movements of the lower air layers and create a general scheme of C. atmosphere; Such is, for example, there was the theory of the atmosphere, this Mori. But, until a sufficient number of facts were collected, until the ratio between the air pressure in these paragraphs and it moves, until these theories, based more on hypotheses, could not give a real idea of that in reality can be performed and accomplished in the atmosphere. Only by the end of last XIX century. It has been accumulated enough for this facts and the dynamics of the atmosphere was designed so much that the opportunity to give real, and not a gudy picture of C. Atmosphere. Honor of solving the issue of the general cycle of air mass in the atmosphere belongs to the American meteorologist William Ferrel - Decisions, so common, complete and correct that all later researchers in this area only developed details or contributed further additions to the main ideas of Ferrel. I basic reasons for all movements in the atmosphere is uneven heating of different points of the earth's surface with sunny rays. The inexpensiveness of heating entails the occurrence of pressure difference over different heated points; And the result of pressure difference is always and invariably appears the movement of air masses from places higher to lower pressure places. Therefore, due to the strong heating of the equatorial latitudes and the very low temperature of the polar countries in both hemispheres, the air adjacent to the earth's surface must come into motion. If, according to the available observations, calculate the average temperatures of various latitudes, the equator will be an average of 45 ° warmer poles. To determine the direction of movement, it is necessary to trace the distribution of pressure but the earth's surface and in the mass of the atmosphere. To eliminate strongly complicating all calculations, the uneven distribution of sushi and waters on the earth's surface, Ferrel did the assumption that dry, and the water is evenly distributed by parallels, and calculated the average temperatures of various parallels, lowering the temperature as it raises to some height above the earth surface and pressure. down below; And then according to this data, it has already calculated pressure on some other heights. The next small plate represents the result of Ferrel counts and gives the pressure distribution on average by latitudes on the surface of the Earth and at altitudes 2000 and 4000 m.
| Table 3. Distribution of pressure on the latitude of land and at altitudes 2000 and 4000 m | ||||||||
| Middle Pressure in the Northern Hemisphere | ||||||||
| On latitude: | 80 ○ | 70 ○ | 60 ○ | 50 ○ | 40 ○ | 30 ○ | 20 ○ | 10 ○ |
| At sea level | 760,5 | 758,7 | 758,7 | 760,07 | 762,0 | 761,7 | 759,2 | 757,9 |
| At an altitude of 2000 m | 582,0 | 583,6 | 587,6 | 593,0 | 598,0 | 600,9 | 600,9 | 600,9 |
| At an altitude of 4000 m | 445,2 | 446,6 | 451,9 | 457,0 | 463,6 | 468,3 | 469,9 | 470,7 |
| Medium pressure in the southern hemisphere | ||||||||
| On latitude: | (equator) | 10 ○ | 20 ○ | 30 ○ | 40 ○ | 50 ○ | 60 ○ | 70 ○ |
| At sea level | 758,0 | 759,1 | 761,7 | 763,5 | 760,5 | 753,2 | 743,4 | 738,0 |
| At an altitude of 2000 m | 601,1 | 601,6 | 602,7 | 602,2 | 597,1 | 588,0 | 577,0 | 569,9 |
| At an altitude of 4000 m | 471,0 | 471,1 | 471,1 | 469,3 | 463,1 | 453,7 | 443,9 | 437,2 |
If you leave until the lowest layer of atmosphere, where the temperature distribution, pressure, as well as the flows, is very uneven, then at some height, as can be seen from the plate, due to the ascending current of heated air near the equator, we find over this latter pressure evenly Reduced to the poles and here achieving its smallest value. With this distribution of pressure at these heights above the earth's surface, a grand stream should be formed, covering a whole hemisphere and relates to the mass of warm, heated air to the low pressure centers - to poles. If we take into account the still deflecting effect of the centrifugal force, which occurs from the daily rotation of the Earth around its axis, which should reject any moving body to the right of the initial direction in the northern, left - in the southern hemispheres, then in the heights under consideration in each hemisphere, the resulting stream has evolved, obviously , In a huge whirlwind, carrying air masses in the direction from the south-west to the northeast in the North, from the North-West to the southeast - in the southern hemisphere.
Observations on the movement of cider clouds and others confirm these theoretical conclusions. As they narrow, with approaching the poles, the circles of the latitude, the speed of the air masses in these vortices will increase, but to a certain limit; Then it is done more constant. Near the pole, flowing air masses should be descended down, giving way to a newly flowing air, forming a downward stream, and then the gear should flow back to the equator. Between both streams should be at some height, the neutral layer of air located alone. Below, however, such proper air mass transfer from the poles to the equator is not observed: the preceding sign indicates that in the lower layer of air the pressure of the atmosphere will be at the highest not on the poles, which it should be with the right corresponding to the top, its distribution. The highest pressure in the lower layer falls on a latitude of about 30 ° -35 ° in both hemispheres; Consequently, from these high pressure centers, the lower flows will be sent to the poles, and to the equator, forming two separate wind systems. The reason for this phenomenon, theoretically clarified by ferrele, is as follows. It turns out that at some height above the earth's surface, depending on the change in the latitude of the place, the magnitude of the gradient and the friction coefficient, the meridional leveling speed of the air movement can fall to 0. This is precisely and occurs in the latitudes. 30 ° -35 °: Here at some height, not only therefore there is no air movement, towards the poles, but even goes, due to its continuous inflow from the equator and from the poles, its accumulation, which leads to an increase in pressure in these pressure latoms below . Thus, at the very surface of the Earth in each hemisphere, there are already mentioned, two current systems: from 30 ° to the poles blow winds aimed at average from the south-west to the northeast in the North, from the North-West to the southeast in the southern hemisphere; From 30 ° to the equator, winds are blowing from St. to UZZ in North, from the SD to the SZ in the southern hemisphere. These two recent wind systems, which in both hemispheres between the equator and the breadth of 31 °, form a wide ring separating in the lower and middle layers of the atmosphere of both ambitious vortices carrying air from the equator to the poles (see also the atmosphere pressure). Where the ascending and downstream air flows are formed, clams are observed; This is precisely the origin of equatorial and tropical silence belts; A similar belt of silence should, for ferrel, exist on the poles.
Where, however, it turns out of the poles to the equator on the bottom reverse air flow? But it is necessary to take into account that, as the sizes of latitude circles are removed from the poles, and, consequently, the area of \u200b\u200bthe belts of equal width occupied by the spreading agents of air are growing rapidly; that the flow rate should quickly decrease inversely proportionate to the increase in these areas; That on the poles, finally, the air is very hot down in the upper layers, the volume of which is very quickly reduced as the pressure of the pressure is increasing. All these reasons are explained quite, why it is difficult, and even directly impossible, to keep track of some distances from the poles behind these reverse bottom streams. Such is in general terms the scheme of the general circulation atmosphere under the assumption of the uniform distribution of sushi and waters through parallels given by ferrele. Observations are fully confirmed. Only in the lower layer of the atmosphere, air flows will be as indicated by the Ferrel itself, much more complicated by this scheme precisely due to the unevenness of the distribution of sushi and water, and the irritations of their heating of the rays of the Sun and their cooling in the absence or reduction of insolation; Mountains and hills also a lot affect the movements of the lowest layers of the atmosphere.
Attentive study of the movements of the atmosphere near the earth's surface shows generally that the vortex systems represent the basic form of such movements. Starting with the grandiose vortices embracing, on Ferrel, every whole hemisphere, vortex How can they be called first order Near the earth's surface, it is necessary to observe the vortex systems that decrease in their sizes, to elementary small and simple vortices inclusive. As a result of the interaction of various streams in its speeds and directions in the field of first-order vortices, near the earth's surface occurs. second-order vortices - Permanent and temporary barometric maxima and minima referred to at the beginning of this article, representing in their origin, as it were, the derivative of previous vortices. The study of the formation of a thunderstorm led A. V. Klosovsky and other researchers to conclude that these phenomena are nothing but similar to the same structure, but incomparably smaller in size relatively with the previous third-order whirlwinds. These vortices occur, apparently, on the outskirts of barometric lows (second-order vortices), it is completely similar to how around a large deepening, formed on the water in the oars, which we row when swimming on a boat are formed small, very rapidly spinning and endangered waterways. It is completely in the same way the second-order barometric minima representing powerful aircrews, with its movement form smaller air ducts, having, compared with their minimum forming, very minor sizes.
If these vortices are accompanied by electrical phenomena, which can be often caused by the appropriate temperature and humidity conditions in a barometric minimum flowing at the bottom of the air, then they are in the form of thunder vortices, accompanied by conventional electrical discharge phenomena, thunder and lightning. If the conditions do not favor the development of thunderstorms, these vortices of the third order we observe in the form of rapidly transient storms, shkvalov, shower, etc. There is, however, to think that these three categories, such a different phenomena, vortex movements The atmosphere is not exhausted. The structure of the tumor, thrombos, etc. Panition shows that in these phenomena we have a case with real vortices; But the dimensions of these fourth-order vortices Even less, even more than more than the vortices of thunderstorms. The study of the movements of the atmosphere leads us, thus, to the conclusion that the movement of the air masses occurs mainly - if not exclusively - by the occurrence of the vortices. The arising under the influence of purely temperature conditions, the first-order whirlpool, covering each hemisphere, is beginning to be laitted near the ground surface by the vortices of smaller sizes; These, in turn, are the cause of even smaller vortices. There is a gradual differentiation of larger vortices into smaller; But the main character of all these vortex systems remains completely the same, starting with larger and to the most minor in size, even in tumor and thrombus.
Regarding the second-order vortices - permanent and temporary barometric maxima and minima - still remains to say. The studies of Hoffmeira, Taisseran de Bora and Guildbandson pointed to a close relationship between the occurrence and especially movement of highs and minima of temporary with changes undergoing maxima and minima constant. Already, the fact that these last with all sorts of changes in the weather in the surrounding areas are very little change their borders or contours, indicates that here we are dealing with some permanent reasons undergoing the above influence of ordinary weather factors. According to Taisseran de Bor, the pressure difference caused by uneven heating or cooling of various parts of the earth's surface, summing up under the influence of the continuous increase in the primary factor for a more or less prolonged period of time, give rise to large barometric maxima and minima. If the primary reason acts continuously or sufficiently long, the result of its action is permanent, stable vortex systems. Having achieved known sizes and sufficient intensity, such permanent maxima and minima are already determinants or regulators of weather in huge areas in their circumference. Such large, permanent maxima and minima have recently received when they turned out their role in the weather phenomena around them, name atmospheric Centers. Due to the invariance in the configuration of the earth's surface and the continuity of the continuity of the primary cause, causing their existence, the position of such highs and minima on the globe is quite definite and unchanged to a certain extent. But, depending on the various conditions, their boundaries and their intensity can change under certain limits. And these changes in their intensity and their outlines, in turn, should respond to the weather not only neighboring, and sometimes even quite remote countries. Thus, the studies of Taisseran de Boru fully established the dependence of weather in Europe from one of the following centers: negative anomalies, accompanied by a decrease in temperature relatively to normal, are caused by the strengthening and expansion of a Siberian maximum or amplification and an overvaluation of the Azores maximum; Anomalies of a positive character - with an increase in temperature against normal - are directly dependent on the movement and intensity of the Icelandic minimum. Hildebrandson went in this direction even further and quite successfully tried to associate changes in the intensity and movement of two named Atlantic centers with changes in not only the Siberian maximum, but also pressure centers on the Indian Ocean.
Aerial masses
Weather observations were widely widespread in the second half of the 19th century. They were necessary for the preparation of synoptic maps showing the distribution of pressure and air temperature, wind and precipitation. As a result of the analysis of these observations, there was an idea of \u200b\u200bthe air masses. This concept made it possible to combine individual elements, identify various weather conditions and give it forecasts.
Aerial mass It is called a large amount of air having horizontal dimensions of several hundred or thousands of kilometers and vertical dimensions - about 5 km, characterized by the approximate homogeneity of temperature and humidity and moving as a single system in one of the current atmospheric circulation (OCC)
The homogeneity of the properties of the air mass is achieved by the formation of it above the homogeneous underlying surface and in similar radiation conditions. In addition, such circulation conditions are needed, in which the air mass would be delayed in the formation area.
The values \u200b\u200bof meteorological elements within the air mass change slightly - their continuity is preserved, horizontal gradients are small. When analyzing meteorological fields as long as we remain in this air mass, it is possible to use linear graphic interpolation with a sufficient approximation during carrying out, for example, isotherm.
A sharp increase in horizontal gradients of meteorological values, approaching the jump-shaking transition from some values \u200b\u200bto another, or at least a change in the value and direction of gradients occurs in the transitional (front zone) between the two air masses. The pseudopotential air temperature reflecting and the actual air temperature and its humidity is adopted as the most characteristic feature of one air mass.
Pseudopotential air temperature - The temperature that air would be taken during the adiabatic process, if first, the entire water steam contained in it was condensed with an unlimited falling pressure and fell out of the air and the distinguished hidden heat would go to heating the air, and then the air would be driven under standard pressure.
Since the more warm air mass is usually more humid, the difference in the pseudopotential temperatures of two adjacent air mass is much greater than the difference in their real temperatures. At the same time, the pseudopotential temperature slowly changes with a height of this air mass. This property helps to determine the simulation of air masses one over the other in the troposphere.
The scale of air mass
Air masses have the same order as the main flows of total atmospheric circulation. The linear length of the air masses in the horizontal direction is measured by thousands of kilometers. Vertically, air masses stretch up a few kilometers of troposphere, sometimes to its upper border.
With local circulation, such as breeze, mountain-valley winds, hair dryers, the air in the circulation flow is also more or less separate by properties and movement from the surrounding atmosphere. However, in this case, it is impossible to talk about the air masses, since the scale of the phenomena here will be different.
For example, a strip covered by the breeze can have a width of only 1-2 dozen kilometers, and therefore will not receive sufficient reflection on the synoptic map. The vertical capacity of the brisk flow is also equal to several hundred meters. Thus, with local circulation, we are dealing not with independent air masses, but only with an indignant state inside the air masses at a short distance.
Objects arising from the interaction of air masses - transition zones (frontal surfaces), frontal cloud cloudiness and precipitation systems, cyclonic perturbations, have the same order of magnitude as the air masses themselves - comparable in area with large parts of the mainland or oceans and their time existence - more than 2 days ( table. four):
Airy mass has clear boundaries separating it from other air masses.
Transition zones between air masses with various properties are called frontal surfaces.
Within the same air mass, it is possible to use graphical interpolation with sufficient approximation, for example, when conducting isotherms. But when moving through the frontal zone from one air mass to another linear interpolation no longer gives the correct idea of \u200b\u200bthe actual distribution of meteorological elements.
Air masses formation foci
The air mass acquires clear characteristics in the formation focus.
The focus of the formation of the air masses must meet certain requirements:
The homogeneity of the underlying water surface or sushi so that the air in the focus is sufficiently similar.
Uniformity of radiation conditions.
Circulation conditions that promote airportation of air in this area.
The foci of the formation is usually areas where the air is lowered, and then spreads in a horizontal direction - anticyclonic systems are responsible for this requirement. Anticyclones are more often than cyclones, there are sediments, therefore the formation of air masses is usually occurring in extensive minor (quasistationary) anticyclones.
In addition, sedimentary and blurred thermal depresses arising over the heated areas of sushi respond to the requirements of the hearth.
Finally, the formation of polar air occurs in part in the upper layers of the atmosphere in low-propelled, extensive and deep central cyclones in high latitudes. In these baric systems, there is a transformation (conversion) of tropical air, drawn into high latitudes in the upper layers of the troposphere, to the polar air. All listed bary systems can also be called air masses already with geographical, but from a synoptic point of view.
Geographical classification of air masses
Air masses are classified, first of all, on the foci of their formation, depending on the location in one of the latitudinal belts - arctic, or antarctic, polar, or moderate latitudes, tropical and equatorial.
According to the geographical classification, air masses can be divided into basic geographic types on the latitudinal zones in which their foci are located:
Arctic or Antarctic air (AV),
Polar, or moderate, air (PV or WC),
Tropical air (TV). These air masses, in addition, are divided into marine (m) and continental (K) air masses: MAV and CAV, MOV and BUV (or MPV and CPV), MTV and KTV.
Equatorial air masses (eV)
As for equatorial latitudes, there is convergence (convergence of flows) and air rise, therefore, air masses are usually applied from the subtropical zone. But sometimes allocate independent equatorial air masses.
Sometimes, except for foci in the exact sense of the word, distinguish areas where in winter air masses are transformed from one type in another when they are moved. These are areas in the Atlantic south of Greenland and in the Pacific Ocean over the Bering and Okhotsk seas, where the CPV turns into MPV, areas over the southeastern part of North America and south of Japan in the Pacific Ocean, where the CPV turns into a MPV in the process of winter monsoon, and District in the south of Asia, where the Asian CPV turns into tropical air (also in the monsoon stream)
Transformation of air mass
With a change in circulation conditions, the air mass is shifted from the focus of its formation into neighboring areas, interacting with other air masses.
When moving, the air mass begins to change its properties - they will already depend not only on the properties of the formation of the formation, but also on the properties of the neighboring air masses, from the properties of the underlying surface, over which the air mass passes, as well as from the duration of the time has passed since the air masses.
These influences can cause changes in the content of moisture in the air, as well as the change in air temperature as a result of the release of hidden heat or heat exchange with the underlying surface.
The process of changing the properties of the air mass is called transformation or evolution.
Transformation associated with air mass movement is called dynamic. The speed of movement of air mass at different heights will be different, the presence of speed shift causes turbulent mixing. If the lower layers of air are heated, instability occurs and convective mixing develops.
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