home Treatment and prevention Illumination zones and thermal zones of the Earth. Heat zones Cold climate zone

Illumination zones and thermal zones of the Earth. Heat zones Cold climate zone

All processes in the atmosphere occur with the participation of solar energy, but not all areas of the earth's surface receive the same amount.

Factors on which the amount of solar radiation depends:

Angle of incidence sun rays: the greatest amount of sun rays is above the equator, the least - above the Arctic Circle. Thus, at the equator, the angle of incidence of the sun's rays reaches 90∘90∘ in March and September (on the days of spring and autumn equinox) and very large in December and June (on the days of the winter and summer solstice).
Transparency of the atmosphere: clouds, dust, smog, smoke reduce the amount of solar radiation reaching the Earth.
Duration daylight hours: in summer, areas near the poles receive significant amount solar radiation.
Absolute altitude of the area: mountain peaks receive more solar radiation than flat surfaces.
The nature of the earth's surface: albedo value, terrain, ocean currents. For example, forests, sand, and plowed, moist, dark soil absorb more energy from the Sun and therefore heat up faster. But in the light, areas covered with snow or ice almost do not heat up, since most of the energy received from the Sun is instantly reflected back into the atmosphere. Water heats up more slowly, but also releases the absorbed energy more slowly.
Distance from the Earth to the Sun: in January the Earth is closer to the Sun and receives more solar energy, at its greatest distance in July.
definition
Heat zones are conditional global regions of the Earth, distinguished based on the distribution of average annual air temperature.
The formation of heat belts is caused by the uneven distribution of solar heat over the spherical surface of the Earth. The boundaries of thermal zones run along conventional lines - the tropics and polar circles.

definition
Tropics (North and South) - parallels that are distant 23∘27’23∘27 “north and south of the equator.

Polar circles (Northern and Southern) - parallels in the Northern and Southern hemispheres with a latitude of 66∘33’66∘33 “.
There are special geographic Maps, which show the summer distribution of air temperature on Earth. On them, the air temperature is indicated either by dots next to which it stands numeric value, or special lines that connect points with the same temperature - isotherms. Red lines indicate the temperature of the warm month of the year, which in the Northern Hemisphere is July. Black or blue lines indicate the temperature of January, the coldest month in the Northern Hemisphere.

There are four types of annual temperature distribution: equatorial, tropical, temperate and polar. According to the characteristics of the summer distribution of air temperature on Earth, seven thermal zones are distinguished, the boundaries of which are isotherms: hot, two moderate, two cold and two zones of eternal cold.

Hot is located on both sides of the equator between the Northern and Southern tropics. The earth's surface receives a lot of solar heat and is well heated due to the fact that the sun's rays fall directly or at a large angle. Average annual temperatures: + 20 + 20 … + 26∘С + 26∘С.

Temperate (North and South) are located between the tropics and the Arctic Circle in both hemispheres. The height of the Sun above the horizon varies depending on the time of year, which leads to a large amplitude of temperature fluctuations and changes in seasons. Average annual temperatures: 0∘0∘ … + 25∘С + 25∘С.

Cold ones (Northern and Southern) are located beyond the polar circles in both hemispheres. The angle of incidence of the sun's rays is minimal; some of the rays are reflected by ice and snow cover, so it is very cold in these zones. Average annual temperatures: below 0∘С0∘С.

The eternal cold belts (Northern and Southern) are located around the poles and are surrounded by the 0∘С0∘С isotherm of the warm month in both hemispheres.

Uneven heating of the earth's surface causes different temperatures air at different latitudes. Latitudinal bands with certain air temperatures are called thermal zones. The belts differ from each other in the amount of heat coming from the Sun. Their extent depending on the temperature distribution is well illustrated by isotherms (From the Greek “iso” - Same, “therma” - Heat). These are lines on a map that connect points with the same temperature.

Hot belt located along the equator, between the Northern and Southern tropics. It is limited on both sides of the 20 0C isotherms. Interestingly, the boundaries of the belt coincide with the boundaries of the distribution of palm trees on land and corals in the ocean. Here the earth's surface receives the most solar heat. Twice a year (December 22 and June 22) at noon the sun's rays fall almost vertically (at an angle of 900). The air from the surface becomes very hot. That's why it's hot there throughout the year.

Temperate zones (in both hemispheres) are adjacent to the hot zone. They stretch in both hemispheres between the Arctic Circle and the Tropics. The sun's rays fall on the earth's surface with some inclination. Moreover, the further north, the greater the slope. Therefore, the sun's rays heat the surface less. As a result, the air heats up less. This is why it is colder in temperate zones than in hot zones. The sun is never at its zenith there. Clearly defined seasons: winter, spring, summer, autumn. Moreover, the closer to the Arctic Circle, the longer and colder the winter. The closer to the tropics, the longer and warmer the summer. The temperate zones on the polar side are limited by the warm month isotherm of 10 0C. It is the limit of forest distribution.

The cold belts (Northern and Southern) of both hemispheres lie between the isotherms of 10 0C and 0 0C of the warmest month. The sun there in winter does not appear above the horizon for several months. And in summer, although it does not go beyond the horizon for months, it stands very low above the horizon. Its rays only glide over the surface of the Earth and heat it weakly. The Earth's surface not only heats, but also cools the air. Therefore, the air temperatures there are low. Winters are cold and harsh, and summers are short and cool.

Two zones of eternal cold (northern and southern) are surrounded by an isotherm with temperatures of all months below 0 0C. This is the kingdom of eternal ice.

So, the heating and lighting of each area depends on the position in the thermal zone, that is, on the geographic latitude. The closer to the equator, the greater the angle of incidence of the sun's rays, the more the surface heats up and the higher the air temperature. And vice versa, with distance from the equator to the poles, the angle of incidence of the rays decreases, and accordingly the air temperature decreases.

It is important to remember that the lines of the tropics and polar circles outside the thermal zones are taken conditionally. Since in reality the air temperature is also determined by a number of other conditions (see the article main and transitional climate zones).

The climatic features of the Earth are determined mainly by the amount of incoming solar radiation on its surface and the characteristics of atmospheric circulation. The amount of solar radiation reaching the Earth depends on geographic latitude.

Solar radiation- the entire totality of solar radiation arriving at the Earth's surface. In addition to visible sunlight, it includes invisible ultraviolet and infrared radiation. In the atmosphere, solar radiation is partially absorbed and partially scattered by clouds. A distinction is made between direct and diffuse solar radiation. Direct solar radiation - solar radiation reaching the earth's surface in the form of parallel rays emanating directly from the Sun. Scattered solar radiation - part of direct solar radiation, scattered by gas molecules, arriving on the earth's surface from the entire vault of heaven. On cloudy days, scattered radiation is the only source of energy in ground layers atmosphere. Total solar radiation includes direct and diffuse solar radiation and reaches the Earth's surface.

Solar radiation is the most important source of energy for atmospheric processes - the formation of weather and climate, and the source of life on Earth. Under the influence of solar radiation, the earth's surface heats up, and from it the atmosphere, moisture evaporates, and the water cycle occurs in nature.

The earth's surface, absorbing solar radiation (absorbed radiation), heats up and itself radiates heat into the atmosphere. The radiation absorbed by the earth's surface is spent on heating the soil, air, and water. The lower layers of the atmosphere largely block terrestrial radiation. The main part of the radiation arriving at the earth's surface is absorbed by arable land (up to 90%) and coniferous forest (up to 80%). Some solar radiation is reflected from the surface (reflected radiation). Newly fallen snow, the surface of water bodies, and sandy deserts have the greatest reflectivity.

The distribution of solar radiation on Earth is zonal. It decreases from the equator to the poles in accordance with the decrease in the angle of incidence of the sun's rays on the earth's surface. The flow of solar radiation to the Earth's surface is also affected by cloudiness and atmospheric transparency.

Compared to the oceans, continents receive more solar radiation due to less (15-30%) cloud cover above them. In the Northern Hemisphere, where the main part of the Earth is occupied by continents, the total radiation is higher than in the Southern Oceanic Hemisphere. In Antarctica, where the air is clean and the atmosphere is highly transparent, a large number of direct solar radiation. However, due to the high reflectivity of the surface of Antarctica, the air temperature is negative.

Thermal zones. Depending on the amount of solar radiation entering the Earth's surface, there are 7 thermal zones on the globe: hot, two moderate, two cold and two perpetual frost zones. The boundaries of thermal zones are isotherms. Hot belt from the north and south it is limited by average annual isotherms of +20 °C (Fig. 9). Two temperate zones to the north and south of the hot zone, they are limited on the equator side by the average annual isotherm of +20 °C, and on the high latitude side by the +10 °C isotherm (the average air temperature of the warmest months - July in the Northern Hemisphere and January in the Southern Hemisphere). The northern border coincides approximately with the forest distribution boundary. Two cold belts north and south of the temperate zone in the Northern and Southern Hemispheres lie between the isotherms of +10 °C and 0 °C of the warmest month. Two belts of eternal frost limited by the 0 °C isotherm of the warmest month from cold zones. The kingdom of eternal snow and ice extends to the North and South Poles.

Rice. 9 Thermal zones of the Earth

Air temperature distribution on Earth. Just like solar radiation, air temperature on Earth varies zonally from the equator to the poles. This pattern is clearly reflected by the isotherm distribution maps of the warmest (July in the Northern Hemisphere, January in the Southern) and coldest (January in the Northern Hemisphere, July in the Southern) months of the year. The “warmest” parallel is 10° N. w. - thermal equator, where average temperature air +28 °C. In summer it shifts to 20° N. latitude, in winter it approaches 5° N. w. Most of the land is located in the Northern Hemisphere, and accordingly the thermal equator moves north.

The air temperature at all parallels in the Northern Hemisphere is higher than at similar parallels in the Southern Hemisphere. Average annual temperature in the Northern Hemisphere is +15.2 °C, and in Southern Hemisphere- +13.2 °C. This is due to the fact that in the Southern Hemisphere the ocean occupies a larger area, and, therefore, more heat is wasted on evaporation from its surface. In addition, the continent of Antarctica, covered with eternal ice, has a cooling effect on the Southern Hemisphere.

The average annual temperature in the Arctic is 10-14 °C higher than in Antarctica. This is largely determined by the fact that Antarctica is covered with an extensive glacial shell, and most of the Arctic is represented by the Arctic Ocean, where warm currents from lower latitudes. For example, the Norwegian Current has a warming effect on the Arctic Ocean.

On both sides of the equator there are equatorial and tropical latitudes, where the average temperature in winter and summer is very high. Over the oceans, isotherms are distributed evenly, almost coinciding with parallels. Along the coasts of continents they are greatly curved. This is explained by the unequal heating of land and ocean. In addition, the air temperature near the coasts is influenced by warm and cold currents and prevailing winds. This is especially noticeable in the Northern Hemisphere, where most of the land is located. (Trace the distribution of temperatures across thermal zones using an atlas.)

In the Southern Hemisphere, the temperature distribution is more uniform. However, it has its own hot areas - the Kalahari Desert and Central Australia, where the temperature in January rises above +45 °C, and in July it drops to -5 °C. The pole of cold is Antarctica, where an absolute minimum of –91.2 °C was recorded.

The annual course of air temperature is determined by the course of solar radiation and depends on geographic latitude. In temperate latitudes, the maximum air temperature is observed in July in the Northern Hemisphere, in January in the Southern Hemisphere, and the minimum in January in the Northern Hemisphere, in July in the Southern Hemisphere. Over the ocean, the maximums and minimums are delayed by a month. The annual amplitude of air temperatures increases with latitude. Largest values it reaches on continents, much smaller - over the oceans, on sea coasts. The smallest annual amplitude of air temperatures (2 °C) is observed at equatorial latitudes. The highest (more than 60 °C) is in subarctic latitudes on the continents.

Bibliography

1. Geography 8th grade. Tutorial for 8th grade institutions of general secondary education with Russian as the language of instruction / Edited by Professor P. S. Lopukh - Minsk “People's Asveta” 2014

Thermal zones of the Earth

Uneven heating of the earth's surface causes different air temperatures at different latitudes. Latitudinal bands with certain air temperatures are called thermal zones. The belts differ from each other in the amount of heat coming from the Sun. Their extent depending on the temperature distribution is well illustrated by isotherms (From the Greek “iso” - Same, “therma” - Heat). These are lines on a map that connect points with the same temperature.

Hot belt located along the equator, between the Northern and Southern tropics. It is limited on both sides of the 20 0 C isotherms. Interestingly, the boundaries of the belt coincide with the boundaries of the distribution of palm trees on land and corals in the ocean. Here the earth's surface receives the most solar heat. Twice a year (December 22 and June 22) at noon the sun's rays fall almost vertically (at an angle of 90 0). The air from the surface becomes very hot. That's why it's hot there throughout the year.

Temperate zones(In both hemispheres) adjacent to the hot zone. They stretch in both hemispheres between the Arctic Circle and the Tropics. The sun's rays fall on the earth's surface with some inclination. Moreover, the further north, the greater the slope. Therefore, the sun's rays heat the surface less. As a result, the air heats up less. This is why it is colder in temperate zones than in hot zones. The sun is never at its zenith there. Clearly defined seasons: winter, spring, summer, autumn. Moreover, the closer to the Arctic Circle, the longer and colder the winter. The closer to the tropics, the longer and warmer the summer. Temperate zones on the polar side are limited by the warm month isotherm of 10 0 C. It is the limit of forest distribution.

Cold belts The (Northern and Southern) hemispheres lie between the 10 0 C and 0 0 C isotherms of the warmest month. The sun there in winter does not appear above the horizon for several months. And in summer, although it does not go beyond the horizon for months, it stands very low above the horizon. Its rays only glide over the surface of the Earth and heat it weakly. The Earth's surface not only heats, but also cools the air. Therefore, the air temperatures there are low. Winters are cold and harsh, and summers are short and cool.

Two belts of eternal cold(northern and southern) are surrounded by an isotherm with temperatures of all months below 0 0 C. This is the kingdom of eternal ice.

Light belts and their characteristics.

Moderate

Cold

It is located between the tropics and the Arctic Circle within the hemisphere.

The sun is never at its zenith

During the year, the angle of incidence of the sun's rays varies greatly, so thermal seasons of the year are distinguished (summer, autumn, winter, spring). Temperatures in summer and winter are very different. For example, at latitude 50 o

t° summer≈ +20°С

t° winter≈ -10°С

Located between the northern and southern tropics.

The sun is at its zenith twice a year. The surface warms up very well all year round; there is no difference between summer and winter temperatures, there are no thermal seasons of the year, average annual t o =+25 o C. During the year, the duration of daylight hours changes slightly. Approximately day=night=12 hours. There is virtually no twilight.

Located inside the Arctic Circle of each hemisphere.

In winter, the Sun does not rise above the horizon at all - the phenomenon of the Polar Night. In summer, the Sun, on the contrary, does not set beyond the horizon - the phenomenon of the Polar Day. The angle of incidence of sunlight even in summer is very small, so the heating of the surface is very weak. Summer temperatures usually do not exceed +10°C. During the long polar night, strong cooling occurs, because... there is no heat flow at all.

Light belts are parts of the Earth's surface limited by the tropics and polar circles and differing in light conditions.

As a first approximation, it is enough to distinguish three zones in each hemisphere: 1) tropical, limited to the tropics, 2) temperate, extending to the Arctic Circle, and 3) polar. The first is characterized by the presence of the Sun at the zenith at each latitude twice a year (once in the tropics) and a small difference in the length of the day between months. The second is characterized by large seasonal differences in the height of the Sun and the length of the day. The third is characterized by a polar night and a polar day, the longitude of which depends on the geographic latitude. North of the Arctic Circle and south of the Antarctic Circle experience polar day (summer) and polar night (winter). The area from the Arctic Circle to the Pole in both hemispheres is called the Arctic.
Polar day is the period when the Sun is at high latitudes does not fall below the horizon around the clock. The length of the polar day increases the further you go to the pole from the Arctic Circle. In the polar circles, the Sun does not set only on the day of the solstice; at 68° latitude, the polar day lasts about 40 days, at the North Pole 189 days, at the South Pole somewhat less, due to the unequal speed of the Earth's orbit in the winter and summer months.
The polar night is a period when the Sun in high latitudes does not rise above the horizon around the clock; a phenomenon opposite to the polar day is observed simultaneously with it at the corresponding latitudes of the other hemisphere. In fact, the polar night is always shorter than the polar day due to the fact that the Sun, when it is not much below the horizon, illuminates the atmosphere and there is no complete darkness (twilight).
However, dividing the Earth into such large belts cannot satisfy practical needs.

On the days of the equinoxes, the height of the midday Sun above the horizon h for different latitudes f is easily determined by the formula: h = 90°-f.
So, in St. Petersburg (ph = 60°) on March 21 and September 23 at noon, the Sun is at an altitude of 90°-60° = 30°. It heats the Earth for 12 hours. In the summer of each hemisphere, when the Sun is above the corresponding tropic, its height at noon increases by 23°27":
A=90°-f+23°27".
For St. Petersburg, for example, on June 21, the altitude of the Sun is: 90°-60°+23°27" = 53°27". The day lasts 18.5 hours.

In winter, when the Sun moves to the opposite hemisphere, its height decreases accordingly and reaches a minimum on the days of the solstices. Then it should be reduced by 23°27".
At the parallel of Leningrad on December 22, the Sun is at an altitude of 90°-60° -23°27" = 6°33" and illuminates the earth's surface for only 5.5 hours.

The described conditions of illumination of the globe, due to the tilt of the earth's axis, represent the radiation, associated with the sun's rays, the basis of the change of seasons.

Not only solar radiation, but also many telluric (terrestrial) factors take part in the formation of the weather, and thus the seasons, so in reality both the seasons and their changes are a complex phenomenon.

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1. Thermal zones of the Earth

The hot zone is located along the equator, between the Northern and Southern tropics. It is limited on both sides of the 20 0C isotherms. Interestingly, the boundaries of the belt coincide with the boundaries of the distribution of palm trees on land and corals in the ocean. Here the earth's surface receives the most solar heat. Twice a year (December 22 and June 22) at noon the sun's rays fall almost vertically (at an angle of 900). The air from the surface becomes very hot. That's why it's hot there throughout the year.

Two zones of eternal cold (northern and southern) are surrounded by an isotherm with temperatures of all months below 0 0C. This is the kingdom of eternal ice.

1.1 Roast

Equatorial belt - zone low pressure, rising air currents, weak winds. Temperatures are high all year round (about +28 °C), air humidity is high. There is a lot of precipitation - about 2000 mm. Seasonal variations average monthly temperatures and precipitation is insignificant.

Subequatorial belts are characterized by seasonal changes air masses: The summer monsoon brings hot and humid equatorial air, while dry continental tropical air dominates in winter. This type of climate with wet summers and dry winters is called monsoon climate.

Tropical zones are characterized by an arid (dry) climate, they contain the greatest deserts in the world: the Sahara, Arabian, and Australian. The air temperature ranges from +20 °C in summer to +15 °C in winter.

1.2 Moderate

IN subtropical zones air masses change from tropical in summer to temperate in winter, and temperatures are above zero throughout the year. However, short-term drops in temperature to negative values and even snowfall are possible. On the plains the snow melts quickly, but in the mountains it can remain for several months. In inland areas the climate is arid, with hot (about +30 °C) dry summers, cool (0...+5 °C), relatively wet (200-250 mm) winters. Changes in air masses and frequent passage atmospheric fronts detects unstable weather. Due to insufficient moisture, landscapes of deserts, semi-deserts, and dry steppes predominate here. Tibet, the world's largest and highest (4-5 km) highland with high-mountain deserts, has a special sharply continental climate with cool summers, harsh winters and little precipitation.

In the Southern Hemisphere, where there are no large continents, and only a narrow part enters the temperate zone South America, island of Tasmania and South New Zealand, the climate is mild oceanic with warm winters and cool summers, uniformly heavy (about 1000 mm) precipitation. And only in Patagonia the climate is transitional to continental, and the moisture is insufficient.

In the Northern Hemisphere, on the contrary, vast land masses dominate and a whole spectrum of climates differing in the degree of continentality has developed. From west to east - from temperate to sharply continental climate - daily and seasonal temperature amplitudes increase, and annual precipitation decreases from 700-600 mm to 300 mm and even to 200-100 mm in the Middle and Central Asia. In summer there is more precipitation than in winter, and this difference is more significant in the center of the continents, especially in Eastern Siberia, due to the very dry anticyclonic winter.

The temperate zone is divided into the northern part with cool summers and relatively harsh winters and the southern part with warm summer and relatively mild winter.. July temperatures vary from -4...-10 °C to +12 °C in the north and up to +30 °C in the south, January temperatures from -5 °C in the west to -25...- 30 °C in the center of the continents, in Yakutia even below -40 °C.

1.2 Cold

The subarctic and subantarctic belts are characterized by seasonal changes in air masses: in the summer it is PV, in the winter it is AB. In the north of Eurasia and North America, the climate is continental and sharply continental with cool, damp summers with temperatures less than +10...+12 °C and long, harsh (up to -40...-50 °C) winters with little snow and large annual temperature amplitudes . In the area of Oymyakon there is the pole of cold of the Northern Hemisphere and the entire planet - (-78 °c). Such conditions contribute to the maintenance of widespread permafrost. There is little precipitation (200-100 mm), but due to low temperatures there is excess moisture. The tundra and forest-tundra that dominate here are very swampy.

The marine climate of the northern and southern coasts is characterized by cool (+3...+5 °c) damp summers, relatively mild (-10...-15 °c) winters, floating sea and continental ice, constant fogs with significant for such low temperatures and precipitation (up to 500 mm). Tundra is widespread along the coasts of continents and islands.

In the Arctic (Greenland and the islands of the Canadian archipelago) and Antarctic belts(Antarctica), predominates continental climate. These are the coldest regions of the Earth - the thermometer does not rise above zero throughout the year, and on the inland Antarctic station"Vostok" recorded an absolute minimum temperature of -89.2 °C (but the "Vostok" station is located at an altitude of 3488 m). Precipitation is less than 100 mm. Here you can hardly see anything other than icy deserts. The Arctic has an oceanic climate. Negative temperatures prevail, but during the polar day it can warm up to +5 °C. There is also little precipitation; the islands are characterized by tundra.

2. Air masses

Large masses of air in the troposphere, comparable in size to a continent or ocean and having more or less the same properties (temperature, humidity, transparency, dust content, etc. - note from geoglobus.ru), are called air masses. They extend upward for several kilometers, reaching the boundaries of the troposphere.

Air masses move from one area of the globe to another, determining the climate and weather in a given area. Each air mass has properties characteristic of the area over which it formed.

Moving to other territories, it carries with it its own weather regime. But passing over a territory with different properties, air masses gradually change, transform, acquiring new qualities.

Depending on the regions of formation, four types of air masses are distinguished: Arctic (in the Southern Hemisphere - Antarctic), temperate, tropical and equatorial. All types are divided into subtypes that have their own characteristic properties. Continental air masses form over continents, and oceanic air masses form over oceans. Shifting with the belts atmospheric pressure throughout the year, air masses occupy not only permanent belts their stay, but seasonally they dominate in neighboring, transitional climatic zones. In the process of general atmospheric circulation, air masses of all types are interconnected.

Air masses that move from a colder earth's surface to a warmer one and that have a lower temperature than the surrounding air are called cold air masses. They bring cooling, but they themselves warm up from below from the warm earth's surface, and powerful Cumulus clouds and heavy rain falls. Particularly severe cold snaps occur in temperate latitudes with the invasion of cold masses from the Arctic and Antarctica - approx. from geoglobus.ru. Cold air masses sometimes reach southern regions Europe and even North Africa, but are most often delayed by the mountain ranges of the Alps. In Asia, Arctic air freely spreads over vast territories, up to the mountain ranges of southern Siberia. IN North America The mountain ranges are located meridianally, so cold arctic air masses penetrate as far as the Gulf of Mexico.

Air masses that have a higher temperature than the surrounding air and arrive at the colder earth's surface are called warm air masses. They bring warming, and they themselves cool from below, and stratus clouds and fogs form. In summer, warm tropical air masses from North Africa sometimes penetrate to the northern regions of Europe and significantly increase the temperature (sometimes up to +30 ° C).

Local, or neutral, air mass is a mass that is in thermal equilibrium with its environment, that is, maintaining its properties day after day. A changing air mass can be either warm or cold, and once the transformation is complete, it becomes local.

Where air masses meet different types, atmospheric fronts form.

Moderate air masses form in temperate latitudes. Those that form over the continent have low temperatures and low moisture content in winter and bring clear and frosty weather. In summer, continental temperate air masses are dry and hot. Temperate air masses formed over the ocean are warm and humid. In winter they bring thaws, and in summer they bring cold temperatures and precipitation.

Arctic and Antarctic air masses form over the icy surface of the polar latitudes. They are characterized by low temperature and a small amount of moisture. They significantly lower the temperature of the areas they invade. In summer, moving towards the center of Eurasia, these air masses gradually warm up, dry out even more and become the cause of dry winds in the southern regions of the West Siberian Lowland.

Tropical air masses are hot at any time of the year. The marine subtype of tropical air masses is characterized by high humidity, while the continental subtype is dry and dusty. The trade winds dominate the oceans in the tropics all year round - approx. from geoglobus.ru. The air masses that form in these areas are characterized by moderately high temperatures from +20 to +27 °C in summer and cool temperatures up to +10 +15 °C in winter. In the areas tropical deserts Extremely dry air masses with average temperatures of +26 +40 °C are formed over the continents.

Equatorial air masses are formed at equatorial latitudes. They have high temperature and high humidity, regardless of where they formed - over the continent or over the ocean. The average temperatures of equatorial air masses in all months of the year range from +24 to +28 °C. Since evaporation in these areas is high, the absolute humidity, A relative humidity even in the driest months of the year above 70%.

3. Atmospheric precipitation

thermal zone air atmospheric

Their education

Atmospheric precipitation is any moisture that falls from the atmosphere onto the earth's surface. These include rain, snow, hail, dew, and frost. Precipitation can fall both from clouds (rain, snow, hail) and from the air (dew, frost).

The main condition of education atmospheric precipitation is the cooling of warm air, leading to condensation of the steam contained in it.

As warm air rises and cools, clouds consisting of water droplets form. Colliding in the cloud, the drops connect and their mass increases. The bottom of the cloud turns blue and it starts to rain. At subzero air temperatures, water droplets in clouds freeze and turn into snowflakes. Snowflakes stick together into flakes and fall to the ground. During snowfall, they may melt a little, and then wet snow falls. It happens that air currents repeatedly lower and raise frozen drops, at which time ice layers grow on them. Finally the drops become so heavy that they fall to the ground like hail. Sometimes hailstones reach the size of a chicken egg.

IN summer time When the weather is clear, the earth's surface cools. It cools the ground layers of air. Water vapor begins to condense on cold objects - leaves, grass, stones. This is how dew is formed. If the surface temperature was negative, then the water droplets freeze, forming frost. Dew usually falls in summer, frost - in spring and autumn. At the same time, both dew and frost can form only in clear weather. If the sky is covered with clouds, then the earth's surface cools slightly and cannot cool the air.

According to the method of formation, convective, frontal and orographic precipitation are distinguished. The general condition for the formation of precipitation is the upward movement of air and its cooling. In the first case, the reason for the rise of air is its heating from warm surface(convection). Such precipitation falls all year round in the hot zone and in summer in temperate latitudes. If warm air rises when interacting with colder air, frontal precipitation forms. They are more characteristic of temperate and cold zones, where warm and cold air masses are more common. The reason for the rise of warm air may be its collision with mountains. In this case, orographic precipitation is formed. They are typical for the windward slopes of mountains, and the amount of precipitation on the slopes is greater than in the adjacent areas of the plains.

The amount of precipitation is measured in millimeters. On average, about 1100 mm of precipitation falls on the earth's surface per year.

Distribution of precipitation on the globe. Atmospheric precipitation on the planet is distributed unevenly. This depends on the geographic location of the area and prevailing winds. The greatest amount of precipitation falls in equatorial (over 2,000 mm) and temperate (over 800 mm) latitudes. Little precipitation (200 mm) falls in tropical and polar latitudes. However, this distribution is disrupted by the nature of the earth's surface: more precipitation falls over the oceans than over land. In the mountains, much more precipitation is “accepted” by those slopes facing the prevailing winds. Thus, in Ukraine, the windward slopes of the Carpathians receive 1500 mm per year, and the leeward ones - half as much -750 mm per year.

The record high annual rainfall on Earth is in the village of Cherrapunji, at the foot of the Himalayas - 23,000 mm. And the wettest place on the planet is considered to be the Hawaiian Islands, where it rains 335 days a year, bringing 12,000 mm of water. Record-breaking dry places where precipitation has not fallen for years are the Atacama desert in South America (1 mm per year) and the Sahara desert in Africa (5 mm per year).

The distribution of precipitation on Earth depends on a number of reasons:

a) from the placement of high and low pressure belts. At the equator and in temperate latitudes, where low pressure areas form, there is a lot of precipitation. In these areas, the air heated by the Earth becomes light and rises, where it meets the cooler layers of the atmosphere, cools, and the water vapor turns into water droplets and falls to the Earth as precipitation. In the tropics (30th latitude) and polar latitudes, where regions are formed high pressure, downward air currents predominate. Cold air descending from upper layers troposphere, contains little moisture. When lowered, it contracts, heats up and becomes even drier. Therefore, in areas high blood pressure There is little precipitation over the tropics and at the poles;

b) the distribution of precipitation also depends on geographic latitude. At the equator and in temperate latitudes there is a lot of precipitation. However, the earth's surface at the equator warms up more than in temperate latitudes, therefore the updrafts at the equator are much more powerful than in temperate latitudes, and therefore, precipitation is stronger and more abundant;

c) the distribution of precipitation depends on the position of the area relative to the World Ocean, since it is from there that the main share of water vapor comes. For example, in Eastern Siberia there is less precipitation than on the East European Plain, since Eastern Siberia is far from the oceans;

d) the distribution of precipitation depends on the proximity of the area to ocean currents: warm currents promote precipitation on the coasts, while cold currents prevent it. Cold currents pass along the western coasts of South America, Africa and Australia, which led to the formation of deserts on the coasts; e) the distribution of precipitation also depends on the topography. On the slopes mountain ranges, facing the humid winds from the ocean, moisture falls noticeably more than on the opposite - this is clearly visible in the Cordillera of America, on the eastern slopes of the mountains Far East, on the southern spurs of the Himalayas. Mountains prevent the movement of moist air masses, and the plain facilitates this.

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