Thermal belt. Thermal zones of the earth What isotherms are the boundaries of thermal zones

05.03.2020

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1. Thermal belts 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 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 0С. 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).

1.1 Roast

The equatorial belt is a zone of low pressure, ascending air currents, and weak winds. Temperatures are high throughout the year (about +28 °C), air humidity is high. There is a lot of precipitation - about 2000 mm. Seasonal fluctuations in average monthly temperatures and precipitation are insignificant.

Subequatorial belts are characterized by a seasonal change of air masses: the summer monsoon brings hot and humid equatorial air, while dry continental tropical air dominates in winter. Such a climate with wet summers and dry winters is called monsoonal.

Tropical zones are characterized by an arid (dry) climate, they have the greatest deserts in the world: Sahara, Arabian, 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 moderate 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, and in the mountains it can lie for several months. In the inland areas, the climate is arid, with hot (about +30 °C) dry summers, cool (0...+5 °C), relatively humid (200-250 mm) winters. The change of air masses and the frequent passage of atmospheric fronts determines unstable weather. Due to insufficient moisture, landscapes of deserts, semi-deserts, and dry steppes predominate here. The largest and highest (4-5 km) uplands of the world Tibet with high-altitude deserts stand out with a special sharply continental climate with cool summers, harsh winters and little rainfall.

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

In the Northern Hemisphere, on the contrary, vast land masses dominate and a whole spectrum of climates differing in degree of continentality is 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 Central and Central Asia. More precipitation falls in summer than in winter, and this difference is more significant in the center of the continents, especially in Eastern Siberia, due to a very dry anticyclonic winter.

In the temperate zone, the northern part with cool summers and relatively severe winters and the southern part with warm summers and relatively mild winters are distinguished. July temperatures vary from -4 ... -10 ° c to +12 ° c in the north and up to +30 ° c in the south, January 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 a seasonal change of air masses: in the summer of the MT, in the winter of the AB. In the north of Eurasia and North America, the climate is continental and sharply continental with cool, damp summers with temperatures below +10...+12 °C and long, severe (up to -40...-50 °C) winters with little snow and large annual temperature ranges. . In the area of the city of Oymyakon there is a cold pole of the Northern Hemisphere and the entire planet - (-78 ° C). Such conditions contribute to the maintenance of ubiquitous permafrost. There is little precipitation (200-100 mm), however, due to low temperatures, moisture is excessive. The tundra and forest-tundra prevailing here are heavily swamped.

The maritime 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 low temperatures rainfall (up to 500 mm). Tundra is widespread along the coasts of the continents and on the islands.

In the Arctic (Greenland and the islands of the Canadian Archipelago) and the Antarctic (Antarctica), the continental climate prevails. These are the coldest regions of the Earth - the thermometer does not rise above zero all year, and at the inland Antarctic station "Vostok" an absolute minimum temperature of -89.2 ° C was recorded (but the station "Vostok" is located at an altitude of 3488 m). Rainfall 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 get warmer up to +5 °C. Precipitation is also low, the islands are characterized by tundra.

2.Air masses

Large air masses in the troposphere, commensurate in size with the mainland or ocean and having more or less the same properties (temperature, humidity, transparency, dust content, etc. - approx. from geoglobus.ru), are called air masses. They extend upwards for several kilometers, reaching the boundaries of the troposphere.

Air masses move from one region 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, the 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 with their own characteristic properties. Continental air masses form over the continents, and oceanic air masses form over the oceans. Shifting along with atmospheric pressure belts throughout the year, air masses occupy not only the permanent belts of their stay, but seasonally dominate in neighboring, transitional climatic zones. In the process of general circulation of the atmosphere, air masses of all types are interconnected.

Air masses that move from a colder earth's surface to a warmer one and which 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, while powerful cumulus clouds form and heavy rains fall. Especially strong cold snaps occur in temperate latitudes during the invasion of cold masses from the Arctic and Antarctica - approx. from geoglobus.ru. Cold air masses sometimes reach the southern regions of Europe and even North Africa, but are most often delayed by the mountain ranges of the Alps. In Asia, arctic air is freely distributed 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 to the Gulf of Mexico.

Masses of air that have a higher temperature than the surrounding air and come to a colder earth's surface are called warm air masses. They bring warming, and they themselves are cooled from below, thus forming stratus clouds and fogs. 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).

A local, or neutral, air mass is a mass that is in thermal equilibrium with its environment, that is, day after day, retaining its properties. The changing air mass can be both warm and cold, and upon completion of the transformation, it becomes local.

Where air masses of different types meet, atmospheric fronts form.

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

Arctic and Antarctic air masses form over the ice surface of 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 to the center of Eurasia, these air masses gradually heat 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. Over the oceans in the tropics, the trade winds dominate all year - approx. from geoglobus.ru. The air masses formed in these areas are characterized by moderately high temperatures from +20 to +27 °С in summer and cool temperatures up to +10 +15 °С in winter. In areas of tropical deserts over the continents, extremely dry air masses are formed with average temperatures of +26 +40 ° С.

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

3. Precipitation

thermal belt air atmospheric

Their education

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

The main condition for the formation of precipitation is the cooling of warm air, leading to the condensation of the vapor contained in it.

When warm air rises and cools, clouds are formed, consisting of water droplets. Colliding in a cloud, the drops are connected, their mass increases. The bottom of the cloud turns blue and it rains. At negative air temperatures, water droplets in the clouds freeze and turn into snowflakes. Snowflakes stick together into flakes and fall to the ground. During a snowfall, they can melt a little, and then it snows. 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, when the weather is clear, the earth's surface cools. It cools the surface layers of air. Water vapor begins to condense on cold objects - leaves, grass, stones. This is how dew forms. 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 a warm surface (convection). Such precipitation falls all year round in the hot zone and in summer in temperate latitudes. If warm air rises when it interacts with colder air, then frontal precipitation is formed. 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 the mountains. In this case, orographic precipitation is formed. They are characteristic of the windward slopes of mountains, and the amount of precipitation on the slopes is greater than on the adjacent parts 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 unevenly distributed. It depends on the geographical location of the area and the prevailing winds. The greatest amount of precipitation falls in the 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 disturbed by the nature of the earth's surface: more precipitation falls over the oceans than over land. In the mountains much more precipitation "takes" those slopes facing the prevailing winds. So, in Ukraine, the windward slopes of the Carpathians receive 1500 mm per year, and the leeward slopes - half as much as -750 mm per year.

I have a record high annual rainfall on Earth in the village of Cherrapunji, at the foot of the Himalayas - 23,000 mm. And the rainiest place on the planet is the Hawaiian Islands, where 335 days a year it happens with rain, which brings 12,000 mm of water. The record dry places where precipitation does not fall for years are the Atacama desert in South America (1 mm per year) and the Sahara 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 areas of low pressure are formed, there is a lot of precipitation. In these areas, the air heated from the Earth becomes light and rises, where it meets the colder layers of the atmosphere, cools, and the water vapor turns into water droplets and falls to the Earth in the form of precipitation. In the tropics (30th latitudes) and polar latitudes, where high pressure areas are formed, descending air currents predominate. Cold air descending from the upper troposphere contains little moisture. When lowered, it shrinks, heats up and becomes even drier. Therefore, in areas of high pressure over the tropics and near the poles, there is little precipitation;

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

c) the distribution of precipitation depends on the position of the terrain relative to the World Ocean, since it is from there that the main share of water vapor comes. For example, less precipitation falls in Eastern Siberia than in 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 contribute to precipitation on the coasts, while cold ones 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 relief. On the slopes of the mountain ranges facing moist winds from the ocean, moisture falls noticeably more than on the opposite ones - this is clearly seen in the Cordillera of America, on the eastern slopes of the mountains of the Far East, on the southern spurs of the Himalayas. Mountains prevent the movement of moist air masses, and the plain contributes to this.

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What are thermal belts?

Solar heat arrives at 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 differ. This is where the concept of climate comes from. The further north a territory is located, the less heat it receives per unit of surface. This is due to the lower rise of the sun at noon.

The very word "climate" in Greek means "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 temperate, hot and cold. Each of them has its own distinctive features.

Cold climate zone

It is located in the region of the Arctic Circle, located both in the North and South Poles of our planet, as far as possible from the equator, and in connection with this, the sun sends only oblique rays to them. That is why in these areas the earth heats up very weakly.

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

Temperate zone

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

The sun in these belts is never at its zenith. Therefore, it does not heat the soil and air very much. Temperate thermal zones are characterized by a clear delineation of seasons. Winter, summer, autumn and spring are observed here. At the same time, the temperature character of these seasons is not the same. The closer an area 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

Above this zone, the sun always rises high and sends direct rays to it. That is why there is always a high temperature here. The dominance of this belt is observed in the tropics. The winter period in this area is the rainy season, and the summer is characterized by drought.

The hot thermal belt of the Earth 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 in this zone almost vertically, that is, at an angle of ninety degrees. The air warms up from the surface of the soil. That is why this area is hot all year round. Palm trees grow only within this belt.

Thus, the thermal belts of the world are represented by five zones. They include two cold, two moderate and one hot. Sometimes in cold thermal zones a region of eternal frost is isolated. 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, a change of polar winter and polar summer is observed. The 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 places on earth. The Arctic, which belongs to the polar zone, passes through Alaska. It includes the island of Greenland. Located in the polar zone north of 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 most severe climate is observed at the poles. There are sea or continental ice. Vegetation is usually absent or represented by lichens and moss.

Mostly migratory birds live in the cold zone. Especially a lot of them on the islands of the Arctic Ocean. There are also animals in this area. They migrate from more southerly areas during the summer season. The fauna is represented by owls and arctic foxes, polar mice and polar bears, walruses, seals and penguins.

The nature of the temperate thermal zone

The territories of these climatic zones receive more light and heat. It's not such a harsh winter here. Summer in the temperate zone is not very hot. The sun is never at its zenith over these areas. Therefore, the climate of the temperate zones is mild, and its changes from warm to cold occur gradually. There are four seasons in these zones: summer, spring, winter and autumn.

The temperate thermal zone passes through the territory of Great Britain, Europe. It contains North Asia and North America. In the Southern Hemisphere, the temperate zone is located on the waters of three oceans. Thus, 98% 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. To a lesser extent, representatives of the fauna of open areas - steppes and deserts.

The nature of the hot thermal zone

Most of Africa is located in this zone. In the hot zone is 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. Throughout the year, these areas are very warm and humid.

The hot thermal zone is characterized by savannahs, evergreens and light forests. Some areas are semi-deserts and deserts.
The animal world is remarkable for its extraordinary diversity. These are birds of prey and running, hippos and antelopes, elephants and zebras, buffaloes, etc.

Thermal belts- These are different areas of the globe that receive an unequal amount of heat from the Sun. There are five thermal zones on the globe: one hot, two temperate and two cold.

In the hot zone, the sun stands overhead, its rays fall down almost vertically, the duration of day and night is approximately the same throughout the year. In the cold zone, the sun never rises high, its rays almost glide over the surface of the earth, the winter day is very short. The temperate zone lies between hot and cold. In the summer in the temperate zone, the sun shines high in the sky, the day is long. In winter, the days are short, the sun does not rise high and almost does not warm the earth.

Most solar heat is received by the area located on both sides of the Equator, between the North and South tropics. It is hot there all year round, and snow never falls on the plains. This territory, stretching from north to south for more than 5 thousand km, is called hot belt.material from the site

Significantly less solar heat is received by the regions of the globe north of the Arctic Circle and south of the Antarctic Circle. It is cold here all year round, and in a short summer the snow and ice do not even have time to melt. The sun does not appear at all for several months, and in summer it is so low that its rays seem to glide over the surface of the Earth (Fig. 129). The area north of the Arctic Circle is called northern cold belt, and south of the Antarctic Circle - southern cold belt.

Between the Arctic Circle and the Northern Tropic stretches northern temperate zone. In the southern hemisphere between the Antarctic Circle and the Tropic of the South is southern temperate zone.

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Thermal belts of the Earth

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 greatest 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 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 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.

Belts of illumination and their characteristics.

Moderate

Cold

It is located between the tropic and the polar circle inside the hemisphere.

The sun is never at its zenith

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

t° summer≈ +20°C

t° winters≈ -10°C

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, the average annual t o \u003d + 25 o C. During the year, the daylight hours change slightly. Approximate day=night=12 hours. Twilight is virtually non-existent.

It is located inside the polar 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 below 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. In the long polar night, a strong cooling occurs, because. no heat gain at all.

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.