Hot thermal zone. Thermal belt. See what "thermal belts" are in other dictionaries

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

To determine average daily temperature it is necessary to measure the temperature four times a day: at 1 am, at 7 am, at 1 pm, at 7 pm. 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 change in air temperature at a latitude of 62 ° N. sh.: 1 - Torshavn Denmark (marine tyne), medium annual temperature 6.3 °C; 2- Yakutsk (continental type) - 10.7 °С

Average annual temperature is the arithmetic average of temperatures for all months of the year. It depends on geographical 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 the ice and snow covered Antarctica.

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

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

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

The highest annual temperatures on Earth are observed on the so-called thermal equator. It does not coincide with the geographic equator and is located at 10 ° N. sh. This is because in the Northern Hemisphere large area occupied by land, and in the Southern Hemisphere, on the contrary, by the oceans, which expend heat on evaporation, and besides this, the influence of ice-covered Antarctica affects. The average annual temperature at the parallel is 10° N. sh. is 27 °C.

Isotherms do not coincide with parallels despite the fact that solar radiation is distributed zonally. They bend, moving from the mainland to the ocean, and vice versa. So, in the Northern Hemisphere in January over the mainland isotherms deviate to the south, and in July - to the north. This is due to the unequal conditions for heating land and water. In winter, land cools, and in summer it heats 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 most heat air is observed at the equator - 27 ° C, in Australia, South America, central and southern Africa. The lowest temperature in January was recorded in the northeast of Asia (Oymyakon, -71 °С) and at the North Pole -41 °С.

The "warmest parallel of July" is the parallel of 20°N. with a temperature of 28 ° C, and the coldest place in July - South Pole with an average monthly temperature-48 °С.

The absolute maximum air temperature was recorded in North America(+58.1 °С). 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 range, and during the year annual temperature range.

The daily temperature amplitude 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 the oceans and seas, the daily temperature amplitude is only 1-2 ° C, and over the steppes and deserts it reaches 15-20 ° C, since the water heats up and cools down more slowly than land ; in addition, it increases in areas with bare soil;
• terrain - due to lowering into the valley of cold air from the slopes;
• cloud cover - with its increase, the daily temperature amplitude decreases, since clouds do not allow the earth's surface to become very hot during the day and cool at night.

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

Annual temperature amplitude 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 most often does not exceed 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 amplitude 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 equatorial zone above the ocean, the annual temperature amplitude is only G, and over the continents - 5-10 °.

The different conditions for heating 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. On cooling, the opposite happens. In addition, when heated, water evaporates, while a significant amount of heat is consumed. It is also important that on land heat spreads practically only in top layer soil, and only a small part of it will be transferred to the depth. In the seas and oceans, a considerable thickness is being heated. This is facilitated by vertical mixing of water. As a result, oceans accumulate heat much more than land, retain it longer and spend it more evenly than land. The oceans heat up more slowly and cool more slowly.

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

Thermal belts

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

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

Rice. 139. Thermal belts of the Earth

Thermal belts of the Earth

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 in the amount of heat coming from the Sun. Their stretching depending on the distribution of temperatures is well illustrated by isotherms (from the Greek "iso" - the 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. It is interesting that 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 gets very hot. Therefore, it is hot there throughout the year.

temperate zones (In both hemispheres) are adjacent to the hot belt. They stretched in both hemispheres between the Arctic Circle and the tropic. The sun's rays fall on earth's surface with some slope. 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. That is why temperate zones are colder than hot ones. The sun is never at its zenith there. Clearly expressed times years: winter, spring, summer, autumn. Moreover, the closer to the Arctic Circle, the longer and colder the winter. The closer to the tropic, the longer and warmer the summer. The temperate zones from the side of the poles are limited by the isotherm of the warm month of 10 0 C. It is the limit of the spread of forests.

cold belts(Northern and southern) of both hemispheres lie between the isotherms 10 0 C and 0 0 C of the warmest month. The sun there in winter for several months does not appear above the horizon. And in the summer, although it does not go beyond the horizon for months, it is 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 temperatures there are low. Winters are cold and harsh, while 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.

So, the heating and lighting of each locality depends on the position in the thermal zone, that is, on the geographical 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 air temperature rises. Conversely, with distance from the equator to the poles, the angle of incidence of the rays decreases, respectively, the air temperature decreases.

Belts of illumination and their characteristics.

Illumination belts are parts of the Earth's surface bounded by the tropics and the polar circles and differing in illumination conditions.

As a first approximation, it is enough to distinguish three zones in each hemisphere: 1) tropical, limited by the tropics, 2) temperate, going 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 (on the tropic one) and a small difference in the length of the day by month. The second is characterized by a large seasonal difference in the height of the Sun and the length of the day. The third is characterized by polar night and polar day, the longitude of which depends on the geographical latitude. North of the Arctic Circle and south of the Antarctic Circle, polar day (summer) and polar night (winter) are observed. The area from the Arctic Circle to the Pole in both hemispheres is called the Arctic.
The polar day is the period when the Sun at high latitudes does not fall below the horizon around the clock. The duration of the polar day is longer, the farther 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 it is somewhat less, due to the unequal speed of the Earth's orbit in the winter and summer half-years.
The polar night is the period when the Sun does not rise above the horizon at high latitudes 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, the division of 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 (φ = 60°) on March 21 and September 23 at noon the Sun is at a height 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 \u003d 90 ° -f + 23 ° 27 ".
For St. Petersburg, for example, on June 21, the height 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".
On the Leningrad parallel 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 inclination of the earth's axis, represent the radiative, associated with the sun's rays, the basis for 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 change are a complex phenomenon.

Thermal belts

Thermal belts

(temperature belts), zones with certain temperature conditions located along parallels around the globe (sometimes with breaks). They are distinguished in accordance with the established criteria: according to the position on the map of isotherms in some months, according to the number of months of the year from cf. a swarm within certain limits, etc. For example, according to the classification of V. P. Köppen, subtropical, temperate, cold and polar thermal zones are distinguished.

Geography. Modern illustrated encyclopedia. - M.: Rosman. Under the editorship of prof. A. P. Gorkina. 2006 .

See what "thermal belts" are in other dictionaries:

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The main pattern in the distribution of heat on Earth - its zoning - allows us to distinguish thermal, or temperature, belts. They do not coincide with the illumination belts formed according to astronomical laws, since the thermal regime depends not only on illumination, but also on a number of telluric factors.

On both sides of the equator, up to approximately 30 ° N. sh. and yu. sh. located hot belt, bounded by an annual isotherm 20°C. Within these limits, wild palm trees and coral buildings are common.

In the middle latitudes are moderate temperature zones. They are limited to 10 isotherms ° Since the warmest month. These isotherms coincide with the distribution boundary woody plants(the lowest average temperatures at which the seeds of trees ripen, 10 ° C; with a lower monthly amount of heat, forests do not regenerate).

In subpolar latitudes stretch cold belts, the polar boundaries of which are the 0°C isotherms of the warmest month. They generally coincide with the tundra zones.

Around the poles are belts of eternal frost, where the temperature of any month is below 0°C. Here lies the eternal snow and ice.

The hot belt, despite its large area, is thermally quite homogeneous. average temperature year varies from 26° at the equator to 20°C at the tropical limits. Annual and daily amplitudes are insignificant. Thermally relatively homogeneous are the cold and eternal frost belts due to their narrowness. The temperate belts, covering latitudes from subtropical to subpolar, are thermally very heterogeneous. Here, the annual temperature at some latitudes reaches 20°C, while at others even the temperature of the warmest month does not exceed 10°C. Latitudinal differentiation of temperate zones is revealed. The northern temperate belt, due to its continentality, is also differentiated in the longitudinal direction: in annual course temperatures here clearly affect the coastal and inland positions.

In temperate zones, in the most nervous approximation, subtropical latitudes are distinguished, temperature regime which provides the growth of subtropical vegetation, moderately warm latitudes, where heat ensures the existence deciduous forests and steppes, and boreal latitudes with a sum of heat sufficient only for the growth of coniferous and small-leaved Trees.

With a general resemblance temperature zones both hemispheres, the thermal dissymmetry of the Earth with respect to the equator clearly stands out. The thermal equator is shifted to the north relative to the geographic one, the northern hemisphere is warmer than the southern, in the south the course of temperature is oceanic, in the north - continental, the Arctic is warmer than the Antarctic.

The thermal conditions of the belts naturally disturb the mountainous countries. Due to the decrease in temperature with height in them

The largest annual amplitudes from 23 to 32 ° C are characteristic of the middle belt largest area continents, in which different heating and cooling of the continents and oceans, the formation of positive and negative temperature anomalies cause a different course of temperature in the ocean and in the depths of the continents.

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 in the amount of heat coming from the Sun. Their stretching depending on the distribution of temperatures is well illustrated by isotherms (from the Greek "iso" - the same, "therma" - heat). These are lines on a map that connect points with the same temperature.

The hot belt is located along the equator, between the Northern and Southern tropics. It is limited on both sides of the 20 0С 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 greatest 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 gets very hot. Therefore, it is hot there throughout the year.

The temperate zones (in both hemispheres) adjoin the hot zone. They stretched in both hemispheres between the Arctic Circle and the tropic. The sun's rays there fall on the earth's surface with a certain slope. 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. That is why temperate zones are colder than hot ones. 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 tropic, the longer and warmer the summer. The temperate zones from the side of the poles are limited by the isotherm of the warm month of 10 0C. It is the limit of the distribution of forests.

The cold zones (Northern and Southern) of both hemispheres lie between the isotherms of 10 0С and 0 0С of the warmest month. The sun there in winter for several months does not appear above the horizon. And in the summer, although it does not go beyond the horizon for months, it is 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 temperatures there are low. Winters are cold and harsh, while 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 0C. This is the realm of eternal ice.

So, the heating and lighting of each locality depends on the position in the thermal zone, that is, on the geographical 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 air temperature rises. Conversely, with distance from the equator to the poles, the angle of incidence of the rays decreases, respectively, 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 climatic zones).