What is the movement of air masses definition. Air masses and their circulation. Air mass movements
Atmospheric circulation diagram
Air in the atmosphere is in constant motion. It moves both horizontally and vertically.
The primary reason for the movement of air in the atmosphere is the uneven distribution of solar radiation and the heterogeneity of the underlying surface. They cause uneven air temperature and, accordingly, atmospheric pressure above the earth's surface.
The pressure difference creates a movement of air that moves from areas of high to areas of low pressure. In the process of moving, air masses are deflected by the force of the rotation of the Earth.
(Remember how bodies move in the northern and southern hemispheres deviate.)
Of course, you have noticed how a light haze forms over the asphalt on a hot summer day. This is heated, light air rising up. A similar but much larger picture can be seen at the equator. Very hot air constantly rises, forming updrafts.
Therefore, a constant low-pressure belt is formed near the surface here.
The air that has risen above the equator in the upper layers of the troposphere (10-12 km) spreads to the poles. Gradually, it cools and begins to descend approximately above 30 t ° north and south latitude.
Thus, an excess of air is formed, which contributes to the formation of a tropical high-pressure belt in the surface layer of the atmosphere.
In the circumpolar regions, the air is cold, heavy and descends, causing downward movements. As a result, high pressure is formed in the near-surface layers of the polar belt.
Active atmospheric fronts form between the tropical and polar high-pressure belts in temperate latitudes. Massively colder air displaces warmer air upwards, causing updrafts.
As a result, a surface low-pressure belt is formed in temperate latitudes.
Map of the Earth's climate zones
If the earth's surface were uniform, atmospheric pressure belts would spread in continuous bands. However, the surface of the planet is an alternation of water and land, which have different properties. The land quickly heats up and cools down.
The ocean, on the contrary, heats up and releases its heat slowly. That is why atmospheric pressure belts are torn into separate sections - areas of high and low pressure. Some of them exist throughout the year, others - in a certain season.
On Earth, high and low pressure belts naturally alternate. High pressure - at the poles and near the tropics, low - at the equator and in temperate latitudes.
Types of atmospheric circulation
There are several powerful links in the circulation of air masses in the Earth's atmosphere. All of them are active and inherent in certain latitudinal zones. Therefore, they are called zonal types of atmospheric circulation.
Near the Earth's surface, air currents move from the tropical high-pressure belt to the equator. Under the influence of the force arising from the rotation of the Earth, they deviate to the right in the Northern Hemisphere and to the left in the Southern.
This is how constant powerful winds are formed - trade winds. In the Northern Hemisphere, the trade winds blow in the direction from the northeast, and in the Southern Hemisphere - from the southeast. So, the first zonal type of atmospheric circulation - trade wind.
Air moves from the tropics to temperate latitudes. Deviating under the influence of the force of the rotation of the Earth, they begin to gradually move from west to east. It is this flow from the Atlantic that covers the temperate latitudes of all of Europe, including Ukraine. Western air transport in temperate latitudes is the second zonal type of planetary atmospheric circulation.
The movement of air from the subpolar belts of high pressure to temperate latitudes, where the pressure is low, is also regular.
Under the influence of the deflecting force of the Earth's rotation, this air moves from the northeast in the Northern Hemisphere and from the southeast - in the Southern Hemisphere. The eastern subpolar flow of air masses forms the third zonal type of atmospheric circulation.
On the atlas map, find the latitudinal zones where various types of zonal air circulation dominate.
Due to the uneven heating of the land and ocean, the zonal pattern of movement of air masses is violated. For example, in the east of Eurasia in temperate latitudes, the western air transfer operates only for half a year - in winter. In summer, when the mainland heats up, the air masses move to land with the coolness of the ocean.
This is how the monsoon air transport occurs. The change in the direction of air movement twice a year is a characteristic feature of the monsoon circulation. The winter monsoon is a flow of relatively cold and dry air from the mainland to the ocean.
summer monsoon- the movement of moist and warm air in the opposite direction.
Zonal types of atmospheric circulation
There are three main zonal type of atmospheric circulation: trade wind, western air transport and eastern circumpolar air mass flow. Monsoonal air transport disrupts the general scheme of atmospheric circulation and is an azonal type of circulation.
General circulation of the atmosphere (page 1 of 2)
Ministry of Science and Education of the Republic of Kazakhstan
Academy of Economics and Law named after U.A. Dzholdasbekova
Faculty of Humanities and Economics Academy
By discipline: Ecology
On the topic: "General circulation of the atmosphere"
Completed by: Tsarskaya Margarita
Group 102 A
Checked by: Omarov B.B.
Taldykorgan 2011
Introduction
1. General information about atmospheric circulation
2. Factors that determine the general circulation of the atmosphere
3. Cyclones and anticyclones.
4. Winds affecting the general circulation of the atmosphere
5. Hair dryer effect
6. Scheme of the general circulation "Planet Machine"
Conclusion
List of used literature
Introduction
On the pages of scientific literature recently, the concept of general circulation of the atmosphere is often encountered, the meaning of which each specialist understands in his own way. This term is systematically used by specialists involved in geography, ecology, and the upper part of the atmosphere.
Increasing interest in the general circulation of the atmosphere is shown by meteorologists and climatologists, biologists and physicians, hydrologists and oceanologists, botanists and zoologists, and of course ecologists.
There is no consensus on whether this scientific direction has emerged recently or research has been going on here for centuries.
Below are the definitions of the general circulation of the atmosphere, as a set of sciences, and the factors influencing it are listed.
A certain list of achievements is given: hypotheses, developments and discoveries that mark certain milestones in the history of this set of sciences and give a certain idea of the range of problems and tasks considered by it.
The distinctive features of the general circulation of the atmosphere are described, as well as the simplest scheme of the general circulation called the "planetary machine" is presented.
1. General information about atmospheric circulation
The general circulation of the atmosphere (lat. Circulatio - rotation, Greek atmos - steam and sphaira - ball) is a set of large-scale air currents in the tropo- and stratospheres. As a result, there is an exchange of air masses in space, which contributes to the redistribution of heat and moisture.
The general circulation of the atmosphere is called the circulation of air on the globe, leading to its transfer from low latitudes to high latitudes and vice versa.
The general circulation of the atmosphere is determined by zones of high atmospheric pressure in the subpolar regions and tropical latitudes and zones of low pressure in temperate and equatorial latitudes.
The movement of air masses occurs both in latitudinal and meridional directions. In the troposphere, the circulation of the atmosphere includes trade winds, westerly air currents of temperate latitudes, monsoons, cyclones and anticyclones.
The reason for the movement of air masses is the unequal distribution of atmospheric pressure and the heating by the Sun of the surface of land, oceans, ice at different latitudes, as well as the deflecting effect on air flows of the Earth's rotation.
The main patterns of atmospheric circulation are constant.
In the lower stratosphere, jet streams of air in temperate and subtropical latitudes are predominantly western, and in tropical latitudes - eastern, and they go at a speed of up to 150 m / s (540 km / h) relative to the earth's surface.
In the lower troposphere, the prevailing directions of air transport differ in geographical zones.
In polar latitudes, easterly winds; in temperate - western with frequent disturbance by cyclones and anticyclones, trade winds and monsoons are most stable in tropical latitudes.
Due to the diversity of the underlying surface, regional deviations - local winds - appear on the form of the general circulation of the atmosphere.
2. Factors that determine the general circulation of the atmosphere
- Uneven distribution of solar energy over the earth's surface and, as a result, uneven distribution of temperature and atmospheric pressure.
- Coriolis forces and friction, under the influence of which air flows acquire a latitudinal direction.
– The influence of the underlying surface: the presence of continents and oceans, the heterogeneity of the relief, etc.
The distribution of air currents in the earth's surface has a zonal character. In the equatorial latitudes - calm or weak variable winds are observed. The trade winds dominate the tropical zone.
The trade winds are constant winds blowing from 30 latitudes to the equator, having a northeasterly direction in the northern hemisphere, and a southeasterly direction in the southern hemisphere. At 30-35? With. and y.sh. - calm zone, so-called. "horse latitudes".
In temperate latitudes, westerly winds prevail (southwest in the northern hemisphere, northwest in the southern hemisphere). In the polar latitudes, easterly (in the northern hemisphere northeast, in the southern hemisphere - southeast) winds blow.
In reality, the system of winds over the earth's surface is much more complicated. In the subtropical belt, the trade winds are disrupted in many areas by the summer monsoons.
In temperate and subpolar latitudes, cyclones and anticyclones have a great influence on the nature of air currents, and on the eastern and northern coasts - monsoons.
In addition, local winds are formed in many areas, due to the characteristics of the territory.
3. Cyclones and anticyclones.
The atmosphere is characterized by eddy movements, the largest of which are cyclones and anticyclones.
A cyclone is an ascending atmospheric vortex with low pressure in the center and a system of winds from the periphery to the center, directed against in the northern hemisphere, and clockwise in the southern hemisphere. Cyclones are divided into tropical and extratropical. Consider extratropical cyclones.
The diameter of extratropical cyclones is on average about 1000 km, but there are more than 3000 km. Depth (pressure in the center) - 1000-970 hPa or less. Strong winds blow in the cyclone, usually up to 10-15 m/s, but can reach 30 m/s and more.
The average speed of the cyclone is 30-50 km/h. Most often, cyclones move from west to east, but sometimes they move from the north, south, and even east. The zone of the greatest frequency of cyclones is the 80th latitude of the northern hemisphere.
Cyclones bring cloudy, rainy, windy weather, in summer - cooling, in winter - warming.
Tropical cyclones (hurricanes, typhoons) form in tropical latitudes; this is one of the most formidable and dangerous natural phenomena. Their diameter is several hundred kilometers (300-800 km, rarely more than 1000 km), but a large difference in pressure between the center and the periphery is characteristic, which causes strong hurricane-force winds, tropical showers, and severe thunderstorms.
An anticyclone is a descending atmospheric vortex with increased pressure in the center and a system of winds from the center to the periphery, directed clockwise in the northern hemisphere and counterclockwise in the southern hemisphere. The dimensions of anticyclones are the same as those of cyclones, but in the late stage of development they can reach up to 4000 km in diameter.
Atmospheric pressure in the center of anticyclones is usually 1020-1030 hPa, but can reach more than 1070 hPa. The highest frequency of anticyclones is over the subtropical zones of the oceans. Anticyclones are characterized by cloudy, rainless weather, with weak winds in the center, severe frosts in winter, and heat in summer.
4. Winds affecting the general circulation of the atmosphere
Monsoons. Monsoons are seasonal winds that change direction twice a year. In summer they blow from the ocean to the land, in winter - from the land to the ocean. The reason for the formation is the uneven heating of land and water in seasons. Depending on the zone of formation, monsoons are divided into tropical and extratropical.
Extratropical monsoons are especially pronounced on the eastern margin of Eurasia. The summer monsoon brings moisture and coolness from the ocean, while the winter monsoon blows from the mainland, lowering the temperature and humidity.
Tropical monsoons are most pronounced in the Indian Ocean basin. The summer monsoon blows from the equator, it is opposite to the trade wind and brings cloudiness, precipitation, softens the summer heat, winter - coincides with the trade wind, strengthens it, bringing dryness.
local winds. Local winds have a local distribution, their formation is associated with the characteristics of a given territory - the proximity of water bodies, the nature of the relief. The most common are breezes, bora, foehn, mountain-valley and katabatic winds.
Breezes (light wind-FR) - winds along the shores of the seas, large lakes and rivers, twice a day changing direction to the opposite: the daytime breeze blows from the reservoir to the shore, the night breeze - from the coast to the reservoir. Breezes are caused by the diurnal variation of temperature and, accordingly, pressure over land and water. They capture a layer of air 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 the continents in tropical latitudes, washed by cold currents and cold water rising off the coast in the upwelling zone.
There it invades inland for tens of kilometers and produces a strong climatic effect: it reduces the temperature, especially in summer by 5-70 C, and in West Africa up to 100 C, increases the relative humidity of the air to 85%, contributes to the formation of fogs and dew.
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, since there are "heat spots" over the cities throughout the year.
Mountain-valley winds 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 air descends. The daytime air rise leads to the formation of cumulus clouds over the slopes of the mountains, at night, when the air descends and the air is adiabatically heated, the cloudiness disappears.
Glacial winds are cold winds that constantly blow from mountain glaciers down slopes and valleys. They are caused by the cooling of the air above the ice. Their speed is 5-7 m/s, their thickness is several tens of meters. They are more intense at night, as they are amplified by the slope winds.
General circulation of the atmosphere
1) Due to the tilt of the Earth's axis and the sphericity of the Earth, the equatorial regions receive more solar energy than the polar regions.
2) At the equator, the air heats up → expands → rises up → a low pressure area is formed. 3) At the poles, the air cools down → condenses → sinks down → a high pressure area forms.
4) Due to the difference in atmospheric pressure, air masses begin to move from the poles to the equator.
Wind direction and speed are also affected by:
- properties of air masses (humidity, temperature…)
- underlying surface (oceans, mountain ranges, etc.)
- rotation of the globe around its axis (Coriolis force) 1) a general (global) system of air currents above the earth's surface, the horizontal dimensions of which are commensurate with the continents and oceans, and the thickness is from several kilometers to tens of kilometers.
trade winds - These are constant winds blowing from the tropics to the equator.
The reason: the equator is always low pressure (updrafts) and the tropics are always high pressure (downdrafts).
Due to the action of the Coriolis force: the trade winds of the Northern Hemisphere have a northeasterly direction (deviate to the right)
Southern Hemisphere trade winds - southeast (deviate to the left)
Northeast winds(in the Northern Hemisphere) and southeast winds(in the southern hemisphere).
Reason: air flows move from the poles to temperate latitudes and, under the influence of the Coriolis force, deviate to the west. Western winds are winds that blow from the tropics to temperate latitudes, predominantly from west to east.
Reason: in the tropics there is high pressure, and in temperate latitudes it is low, so part of the air from the V.D region moves to the H, D, region. When moving under the influence of the Coriolis force, air currents deviate to the east.
Westerly winds bring warm and humid air to Estonia. air masses are formed over the waters of the warm North Atlantic Current.
The air in the cyclone moves from the periphery to the center;
In the central part of the cyclone, the air rises and
It cools, so clouds and precipitation form;
During cyclones, cloudy weather with strong winds prevails:
summer- rainy and cold
winter- with thaws and snowfalls.
Anticyclone is an area of high atmospheric pressure with a maximum in the center.
air in an anticyclone moves from the center to the periphery; in the central part of the anticyclone, the air descends and heats up, its humidity drops, the clouds dissipate; with anticyclones, clear calm weather is established:
summer is hot
in winter it is frosty.
Atmospheric circulation
Definition 1
Circulation It is a system for the movement of air masses.
Circulation can be general on the scale of the entire planet and local circulation, which occurs over individual territories and water areas. Local circulation includes day and night breezes that occur on the coasts of the seas, mountain-valley winds, glacial winds, etc.
Local circulation at certain times and in certain places can be superimposed on the currents of the general circulation. With the general circulation of the atmosphere, huge waves and whirlwinds arise in it, which develop and move in different ways.
Such atmospheric disturbances are cyclones and anticyclones, which are characteristic features of the general circulation of the atmosphere.
As a result of the movement of air masses, which occurs under the action of centers of atmospheric pressure, the territories are provided with moisture. As a result of the fact that air movements of different scales simultaneously exist in the atmosphere, overlapping each other, atmospheric circulation is a very complex process.
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The movement of air masses on a planetary scale is formed under the influence of 3 main factors:
These factors complicate the general circulation of the atmosphere.
If the earth were uniform and not rotating around its axis - then the temperature and pressure at the earth's surface would correspond to thermal conditions and be of a latitudinal nature. This means that the decrease in temperature would occur from the equator to the poles.
With this distribution, warm air rises at the equator, while cold air sinks at the poles. As a result, it would accumulate at the equator in the upper part of the troposphere, and the pressure would be high, and at the poles it would be reduced.
At altitude, the air would flow in the same direction and lead to a decrease in pressure over the equator and its increase over the poles. The outflow of air near the earth's surface would occur from the poles, where the pressure is high towards the equator in the meridional direction.
It turns out that the thermal cause is the first cause of atmospheric circulation - different temperatures lead to different pressures at different latitudes. In reality, pressure is low at the equator, and high at the poles.
On a uniform rotating Earth in the upper troposphere and lower stratosphere, the winds during their outflow to the poles in the northern hemisphere should deviate to the right, in the southern hemisphere - to the left and at the same time become westerly.
In the lower troposphere, winds flowing from the poles towards the equator and deviating would become easterly in the northern hemisphere, and southeasterly in the southern hemisphere. The second reason for the circulation of the atmosphere is clearly visible - dynamic. The zonal component of the general circulation of the atmosphere is due to the rotation of the Earth.
The underlying surface with an uneven distribution of land and water has a significant impact on the general circulation of the atmosphere.
Cyclones
The lower layer of the troposphere is characterized by eddies that appear, develop and disappear. Some eddies are very small and go unnoticed, while others have a great influence on the planet's climate. First of all, this applies to cyclones and anticyclones.
Definition 2
Cyclone is a huge atmospheric vortex with low pressure in the center.
In the Northern Hemisphere, the air in the cyclone moves counterclockwise, in the Southern Hemisphere - clockwise. Cyclonic activity in middle latitudes is a feature of atmospheric circulation.
Cyclones arise due to the rotation of the Earth and the deflecting force of Coriolis, and in their development they go through stages from inception to filling. As a rule, the occurrence of cyclones occurs on atmospheric fronts.
Two air masses of opposite temperature, separated by a front, are drawn into a cyclone. Warm air at the interface intrudes into the cold air region and is deflected to high latitudes.
The balance is disturbed, and the cold air in the rear is forced to penetrate into low latitudes. There is a cyclonic bend of the front, which is a huge wave moving from west to east.
The wave stage is first stage cyclone development.
Warm air rises and slides over the frontal surface at the front of the wave. The resulting waves with a length of $1000$ km and more are unstable in space and continue to develop.
At the same time, the cyclone moves to the east at a speed of $100$ km per day, the pressure continues to fall, and the wind becomes stronger, the wave amplitude increases. it second stage is the stage of a young cyclone.
On special maps, a young cyclone is outlined by several isobars.
With the advancement of warm air to high latitudes, a warm front forms, and the advancement of cold air into tropical latitudes forms a cold front. Both fronts are part of a single whole. A warm front moves more slowly than a cold front.
If a cold front catches up with a warm front and merges with it, a occlusion front. Warm air rises and twists in a spiral. it third stage cyclone development - the stage of occlusion.
Fourth stage– its completion is final. There is a final pushing of warm air upwards and its cooling, temperature contrasts disappear, the cyclone becomes cold over its entire area, slows down its movement and finally fills up. From inception to filling, the life of a cyclone lasts from $5$ to $7$ days.
Remark 1
Cyclones bring cloudy, cool and rainy weather in summer and thaws in winter. Summer cyclones move at a speed of $400-$800 km per day, winter - up to $1000 km per day.
Anticyclones
Cyclonic activity is associated with the emergence and development of frontal anticyclones.
Definition 3
Anticyclone- This is a huge atmospheric vortex with high pressure in the center.
Anticyclones are formed in the rear of the cold front of a young cyclone in cold air and have their own stages of development.
There are only three stages in the development of an anticyclone:
General circulation of the atmosphere
The objects of study of the general circulation of the atmosphere are moving cyclones and anticyclones of temperate latitudes with their rapidly changing meteorological conditions: trade winds, monsoons, tropical cyclones, etc. Typical features of the general circulation of the atmosphere, stable in time or recurring more often than others, are revealed by averaging meteorological elements over long periods of time. long-term observation periods,
On fig. 8, 9 shows the average long-term wind distribution near the earth's surface in January and July. In January, i.e.
in winter, in the Northern Hemisphere, giant anticyclonic eddies are clearly visible over North America and a particularly intense eddy over Central Asia.
In summer, anticyclonic eddies over the land are destroyed due to the heating of the continent, and over the oceans, such eddies are significantly enhanced and propagate to the north.
Surface pressure in millibars and prevailing air currents
Due to the fact that in the troposphere the air in the equatorial and tropical latitudes is warmed up much more intensively than in the polar regions, the air temperature and pressure gradually decrease in the direction from the equator to the poles. As meteorologists say, the planetary gradient of temperature and pressure is directed in the middle troposphere from the equator to the poles.
(In meteorology, the gradient of temperature and pressure is taken in the opposite direction, compared to physics.) Air is a highly mobile medium. If the Earth did not rotate around its axis, then in the lower layers of the atmosphere the air would flow from the equator to the poles, and in the upper layers it would return back to the equator.
But the Earth rotates at an angular velocity of 2p/86400 radians per second. Air particles, moving from low latitudes to high latitudes, retain large linear velocities relative to the earth's surface, acquired at low latitudes, and therefore deviate as they move to the east. A west-east air transport is formed in the troposphere, which is reflected in Fig. ten.
However, such a correct regime of currents is observed only on maps of average values. "Snapshots" of air currents give very diverse, each time new, non-repeating positions of cyclones, anticyclones, air currents, zones of meetings of warm and cold air, i.e., atmospheric fronts.
Atmospheric fronts play an important role in the general circulation of the atmosphere, since significant transformations of the energy of air masses from one type to another take place in them.
On fig. 10 schematically shows the position of the main frontal sections in the middle troposphere and near the earth's surface. Numerous weather phenomena are associated with atmospheric fronts and frontal zones.
Here, cyclonic and anticyclonic eddies are born, powerful clouds and precipitation zones are formed, and wind intensifies.
When an atmospheric front passes through a given point, a noticeable cooling or warming is usually clearly observed, and the whole character of the weather changes sharply. Interesting features are found in the structure of the stratosphere.
Planetary frontal zone in the middle troposphere
If heat is located in the troposphere near the equator; air masses, and at the poles - cold, then in the stratosphere, especially in the warm half of the year, the situation is just the opposite, at the poles the air is relatively warmer here, and at the equator it is cold.
The temperature and pressure gradients are directed in the opposite direction with respect to the troposphere.
The influence of the deflecting force of the Earth's rotation, which led to the formation of west-east transport in the troposphere, creates a zone of east-west winds in the stratosphere.
Average location of jet stream axes in the Northern Hemisphere in winter
The highest wind speeds and, consequently, the highest kinetic energy of air are observed in jet streams.
Figuratively speaking, jet streams are air rivers in the atmosphere, rivers flowing near the upper boundary of the troposphere, in the layers separating the troposphere from the stratosphere, i.e., in layers close to the tropopause (Fig. 11 and 12).
Wind speed in jet streams reaches 250 - 300 km/h - in winter; and 100 - 140 km / h - in summer. Thus, a low-speed aircraft, falling into such a jet stream, can fly "backward".
Average location of jet stream axes in the Northern Hemisphere in summer
The length of the jet streams reaches several thousand kilometers. Below the jet streams in the troposphere, there are wider and slower air "rivers" - planetary high-altitude frontal zones, which also play an important role in the general circulation of the atmosphere.
The occurrence of high wind speeds in jet streams and in planetary high-altitude frontal zones is due to the presence here of a large difference in air temperatures between neighboring air masses.
The presence of a difference in air temperature, or, as they say, "temperature contrast", leads to an increase in wind with height. The theory shows that this increase is proportional to the horizontal temperature gradient of the considered air layer.
In the stratosphere, due to the reversal of the meridional air temperature gradient, the intensity of jet streams decreases and they disappear.
Despite the great extent of planetary high-altitude frontal zones and jet streams, they, as a rule, do not encircle the entire globe, but end where horizontal temperature contrasts between air masses weaken. Most often and sharply, temperature contrasts are manifested in the polar front, which separates air from temperate latitudes from tropical air.
The position of the axis of the high-altitude frontal zone with a slight meridional exchange of air masses
Planetary high-altitude frontal zones and jet streams often occur in the polar front system. Although, on average, planetary high-altitude frontal zones have a direction from west to east, in specific cases, the direction of their axes is very diverse. Most often in temperate latitudes, they have a wave-like character. On fig.
13, 14 show the positions of the axes of the high-altitude frontal zones in cases of stable west-east transport and in cases of developed meridional exchange of air masses.
An essential feature of air currents in the stratosphere and mesosphere over the equatorial and tropical regions is the existence there of several layers of air with almost opposite directions of strong winds.
The emergence and development of this multilayer structure of the wind field changes here at certain, but not quite exactly coinciding, intervals of time, which can also serve as some prognostic sign.
If we add to this that the phenomenon of sharp warming in the polar stratosphere, which regularly occurs in winter, is in some way connected with the processes in the stratosphere occurring in tropical latitudes, and with the tropospheric processes of temperate and high latitudes, then it becomes clear how complex and whimsical the development of those atmospheric processes that directly affect the weather regime in temperate latitudes.
The position of the axis of the high-altitude frontal zone with a significant meridional exchange of air masses
Of great importance for the formation of large-scale atmospheric processes is the state of the underlying surface, especially the state of the upper active water layer of the World Ocean. The surface of the World Ocean is almost 3/4 of the entire surface of the Earth (Fig. 15).
sea currents
Due to the high heat capacity and the ability to mix easily, ocean waters store heat for a long time during encounters with warm air in temperate latitudes and throughout the year in southern latitudes. The stored heat with sea currents is carried far to the north and warms nearby areas.
The heat capacity of water is several times greater than the heat capacity of the soil and rocks that make up the land. The heated water mass serves as a heat accumulator with which it supplies the atmosphere. At the same time, it should be noted that the land reflects the sun's rays much better than the surface of the ocean.
The surface of snow and ice reflects the sun's rays especially well; 80-85% of all solar radiation falling on the snow is reflected from it. The surface of the sea, on the contrary, absorbs almost all the radiation that falls on it (55-97%). As a result of all these processes, the atmosphere receives only 1/3 of all incoming energy directly from the Sun.
The remaining 2/3 of the energy it receives from the underlying surface heated by the Sun, primarily from the water surface. Heat transfer from the underlying surface to the atmosphere occurs in several ways. First, a large amount of solar heat is spent on the evaporation of moisture from the surface of the ocean into the atmosphere.
When this moisture condenses, heat is released, which heats the surrounding layers of air. Secondly, the underlying surface gives off heat to the atmosphere through turbulent (i.e., vortex, disordered) heat transfer. Thirdly, heat is transferred by thermal electromagnetic radiation. As a result of the interaction of the ocean with the atmosphere, important changes occur in the latter.
The layer of the atmosphere into which the heat and moisture of the ocean penetrates, in cases where cold air invades the warm ocean surface, reaches 5 km or more. In those cases when warm air invades the cold water surface of the ocean, the height to which the influence of the ocean extends does not exceed 0.5 km.
In cases of cold air intrusion, the thickness of its layer, which is affected by the ocean, depends primarily on the magnitude of the water-air temperature difference. If the water is warmer than the air, then powerful convection develops, i.e., disordered ascending air movements, which lead to the penetration of heat and moisture into the high layers of the atmosphere.
On the contrary, if the air is warmer than water, then convection does not occur and the air changes its properties only in the lowest layers. Over the warm Gulf Stream in the Atlantic Ocean, with the intrusion of very cold air, the heat transfer of the ocean can reach up to 2000 cal/cm2 per day and extends to the entire troposphere.
Warm air can lose 20-100 cal/cm2 per day over the cold ocean surface. The change in the properties of the air that hits a warm or cold oceanic surface occurs quite quickly - such changes can be noticed at a level of 3 or 5 km already a day after the start of the invasion.
What increments of air temperature can be as a result of its transformation (change) above the underlying water surface? It turns out that in the cold half-year the atmosphere over the Atlantic warms up by 6° on average, and sometimes it can warm up by 20° per day. The atmosphere can cool by 2-10° per day. It is estimated that in the north of the Atlantic Ocean, i.e.
where the most intense transfer of heat from the ocean to the atmosphere occurs, the ocean gives off 10-30 times more heat than it receives from the atmosphere. Naturally, the heat reserves in the ocean are replenished by the influx of warm oceanic waters from tropical latitudes. Air currents distribute the heat received from the ocean for thousands of kilometers. The warming effect of the oceans in winter leads to the fact that the difference in air temperature between the northeastern parts of the oceans and continents is 15-20° at latitudes of 45-60 ° near the earth's surface, and 4-5 ° in the middle troposphere. For example, the warming effect of the ocean on the climate of northern Europe has been well studied.
The northwestern part of the Pacific Ocean in winter is under the influence of the cold air of the Asian continent, the so-called winter monsoon, which propagates 1-2 thousand km deep into the ocean in the water layer and 3-4 thousand km in the middle troposphere (Fig. 16) .
Annual amounts of heat carried by sea currents
In summer, it is colder over the ocean than over the continents, so the air coming from the Atlantic Ocean cools Europe, and the air from the Asian continent warms the Pacific Ocean. However, the picture described above is typical for average circulation conditions.
Day-to-day changes in the magnitude and in the direction of heat fluxes from the underlying surface to the atmosphere and back are very diverse and have a great influence on the change in the atmospheric processes themselves.
There are hypotheses according to which the features of the development of heat exchange between different parts of the underlying surface and the atmosphere determine the stable nature of atmospheric processes over long periods of time.
If the air warms up over the anomalously (above normal) water surface of one or another part of the World Ocean in the temperate latitudes of the Northern Hemisphere, then an area of high pressure (baric ridge) is formed in the middle troposphere, along the eastern periphery of which the transfer of cold air masses from the Arctic begins, and in its western part - the transfer of warm air from tropical latitudes to the north. Such a situation can lead to the preservation of a long-term weather anomaly near the earth's surface in certain areas - dry and hot or rainy and cool in summer, frosty and dry or warm and snowy in winter. Cloudiness plays a very significant role in the formation of atmospheric processes by regulating the flow of solar heat to the earth's surface. Cloud cover significantly increases the proportion of reflected radiation and thereby reduces the heating of the earth's surface, which, in turn, affects the nature of synoptic processes. It turns out some kind of feedback: the nature of the circulation of the atmosphere affects the creation of cloud systems, and cloud systems, in turn, affect the change in circulation. We have listed only the most important of the studied "terrestrial" factors influencing the formation of weather and air circulation. The activity of the Sun plays a special role in the study of the causes of changes in the general circulation of the atmosphere. Here one should distinguish between changes in the circulation of air on the Earth in connection with changes in the total heat flux coming from the Sun to the Earth as a result of fluctuations in the value of the so-called solar constant. However, as recent studies show, in reality it is not a strictly constant value. The energy of the circulation of the atmosphere is continuously replenished due to the energy sent by the Sun. Therefore, if the total energy sent by the Sun fluctuates significantly, then this can affect the change in circulation and weather on Earth. This issue has not yet been sufficiently studied. As for the change in solar activity, it is well known that various disturbances arise on the surface of the Sun, sunspots, torches, floccules, prominences, etc. These disturbances cause temporary changes in the composition of solar radiation, the ultraviolet component and the corpuscular (i.e., consisting of charged particles, mainly protons) radiation from the Sun. Some meteorologists believe that the change in solar activity is associated with tropospheric processes in the Earth's atmosphere, that is, with the weather.
The latter statement needs more research, mainly due to the fact that the well-manifested 11-year cycle of solar activity is not clearly visible in the weather conditions on Earth.
It is known that there are whole schools of meteorologists-forecasters who quite successfully predict the weather in connection with changes in solar activity.
Wind and General Atmospheric Circulation
Wind is the movement of air from areas of higher air pressure to areas of lower pressure. The wind speed is determined by the difference in atmospheric pressure.
The influence of wind in navigation must be constantly taken into account, since it causes the ship to drift, storm waves, etc.
Due to the uneven heating of various parts of the globe, there is a system of atmospheric currents on a planetary scale (the general circulation of the atmosphere).
The air flow consists of separate vortices randomly moving in space. Therefore, the wind speed, measured at any point, continuously changes with time. The greatest fluctuations in wind speed are observed in the surface layer. In order to be able to compare wind speeds, a height of 10 meters above sea level was taken as a standard height.
Wind speed is expressed in meters per second, wind strength - in points. The ratio between them is determined by the Beaufort scale.
Beaufort scale
Wind speed fluctuations are characterized by the gust coefficient, which is understood as the ratio of the maximum speed of gusts of wind to its average speed obtained over 5-10 minutes.
As the average wind speed increases, the gust factor decreases. At high wind speeds, the gust factor is approximately 1.2 - 1.4.
The trade winds are winds that blow all year in one direction in the zone from the equator to 35 ° N. sh. and up to 30 ° S sh. Stable in direction: in the northern hemisphere - northeast, in the south - southeast. Speed - up to 6 m / s.
Monsoons are winds of temperate latitudes that blow from the ocean to the mainland in summer and from the mainland to the ocean in winter. Reach speeds of 20 m/s. Monsoons bring dry, clear and cold weather to the coast in winter, cloudy in summer, with rain and fog.
Breezes are caused by uneven heating of water and land during the day. In the daytime, there is a wind from the sea to the land (sea breeze). At night from the chilled coast - to the sea (coastal breeze). Wind speed 5 - 10 m/s.
Local winds arise in certain areas due to the features of the relief and differ sharply from the general air flow: they arise as a result of uneven heating (cooling) of the underlying surface. Detailed information about local winds is given in sailing directions and hydrometeorological descriptions.
Bora is a strong and gusty wind that blows down a mountainside. Brings a significant chill.
It is observed in areas where a low mountain range borders the sea, during periods when atmospheric pressure increases over land and the temperature drops compared to pressure and temperature over the sea.
In the area of Novorossiysk Bay, bora acts in November - March with average wind speeds of about 20 m/s (individual gusts can be 50 - 60 m/s). The duration of action is from one to three days.
Similar winds are observed on Novaya Zemlya, on the Mediterranean coast of France (mistral) and off the northern shores of the Adriatic Sea.
Sirocco - hot and humid wind of the central part of the Mediterranean Sea is accompanied by clouds and precipitation.
Tornadoes are whirlwinds over the sea with a diameter of up to several tens of meters, consisting of water spray. They exist up to a quarter of a day and move at a speed of up to 30 knots. The wind speed inside the tornado can reach up to 100 m/s.
Storm winds occur mainly in areas with low atmospheric pressure. Tropical cyclones reach especially great force, at which the wind speed often exceeds 60 m/s.
Strong storms are also observed in temperate latitudes. When moving, warm and cold air masses inevitably come into contact with each other.
The transition zone between these masses is called an atmospheric front. The passage of the front is accompanied by a sharp change in the weather.
The atmospheric front can be in a stationary state or in motion. Distinguish warm, cold fronts, as well as fronts of occlusion. The main atmospheric fronts are: arctic, polar and tropical. On synoptic maps, fronts are depicted as lines (front line).
A warm front is formed when warm air masses push against cold air masses. On weather maps, a warm front is marked with a solid line with semicircles along the front, indicating in the direction of colder air and the direction of movement.
As the warm front approaches, pressure begins to drop, clouds thicken, and heavy precipitation falls. In winter, when the front passes, low stratus clouds usually appear. The temperature and humidity of the air are slowly rising.
When a front passes, temperature and humidity usually increase rapidly, and the wind increases. After the passage of the front, the direction of the wind changes (the wind turns clockwise), the pressure drop stops and its weak growth begins, the clouds dissipate, and precipitation stops.
A cold front is formed when cold air masses advance on warmer ones (Fig. 18.2). On weather maps, a cold front is shown as a solid line with triangles along the front indicating warmer temperatures and direction of movement. The pressure in front of the front falls strongly and unevenly, the ship enters the zone of showers, thunderstorms, squalls and strong waves.
An occluded front is a front formed by the confluence of warm and cold fronts. Represented by a solid line with alternating triangles and semicircles.
Warm front section
cold front section
A cyclone is an atmospheric vortex of huge (hundreds to several thousand kilometers) diameter with reduced air pressure in the center. Air in a cyclone circulates counterclockwise in the northern hemisphere and clockwise in the southern.
There are two main types of cyclones - extratropical and tropical.
The first are formed in temperate or polar latitudes and have a diameter of thousands of kilometers at the beginning of development, and up to several thousand in the case of the so-called central cyclone.
A tropical cyclone is a cyclone formed in tropical latitudes; it is an atmospheric vortex with reduced atmospheric pressure in the center with storm wind speeds. Formed tropical cyclones move along with air masses from east to west, while gradually deviating to high latitudes.
Such cyclones are also characterized by the so-called. "eye of the storm" - the central area with a diameter of 20 - 30 km with relatively clear and calm weather. About 80 tropical cyclones are observed annually in the world.
View of the cyclone from space
Tropical cyclone paths
In the Far East and Southeast Asia, tropical cyclones are called typhoons (from the Chinese tai feng - big wind), and in North and South America - hurricanes (Spanish huracán, named after the Indian god of the wind).
It is generally accepted that a storm turns into a hurricane at a wind speed of more than 120 km / h, at a speed of 180 km / h a hurricane is called a strong hurricane.
7. Wind. General circulation of the atmosphere
Lecture 7. Wind. General circulation of the atmosphere
Wind – this is the movement of air relative to the earth's surface, in which the horizontal component predominates. When an upward or downward wind movement is considered, the vertical component is also taken into account. The wind is characterized direction, speed and gust.
The reason for the occurrence of wind is the difference in atmospheric pressure at different points, determined by the horizontal baric gradient. The pressure is not the same, primarily due to the different degrees of heating and cooling of the air, and decreases with height.
To represent the distribution of pressure on the surface of the globe, pressure is applied to geographical maps, measured at the same time at different points and reduced to the same height (for example, to sea level). Points with the same pressure are connected by lines - isobars.
In this way, areas of increased (anticyclones) and low (cyclones) pressure are identified, as well as the direction of their movement for weather forecasting. Isobars can be used to determine how much pressure changes with distance.
In meteorology, the concept horizontal baric gradient is the change in pressure per 100 km along a horizontal line perpendicular to the isobars from high pressure to low pressure. This change is usually 1-2 hPa/100 km.
The movement of air occurs in the direction of the gradient, but not in a straight line, but more complicated, due to the interaction of forces that deflect the air due to the rotation of the earth and friction. Under the influence of the Earth's rotation, the air movement deviates from the baric gradient to the right in the northern hemisphere, to the left in the southern hemisphere.
The largest deviation is observed at the poles, and at the equator it is close to zero. The friction force reduces both the wind speed and the deviation from the gradient as a result of contact with the surface, as well as inside the air mass due to different speeds in the layers of the atmosphere. The combined influence of these forces deviates the wind from the gradient over land by 45-55o, over the sea - by 70-80o.
With an increase in altitude, the wind speed and its deviation increase up to 90 ° at a level of about 1 km.
Wind speed is usually measured in m / s, less often - in km / h and points. The direction is taken from where the wind blows, determined in rhumbs (there are 16 of them) or angular degrees.
Used for wind observations vane, which is installed at a height of 10-12 m. A hand-held anemometer is used for short-term observations of the speed in field experiments.
Anemorumbometer allows you to remotely measure the direction and speed of the wind , anemorumbograph continuously records these indicators.
The diurnal variation of wind speed over the oceans is almost not observed and is well pronounced over land: at the end of the night - a minimum, in the afternoon - a maximum. The annual course is determined by the laws of the general circulation of the atmosphere and differs in regions of the globe. For example, in Europe in summer - the minimum wind speed, in winter - the maximum. In Eastern Siberia, the opposite is true.
The direction of the wind in a particular place changes often, but if we take into account the frequency of winds of different rhumbs, we can determine that some are more frequent. For such a study of directions, a graph called the wind rose is used. On each straight line of all points, the observed number of wind events for the desired period is plotted and the obtained values \u200b\u200bare connected on the points with lines.
The wind contributes to maintaining the constancy of the gas composition of the atmosphere, mixing the air masses, transports moist sea air deep into the continents, providing them with moisture.
The adverse effect of wind for agriculture can be manifested in increased evaporation from the soil surface, causing drought, and wind erosion of soils is possible at high wind speeds.
The speed and direction of the wind must be taken into account when pollinating fields with pesticides, when irrigating with sprinklers. The direction of the prevailing winds must be known when laying forest belts, snow retention.
local winds.
The local winds are called winds that are characteristic only for certain geographical areas. They are of particular importance in their influence on weather conditions, their origin is different.
breezes – winds near the coastline of the seas and large lakes, which have a sharp diurnal change in direction. Happy sea breeze blows ashore from the sea, and at night - coastal breeze blows from land to sea (Fig. 2).
They are pronounced in clear weather during the warm season, when the overall air transport is weak. In other cases, for example, during the passage of cyclones, breezes can be masked by stronger currents.
Wind movement during breezes is observed at several hundred meters (up to 1-2 km), with an average speed of 3-5 m/s, and in the tropics - and more, penetrating tens of kilometers deep into land or sea.
The development of breezes is associated with the diurnal variation of land surface temperature. During the day, the land heats up more than the surface of the water, the pressure above it becomes lower and air is transferred from the sea to the land. At night, the land cools faster and stronger, air is transferred from land to sea.
The daytime breeze lowers the temperature and increases the relative humidity, which is especially pronounced in the tropics. For example, in West Africa, when sea air moves to land, the temperature can decrease by 10 ° C or more, and relative humidity can increase by 40%.
Breezes are also observed on the shores of large lakes: Ladoga, Onega, Baikal, Sevan, etc., as well as on large rivers. However, in these areas the breezes are smaller in their horizontal and vertical development.
Mountain valley winds are observed in mountain systems mainly in summer and are similar to breezes in their daily periodicity. During the day, they blow up the valley and along the slopes of the mountains as a result of heating by the sun, and at night, when cooled, the air flows down the slopes. Nighttime air movement can cause frost, which is especially dangerous in the spring when gardens are in bloom.
Föhn –warm and dry wind blowing from the mountains to the valleys. At the same time, the temperature of the air rises significantly and its humidity drops, sometimes very quickly. They are observed in the Alps, in the Western Caucasus, on the southern coast of Crimea, in the mountains of Central Asia, Yakutia, on the eastern slopes of the Rocky Mountains and in other mountain systems.
Foehn is formed when an air current crosses a ridge. Since a vacuum is created on the leeward side, the air is sucked down in the form of a downward wind. The descending air heats up according to the dry adiabatic law: by 1°C for every 100 m of descent.
For example, if at an altitude of 3000 m the air had a temperature of -8o and a relative humidity of 100%, then, having descended into the valley, it would heat up to 22o, and the humidity would decrease to 17%. If the air rises up the windward slope, then water vapor condenses and clouds form, precipitation falls, and the descending air will be even drier.
The duration of hair dryers is from several hours to several days. A hair dryer can cause intense snowmelt and floods, dries up soils and vegetation until they die.
Bora–it is a strong, cold, gusty wind that blows from low mountain ranges towards warmer seas.
Bora is best known in the Novorossiysk Bay of the Black Sea and on the Adriatic coast near the city of Trieste. Similar to boron in origin and manifestation north in the region of
Baku, mistral on the Mediterranean coast of France, northser in the Gulf of Mexico.
Bora occurs when cold air masses pass through the coastal ridge. The air flows down under the force of gravity, developing a speed of more than 20 m / s, while the temperature is greatly reduced, sometimes by more than 25 ° C. Bora fades a few kilometers from the coast, but sometimes it can capture a significant part of the sea.
In Novorossiysk, bora is observed about 45 days a year, more often from November to March, with a duration of up to 3 days, rarely up to a week.
General circulation of the atmosphere
General circulation of the atmosphere– it is a complex system of large air currents that carry very large masses of air over the globe.
In the atmosphere near the earth's surface in polar and tropical latitudes, eastward transport is observed, in temperate latitudes - westward.
The movement of air masses is complicated by the rotation of the Earth, as well as by the relief and the influence of areas of high and low pressure. The deviation of the winds from the prevailing directions is up to 70o.
In the process of heating and cooling of huge masses of air over the globe, areas of high and low pressure are formed, which determine the direction of planetary air currents. Based on long-term average values of pressure at sea level, the following regularities were revealed.
On both sides of the equator there is a low pressure zone (in January - between 15o north latitude and 25o south latitude, in July - from 35o north latitude to 5o south latitude). This area, called equatorial depression, extends more to the hemisphere where it is summer in a given month.
In the direction to the north and south of it, the pressure increases and reaches its maximum values in subtropical high pressure zones(in January - at 30 - 32o north and south latitude, in July - at 33-37o N and 26-30o S). From the subtropics to temperate zones, the pressure drops, especially significantly in the southern hemisphere.
The minimum pressure is in two subpolar low pressure zones(75-65o N and 60-65o S). Further towards the poles, the pressure increases again.
In accordance with pressure changes, the meridional baric gradient is also located. It is directed from the subtropics on the one hand - to the equator, on the other - to subpolar latitudes, from the poles to subpolar latitudes. This is consistent with the zonal direction of the winds.
Over the Atlantic, Pacific and Indian Oceans, northeast and southeast winds very often blow - trade winds. Western winds in the southern hemisphere, at latitudes of 40-60o, go around the entire ocean.
In the northern hemisphere, at temperate latitudes, westerly winds are constantly expressed only over the oceans, and over the continents, the directions are more complicated, although westerlies also predominate.
East winds of the polar latitudes are clearly observed only along the outskirts of Antarctica.
In the south, east and north of Asia, there is a sharp change in the direction of the winds from January to July - these are areas monsoons. The causes of monsoons are similar to those of breezes. In summer, the mainland of Asia heats up strongly and an area of low pressure spreads over it, where air masses rush from the ocean.
The resulting summer monsoon causes large amounts of precipitation, often showers. In winter, high pressure sets in over Asia due to the more intense cooling of the land, compared to the ocean, and cold air moves to the ocean, forming a winter monsoon with clear, dry weather. Monsoons penetrate more than 1000 km in a layer above land up to 3-5 km.
Air masses and their classification.
air mass- this is a very large amount of air, which covers an area of millions of square kilometers.
In the process of general circulation of the atmosphere, the air is divided into separate air masses, which remain for a long time over a vast territory, acquire certain properties and cause various types of weather.
Moving to other regions of the Earth, these masses bring with them their own weather regime. The predominance of air masses of a certain type (types) in a particular area creates a characteristic climatic regime of the area.
The main differences between air masses are: temperature, humidity, cloudiness, dustiness. For example, in summer the air over the oceans is more humid, colder, cleaner than over land at the same latitude.
The longer the air is over one area, the more it undergoes changes, so air masses are classified according to the geographical zones where they formed.
There are main types: 1) arctic (antarctic), which move from the poles, from high pressure zones; 2) temperate latitudes“polar” – in the northern and southern hemispheres; 3) tropical- move from the subtropics and tropics to temperate latitudes; four) equatorial- formed over the equator. In each type, marine and continental subtypes are distinguished, differing primarily in temperature and humidity within the type. The air, being in constant motion, passes from the area of formation to the neighboring ones and gradually changes its properties under the influence of the underlying surface, gradually turning into a mass of another type. This process is called transformation.
cold air masses are called those that move to a warmer surface. They cause a chill in the areas where they come.
When they move, they themselves warm up from the earth's surface, so large vertical temperature gradients arise inside the masses and convection develops with the formation of cumulus and cumulonimbus clouds and heavy rainfall.
Air masses moving to a colder surface are called warm masses. They bring warmth, but they themselves are cooled from below. Convection does not develop in them and stratus clouds predominate.
Neighboring air masses are separated from each other by transition zones, which are strongly inclined to the Earth's surface. These zones are called fronts.
The atmosphere is not uniform. In its composition, especially near the earth's surface, air masses can be distinguished.
Air masses are separate large volumes of air that have certain common properties (temperature, humidity, transparency, etc.) and move as a whole. However, within this volume, the winds can be different. The properties of the air mass are determined by the region of its formation. It acquires them in the process of contact with the underlying surface, over which it forms or lingers. Air masses have different properties. For example, the air of the Arctic has low temperatures, while the air of the tropics has high temperatures in all seasons of the year, the air of the North Atlantic differs significantly from the air of the Eurasian continent. The horizontal dimensions of the air masses are enormous, they are commensurate with the continents and oceans or their large parts. There are main (zonal) types of air masses that form in belts with different atmospheric pressure: arctic (antarctic), temperate (polar), tropical and equatorial. Zonal air masses are divided into maritime and continental - depending on the nature of the underlying surface in the area of their formation.
Arctic air is formed over the Arctic Ocean, and in winter also over the north of Eurasia and North America. The air is characterized by low temperature, low moisture content, good visibility and stability. Its intrusions into temperate latitudes cause significant and sharp cooling and determine predominantly clear and slightly cloudy weather. Arctic air is divided into the following varieties.
Maritime Arctic air (mAv) - formed in the warmer, ice-free European Arctic with higher temperature and higher moisture content. Its incursions into the mainland in winter cause warming.
Continental arctic air (cAv) - formed over the Central and Eastern icy Arctic and the northern coast of the continents (in winter). Air has very low temperatures, low moisture content. The invasion of the KAV on the mainland causes a strong cooling in clear weather and good visibility.
An analogue of the Arctic air in the Southern Hemisphere is the Antarctic air, but its influence extends mainly to the adjacent sea surfaces, less often to the southern tip of South America.
Moderate (polar) air. This is the air of temperate latitudes. It also has two subtypes. Continental temperate air (CW), which is formed over the vast surfaces of the continents. In winter it is very chilled and stable, the weather is usually clear with hard frosts. In summer, it gets very warm, ascending currents arise in it, clouds form, it often rains, thunderstorms are observed. Marine temperate air (MOA) is formed in the middle latitudes over the oceans, and is transported to the continents by westerly winds and cyclones. It is characterized by high humidity and moderate temperatures. In winter, MUW brings cloudy weather, heavy rainfall and higher temperatures (thaws). In summer it also brings a lot of cloudiness, rains; the temperature drops as it enters.
Temperate air penetrates into the polar, as well as subtropical and tropical latitudes.
Tropical air is formed in tropical and subtropical latitudes, and in summer - in continental regions in the south of temperate latitudes. There are two subtypes of tropical air. Continental tropical air (cT) is formed over land, characterized by high temperatures, dryness and dustiness. Marine tropical air (mTw) is formed over tropical areas (tropical ocean zones), characterized by high temperature and humidity.
Tropical air penetrates into temperate and equatorial latitudes.
Equatorial air is formed in the equatorial zone from tropical air brought by the trade winds. It is characterized by high temperatures and high humidity throughout the year. In addition, these qualities are preserved both over land and over the sea, therefore, equatorial air is not divided into marine and continental subtypes.
Air masses are in constant motion. Moreover, if the air masses move to higher latitudes or to a colder surface, they are called warm, since they bring warming. Air masses moving to lower latitudes or to a warmer surface are called cold air masses. They bring coldness.
Moving to other geographical areas, air masses gradually change their properties, primarily temperature and humidity, i.e. move into other types of air masses. The process of transformation of air masses from one type to another under the influence of local conditions is called transformation. For example, tropical air, penetrating towards the equator and into temperate latitudes, is transformed into equatorial and temperate air, respectively. Marine temperate air, once in the depths of the continents, cools in winter, and heats up in summer and always dries up, turning into temperate continental air.
All air masses are interconnected in the process of their constant movement, in the process of the general circulation of the troposphere.
air masses- large volumes of air in the lower part of the earth's atmosphere - the troposphere, having horizontal dimensions of many hundreds or several thousand kilometers and vertical dimensions of several kilometers, characterized by an approximate horizontal uniformity of temperature and moisture content.
Kinds:Arctic or Antarctic air(AB), temperate air(UV), tropical air(TV) equatorial air(EV).
The air in the ventilation layers can move in the form laminar or turbulent flow. concept "laminar" means that the individual air flows are parallel to each other and move in the ventilation space without turbulence. When turbulent flow its particles move not only in parallel, but also make transverse motion. This leads to vortex formation over the entire cross section of the ventilation duct.
The state of the air flow in the ventilation space depends on: Air flow velocity, Air temperature, Cross-sectional area of the ventilation duct, Forms and surfaces of building elements at the border of the ventilation duct.
In the earth's atmosphere, air movements of various scales are observed - from tens and hundreds of meters (local winds) to hundreds and thousands of kilometers (cyclones, anticyclones, monsoons, trade winds, planetary frontal zones).
The air is constantly moving: it rises - an upward movement, it falls - a downward movement. The movement of air in a horizontal direction is called wind. The reason for the occurrence of wind is the uneven distribution of air pressure on the surface of the Earth, which is caused by an uneven distribution of temperature. In this case, the air flow moves from places with high pressure to the side where the pressure is less.
With the wind, the air does not move evenly, but in shocks, gusts, especially near the surface of the Earth. There are many reasons that affect the movement of air: the friction of the air flow on the surface of the Earth, encountering obstacles, etc. In addition, air flows under the influence of the rotation of the Earth deviate to the right in the northern hemisphere, and to the left in the southern hemisphere.
Invading areas with different thermal properties of the surface, the air masses are gradually transformed. For example, temperate marine air, entering the land and moving deep into the mainland, gradually heats up and dries up, turning into continental air. The transformation of air masses is especially characteristic of temperate latitudes, which are occasionally invaded by warm and dry air from tropical latitudes and cold and dry air from subpolar latitudes.
The movement of air masses should lead, first of all, to the smoothing of baric and temperature gradients. However, on our rotating planet with different heat capacity properties of the earth's surface, different heat reserves of land, seas and oceans, the presence of warm and cold ocean currents, polar and continental ice, the processes are very complex and often the heat content contrasts of various air masses not only do not smooth out, but vice versa , increase.[ ...]
The movement of air masses above the Earth's surface is determined by many reasons, including the rotation of the planet, the uneven heating of its surface by the Sun, the formation of zones of low (cyclones) and high (anticyclones) pressure, flat or mountainous terrain, and much more. In addition, at different heights, the speed, stability and direction of air flows are very different. Therefore, the transfer of pollutants entering different layers of the atmosphere proceeds at different rates and sometimes in other directions than in the surface layer. With very strong emissions associated with high energies, pollution falling into high, up to 10-20 km, layers of the atmosphere can move thousands of kilometers within a few days or even hours. Thus, the volcanic ash thrown out by the explosion of the Krakatau volcano in Indonesia in 1883 was observed in the form of peculiar clouds over Europe. Radioactive fallout of varying intensity after testing especially powerful hydrogen bombs fell on almost the entire surface of the Earth.[ ...]
The movement of air masses - the wind resulting from the difference in temperature and pressure in different regions of the planet affects not only the physical and chemical properties of the air itself, but also the intensity of heat transfer, changes in humidity, pressure, chemical composition of air, reducing or increasing the amount pollution.[ ...]
The movement of air masses can be in the form of their passive movement of a convective nature or in the form of wind - due to the cyclonic activity of the Earth's atmosphere. In the first case, the settlement of spores, pollen, seeds, microorganisms and small animals is ensured, which have special adaptations for this - anemochores: very small sizes, parachute-like appendages, etc. (Fig. 2.8). All this mass of organisms is called aeroplankton. In the second case, the wind also carries aeroplankton, but over much longer distances, while it can also carry pollutants to new zones, etc.[ ...]
The movement of air masses (wind). As is known, the reason for the formation of wind flows and the movement of air masses is the uneven heating of different parts of the earth's surface, associated with pressure drops. The wind flow is directed towards lower pressure, but the rotation of the Earth also affects the circulation of air masses on a global scale. In the surface layer of air, the movement of air masses affects all meteorological factors of the environment, i.e., the climate, including temperature, humidity, evaporation from the land and sea, as well as plant transpiration.[ ...]
ANOMALOUS CYCLONE MOVEMENT. The movement of a cyclone in a direction sharply divergent from the usual, i.e., from the eastern half of the horizon to the western or along the meridian. A.P.C. is associated with the anomalous direction of the leading flow, which in turn is due to the unusual distribution of warm and cold air masses in the troposphere.[ ...]
AIR MASS TRANSFORMATION. 1. A gradual change in the properties of the air mass during its movement due to changes in the conditions of the underlying surface (relative transformation).[ ...]
The third reason for the movement of air masses is dynamic, which contributes to the formation of high pressure areas. Due to the fact that the most heat comes to the equatorial zone, air masses rise up to 18 km here. Therefore, intensive condensation and precipitation in the form of tropical showers are observed. In the so-called "horse" latitudes (about 30° N and 30° S), cold dry air masses, descending and heating adiabatically, intensively absorb moisture. Therefore, in these latitudes, the main deserts of the planet naturally form. They mainly formed in the western parts of the continents. The westerly winds coming from the ocean do not contain enough moisture to transfer to the descending dry air. Therefore, there is very little rainfall.[ ...]
The formation and movement of air masses, the location and trajectory of cyclones and anticyclones are of great importance for making weather forecasts. A synoptic map provides a visual representation of the state of the weather at the moment over a vast territory.[ ...]
WEATHER TRANSFER. The movement of certain weather conditions along with their "carriers" - air masses, fronts, cyclones and anticyclones.[ ...]
In a narrow border strip separating air masses, frontal zones (fronts) arise, characterized by an unstable state of meteorological elements: temperature, pressure, humidity, wind direction and speed. Here, with exceptional clarity, the most important principle in physical geography of the contrast of environments is manifested, which is expressed in a sharp activation of the exchange of matter and energy in the zone of contact (contact) of natural complexes of different properties and their components (F. N. Milkov, 1968). The active exchange of matter and energy between air masses in the frontal zones is manifested in the fact that it is here that the origin, movement with a simultaneous increase in power and, finally, the extinction of cyclones take place.[ ...]
Solar energy causes planetary movements of air masses as a result of their uneven heating. Grandiose processes of atmospheric circulation arise, which are of a rhythmic nature.[ ...]
If in a free atmosphere with turbulent movements of air masses this phenomenon does not play a noticeable role, then in a stationary or low-moving indoor air, this difference should be taken into account. In close proximity to the surface of various bodies, we will have a layer with a certain excess of negative air ions, while the surrounding air will be enriched with positive air ions.[ ...]
Non-periodic weather changes are caused by the movement of air masses from one geographical area to another in the general atmospheric circulation system.[ ...]
Due to the fact that at high altitudes the speed of movement of air masses reaches 100 m/s, ions moving in a magnetic field can be displaced, although these displacements are insignificant compared to the transfer in a stream. For us, it is important that in the polar zones, where the lines of force of the Earth's magnetic field are closed on its surface, the distortions of the ionosphere are very significant. The number of ions, including ionized oxygen, in the upper layers of the atmosphere of the polar zones is reduced. But the main reason for the low ozone content in the region of the poles is the low intensity of solar radiation, which falls even during the polar day at small angles to the horizon, and is completely absent during the polar night. In itself, the screening role of the ozone layer in the polar regions is not so important precisely because of the low position of the Sun above the horizon, which excludes the high intensity of UV radiation of the surface. However, the area of the polar "holes" in the ozone layer is a reliable indicator of changes in the total ozone content in the atmosphere.[ ...]
The translational horizontal movements of water masses associated with the movement of significant volumes of water over long distances are called currents. Currents arise under the influence of various factors, such as wind (i.e., friction and pressure of moving air masses on the water surface), changes in the distribution of atmospheric pressure, uneven distribution of the density of sea water (i.e., the horizontal pressure gradient of waters of different densities at equal depths), the tidal forces of the Moon and the Sun. The nature of the movement of masses of water is also significantly influenced by secondary forces, which themselves do not cause it, but manifest themselves only in the presence of movement. These forces include the force that arises due to the rotation of the Earth - the Coriolis force, centrifugal forces, friction of the waters on the bottom and coasts of the continents, internal friction. The distribution of land and sea, the topography of the bottom and the outlines of the coasts have a great influence on sea currents. Currents are classified mainly by origin. Depending on the forces that excite them, the currents are combined into four groups: 1) frictional (wind and drift), 2) gradient-gravitational, 3) tidal, 4) inertial.[ ...]
Wind turbines and sailing ships are propelled by the movement of air masses due to heating it by the sun and creating air currents or winds. one.[ ...]
MOTION CONTROL. The formulation of the fact that the movement of air masses and tropospheric disturbances mainly occurs in the direction of the isobars (isohypses) and, consequently, the air currents of the upper troposphere and lower stratosphere.[ ...]
This, in turn, may lead to a violation of the movement of air masses near industrial areas located next to such a park and increased air pollution.[ ...]
Most weather phenomena depend on whether air masses are stable or unstable. With stable air, vertical movements in it are difficult, with unstable air, on the contrary, they develop easily. The stability criterion is the observed temperature gradient.[ ...]
Hydrodynamic, closed type with adjustable air cushion pressure, with pulsation dampener. Structurally, it consists of a body with a lower lip, a collector with a tilting mechanism, a turbulator, an upper lip with a mechanism for vertical and horizontal movement, mechanisms for fine adjustment of the outlet slot profile with the ability to automatically control the transverse profile of the paper web. The surfaces of the parts of the box that come into contact with the mass are carefully polished and electropolished.[ ...]
The potential temperature, in contrast to the molecular temperature T, remains constant during dry adiabatic movements of the same air particle. If in the process of moving the air mass its potential temperature has changed, then there is an inflow or outflow of heat. The dry adiabat is a line of equal potential temperature.[ ...]
The most typical case of dispersion is the movement of a gas jet in a moving medium, i.e., during the horizontal movement of air masses of the atmosphere.[ ...]
The main reason for short-period OS oscillations, according to the concept put forward in 1964 by the author of the work, is the horizontal movement of the ST axis, which is directly related to the movement of long waves in the atmosphere. Moreover, the direction of the wind in the stratosphere over the place of observation does not play a significant role. In other words, short-term OS fluctuations are caused by a change in air masses in the stratosphere above the observation site, since these masses separate ST.[ ...]
The state of the free surface of reservoirs, due to the large area of their surface, is strongly influenced by the wind. The kinetic energy of the air flow is transferred to the masses of water through friction forces at the interface between two media. One part of the transferred energy is spent on the formation of waves, and the other part is used to create a drift current, i.e. progressive movement of the surface layers of water in the direction of the wind. In reservoirs of limited size, the movement of water masses by a drift current leads to a distortion of the free surface. At the windward coast, the water level drops - a wind surge occurs, at the leeward coast the level rises - a wind surge occurs. At the Tsimlyansk and Rybinsk reservoirs, level differences of 1 m or more were recorded near the leeward and windward shores. With a long wind, the skew becomes stable. Masses of water that are brought to the leeward coast by a drift current are diverted in the opposite direction by a near-bottom gradient current.[ ...]
The results obtained are based on solving the problem for stationary conditions. However, the considered scales of the terrain are relatively small and the time of movement of the air mass ¿ = l:/u is small, which allows us to limit ourselves to the parametric consideration of the characteristics of the oncoming air flow.[ ...]
But the icy Arctic creates difficulties in agriculture not only because of cold and long winters. Cold, and therefore dehydrated arctic: air masses do not warm up during spring-summer movement. The higher the temperature, the more! moisture is needed to saturate it. I. P. Gerasimov and K. K. Mkov noted that “at present, a simple increase in the ice cover of the Arctic Basin causes. . . zas; in Ukraine and the Volga region” 2.[ ...]
In 1889, a giant cloud of locusts flew from the coast of North Africa across the Red Sea to Arabia. The movement of insects lasted a whole day, and their mass was 44 million tons. V.I. Vernadsky regarded this fact as evidence of the enormous power of living matter, an expression of the pressure of life, striving to capture the entire Earth. At the same time, he saw in this a biogeochemical process - the migration of elements included in the biomass of the locust, a completely special migration - through the air, over long distances, not consistent with the usual mode of movement of air masses in the atmosphere.[ ...]
Thus, the main factor determining the speed of katabatic winds is the temperature difference between the ice cover and the atmosphere 0 and the angle of inclination of the ice surface. The movement of the cooled air mass down the slope of the ice dome of Antarctica is enhanced by the effects of the fall of the air mass from the height of the ice dome and the influence of baric gradients in the Antarctic High. Horizontal baric gradients, being an element of the formation of katabatic winds in Antarctica, contribute to an increase in the outflow of air to the periphery of the continent, primarily due to its supercooling near the surface of the ice sheet and the slope of the ice dome towards the sea.[ ...]
The analysis of synoptic maps is as follows. According to the information plotted on the map, the actual state of the atmosphere at the time of observation is established: the distribution and nature of air masses and fronts, the location and properties of atmospheric disturbances, the location and nature of clouds and precipitation, temperature distribution, etc. for given conditions of atmospheric circulation. By compiling maps for different periods, you can follow them for changes in the state of the atmosphere, in particular, for the movement and evolution of atmospheric disturbances, the movement, transformation and interaction of air masses, etc. The presentation of atmospheric conditions on synoptic maps provides a convenient opportunity for information about the state of the weather.[ . ..]
Atmospheric macroscale processes studied with the help of synoptic maps and which are the cause of the weather regime over large geographic areas. This is the emergence, movement and change in the properties of air masses and atmospheric fronts; the emergence, development and movement of atmospheric disturbances - cyclones and anticyclones, the evolution of condensation systems, intramass and frontal, in connection with the above processes, etc.[ ...]
Until aerial chemical treatment is completely excluded, it is necessary to make improvements in its application through the most careful selection of objects, reducing the likelihood of "demolitions" - movements of sawing air masses, controlled dosage, etc. For primary care in clearings through the use of herbicides, it is advisable to use typological diagnostics to a greater extent clearings. Chemistry is a powerful means of forest care. But it is important that chemical care does not turn into poisoning of the forest, its inhabitants and visitors.[ ...]
In the nature around us, water is in constant motion - and this is just one of the many natural cycles of substances in nature. When we say “movement”, we mean not only the movement of water as a physical body (flow), not only its movement in space, but, above all, the transition of water from one physical state to another. In Figure 1 you can see how the water cycle works. On the surface of lakes, rivers and seas, water under the influence of the energy of sunlight turns into water vapor - this process is called evaporation. In the same way, water evaporates from the surface of the snow and ice cover, from the leaves of plants and from the bodies of animals and humans. Water vapor with warmer air flows rises to the upper atmosphere, where it gradually cools and again turns into a liquid or turns into a solid state - this process is called condensation. At the same time, water moves with the movement of air masses in the atmosphere (winds). From the resulting water droplets and ice crystals, clouds are formed, from which, in the end, rain or snow falls on the ground. Water returned to earth in the form of precipitation flows down the slopes and collects in streams and rivers that flow into lakes, seas and oceans. Part of the water seeps through the soil and rocks, reaches groundwater and groundwater, which also, as a rule, have a runoff into rivers and other water bodies. Thus, the circle closes and can be repeated in nature indefinitely.[ ...]
SYNOPTIC METEOROLOGY. Meteorological discipline, which took shape in the second half of the XIX century. and especially in the 20th century; the doctrine of atmospheric macroscale processes and weather forecasting based on their study. Such processes are the emergence, evolution and movement of cyclones and anticyclones, which are closely related to the emergence, movement and evolution of air masses and fronts between them. The study of these synoptic processes is carried out with the help of a systematic analysis of synoptic maps, vertical sections of the atmosphere, aerological diagrams and other auxiliary means. The transition from a synoptic analysis of circulation conditions over large areas of the earth's surface to their forecast and to the forecast of weather conditions associated with them is still largely reduced to extrapolation and qualitative conclusions from the provisions of dynamic meteorology. However, in the last 25 years, the numerical (hydrodynamic) forecast of meteorological fields has been increasingly used by numerically solving the equations of atmospheric thermodynamics on electronic computers. See also the weather service, weather forecast and a number of other terms. Common synonym: weather forecast.[ ...]
The case of jet propagation analyzed by us is not typical, since there are very few calm periods in almost any area. Therefore, the most typical case of scattering is the movement of a gas jet in a moving medium, i.e., in the presence of a horizontal movement of atmospheric air masses.[ ...]
It is obvious that simply the air temperature T is not a conservative characteristic of the heat content of the air. So, with a constant heat content of an individual volume of air (turbulent mole), its temperature can vary depending on the pressure (1.1). Atmospheric pressure, as we know, decreases with height. As a result, vertical movement of air leads to changes in its specific volume. In this case, the work of expansion is realized, which leads to changes in the temperature of air particles even in the case when the processes are isentropic (adiabatic), i.e. there is no heat exchange of an individual mass element with the surrounding space. Changes in the temperature of the air moving vertically will correspond to dry diabatic or wet diabatic gradients, depending on the nature of the thermodynamic process.
The general circulation of the atmosphere is the circulation of air masses that extends throughout the planet. They are carriers of various elements and energy throughout the atmosphere.
Intermittent and seasonal placement of thermal energy causes air currents. This leads to different heating of the soil and air in various areas.
That is why solar influence is the founder of the movement of air masses and atmospheric circulation. Air traffic on our planet is completely different - reaching several meters or tens of kilometers.
The simplest and most understandable scheme for the circulation of the atmosphere of the ball was created many years ago and is used today. The movement of air masses is invariable and non-stop, they move around our planet, creating a vicious circle. The speed of movement of these masses is directly related to solar radiation, interaction with the ocean and the interaction of the atmosphere with the soil.
Atmospheric movements are caused by the instability of the distribution of solar heat throughout the planet. The alternation of opposite air masses - warm and cold - their constant jumping up and down, forms various circulation systems.
Heat is obtained by the atmosphere in three ways - using solar radiation, with the help of steam condensation and heat exchange with the earth cover.
Humid air is also important for saturating the atmosphere with heat. The tropical zone of the Pacific Ocean plays a huge role in this process.
Air currents in the atmosphere
(Air currents in the Earth's atmosphere)
Air masses differ in their composition, depending on the place of origin. Air flows are divided into 2 main criteria - continental and sea. Continental ones form above the soil cover, so they are little moistened. Marines, on the other hand, are very wet.
The main air currents of the Earth are the trade winds, cyclones and anticyclones.
The trade winds form in the tropics. Their movement is directed towards the equatorial territories. This is due to pressure differences - at the equator it is low, and in the tropics it is high.
(Trade winds (trade winds) are displayed in red on the diagram)
The formation of cyclones occurs above the surface of warm waters. Air masses move from the center to the edges. Their influence is characterized by heavy rainfall and strong winds.
Tropical cyclones act over the oceans in equatorial territories. They form at any time of the year, causing hurricanes and storms.
Anticyclones form over continents where humidity is low, but there is a sufficient amount of solar energy. Air masses in these streams move from the edges to the central part, where they heat up and gradually decrease. That is why cyclones bring clear and calm weather.
Monsoons are variable winds that change direction seasonally.
Secondary air masses, such as typhoons and tornadoes, tsunamis, are also distinguished.