Types of local winds. Local winds
Local winds refer to winds that are characteristic only of certain geographical areas. Their origin is different.
Firstly, local winds may be a manifestation of local circulations, independent of the general circulation of the atmosphere and superimposed on it. Such are, for example, breezes along the shores of seas and large lakes. Differences in the heating of the shore and water during the day and night create local circulation along the shoreline. At the same time, in the surface layers of the atmosphere, the wind blows during the day from the sea to the warmer land, and at night, on the contrary, from the cooled land to the sea. Mountain-valley winds also have the character of local circulation. See below for more details.
Secondly, local winds can represent local changes (disturbances) in the currents of the general circulation of the atmosphere under the influence of orography or topography of the area. Such, for example, is the foehn - a warm wind blowing along mountain slopes into valleys when the current of the general circulation crosses a mountain range. The downward movement of the foehn, associated with an increase in air temperature, is a consequence of the influence of the ridge on the general circulation flow. The influence of orography also explains boron and its various varieties.
Terrain may also cause winds to increase in some areas to speeds significantly higher than those in neighboring areas. Such locally enhanced winds of one direction or another are also known in different areas under different names as local winds. Sometimes special properties are given to the local wind by the passage of air over a very hot and dry surface, such as a desert, or, conversely, over a highly evaporating (water) surface.
Thirdly, local winds also refer to such strong winds or winds with special properties in a certain area, which are essentially general circulation currents. The intensity of their manifestation and their specificity for a given geographical area are a consequence of the general circulation mechanism itself, the very geographical distribution of synoptic processes. In this sense it is called a local wind, for example, the sirocco on the Mediterranean Sea.
In addition to the sirocco, numerous local winds are known in various places on the Earth, bearing special names, such as samum, khamsin, Afghan, etc. Mention of such winds can be found in the physiographic or climatic characteristics of individual areas.
Breezes are winds near the coastlines of seas and large lakes that have a sharp daily change in direction. During the day, the sea breeze blows in the lower few hundred meters (sometimes in a layer of more than a kilometer) towards the shore, and at night the shore breeze blows from the shore to the sea. Wind speed during breezes is about 3-5 m/sec, in the tropics and more. Breezes are clearly expressed in cases where the weather is clear and the general air transport is weak, as happens, for example, in the inner parts of anticyclones. Otherwise, the general movement of air in a certain direction masks the breezes, as always happens during the passage of cyclones.
Particularly pronounced breeze circulation is observed in subtropical anticyclones, for example on desert coasts, where daily temperature changes over land are large and overall pressure gradients are small.
But well-developed breezes are observed in the warm season (from April to September) and in such mid-latitude seas as the Black, Azov, and Caspian.
Breezes are associated with the daily variation of land surface temperature
Mountain-valley winds
In mountain systems, winds with a daily frequency, similar to breezes, are observed. These are mountain-valley winds. During the day, the valley wind blows from the throat of the valley up the valley and also up the mountain slopes. At night, the mountain wind blows down the slopes and down the valley towards the plain. Mountain-valley winds are well expressed in many valleys and basins of the Alps, Caucasus, Pamirs and other mountainous countries, mainly in the warm half of the year. Their vertical power is significant and measured in kilometers: the winds fill the entire cross-section of the valley, right up to the crests of its side ridges. As a rule, they are not strong, but sometimes reach 10 m/sec or more.
A foehn is a warm, dry and gusty wind that sometimes blows from the mountains to the valleys. The air temperature with a hairdryer increases significantly and sometimes very quickly; relative humidity drops sharply, sometimes to very low values. At the beginning of the foehn, sharp and rapid fluctuations in temperature and humidity can be observed due to the meeting of the warm air of the foehn with the cold air filling the valleys. Foehn gustiness indicates strong turbulence in the foehn flow. The duration of the hairdryer can be from several hours to several days, sometimes with interruptions (pauses).
Hairdryers have been known in the Alps since ancient times. They are very common in the Western Caucasus, both on the northern and southern slopes of the ridge.
A prolonged and intense heat gun can lead to rapid melting of snow in the mountains, an increase in the level and overflow of mountain rivers, etc. In summer, a hair dryer, due to its high temperature and dryness, can have a detrimental effect on vegetation. In the Transcaucasus (Kutaisi region) it happens that during the summer hairdryers the foliage of trees dries out and falls off.
But a foehn can also be observed in Arctic air, when the latter, for example, flows through the Alps or the Caucasus and falls along the southern slopes. Even in Greenland, the flow of air from a three-kilometer-high ice plateau onto the fiords creates very strong increases in temperature. In Iceland, hairdryers have seen temperatures rise by almost 30° in a few hours.
When the ridge flows in an air current, standing waves, so-called foehn waves, with an amplitude of several kilometers can arise, sometimes leading to the formation of lenticular clouds. These waves propagate upward to a height several times greater than the height of the ridge.
Bora is a strong cold and gusty wind blowing from low mountain ranges towards a fairly warm sea. Bora has long been known in the area of Novorossiysk Bay on the Black Sea and on the Adriatic coast of Yugoslavia, in the Trieste region. Similar phenomena were discovered on Novaya Zemlya and in some other places. Sarma near the Olkhon Gate on Lake Baikal also belongs to the type of bora. Nord in the Baku region, Mistral on the Mediterranean coast of France, from Montpellier to Toulon, and North in the Gulf of Mexico (Mexico, Texas) are quite similar to bora in origin and manifestations.
Bora occurs in Novorossiysk, as in the Adriatic, in cases where a cold front approaches the coastal ridge from the northeast. Cold air immediately crosses the low ridge. Falling down the mountain ridge under the influence of gravity, the air acquires significant speed: in Novorossiysk in January, the wind speed during boron averages above 20 m/sec. Falling on the surface of the water, this downward wind creates a strong disturbance. At the same time, the air temperature drops sharply, which was quite high over the warm sea before the bora began.
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MINISTRY OF TRANSPORT OF THE RUSSIAN FEDERATION
FEDERAL STATE BUDGET EDUCATIONAL INSTITUTION OF HIGHER EDUCATION
“ULYANOVSK INSTITUTE OF CIVIL AVIATION NAMED AFTER CHIEF MARSHAL OF AVIATION B.P. BUGAEV"
Department of Air Traffic Control and Navigation
Academic discipline: “Aviation Meteorology”
on the topic: “Local winds”
Completed by: cadet of training group D-14-2
Kulagin Yu.V.
Checked by: senior teacher Department of ATC and N Buzaeva S.V.
Ulyanovsk 2016
1. Local winds
wind atmosphere sirocco
Local winds are winds that differ in some way from the main character of the general circulation of the atmosphere, but, like constant winds, regularly repeat and have a noticeable impact on the weather regime in a limited part of the landscape or water area.
Local winds include a breeze that changes its direction twice a day, mountain-valley winds, bora, foehn, dry winds, samum and many others.
The occurrence of local winds is associated mainly with the difference in temperature conditions over large bodies of water (breezes) or mountains, their extension relative to general circulation flows and the location of mountain valleys (fen, bora, mountain-valley), as well as with changes in the general circulation of the atmosphere by local conditions (the very , sirocco, khamsin). Some of them are essentially air currents of the general circulation of the atmosphere, but in a certain area they have special properties, and therefore they are classified as local winds and given their own names.
For example, on Baikal alone, due to the difference in heating of water and land and the complex arrangement of steep ridges with deep valleys, at least 5 local winds are distinguished: Barguzin - warm northeastern, mountain - northwestern wind, causing powerful storms, Sarma - sudden western wind, reaching hurricane force up to 80 m/s, valley winds - southwestern kultuk and southeastern shelonik.
Bora (Italian bora, from the Greek vpsEbt - north wind; “boreas” - cold north wind) is a strong cold gusty local wind that occurs when a flow of cold air encounters a hill on its way; Having overcome the obstacle, the bora hits the coast with enormous force. The vertical dimensions of the bora are several hundred meters. As a rule, it affects small areas where low mountains directly border the sea.
In Russia, the forests of Novorossiysk Bay and Gelendzhik Bay (where they have a northeastern direction and blow more than 40 days a year), Novaya Zemlya, the shores of Lake Baikal (Sarma near the Olkhon Gate Strait), and the Chukotka city of Pevek (the so-called “yuzhak”) are especially strong. ). In Europe, the most famous are the forests of the Adriatic Sea (in the area of the cities of Trieste, Rijeka, Zadar, Senj, etc.). In Croatia the wind is called boomra. The “nord” wind in the Baku region, the mistral on the Mediterranean coast of France from Montpellier to Toulon, and the “north ser” in the Gulf of Mexico are also similar to bora. The duration of the bora is from a day to a week. The daily temperature difference during bora can reach 40 °C.
Scheme of bora occurrence
Bora occurs in Novorossiysk and the Adriatic coast in cases where a cold front approaches the coastal ridge from the northeast. The cold front immediately passes over a low ridge. Under the influence of gravity, cold air flows down the mountain range, acquiring greater speed.
Before the appearance of the bora, thick clouds can be observed at the tops of the mountains, which the residents of Novorossiysk call “beard”. Initially, the wind is extremely unstable, changing direction and strength, but gradually acquires a certain direction and enormous speed - up to 60 m/s at the Markotkhsky pass near Novorossiysk. In 1928, a wind gust of 80 m/s was recorded. On average, the wind speed during boron reaches more than 20 m/s in the Novorossiysk region in winter. Falling on the surface of the water, this downdraft generates gale force winds, causing strong rough seas. At the same time, the air temperature drops sharply, which before the start of the bora was quite high over the warm sea.
Sometimes boron causes significant destruction in the coastal strip (for example, in Novorossiysk in 2002, bora caused the death of several dozen people); at sea the wind contributes to strong waves; increased waves flood the shores and also cause destruction; during severe frosts (in Novorossiysk about? 20...? 24 °C) they freeze and an ice crust forms (on the Adriatic the only place where an ice crust forms is the city of Senj). Sometimes bora is felt far from the coast (on the Black Sea 10-15 kilometers deep into the sea, on the Adriatic, at some synoptic positions it covers a significant part of the sea).
3. Mistral
Mistral (French mistral) is a cold northwest wind that blows from the Cevennes to the Mediterranean coast of France in the spring months and is a real scourge of agriculture in the Rhone Valley and all of Provence. The mistral is a type of katabatic wind. Often the wind is so strong that it uproots trees. In any case, its constant influence is noticeable on solitary trees, which are often tilted to the south.
In the eastern part of the Cote d'Azur, the effect of the mistral is much weaker.
The Mistral is formed when the Atlantic anticyclone and the North Sea cyclone meet.
A tree grown in a constantly blowing mistral.
4. Pampero
Pampero (Spanish pampero, plural pampemros - “wind from the pampa”) is a cold stormy south or southwest wind in the eastern part of Argentina, Uruguay and Paraguay, sometimes with rain. Associated with incursions of Antarctic air.
They usually occur suddenly after warm northern winds, carry clouds of dust and are accompanied by a rapid increase in pressure and a decrease in temperature. Their properties are quite consistent with the cold, dry northwest winds off the eastern coasts of Asia and North America. On the shore, pampero is often replaced by cold and strong, but humid, southeast winds. In open space, wind speed reaches 25 m/s.
The first stage is usually called Pampero Hamedo (“wet pampero”), bringing showers and snowfall, and the second stage is Pampero Seco (“dry pampero”), which turns into the dust storm Pampero Sucio. Although pampero can occur at any time of the year, it is usually worst during the early summer in the Southern Hemisphere, between October and January.
Dry cold diapers carry a huge amount of dust and small pebbles. Due to wind-driven storms, shipping is difficult off the coast of Patagonia. Pampero, as well as the sultry north wind “norte”, blow away the soil layer, forming dune areas.
Föhn (German Föhn, from Latin favonius - the Roman equivalent of Zephyr) is a strong, gusty, warm and dry local wind blowing from the mountains to the valleys.
Cold air from the highlands quickly falls down through relatively narrow intermountain valleys, which leads to its adiabatic heating. When descending for every 100 m, the air warms up by approximately 1 °C. Descending from a height of 2500 m, it heats up by 25 degrees and becomes warm, even hot. Usually the hairdryer lasts less than a day, but sometimes the duration reaches 5 days, and changes in temperature and relative humidity can be rapid and abrupt.
Hairdryers are especially frequent in spring, when the intensity of the general circulation of air masses sharply increases. Unlike a foehn, bora is formed when masses of dense cold air invade.
6. Sirocco
Scirocco is rarely scirocco, (Italian scirocco, from Arabic FSUE - sharq - east) - a strong south or southwest wind in Italy, and this name is also applied to the wind of the entire Mediterranean basin, originating in North Africa, the Middle East and having its own name and its own characteristics in different regions.
The difference between this regular air flow in some ways and the main character of the general circulation of the atmosphere, as well as a noticeable influence on the weather regime in the Mediterranean region, makes it possible to classify the sirocco as a local wind. The direction is south, southeast or east (sometimes even southwest). In the centers of formation, and when it passes through the mountains in southern Europe, on the leeward side it acquires the character of a foehn. Occurs at all times of the year; in summer - less often, in spring and autumn - more often. It reaches its greatest strength in March and November. In some regions, it sometimes reaches speeds of up to 100 km/h (55 knots - hurricane force), reaching gale force (from 2 to 9 on the Beaufort scale), although in some places it is considered a moderate wind. Usually worsens in the afternoon, and weakens in the evening and at night. It blows for 2-3 days in a row, but can last half a day or many days. It has a depressing effect on people.
Sirocco originates in the depths of the Arabian and North African deserts. It originates in warm, dry, tropical air masses that move north toward low pressure eastward across the Mediterranean Sea. Hot, dry continental air mixes with cooler, wetter air from the offshore cyclone and moves counterclockwise toward the southern coast of Europe. On its way through the Mediterranean Sea, it becomes more humid, but nevertheless often dries out the vegetation of southern Europe, also bringing large masses of dust.
The sirocco is generally considered to be a stifling, scalding, very dusty wind with high temperatures (up to 35 °C at night) and low relative humidity (see dry wind), however, in some areas of the Mediterranean it is a warm, moist sea wind. It sometimes causes dusty, dry weather along the northern coast of Africa, storms in the Mediterranean and cold, wet weather in Europe. It causes dry fogs and dusty haze.
Dust brought by sirocco can damage mechanical devices and enter living spaces. Sirocco is unhealthy regardless of whether it is wet or dry. Some sirocco cause nervous disorders, headaches, neuralgia, weakness, sleep disturbances, increased irritability, etc., even to the point of insanity. There are even legends that crimes committed during the sirocco were once forgiven, being attributed to its maddening dryness and heat.
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Local winds are called winds that have local distribution. They arise in connection with the geographical features of the territory: the presence of large bodies of water, the specific orography of the region, etc.
Local winds of various origins include breezes, mountain-valley winds, slope winds, glacial winds, foehn, and bora.
Breezes(fr. brise- light wind) - winds along the shores of seas, large lakes and rivers, changing direction twice a day to the opposite: the daytime breeze blows from the reservoir to the shore, the night breeze - from the shore to the reservoir. Breezes are caused by the daily variation of temperature and, accordingly, pressure over land and water. They capture a layer of air of 1–2 km. Their speed is low - 3 - 5 m/s. A very strong daytime sea breeze is observed on the western desert coasts of continents in tropical latitudes, washed by cold currents and cold water rising off the coast in the upwelling zone. There it invades tens of kilometers inland and produces a strong climatic effect: it reduces the temperature, especially in summer, by 5–7 °C, and in West Africa by 10 °C, increases relative air humidity to 85%, promotes the formation of fogs and grew up
Phenomena similar to daytime sea breezes can be observed on the outskirts of large cities, where there is a circulation of colder air from the suburbs to the center, as “heat spots” exist over the cities throughout the year.
Mountain-valley winds and slope winds in the mountains they have a daily periodicity: during the day the wind blows up the valley and along the mountain slopes, at night, on the contrary, the cooled, heavier air descends down. The rise of air during the day leads to the formation of cumulus clouds over the slopes of the mountains; at night, the cloudiness disappears due to the sinking and adiabatic heating of the air.
Glacial (katabatic) winds – These are cold winds that constantly blow from mountain glaciers down the slopes and valleys. They are caused by cooling of the air above the ice. Their speed is 5–10 m/s, but along the edges of ice caps on the coasts of Antarctica and Greenland it can increase to 20 m/s. The power of the drain air flows is several tens or hundreds of meters. They are more intense at night, as they are amplified by slope winds.
Rice. 69. Scheme of hair dryer formation (according to I. I. Guralnik)
Hairdryer- a warm, dry, gusty wind blowing from the mountains to the valleys or foothills. With a hairdryer, the temperature at the foot of the leeward side of the mountains can rise by tens of degrees in a few hours, and the relative humidity can drop to 10–20%. The duration of hair dryers ranges from several hours to several days. The hair dryer is formed due to the fact that when ascending the windward slope of the mountains, the air in the lower part of the path to the level of condensation is cooled along a dry adiabatic gradient (1°/100 m), and the upper part of the path is cooled along a wet adiabatic gradient (0.5 °/100 m). As the air descends, it heats up dry adiabatically and arrives at the foot of the mountains or in the valley with a higher temperature. The absolute and relative humidity of the hair dryer, on the contrary, is reduced. The decrease in absolute air humidity is due to the formation of clouds and orographic precipitation on the windward slopes of the mountains. In addition, the relative humidity in the hair dryer decreases as the temperature rises and, accordingly, the maximum air humidity increases. The foehn effect is more significant at higher mountain altitudes and in the cold half of the year, when the initial relative air humidity is higher and therefore the level of condensation on the windward side of the ridge is lower (Fig. 69).
The climatic effect of a hairdryer is significant, especially if it is intense and long-lasting. In places where hair dryers constantly develop, abnormally elevated air temperatures are observed. A hairdryer can lead to avalanches, rapid melting of snow in the mountains and overflows of mountain rivers fed by glaciers and snow. In spring, a hair dryer can cause premature flowering of garden plants or the death of inflorescences. In summer it either accelerates the ripening of bread and fruit or has a detrimental effect on them. As a result of the hairdryer, summer leaf fall often occurs. Fen are frequent in the Alps (Innsbruck - 75 days a year), in the Western Caucasus and Transcaucasia (Kutaisi - 114 days), in Altai (Lake Teletskoye - 150 days), on the southern slope of the Crimean Mountains, on the northern slope of Kopetdag (local name for fen - harmsil), on the eastern slope of the Rocky Mountains, on the eastern leeward slope of the Sierra Nevada Mountains, at the foot of which is the hot, arid depression of Death Valley, in the Mojave Desert and in many other mountains.
Bora– a strong, cold, gusty wind blowing from low mountains towards the relatively warm sea. Bora has been fairly well studied in the area of Novorossiysk Bay on the Black Sea, where it occurs on average 46 days a year. Similar winds are observed on the Adriatic coast - in Yugoslavia and Italy, near the city of Trieste, in the south of France (mistral), near Baku (north), on Lake Baikal (Sarma) and in other places. Bora occurs in winter, from November to March, when a cold front approaches the low ridges along the coast from the landward side. In the Novorossiysk region, a strong cold wind rushes down from the mountain slope of the Varada ridge, through the Markhotsky pass, and acquires a speed of more than 20 m/s, causing destruction on land. On the surface of the water, a storm wind produces strong waves. At the same time, the air temperature drops sharply, often to sub-zero values. When water hits ships and coastal buildings, it quickly freezes, covering them with an icy crust. A preventive measure to combat bora is for ships to go out to the open sea several tens of kilometers from the coast, where the wind subsides.
1. Before the flight and taking up an air traffic services shift, analyze aerosynoptic materials, paying special attention to AT-400, 300 and 200 hPa maps, atmospheric radio sounding data, maps of maximum winds (Fig. 11.9).
2. If a tailwind is observed during the flight, it is necessary to use it. In this case, it is recommended to fly in its central part or on the right side.
4. The ST can be crossed 1.5…2.0 km below the axis or above the tropopause.
5. If you enter a bumpy area associated with a downwind ST, you must change flight level or deviate to the right (taking into account the temperature deviation from the ST).
7. When an ST is detected, the aircraft commander must immediately inform the controller about its direction, speed and phenomena associated with it.
8. You can detect a ST in flight by cloud stripes stretching along its direction,
and on the demolition of the aircraft, in this case:
If a strong left drift is observed and the air temperature rises, then the aircraft enters the ST from the left side;
If there is a strong right drift and the air temperature decreases, then the aircraft enters the ST from the right side;
If during horizontal flight along the ST the air temperature remains constant and the ground speed increases (decreases), then the ST is tailwind (headwind).
In certain areas, under the influence of local physical and geographical conditions, air currents are formed that have a relatively small horizontal and vertical extent and differ in characteristic features. Such air currents are called local winds . They can arise due to uneven heating of the underlying surface (land, water, mountain slopes and valleys) or due to the peculiarities of air flow around orographic obstacles. Local winds include breezes, mountain-valley winds, glacial winds, bora, foehn and others.
Breezes- these are winds with daily periodicity that occur on the coasts of seas, large lakes and wide rivers. The reason for their occurrence is uneven heating and cooling of land and sea during the day, approx.
Daytime (sea) breeze blows from a cold water surface onto a heated land, and night (shore) breeze - from cooled land to a warmer water surface (Fig. 10.7).
The sea breeze appears around 9...11 a.m. local time, spreads inland to 20...40 km, its vertical thickness reaches several hundred meters (sometimes up to 1000 m). Maximum speeds reach 4...6 m/s and are observed in the afternoon.
The coastal breeze forms after sunset and during the night penetrates 8...10 km deep into the sea.
Rice. 10.7. Breeze circulation formation scheme
In temperate latitudes, breezes are observed in the warm half of the year; they are more clearly expressed in clear weather, if the general air transport is absent or weakened. Above the breeze there is a wind of the opposite direction of approximately the same vertical power, called antibreeze .
Well-developed breezes are observed on the Black, Azov and Caspian Seas, weaker on the White Sea, on Lakes Ladoga and Onega. In tropical areas, breezes are observed all year round.
When flying in areas where breeze circulation is observed, it is necessary to take into account the change in wind directions near the ground and at the height of the circle in the morning and evening hours.
Mountain-valley winds- like breezes, they have a daily periodicity and arise due to uneven heating and cooling of mountain slopes and valleys day and night (Fig. 10.8).
Rice. 10.8. Scheme of formation of mountain-valley winds
During the day, mountain slopes and the air adjacent to them heat up faster and more strongly than air away from the slopes. As a result, lighter warm air rises up the mountain slopes. This wind is called valley .
At night, the mountain slopes and the air adjacent to them cool faster than the air removed from the slopes. Therefore, colder air falls down along the slopes. This is how it will be formed mountain wind .
The speed of valley winds usually does not exceed 3...6 m/s, and the speed of mountain winds
can reach 20 m/s or more. This can lead to severe bumpiness and sudden downward thrusts of aircraft.
Glacial winds blow over the glacier downstream of the glacier. They do not have a daily periodicity, because the glacier cools the air throughout the day. There is usually an inversion above the glacier, so cold air blows (flows) down. Over the glaciers of the Caucasus, the speed of such winds reaches 5...7 m/s. Glacial winds in
observed on a huge scale in Antarctica. Here they are called katabatic winds . Due to the fact that the movement of air in this case is influenced not only by the force of the horizontal baric gradient, but also by the force of gravity of the Earth, the speed of katabatic winds reaches 20 m/s or more.
Bora- this is a strong cold gusty wind that occurs when cold air falls from low coastal mountains onto the coast and a fairly warm sea. The most famous is the Novorossiysk bora (on average 46 days a year) on the northeastern coast of the Black Sea (Fig. 10.9).
Rice. 10.9. Scheme of the Novorossiysk forest in the stage of collapse
It is formed in those cases when an area of high pressure is established over the Krasnodar Territory of Russia, and low pressure is established over the Black Sea. The cold air mass accumulates in front of the Markhotsky pass (height 450 m) and, reaching its peak in front of Novorossiysk, falls down. Wind speed reaches 40...60 m/s or more. Cold air, mixing with warm air near the surface of the sea, reaches a state of saturation. If the air temperature is below 0°C, favorable conditions are created for the formation of ice.
Local bora-type winds in various geographical areas are called: Sarma - near the Olkhovsky Gate on Lake Baikal; Nord - in the Baku region; Mistral - on the Mediterranean coast of France (from Montpellier to Toulon); Northser - in the Gulf of Mexico (Mexico, Texas); Oroshi is on the ocean coast of Japan.
Föhn- this is a dry, warm, gusty wind that occurs when air currents cross large mountain ranges and spreads far into the plain. It can be observed at any time of the year and day. The main reason for its formation is the flow of air over the top of the mountain. Relatively warm air rises up along the windward slope and is cooled to a condensation level of 1°C for every 100 m, above the condensation level - by an average of 0.5°C for every 100 m. The rise of air will be accompanied by condensation of water vapor, the formation clouds and precipitation (Fig. 10.10). Having reached the top of the mountain, the air will begin to flow over it and fall along the slope on the leeward side of the mountain. As it descends, the air will warm up by 1° per 100 m; as a result, the clouds on the leeward side are washed away, and the air in the valley arrives dry and warm.
Rice. 10.10. Föhn formation diagram
Changes in temperature and humidity can be very rapid and dramatic:
In 1…2 hours the temperature can rise by 30…40°C. The duration of the foehn varies from several hours to 5 days or more. The foehn speed fluctuates from calm to 15...20 m/s; foehn speeds of 30...40 m/s were observed.
When flying in areas where foehn is observed, suction may occur.
aircraft towards the mountain, sometimes there are sharp drops down.
Foehn can occur in all mountainous regions, they are especially frequent in the Alps,
The Carpathians, the Caucasus, the mountains of Central Asia and the Far East.
Education local winds associated with the nature of the underlying surface (orography, type of surface - water or land) and temperature. Local winds of thermal origin include breezes. They are better expressed in cloudless anticyclonic weather and appear especially often on the western coasts of the tropics, where heated continents are washed by the waters of cold currents. We grouped other local winds depending on their properties and origin (temperature or type of landscape over which they form) into three groups: cold, mountain-valley and desert. Separately, the local names of the winds of Baikal were given.
Local winds |
Description of the wind |
Cold local winds: |
|
Blizzard |
cold piercing wind of storm force in Canada and Alaska (analogous to a blizzard in Siberia). |
Bora (Greek “boreas” - north wind) |
a strong, gusty wind blowing mainly in the winter months from mountain ranges on the sea coast. Occurs when a cold wind (high pressure) passes over a ridge and displaces warm, less dense air (low pressure) on the other side. In winter it causes severe cooling. Occurs in the northwest coast of the Adriatic Sea. Black Sea (near Novorossiysk), on Lake Baikal. Wind speed during boron can reach 60 m/s, its duration is several days, sometimes up to a week. |
dry, cold, north or northeast wind in mountainous areas of France and Switzerland |
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Borasco, burraska (Spanish “borasco” - small bora) |
strong squall with thunderstorm over the Mediterranean Sea. |
small intense vortex in Antarctica. |
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cold north wind in Spain. |
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a cold wind from Siberia, bringing sharp cold snaps, frosts and snowstorms in Kazakhstan and the deserts of Central Asia. |
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a sea breeze that softens the heat on the northern coast of Africa. |
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cold northeast wind blowing over the lower part of the Danube Lowland. |
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Levantine |
eastern strong, humid wind, accompanied by cloudy weather and rain in the cold half of the year over the Black and Mediterranean seas. |
cold north wind over the coast of China. |
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Mistral |
the invasion of cold, strong and dry wind from the polar regions of Europe along the Rhone River valley on the coast of the Gulf of Lyon in France from Montpellier to Toulon in the winter-spring period (February, March). |
Meltemi |
northern summer wind in the Aegean Sea. |
cold north wind in Japan, blowing from the polar regions of Asia. |
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bora-type wind only in the Baku region (Azerbaijan). |
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Norther, norther (eng. “norther” - north) |
strong cold and dry winter (November - April) northerly wind blowing from Canada to the USA, Mexico, Gulf of Mexico, all the way to northern South America. Accompanied by rapid cooling, often with showers, snowfalls, and ice. |
cold southerly storm wind in Argentina. Accompanied by rain and thunderstorms. Then the cooling rate reaches 30 °C per day, atmospheric pressure rises sharply, and cloudiness dissipates. |
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strong winter wind in Siberia, lifting snow from the surface, resulting in reduced visibility to 2-5 m. |
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Mountain-valley winds: föhns (Bornan, Breva, Talvind, Chelm, Chinook, Garmsil) - warm, dry, gusty winds that cross the ridges and blow from the mountains along the slope into the valley, lasting less than a day. In different mountain regions, foehn winds have their own local names. |
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breeze in the Swiss Alps blowing from the river valley. Drance to the middle part of Lake Geneva. |
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afternoon valley wind combined with a breeze on Lake Como (Northern Italy). |
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Garmsil |
strong dry and very hot (up to 43 °C and above) wind on the northern slopes of the Kopetdag and the lower parts of the Western Tien Shan. |
pleasant valley wind in Germany. |
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Chinook (or Chinook) |
a dry and warm southwesterly wind on the eastern slopes of the North American Rockies, which can cause very large temperature fluctuations, especially in winter. There is a known case when in January, in less than a day, the air temperature increased by 50°: from -31° to + 19°. Therefore, the Chinook is called the “snow eater” or “snow eater”. |
Desert winds: Samum, Sirocco, Khamsin, Khabub - dry, very hot dusty or sandy winds. |
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dry hot western or southwestern wind in the Northern deserts. Africa and Arabia, swoops in like a whirlwind, covers the Sun and sky, rages for 15-20 minutes. |
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dry, hot, strong wind of southern directions, blowing to the Mediterranean countries (France, Italy, Balkans) from the deserts of North Africa and Arabia; lasts several hours, sometimes days. |
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sweltering hot and dusty wind blowing over Gibraltar and south-east Spain, |
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This is a wind with high temperature and low air humidity in steppes, semi-deserts and deserts; it forms along the edges of anticyclones and continues for several days, increasing evaporation, drying out the soil and plants. Prevails in the steppe regions of Russia, Ukraine, Kazakhstan and the Caspian region. |
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dust or sandstorm in northeast Africa and the Arabian Peninsula. |
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Khamsin (or "fifty-day journal") |
hot gale in Egypt, blowing from Arabia for up to 50 days in a row. |
Harmattan |
local name for the northeast trade wind blowing from the Sahara to the Gulf of Guinea; brings dust, high temperatures and low humidity. |
analogue of khamsin in Central Africa. |
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Eblis ("dust devil") |
a sudden rise of heated air on a windless day in the form of a whirlwind, carrying sand and other objects (plants, small animals) to a very high altitude. |
Other local winds: |
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dusty southern or southwestern wind blowing from Afghanistan along the valleys of the Amu Darya, Syr Darya, and Vakhsh. It oppresses vegetation, covers fields with sand and dust, and removes the fertile layer of soil. In early spring it is accompanied by downpours and cold snaps leading to frosts, destroying cotton seedlings. In winter, it is sometimes accompanied by wet snow and leads to frostbite and death of livestock caught on the plains. |
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strong wind from the Caspian Sea, bringing surge floods to the lower reaches of the Volga. |
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southeast trade wind in the Pacific Ocean (for example, near the Tonga Islands). |
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Cordonazo |
strong southerly winds along the west coast of Mexico. |
the sea breeze blowing from the Pacific Ocean to the coast of Chile is especially strong in the afternoon in Valparaiso, which is why port operations are even suspended. Its antipode - the coastal breeze - is called terrap. |
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Zonda (sondo) |
strong northern or western dry and hot foehn-type wind on the eastern slopes of the Andes (Argentina). It has a depressing effect on people. |
prevails in the eastern part of the Mediterranean Sea, warm, brings rain and storms (in the western part of the Mediterranean Sea it is lighter) |
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fair wind on rivers and lakes. |
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Tornado (Spanish: Tornado) |
a very strong atmospheric vortex over land in North America, characterized by high frequency, formed as a result of the collision of cold masses from the Arctic and warm masses from the Caribbean. |
Winds of Baikal: |
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Verkhovik, or hangar |
north wind, overpowering other winds. |
Barguzin |
northeast storm wind blows in the central part of the lake from the Barguzin Valley across and along Lake Baikal |
local southwesterly gale bringing cloudy weather. |
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Harahaiha |
autumn-winter northwest wind. |
southeast storm wind blowing from the river valley. Goloustnoy. |
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cold strong chilling winter wind blows along the river valley. Sarma. |
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A source of information: Romashova T.V. Geography in figures and facts: Educational manual/ - Tomsk: 2008.