Thermal belt. Heat zones What kind of heat zone does not exist on earth?

The spherical shape of the Earth determines the uneven distribution of solar heat on its surface and the formation of thermal zones: hot, moderately hot (northern and southern), moderate, moderately cold and cold.

The hot zone is located approximately between 30°N. and 30° S, moderately hot ones lie between 30 and 40°, moderate ones - between 40 and 60°, and between them and the polar regions there are moderately cold zones. However, due to the location of the land among the World Ocean, as well as depending on the size and configuration of the continents, atmospheric circulation and sea currents, the belt boundaries deviate significantly from the indicated latitudes.

In the hot zone, thermal conditions are favorable for the development of organic life. There are no frosts. The radiation balance is 65-75 kcal/cm 2 year, the annual sums of active temperatures (i.e. the sum of average daily temperatures above 10°C) are 7-10 thousand degrees. Heat-loving vegetation grows all year round. However, along with evergreen moist forests, savannas and even deserts develop in this thermal zone - the result of uneven distribution of moisture.

In moderately hot (subtropical) zones, the amount of incoming heat is somewhat less, and most importantly, it varies with the seasons. The radiation balance ranges from 50 to 65 kcal/cm2 year. The sum of active temperatures is 4 -7 thousand degrees. Although the average temperature of the coldest month is above 4°C, frosts are possible. Plants experience a short period of vegetative dormancy.

Temperate thermal zones have a pronounced seasonality of the thermal regime with a long cold period, which leads to seasonal vegetation growth. A decrease in the radiation balance to 25-50 kcal/cm 2 year, the sum of active temperatures of 700-4000 degrees, and the seasonal rhythm of heat determine the growth of coniferous and deciduous trees in these zones. Along with these forests, steppes and even deserts are common in temperate zones.

In moderately cold (subarctic and subantarctic) zones, the radiation balance ranges from 10 to 25 kcal/cm 2 year, the average temperature of the warmest month does not rise above 10°C, but does not fall below 5°C, the sum of active temperatures is 200-600 degrees, thermal conditions allow only shrubby, herbaceous and moss-lichen vegetation to grow. The growing season for northern grasses lasts about three months, and for trees and shrubs - about a month. Therefore, the vegetation cover is dominated by perennials.

The thermal conditions of cold (polar) regions are unfavorable for the development of life. More heat is expended here on evaporation from the snow-glacial surface than it comes from the Sun (radiation balance below 10 kcal/cm 2 year). The average temperature of the warmest month does not exceed 5°C.

The daily rotation of the Earth determines the closedness of the thermal zones around the planet, and the annual movement around the Sun with the tilt of the earth's axis determines the seasonal displacement of the thermal equator (the region of maximum temperatures) and the seasonal rhythm of heat in each zone.

Uneven heating of the lower troposphere across thermal zones contributes to the formation of the main types of air masses. They differ in type, moisture content, dust content and other properties. At the same latitudes, maritime and continental air masses are distinguished.

The thermal zonality of the earth's surface and the uneven heating of land and ocean determine the general circulation of the atmosphere and water in the World Ocean, which play a huge role in the transfer of heat and moisture from the ocean to land and from one latitude to another. This causes not only belt, but also sector-zonal differentiation of the geosphere.

In general, zonality in the distribution of solar heat on the earth's surface causes zonality in atmospheric circulation, hydrothermal regime, and zonality in the development and distribution of vegetation and soils.

The heating of the soil and the illumination of any territory are directly dependent on the thermal zone in which it is located. This, in turn, is influenced by geographic latitude.

What are thermal belts?

Solar heat reaches high and low latitudes differently. This is due to the fact that the angles of inclination of the rays of our star to the surface of the Earth are different. This is where the concept of climate came from. The further north a territory is located, the less heat it receives per unit surface area. This is due to the lower rise of the sun at midday.

The word “climate” itself is translated from Greek as “slope”. It depends on the geographical location of a particular area and is determined by atmospheric pressure, humidity and average air temperature throughout the year.
There are three thermal zones on Earth. It is moderate, hot and cold. Each of them has its own distinctive features.

Cold climate zone

It is located in the Arctic Circle, located in both the North and South Poles of our planet, which are as far away from the equator as possible, and therefore the sun sends only oblique rays to them. That is why in these areas the earth heats up very little.

Winters in these areas are long and harsh, and summers are short and cool. There are several months a year when the sun's rays do not reach the Arctic Circle at all. This period is the polar night. The temperature here at this time can drop to eighty-nine degrees.

Temperate zone

These thermal zones are also found in two hemispheres. In their territories, oblique rays of the sun weakly warm the earth in winter. In summer the sun illuminates them more intensely. There are moderate thermal zones between the Arctic Circle and two parallels. In the north is Cancer, and in the south is the Tropics of Capricorn.

The sun in these belts is never at its zenith. Therefore, it does not warm the soil and air very much. Temperate thermal zones are characterized by a clear demarcation of seasons. Winter, summer, autumn and spring are observed here. Moreover, the temperature character of these seasons is not the same. The closer the region is to the Arctic Circle, the colder the winter on its territory. Conversely, summers are warmer and longer as the territory approaches the tropics.

Hot belt

The sun always rises high above this zone and sends direct rays onto it. That is why the temperature here is constantly high. The dominance of this belt is observed in the tropics. Winter in this area is the rainy season, and summer is characterized by drought.

The Earth's hot thermal belt is located between the South and along the equator. Twice during the year, namely at noon on June 22 and December 22, the sun's rays fall almost vertically in this zone, that is, at an angle of ninety degrees. The air from the soil surface becomes very hot. That is why it is hot in this area all year round. Only within this belt do palm trees grow.

Thus, the thermal zones of the world are represented by five zones. They include two cold, two moderate and one hot. Sometimes in cold thermal zones an area of ​​eternal frost is identified. It is located directly near the poles, and the average annual temperature here does not rise above zero.

The thermal zones of Russia are cold and temperate. The north of the country is characterized by a harsh climate. At the same time, there is a change between polar winter and polar summer. More southern territories have a mild climate and pronounced seasonality.

The nature of the cold thermal zone

The polar zones of our planet are constantly covered with snow and ice. These are the coldest areas on Earth. The Arctic, which belongs to the polar zone, runs through Alaska. It includes the island of Greenland. Located in the polar zone of northern Canada and Russia.

Antarctica, located in the Southern Hemisphere, is the southern polar zone. The continent of Antarctica is located there.

The cold thermal zone, which is characterized by a lack of heat, does not have forests. The soil in these areas is swampy. In some places you can find areas of permafrost. The harshest climate is observed at the poles. Sea or continental ice appears there. Vegetation is usually absent or represented by lichens and moss.

Mostly migratory birds live in the cold zone. There are especially many of them on the islands of the Arctic Ocean. Animals are also found in this area. They migrate from more southern regions during the summer season. The fauna is represented by owls and arctic foxes, polar mice and polar bears, walruses, seals and penguins.

Nature of the temperate thermal zone

The territories of these climatic zones receive more light and heat. The winter here is not so harsh. Summer in the temperate thermal zone is not very hot. The sun is never at its zenith over these territories. Therefore, the climate of temperate zones is mild, and its changes from warm to cold occur gradually. These zones have four seasons: summer, spring, winter and autumn.

The temperate thermal zone passes through the territory of Great Britain and Europe. It contains Northern Asia and North America. In the Southern Hemisphere, the temperate zone is located in the waters of three oceans. Thus, 98% percent of its area is occupied by water. The temperate zone in the Southern Hemisphere runs through Australia and New Zealand. It covers southern South Africa and South America.

The nature of this thermal zone is very diverse. These are taiga, semi-deserts and deserts, as well as steppes.

The animal world is quite homogeneous. It is mainly represented by forest animals that lead a sedentary lifestyle. Representatives of the fauna of open areas - steppes and deserts - are less common.

The nature of the hot thermal zone

Most of Africa is located in this zone. The hot zone is located in the south of India and Asia. This zone includes Central America, New Guinea, northern Australia and northern South America.

There is no seasonality near the equator. These areas are very warm and humid throughout the year.

The hot thermal zone is characterized by savannas, evergreens and woodlands. In some areas there are semi-deserts and deserts.
The fauna is extremely diverse. These are birds of prey and running birds, hippopotamuses and antelopes, elephants and zebras, buffalos, etc.

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 of the sun's rays: the greatest number of sun rays is above the equator, the least - above the Arctic Circle. Thus, at the equator, the angle of incidence of solar rays reaches 90∘90∘ in March and September (on the days of the spring and autumn equinoxes) and is very large in December and June (on the days of the winter and summer solstices).
Transparency of the atmosphere: clouds, dust, smog, smoke reduce the amount of solar radiation reaching the Earth.
Length of Daylight: During the summer, areas near the poles receive significant amounts of 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 geographical maps that show the summer distribution of air temperature on Earth. On them, air temperature is indicated either by points next to which its numerical value appears, or by special lines that connect points with the same temperature - isotherms. The red lines indicate the temperature of the warmest month of the year, which is July in the Northern Hemisphere. 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.

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 the surface layers of the 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. Antarctica, where the air is clean and the atmosphere is highly transparent, receives a large amount 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 the average air temperature is +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. The average annual temperature in the Northern Hemisphere is +15.2 °C, and in the 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 by an extensive glacial shell, and most of the Arctic is represented by the Arctic Ocean, where warm currents penetrate 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. It reaches its highest values ​​on continents, and much lower values ​​over oceans and 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. Textbook for the 8th grade of general secondary education institutions with Russian as the language of instruction / Edited by Professor P. S. Lopukh - Minsk “People's Asveta” 2014

During the day the air temperature changes. The lowest temperature is observed before sunrise, the highest - at 14-15 hours.

To determine average daily temperature, You need to measure your temperature four times a day: at 1 a.m., at 7 a.m., at 1 p.m., at 7 p.m. The arithmetic mean of these measurements is the average daily temperature.

The air temperature changes not only during the day, but also throughout the year (Fig. 138).

Rice. 138. Head course of air temperature at latitude 62° N. latitude: 1 - Torshavn Denmark (sea mud), average annual temperature 6.3 ° C; 2- Yakutsk (continental type) - 10.7 °C

Average annual temperature is the arithmetic average of temperatures for all months of the year. It depends on geographic latitude, the nature of the underlying surface and the transfer of heat from low to high latitudes.

The Southern Hemisphere is generally colder than the Northern Hemisphere due to Antarctica being covered in ice and snow.

The warmest month of the year in the Northern Hemisphere is July, and the coldest month is January.

Lines on maps connecting points with the same air temperature are called isotherms(from the Greek isos - equal and therme - heat). Their complex arrangement can be judged from maps of January, July and annual isotherms.

The climate at the corresponding parallels in the Northern Hemisphere is warmer than at similar parallels in the Southern Hemisphere.

The highest annual temperatures on Earth are observed in the so-called thermal equator. It does not coincide with the geographic equator and is located at 10° N. w. This is explained by the fact that in the Northern Hemisphere a large area is occupied by land, and in the Southern Hemisphere, on the contrary, there are oceans that waste heat on evaporation, and in addition, the influence of ice-covered Antarctica is felt. The average annual temperature at the parallel is 10° N. w. is 27 °C.

Isotherms do not coincide with parallels despite the fact that solar radiation is distributed zonally. They bend, moving from the continent to the ocean, and vice versa. Thus, in the Northern Hemisphere in January over the continent, isotherms deviate to the south, and in July - to the north. This is due to the unequal heating conditions of land and water. In winter, land cools, and in summer it warms up faster than water.

If we analyze isotherms in the Southern Hemisphere, then in temperate latitudes their course is very close to parallels, since there is little land there.

In January, the highest air temperature is observed at the equator - 27 ° C, in Australia, South America, central and southern Africa. The lowest January temperature was recorded in northeast Asia (Oymyakon, -71 °C) and at the North Pole -41 °C.

The “warmest July parallel” is the parallel of 20° N latitude. with a temperature of 28 °C, and the coldest place in July is the south pole with an average monthly temperature of -48 °C.

The absolute maximum air temperature was recorded in North America (+58.1 °C). The absolute minimum air temperature (-89.2 °C) was recorded at the Vostok station in Antarctica.

Observations revealed the existence of daily and annual fluctuations in air temperature. The difference between the highest and lowest air temperatures during the day is called daily amplitude, and during the year - annual temperature range.

The daily temperature range depends on a number of factors:

• latitude of the area - decreases when moving from low to high latitudes;
• the nature of the underlying surface - it is higher on land than over the ocean: over oceans and seas the daily temperature amplitude is only 1-2 °C, and over steppes and deserts it reaches 15-20 °C, since water heats up and cools down more slowly than land ; in addition, it increases in areas with bare soil;
• terrain - due to cold air descending into the valley from the slopes;
• cloudiness - with its increase, the daily temperature amplitude decreases, since clouds do not allow the earth's surface to heat up strongly during the day and cool down at night.

The magnitude of the daily amplitude of air temperature is one of the indicators of the continental climate: in deserts its value is much greater than in areas with a marine climate.

Annual temperature range has patterns similar to the daily temperature amplitude. It depends mainly on the latitude of the area and the proximity of the ocean. Over the oceans, the annual temperature amplitude is most often no more than 5-10 °C, and over the interior regions of Eurasia - up to 50-60 °C. Near the equator, average monthly air temperatures differ little from each other throughout the year. At higher latitudes, the annual temperature range increases, and in the Moscow region it is 29 °C. At the same latitude, the annual temperature amplitude increases with distance from the ocean. In the equator zone above the ocean, the annual temperature amplitude is only G, and above the continents it is 5-10°.

The different heating conditions for water and land are explained by the fact that the heat capacity of water is twice that of land, and with the same amount of heat, land heats up twice as fast as water. When cooling, the opposite happens. In addition, when heated, water evaporates, which consumes a significant amount of heat. It is also important that on land heat spreads almost only in the top layer of soil, and only a small part of it is transferred into the depths. In the seas and oceans, significant thicknesses are heating up. This is facilitated by vertical mixing of water. As a result, the oceans accumulate much more heat than land, retain it longer, and expend it more evenly than land. The oceans are warming more slowly and cooling more slowly.

The annual temperature range in the Northern Hemisphere is 14 °C, and in the Southern Hemisphere - 7 °C. For the globe, the average annual air temperature at the earth's surface is 14 °C.

Heat zones

The uneven distribution of heat on Earth depending on the latitude of the place allows us to highlight the following thermal belts, the boundaries of which are isotherms (Fig. 139):

• the tropical (hot) zone is located between the annual isotherms + 20 °C;
• temperate zones of the Northern and Southern Hemispheres - between the annual isotherms of +20 °C and the isotherm of the warmest month +10 °C;
• the polar (cold) belts of both hemispheres are located between the isotherms of the warmest month +10 °C and O °C;
• Perpetual frost belts are limited by the 0 °C isotherm of the warmest month. This is the kingdom of eternal snow and ice.

Rice. 139. Thermal zones of the Earth