Monsoons are steady winds. Monsoons. Influence of wind activity
Trade winds and monsoons
If, observing the direction of the wind in the equatorial regions of Africa, you make a map, then the two most common types of wind roses will appear on it:
a) roses with a clearly defined predominance of the wind direction of one or more points. Such roses are characteristic of most of the mainland, where both trade winds and monsoon air currents are noted;
b) roses, reflecting almost all known wind directions, combined with a large number of calms. These roses characterize the variability of wind direction in the equatorial and subequatorial zones.
What are the trade winds and monsoons? Monsoons are air currents that form over the surface of the ocean and head towards the coast; As a rule, monsoons carry moist air masses. The trade winds are dry winds that occur over the surface of the ocean, but not over the continents.
On the January wind map, the area located in the Congo stands out. There are weak and unstable winds with a large number of calms. The northern coast of the Gulf of Guinea is throughout the year under the influence of the monsoon, which has a predominantly southern and southwestern direction. At the same time, in winter (in January), the monsoon is somewhat less pronounced than in other seasons. According to meteorological observations, the wind from the sea is 47% with a fairly high percentage of calm - 28%. The opposite eastern coast of equatorial Africa is in the zone of action of the Indian monsoon, which reaches its maximum power in January.
In July, the wet monsoon enters the mainland from the Gulf of Guinea. In the region of the eastern coast of Africa, from the side of the Indian Ocean, the southeast trade wind penetrates far into the mainland, which in the extreme east of Africa (the Somali Peninsula) takes a southwesterly direction and subsequently merges with the Indian summer monsoon. The direction of the wind in the monsoon, especially in the equatorial part of the mainland, is very stable.
In October, the position of air masses, which determine the main distribution of currents and wind directions, in general terms coincides with April. There are differences only in the number of calms, since the autumn average monthly wind speeds are usually less than the spring ones, and weak winds are a frequent occurrence here.
In the Congo basin, weak wind speeds are noted: less than 2 m / s. This can be explained by the hollow terrain. In addition, the Congo Basin coincides in its geographical position with the area of high pressure, located south of the equatorial calm zone, which enhances the effect of wind weakening and puts this area on a par with the famous "horse latitudes", which are characterized by frequent calm.
During the monsoons, sometimes deep tropical cyclones occur, which have tremendous destructive power. A tropical cyclone is an unstoppable filling of a zone of low atmospheric pressure. Ascending air currents in the low pressure zone lead to the condensation of huge masses of water vapor, the release of a large amount of heat, which in turn enhances the upward movement of the wind. The formation of cyclones occurs on the tropical front - the boundary zone between the trade winds of the northern and southern hemispheres or between the trade winds and monsoons. In the initial stages, tropical cyclones are areas of low pressure. Only a part of them subsequently turns into a cyclone with a hurricane force of wind. When the differences in air density are small, an ordinary wind arises, but the greater the difference, the stronger the wind. In the center of the cyclone, a relatively stable zone of complete calm appears, moving over the surface of the Earth. It is located in the center of the crushing winds revolving around it and is called the "eye". On the path of such cyclones, catastrophic floods were repeatedly observed due to prolonged and intense downpours (with daily amounts up to 400-500 mm), hurricane winds up to 50-60 m/s, a continuous veil of large clouds, covering the entire sky and dropping to 50 -200 m above ground level. And, of course, in such a meteorological situation, there is always an increased relative humidity of the air. Although such conditions rarely occur, they are nevertheless of great danger, since they cause disasters and lead to destruction over vast areas.
Strong dry winds, which often cause dust storms, also cause great trouble to the inhabitants of equatorial Africa. On the territory of West Africa, these are the winds, called harmatan. During a storm, the air is so saturated with the smallest dust particles that visibility is significantly reduced even within a radius of several meters.
Types of winds
Breeze - wind blowing from the coast to the sea and from the sea to the coast; in the first case it is called a coastal breeze, and in the second - a sea breeze.
Monsoon is a periodic wind that changes its direction depending on the season. Monsoons are observed mainly in the tropical zone.
Trade winds - winds blowing with a fairly constant force of three or four points; their direction is not always kept constant, but varies, however, within narrow limits.
In folk beliefs, it is endowed with the properties of a demonic creature. The power of the Wind, its destructive (along with hail , storm, blizzard) or a beneficial force (similar to rain or sunbeams) makes it necessary to appease the Wind: talk to it affectionately, “feed” and even make a sacrifice to it. The division of the Winds into “good” ones (for example, such as “holy air” - a favorable, tail Wind) and into “evil” ones, the most striking embodiment of which is a whirlwind, is also characteristic. .
In Slavic beliefs, the Wind lives in places far away, mysterious and unattainable. This is a dense forest, and an uninhabited island in the ocean, foreign lands on the other side of the sea, a steep, high mountain, etc. In the southern Russian regions, the Wind was imagined as an angry old man who lives "beyond the sea."
In accordance with the Indo-European views on the Wind as the "breath of the Earth", various abysses, pits and caves were considered to be its places of residence. According to the ideas of the southern Slavs, such caves and abysses are guarded by flying snakes, a one-eyed witch or a blind old man, unsuccessfully trying to close the hole from which the Wind comes out.
Winds can obey a higher deity: in the Word of Igor's Campaign "Winds -" Stribog's grandchildren " . According to Russian beliefs, there are many winds, but there are four main ones (corresponding to the four cardinal points); they “sit in the corners of the earth”, the eldest among them is called the “vortex chieftain”: all the others obey him, he also sends Winds and whirlwinds to blow wherever he wants. In the northern Russian tradition, the “wind king”, “moisy wind”, “Luk wind”, as well as “Sedorikha” - the north wind are known. In the Vologda bylichka it is said that the twelve winds are chained to a rock in the middle of the ocean; breaking off the chain, they fall to the ground.
The idea of the Wind as animated, moving along air The essence was also expressed in the desire of a person to invite, to call the Wind in those cases when it is necessary for economic and other needs (when winnowing the grain, for the operation of mills, etc.). The most common way to call the Wind in a calm was considered a whistle, less often - singing. To cause a fair wind, it was customary for Russian sailors, especially Pomors, to whistle. Women of the coastal Pomeranian villages went out to the sea in the evening "Pray for the wind not to be angry" helped their loved ones at sea. Standing facing the east, they in a singsong voice turned to the desired eastern wind with a request to “pull” and promised him "boil porridge and bake pancakes". In the Ryazan province, in order to evoke the Wind when winnowing the gin, the old women blew with all their might in the direction from which they were waiting for him, and waved their hands, showing him the right direction. Among the Belarusians, the miller had to be able to “forbid the wind”: in particular, to call it in a lull, throwing handfuls of flour from the top of the mill.
A gift or sacrifice to the Wind is found among all Slavs. The wind was "fed" with bread, flour, cereals, meat, the remains of festive dishes; Slovenes threw ashes from the bones of an animal, giblets towards the Wind. To calm the strong wind, in Croatia and Bosnia they burned parts of clothes, old shoes. In eastern Poland, inviting Wind during the heat, he was promised to give the girl, calling her by name: "Blow, breeze, blow, we'll give you Anusya" etc.
The appearance of the Wind is often associated with the common Slavic ideas about the Wind as the location of souls and Demons. The soul (in the form of breath, breath) was identified with air, wind, whirlwind. It was believed that the souls of great sinners fly with the Wind; strong Wind means someone's violent death. According to Polish and Slovak beliefs, the moans of the gallows are heard in the howling Wind. Belarusians believe that a cold wind blows from the side where the man drowned. The wind on the day of commemoration of the dead among the Kashubians means the cry of the soul. According to Ukrainian beliefs, the appearance of the "walking" dead is accompanied by gusts of wind. In the Vologda province, it was believed that a quiet breeze arises from the breath of angels, and a stormy breeze is the result of the action of devilish forces. V. accompanies the appearance of such demons as the pitchfork among the southern Slavs, the “flyer” and the “vitrenitsa”, the “vetrenik” - in the Carpathians, the witch , hell - among the eastern and western Slavs.
According to other ideas, the Wind appears because the "devil" plays the willow pipe, the Wind's assistants blow into the bellows, the blacksmiths inflate the bellows, the trees collapse, the sea waves rise, etc. To prevent the Wind, various prohibitions are observed: you cannot beat the ground with a stick, a whip, destroy an anthill, burn an old broom , blow on the fire at Christmas, curse the Wind and more.
"Evil" Winds are sources of disease. The most terrible are the spirits-Winds that attack people and cause epilepsy, a mental disorder. According to the beliefs of the southern Slavs, "wild" and "mad" winds cause rabies in people and animals. They carry various diseases and small, quiet breezes: “red”, “white”, “blue”, “yellow”, etc.
Along with the breath of the Wind, not only an infection, an epidemic, but also damage spreads. For example, according to Russian beliefs, healers and sorcerers spoil people with slander, a potion, or even like this: “they let it go in the wind.”
In Poland, they said about the enchantress that she casts spells on the Wind, as if "sowing".
To get rid of illness, spoilage, etc. in conspiracies and spells, the motif of the departure of "evil spirits" along with the Wind is used, for example, among Belarusians: “Let’s go, hira (sickness, illness, trash), wind up the wind!” Similar "appeals" to the disease are known among the Bulgarians: "The wind brought you, the wind carried you". And, on the contrary, it is impossible to allow the wind to blow away the straw on which the dead man lay; you can’t dry baby diapers in the wind, otherwise the memory or thoughts of the child will fly away with the wind.
Monsoons(French mousson, from Arabic mausim - season), stable seasonal air transfers near the earth's surface and in the lower part of the troposphere. Characterized by sharp changes in direction from winter to summer and from summer to winter, manifested over vast areas of the Earth. In each of the seasons, one direction of the wind noticeably prevails over the others, and when the season changes, it changes by 120-180 °. M. cause a sharp change in weather (dry, slightly cloudy to wet, rainy, or vice versa). For example, over India there is a summer (wet) southwestern monsoon and a winter (dry) northeastern monsoon. Transitional relatively short periods with variable winds are observed between the monsoons.
Winds have the greatest stability and speed in some areas of the tropics (especially in equatorial Africa, the countries of South and Southeast Asia, and in the southern hemisphere up to the northern parts of Madagascar and Australia). In a weaker form and in limited areas, M. are also found in subtropical latitudes (in particular, in the southern Mediterranean Sea and in North Africa, in the Gulf of Mexico, in eastern Asia, in South America, in southern Africa and Australia) . M. are also noted in some regions of middle and high latitudes (for example, in the Far East, in southern Alaska, along the northern outskirts of Eurasia). In a number of places, there is only a tendency towards the formation of M., for example, there is a seasonal change in the prevailing wind directions, but the latter are characterized by less intra-seasonal stability.
Monsoon air currents, like all manifestations of the general circulation of the atmosphere, are due to the location and interaction of areas of low and high atmospheric pressure (cyclones and anticyclones). The specificity lies in the fact that during M. the mutual arrangement of these areas persists for a long time (during the whole season of the year), violations of this arrangement correspond to interruptions in M. In those regions of the Earth where cyclones and anticyclones are characterized by rapid movement and frequent change, M. does not arise. The vertical power of monsoon currents in the tropics is 5-7 km, in winter - 2-4 km, above there is a general air transport characteristic of the corresponding latitudes (eastern - in the tropics, western - in higher latitudes).
The main cause of meteorism is the seasonal movement of areas of atmospheric pressure and wind associated with changes in the intake of solar radiation and, as a consequence, with differences in the thermal regime on the Earth's surface. From January to July, areas of low atmospheric pressure near the equator and the poles, as well as 2 zones of subtropical anticyclones in each hemisphere, shift to the north, and from July to January - to the south. Along with these planetary atmospheric pressure zones, the associated wind zones also move , which also have global dimensions - the equatorial zone of westerly winds, easterly transfers in the tropics (trade winds), westerly winds of temperate latitudes. M. are observed in those places on the Earth that during one of the seasons are located inside one such zone, and in the opposite season of the year - inside the neighboring one, and where, in addition, the wind regime during the season is quite stable. Thus, the distribution of M. in general terms is subject to the laws of geographical zoning.
Another reason for the formation of M. is the uneven heating (and cooling) of the sea and large land masses. For example, over the territory of Asia in winter there is a tendency to a greater frequency of anticyclones, and in summer - cyclones, in contrast to the adjacent waters of the oceans. Due to the presence of a huge continent in the north, the equatorial westerly winds in the Indian Ocean basin penetrate far into South Asia in summer, forming the summer southwestern monsoon. In winter, these winds give way to the northeast trade winds (winter monsoon). In extratropical latitudes, due to stable winter anticyclones and summer cyclones over Asia, monsoons are also observed in the Far East - within the USSR (summer - southern and southeastern, winter - northern and northwestern) and on the northern outskirts of Eurasia (in summer, the predominance of northeast, in winter - south and southwest winds).
Air flow is a rather variable phenomenon in the natural world. The wind can subside or blow with new force, and also change its original direction. But there are winds that always have one direction, change it quite rarely. In this article, we will consider in detail what the trade winds and monsoons are, what is their activity and occurrence.
Types of winds
Wind is the air flow that moves above the ground in a horizontal direction. This natural phenomenon occurs due to the difference in atmospheric pressure. Air flows always originate in a zone of high pressure, and from there they are directed to an area of its decrease.
When the globe rotates, the direction of the winds changes. Therefore, in the north, air currents deviate to the right side, and in the southern hemisphere to the left. It is also possible that the wind will randomly occur when the weather changes.
Specialists in the field of meteorology also distinguish constant winds that almost never change direction. The most important of these are breezes, monsoons and trade winds.
trade winds
The trade winds are steady winds resulting from differences in atmospheric pressure in the two hemispheres and at the equator. But, interestingly, they are formed only in the tropical region.
In addition, trade winds are winds that deviate due to the rotation of the globe. In the northern hemisphere, their flows are directed to the southwest from the northeast, and in the south there is a reverse deviation - from the southeast to the northwest.
It is worth noting that the definition of the word "trade winds" is the same in all encyclopedias. These are winds that are stable in terms of humidity and temperature, which are the main factor in the formation of climate in a particular area.
From the foregoing, it became clear what the trade winds are. But what is their origin?
What does the word "trades" mean?
In any explanatory dictionary, windiness is characterized as changeability and inconstancy. But the trade winds are something that breaks this statement.
The ancient navigators were aware of the fact of their positive impact. In such winds as the trade winds, this influence was expressed in the fact that, according to signs, an even breath meant a successful outcome of the entire sea voyage. After all, air currents pushed the ships in the right direction.
Spanish travelers gave such winds a special name, which sounded like “viento de pasade” - this is something that has a beneficial effect on movement. German and Dutch navigators also included the term pasade.
In Russian, the word "trade winds" appeared thanks to Peter the Great. It should be noted that such natural phenomena are not typical for our country, they are most often found in tropical zones. Being far from the equatorial zone, the trade winds weaken and can only spread in open space above the water surface. But in this case, the strength of the trade winds does not exceed 3 or 4 points. Near land, the trade winds gradually develop or transform into monsoons.
Origin of the trade winds
Climatic and weather conditions in a certain area have a special influence on the process of wind formation. In some parts of our planet, such an impact is the result of the formation of a specific local cyclone wind. Such air masses, along with constant ones, play an important role in the circulation process, and also form climatic conditions in certain zones and regions of the Earth.
On the globe, the sun's rays warm most of all the equator and the nearest zones to it, so the air there always has a high temperature. For this reason, in the area close to the equator, the updraft of air is stable.
Cold air masses rush from the northern and southern belts to the place where the air rises. The inertial force of rotation helps the air masses to deviate slightly to the side, and not only move straight along a given trajectory. Therefore, the trade winds are winds that blow with a slight deviation to the side.
The cold air, rising, continues to cool even more, which leads to its gradual lowering, but the air outflow directs it back and the Coriolis law works here. Then there are upper trade winds (this phenomenon is also called counter-trade winds).
Monsoons
What are monsoons? Both trade winds in geography and monsoons are winds that differ in several features. Monsoons appear as a result of pressure drops that occur due to temperature differences. The main feature of these winds is that they have the opposite direction at any time of the year. Monsoons blow either from water to land or vice versa.
In winter, the air above the water is warmer than above the ground, and the pressure is lower, so the flows are directed to the sea. In the summer, the process is reversed. Precipitation is caused by winds blowing from the sea to the land.
In the tropics, monsoon activity is quite high. An example is India, where the mountains help stop damp winds. That is why Burma, North India and Nepal suffer from high rainfall. In addition, India almost always has a humid summer.
Origin of the monsoons
Monsoons owe their appearance to the annual cycle of distribution of atmospheric pressure. During a hot period, the earth warms up faster than water, and heat penetrates into the lower atmosphere. The heated air masses rush upwards, and a zone of low pressure appears above the ground.
The air pocket is filled with cold air, which is distributed over the water surface. Winds moving from water to land bring precipitation. Unlike the monsoons, the trade winds cannot do this.
Influence of wind activity
It is not the wind itself that falls under the interest of specialists, but the reasons that can cause it, and places where its pronounced activity is observed. Monsoons and trade winds are the winds of the tropical zones. Moreover, the trade winds can blow all year from one hemisphere to another and vice versa, but the monsoons are considered seasonal winds, which have different directions at different times of the year. Often this is typical of the Indian Ocean.
The described winds have a great influence on the climate. For example, Indochina suffers from dry weather in the summer due to northeasterly air currents. The way of life of the population of those countries depends only on the change of the season, each of which brings its own natural phenomena. Based on climatic conditions, people determine when to start agricultural work and when it can be completed.
In addition, the influence of the trade winds and monsoons was known to the ancient navigators. These air masses helped them make historical journeys across the seas and oceans.
What is opposite change their direction twice a year. The winter monsoon moves from land to sea, while the summer monsoon moves from sea to land. Typical areas of monsoons are the eastern coasts of the continents, as well as the tropical latitudes of the northern hemisphere.
Monsoons have the greatest stability and wind speed in some areas of the tropics (especially in equatorial Africa, the countries of South and Southeast Asia and in the Southern Hemisphere up to the northern parts of Madagascar and Australia). In a weak form and in limited areas, the monsoon also appears in subtropical latitudes (in particular, in the south of the Mediterranean Sea and in North Africa, in the Gulf of Mexico, in eastern Asia, in South America, in southern Africa and Australia). monsoons are also observed in some regions of middle and high latitudes (for example, in the Far East, in southern Alaska, along the northern margin of Eurasia). In a number of places, only a tendency towards the formation of a monsoon is outlined, for example, there is a seasonal change in the prevailing wind directions, but the latter are characterized by less seasonal stability.
Monsoon air currents, and all manifestations of the general circulation of the atmosphere, are due to the location and interaction of areas of low and high atmospheric pressure (cyclones and anticyclones). The specificity lies in the fact that during monsoons, the mutual arrangement of these areas persists for a long time (during the whole season of the year), violations of this arrangement correspond to interruptions in the monsoon. In those regions of the Earth where cyclones and anticyclones are characterized by rapid movement and frequent change, monsoons do not occur. The vertical power of the monsoon currents in the tropics is 5-7 km in summer, 2-4 km in winter, the general air transport characteristic of the corresponding latitudes is observed above (east - in the tropics, west - in higher latitudes).
The main cause of the monsoon is the seasonal movement of atmospheric pressure and wind areas associated with changes in the intake of solar radiation and, as a result, with differences in the thermal regime on the Earth's surface. From January to July, areas of low atmospheric pressure near the equator and the poles, as well as two zones of subtropical anticyclones in each hemisphere, move northward, and from July to January - southward. Together with these planetary zones of atmospheric pressure, the wind zones associated with them, which also have global dimensions, move - the equatorial zone of westerly winds, easterly transfers in the tropics (trade winds), westerly winds of temperate latitudes. Monsoons are observed in those parts of the Earth that during one of the seasons are located inside one such zone, and in the opposite season of the year - inside the neighboring one, and where, in addition, the wind regime during the season is quite stable. Thus, the distribution of monsoons is generally determined by the laws of geographic zoning.
Another reason for the formation of monsoons is the uneven heating (and cooling) of the sea and large land masses. For example, over the territory of Asia in winter there is a tendency to a greater frequency of anticyclones, and in summer - cyclones, in contrast to the waters of the adjacent oceans. Due to the presence of a huge mainland in the north, equatorial westerly winds in the Indian Ocean basin penetrate far into South Asia in summer, forming the summer southwest monsoon. In winter, these winds give way to the northeast trade wind (winter monsoon). In extratropical latitudes, due to stable winter anticyclones and elderly cyclones over Asia, monsoons are also observed in the Far East of Russia (summer - south and southeast, winter - north and south) and on the northern margin of Eurasia (in summer, the predominance of the northeast, in winter - south and southwest winds).
Causes of air movement
Atmospheric air is in constant and continuous motion. The movement of air can be ascending, in which it rises and descending, in which the air descends. There is another movement - horizontal.
Definition 1
Horizontal air movement is called wind.
Air movement depends on atmospheric pressure and temperature. In addition to these main reasons, the movement is influenced by friction on the Earth's surface, a meeting with some kind of obstacle, and the deflecting Coriolis force. In the Northern Hemisphere, due to this Coriolis force, air currents are deflected right, in the southern hemisphere to the left.
Remark 1
Air flow in this case, it always moves from a region of high pressure to a region of low pressure.
Any wind has its own direction, strength and speed, which depends on pressure. If the pressure difference between two adjacent territories is large, the wind speed will increase. On average, near the Earth's surface, the long-term wind speed reaches $4-9$ m/s, sometimes it happens $15$ m/s. Storm winds blow at speeds up to $30$ m/s, with gusts up to $60$ m/s. Tropical hurricanes reach up to $65 m/s, and in gusts they reach $120 m/s.
In addition to meters per second, kilometers per hour, wind speed is also measured in points on a scale Beaufort from $0-13$. From speed the wind depends on it force, which shows dynamic pressure airflow to any surface. Wind force is measured in kilograms per square meter.
The side of the horizon from which the wind blows determines its direction. To indicate its direction, eight main points are used, i.e. four main sides of the horizon and four intermediate ones. The direction of the wind will be related to the pressure and deflecting Coriolis force. In their origin, meaning and character, the winds are very diverse.
For temperate latitudes, westerly winds are characteristic, because the westerly transfer of air masses dominates there - these are north-western, western and south-western winds. In the northern and southern hemispheres, this region occupies vast spaces. The winds of the polar regions blow from the poles to moderate latitudes, i.e. to areas of low pressure. In the Arctic, northeasterly winds blow clockwise, while in the Antarctic, southeasterly winds blow counterclockwise. Antarctic winds are faster and more stable. Trade winds dominate in tropical latitudes.
Constant winds
Remark 2
Constant winds blow throughout the year in one direction from areas of high to areas of low atmospheric pressure. These include - trade winds, westerly winds, Arctic and Antarctic winds.
Definition 2
trade winds- these are constant winds of tropical latitudes blowing from 30 parallels towards the equator.
The name of this constant wind was given by the Spaniards, calling it "Viento de pasada", which means "the wind that favors the move." The trade winds blow at a speed of $5-6$ m/s and cover a layer of air with a height of $15-16$ km. Powerful ocean currents are associated with them - in the Atlantic Ocean the Antilles Current and the Brazilian Current, in the Pacific Ocean Mindanao and the East Australian, Mozambique Current in the Indian Ocean. The area of the planet, blown by the trade winds, has a peculiar climate - mostly cloudy warm weather with little rainfall prevails there. On land, this climate favors the formation of deserts and semi-deserts. In the Northern Hemisphere, the trade winds are directed from the northeast, and in the Southern Hemisphere from the southeast to the equator.
Definition 3
westerly winds- these are constant winds of temperate latitudes blowing from the tropics to the 60th parallel.
Tropical air normalizes the temperature of temperate latitudes and makes it favorable for human life. Temperate latitudes are the meeting point of warm and cold air masses. Warm air masses come from the tropics, and cold air masses come from the polar regions. As a result of their contact, cyclones and anticyclones. The temperate belt itself is an area of low pressure, so quite strong air masses come here. Here the western transport of air masses dominates, half of them are formed in the north, and the other half are formed in the east, and they all blow in the same western direction. In general, westerly winds soften the weather - the summer will be cool with a chance of rain. Winter will be accompanied by thaws and heavy snowfalls. The north wind will bring cold, and the south wind will bring warmth. The east wind is less predictable - it can be both warm and cold, but there will not be much precipitation either in summer or in winter.
The polar type of climate forms two zones - arctic and antarctic. Polar air masses will be constant for this area of the planet throughout the year. Arctic the polar wind is strong enough blowing to temperate latitudes in a clockwise direction. It blows only in a southerly direction and comes to the northern coast of Eurasia, North America. Along with this wind comes a sharp cold snap. In the southern hemisphere, the polar wind is called Antarctic and blows only to the north counterclockwise, moving towards temperate latitudes. The wind is very strong and cold.
seasonal winds
Definition 4
seasonal periodic winds are called, the direction of which changes half a year.
One of these winds is monsoons.
Definition 5
Monsoons These are winds that change direction with the seasons.
Monsoons are stable and cover vast areas. Their stability is related to the distribution of atmospheric pressure during each season. The reason for the occurrence of monsoons is the different heating of land and water during the year, which means that there is a winter monsoon and summer. When the monsoons change in spring and autumn, the stability of the wind regime is disturbed. winter monsoon blows from land to sea, because during this period the mainland is cold, which means that the pressure above it will be high. In summer, when the land warms up, the pressure becomes lower and moist air from the ocean moves to land - this summer monsoon. Dry, slightly cloudy winter weather changes to rainy weather in summer.
In different regions of the planet, the nature of the circulation of the atmosphere will be different. This determines the differences in the causes and nature of the monsoons, therefore, they distinguish extratropical and tropical monsoons.
extratropical monsoons are characteristic of temperate and polar latitudes. The result of their formation is different pressure over land and sea in seasons. As a rule, extratropical monsoons form in the Far East, Northeast China, and Korea.
Tropical monsoons due to the fact that the seasons of the year the Northern and Southern hemispheres heat up and cool down differently. This leads to the fact that, according to the seasons of the year, the atmospheric pressure zones relative to the equator are shifted to the hemisphere in which at a given time summer and trade winds penetrate there. The trade wind regime is replaced for the tropics by the winter monsoon. Such a change is facilitated by the westerly flow of air in the zone of low atmospheric pressure at the equator, which is shifting along with other zones. Tropical monsoons are persistent in the northern Indian Ocean.
On the coasts of the seas and oceans, winds are formed, called breezes. These winds are of local importance and blow from sea to land during the day, and at night they change their direction to the opposite - from land to sea. As a result, day and night breezes are distinguished. Land in the daytime heats up faster than water and a low atmospheric pressure is established above it. Over water in the same period, the pressure will be higher, because it heats up much more slowly. As a result, air from the sea begins to move to land. At night, reduced pressure is noted above the water, because it has not had time to cool yet, and the air will move from land to sea.
The coastal breeze will change to a sea breeze shortly before noon, and in the evening the sea breeze will become a coastal breeze. Breezes can form along the shores of large lakes, large reservoirs, and rivers. From the coastline, they penetrate to land for tens of kilometers and are especially frequent in summer with clear and calm weather.
Which of us in childhood did not read adventure books about distant wanderings, noble sailors and fearless pirates?
When we pronounce the words "monsoon" and "trade winds", we evoke precisely these romantic pictures: distant tropical seas, uninhabited islands covered with lush greenery, the sound of swords and white sails on the horizon.
Meanwhile, everything is much more prosaic: monsoons and trade winds are well-known names that have a significant impact on the formation of weather not only in tropical areas, but throughout the planet.
Monsoons
Monsoons are called winds with a stable direction, characteristic of the tropical belt and some coastal countries of the Far East. In summer, monsoons blow from the ocean towards land, in winter - in the opposite direction. They form a peculiar type of climate, called monsoon, a characteristic feature of which is a high level of air humidity in the summer.
One should not think that in areas where the monsoon prevails, there are no other winds. But winds of other directions appear from time to time and blow for short periods, while the monsoon is the predominant wind, especially during winter and summer. The autumn-spring periods are transitional, at which time the stable wind regime is disturbed.
Origin of the monsoons
The appearance of monsoons is entirely related to the annual cycles of atmospheric pressure distribution. In summer, the land heats up more than the ocean, and this heat is transferred to the lower atmospheric layer. The heated air rushes up, and a zone of low atmospheric pressure forms over the land.
The resulting lack of air is immediately filled with a colder air mass located above the ocean surface. It contains a large amount of moisture evaporated from the water surface.
Moving in the direction of land, the air from the sea carries this moisture and spills it onto the surface of coastal areas. Therefore, the monsoonal climate is more humid in summer than in winter.
With the onset of the winter period, the winds change their direction, since at this time the land surface warms up less actively, and the air above it turns out to be colder than over the sea surface, which explains the change in the direction of the monsoon at this time.
Monsoon geography
The monsoon climate is most typical for the equatorial regions of Africa, the northern coast of Madagascar, many states of Southeast and South Asia, as well as the equatorial part of the Southern Hemisphere, including the northern coast of Australia.
The influence of the monsoons is experienced by the states of the Caribbean, the southern Mediterranean Sea and some other areas, but in a weaker form.
trade winds
The trade winds are called winds that blow steadily in the tropical zone all year round due to the inertial force of the Earth's rotation and the climatic features of the tropics. 
In the Northern Hemisphere, the trade winds blow from the northeast, and in the Southern Hemisphere, from the southeast. The trade winds are most stable above the sea surface, while the land relief introduces certain changes in their direction.
The name "trade wind" comes from the Spanish expression "viento de pasada" - a wind that favors movement. During the Age of Discovery, when Spain was the queen of the seas, the trade winds served as the main factor favoring the movement of sailing ships between the European mainland and the New World.
How are trade winds formed?
The equatorial zone of our planet experiences the strongest heating by the sun's rays, so the air in the lower atmosphere always has a fairly high temperature. Because of this, there is a stable updraft in areas close to the equator.
In place of the rising air, colder air masses immediately rush from both subtropical belts - northern and southern. Due to the Coriolis force - the inertial force of the Earth's rotation - these air currents do not move strictly in the south and north directions, but are deflected, acquiring a southeast and northeast direction. 
The cold air rising up cools and sinks down, but due to the outflow of air in the northern and southern temperate zones, it rushes there and also experiences the action of the Coriolis force. These winds blowing in the upper atmosphere are called the upper trade winds, or counter trade winds.
Geography of the trade winds
The trade winds are the prevailing winds along the entire equatorial belt, except for the coastal zone of the Indian Ocean, where, due to the geographical features of the coastline, they turn into monsoons.