Question 1. What is the feature of the distribution of sunlight over the surface of the Earth?
The fact that the axis of rotation of the Earth is slightly inclined to the plane of the Earth's orbit. The angle formed by the earth's axis and the plane of the orbit is 66.5.
Question 2. What areas of the earth receive the most sunlight? Least amount?
The equatorial zone and the tropics receive the greatest amount of light. The North and South poles receive the least amount of light.
Question 3. What special days associated with different levels of illumination of the Earth are on the calendar?
The vernal equinox is March 21, the autumn equinox is September 23. The summer solstice is June 22, the winter solstice is December 22.
Question 4. How would the degree value of the geographical latitude of the tropics and polar circles change with a change in the angle of inclination of the earth's axis?
They would change the value of latitude along with the earth's axis.
Question 5. What is the tropic?
The tropic is a parallel on which on the days of the solstices the sun at noon is at its zenith, that is, exactly overhead.
Question 6. What parallels on the map are called the polar circles?
The polar circles are the parallels behind which the polar nights and days are observed.
Question 7. What is the value of the latitude of points located in the tropics, polar circles?
The tropics have a constant value of the geographical latitude - 23.5 ". The Arctic circles have a constant value of the geographical latitude - 66.5 °.
Question 8. What is an illumination belt?
Illumination belts are called areas of the planet that are illuminated in different ways by the sun and receive different amounts of heat.
Question 9. What are the belts of illumination?
The part of the globe that lies between the two tropics is called the Tropical Illumination Belt. The North and South polar belts are the coldest and harshest regions on our planet. There are two temperate zones between the tropical and polar zones of illumination.
Question 10. What are the boundaries of the light belts?
The tropics and polar circles are the boundaries of the zones of illumination.
Question 11. What is the minimum length of the polar night?
The shortest polar night (almost two days) is observed at a latitude of ≈ 67 ° 3 ′ n. NS.
Question 12. At what angle of inclination of the earth's axis in your settlement could be observed polar night and day?
To observe polar day and night, it is necessary that the angle of inclination of the earth's axis is 56 °.
Question 13. Make a description of the natural conditions characteristic of different zones of illumination.
The tropics are characterized by a humid tropical climate, the closer to the equator, the more arid climate. The temperate zones are characterized by a warm climate, with warm (sometimes hot) summers and cool (sometimes cold) winters. The polar circles are characterized by a cold and very cold climate.
With the help of this video tutorial, you can independently study the topic "The distribution of sunlight and heat". First, discuss what determines the change of seasons, study the diagram of the Earth's annual rotation around the Sun, paying special attention to the four most remarkable dates in terms of solar illumination. Then you will find out what determines the distribution of sunlight and heat on the planet and why it is uneven.
Rice. 2. Illumination of the Earth by the Sun ()
In winter, the southern hemisphere of the Earth is better illuminated, in summer - the northern one.
Rice. 3. Scheme of the annual rotation of the Earth around the Sun
Solstice (summer solstice and winter solstice) - moments when the Sun's height above the horizon at noon is highest (summer solstice, June 22) or lowest (winter solstice, December 22). In the southern hemisphere, the opposite is true. On June 22, the greatest illumination by the Sun is observed in the Northern Hemisphere, the day is longer than the night, a polar day is observed beyond the polar circles. In the southern hemisphere, again, the opposite is true (i.e. all this is typical for December 22).
Polar Circles (Arctic Circle and Antarctic Circle) - parallels, respectively, with latitude north and south about 66.5 degrees. North of the Arctic Circle and south of the Antarctic Circle, there is a polar day (in summer) and a polar night (in winter). The area from the Arctic Circle to the Pole in both hemispheres is called the Arctic Circle. Polar day - a period when the Sun at high latitudes does not descend beyond the horizon around the clock.
polar night - the period when the Sun at 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.
Rice. 4. Scheme of the illumination of the Earth by the Sun by zones ()
Equinox (vernal equinox and autumnal equinox) - moments when the sun's rays touch both poles and fall vertically at the equator. The spring equinox occurs on March 21st, and the autumnal equinox on September 23rd. These days both hemispheres are lit the same, day is equal to night,
The main reason for the change in air temperature is a change in the angle of incidence of sunlight: the more vertically they fall on the earth's surface, the better they warm it up.
Rice. 5. The angles of incidence of the sun's rays (at the position of the Sun 2, the rays warm up the earth's surface better than at position 1) ()
On June 22, the sun's rays fall most steeply on the northern hemisphere of the Earth, thereby warming it up to the greatest extent.
Tropics - The Northern Tropic and the Southern Tropic are parallels, respectively, with the north and south latitudes of about 23.5 degrees. On one of the solstice days, the Sun at noon is above them at its zenith.
The tropics and polar circles divide the Earth into light belts. Illumination belts - parts of the Earth's surface bounded by the tropics and polar circles and differing in lighting conditions. The warmest zone of illumination is tropical, the coldest is the polar one.
Rice. 6. Light belts of the Earth ()
The sun is the main luminary, on the position of which the weather on our planet depends. The moon and other cosmic bodies have an indirect effect.
Salekhard is located on the line of the Arctic Circle. An obelisk to the Arctic Circle has been erected in this city.
Rice. 7. Obelisk to the Arctic Circle ()
Cities where you can watch the polar night: Murmansk, Norilsk, Monchegorsk, Vorkuta, Severomorsk, etc.
Homework
Clause 44.
1. Name the days of the solstice and the days of the equinox.
Bibliography
The main
1. An initial course in geography: textbook. for 6 cl. general education. institutions / T.P. Gerasimova, N.P. Neklyukova. - 10th ed., Stereotype. - M .: Bustard, 2010 .-- 176 p.
2. Geography. 6th grade: atlas. - 3rd ed., Stereotype. - M .: Bustard; DIK, 2011 .-- 32 p.
3. Geography. 6th grade: atlas. - 4th ed., Stereotype. - M .: Bustard, DIK, 2013 .-- 32 p.
4. Geography. 6 cl .: cont. maps: M .: DIK, Bustard, 2012 .-- 16 p.
Encyclopedias, dictionaries, reference books and statistical collections
1. Geography. Modern Illustrated Encyclopedia / A.P. Gorkin. - M .: Rosmen-Press, 2006 .-- 624 p.
Literature for preparing for the State Examination and the Unified State Exam
1. Geography: Initial course: Tests. Textbook. manual for students of 6 cl. - M .: Humanit. ed. center VLADOS, 2011 .-- 144 p.
2. Tests. Geography. 6-10 grades: Teaching aid / A.A. Letyagin. - M .: OOO "Agency" KRPA "Olymp": "Astrel", "AST", 2001. - 284 p.
1.Federal Institute of Pedagogical Measurements ().
2. Russian Geographical Society ().
3.Geografia.ru ().
It decreases from the equator to the poles, which is the result of the spherical shape of the planet. The height of the noon Sun near the equator and at the equator will be the highest, and at the Poles of the planet - the smallest. This leads to the fact that each unit of the area of solar heat and light receives less and less.
Remark 1
As a result of such an uneven distribution of solar heat and light, the Earth's surface was divided into five belts of illumination, the boundaries of which are the tropics and polar circles:
- Hot Light Belt;
- Two moderate zones of illumination;
- Two cold zones of illumination.
The reason for the formation of these belts is the inclination of the axis of rotation of the planet to the orbital plane, as well as the movement of the Earth around the Sun.
Definition 1
Illumination Belt- This is a part of the Earth's surface, bounded by the tropics and polar circles with their own lighting conditions. Illumination is the flux of sunlight falling on a unit of surface.
The belts differ from each other in the height of the noon Sun above the horizon, in the length of the day and in thermal conditions. Once a year ($ 22 in June and $ 22 in December), the sun's rays fall steeply in the North and South Tropics. The polar day and the polar night also happen once a year ($ 22 in December and $ 22 in June), which is typical for the Arctic and Southern Polar Circle. Illumination belts are characterized by different air temperatures and different natural conditions.
Hot Belt of Illumination
This belt covers $ 2/5 $ or about $ 40 \% $ of the Earth's surface and is located between the North and South tropics. The sun in this belt is always high above the horizon, so the surface warms up very well. There is no difference between summer and winter temperatures, and there are no thermal seasons. The average annual air temperature is $ + 25 $ degrees. The length of daylight hours and the length of the night are approximately the same and amount to $ 12 per hour. There is no twilight. The sun is twice a year at its zenith - in the Northern and Southern tropics. The boundaries of the hot zone coincide with the boundaries of the distribution of palm trees on land and corals in the ocean. The territory of this belt is called "hot", because it receives the largest amount of heat throughout the year.
Moderate light belts
There are two of these light belts on Earth - one in the Northern Hemisphere, the other in the Southern Hemisphere. Both of them adjoin the hot zone and are located between the polar circles and the tropics. In contrast to the hot belt of illumination, the sun's rays here fall on the Earth's surface already at a certain tilt. To the north, this tilt will increase, which means that the Earth's surface is warming up less and temperatures will be lower. In temperate zones of illumination, the Sun is never at its zenith. The seasons are clearly defined here. As we approach the Arctic Circle, winter becomes long and cold; as we approach the tropic, summer becomes warmer and longer. From the side of the poles, the moderate belts of illumination are limited by the $ + 10 $ degrees isotherm. This is the border of the spread of forests. More than half of the earth's surface is in the moderate zones of illumination. In summer, near the polar circles, there is such a phenomenon as white nights, which can be observed in northern cities located at the latitude of St. Petersburg. In summer, the length of the day, depending on the geographic latitude, is much longer than the length of the night. In winter, the length of the night increases.
Cold belts of illumination
One cold belt of illumination is located in the Northern Hemisphere, the other in the Southern Hemisphere. They occupy only $ 8 \% $ of the territory and are located inside the polar circles. The conditions for the distribution of solar heat and light in these lighting belts are the most interesting. The sun in winter is not shown at all because of the horizon, the polar night sets in. In the summer period, the Sun does not have time to hide behind the horizon, so a polar day is observed. Towards the poles, the duration of polar days and nights increases and reaches six months. Winters are cold and harsh, while summers are cool and short. Even in summer, the angle of incidence of the sun's rays is very small, so the surface heats up weakly. During the polar night, the influx of heat is completely absent and strong cooling occurs. The North and South Poles are the kingdoms of eternal ice.
Definition 2
Polar day- this is the period during which the Sun at high latitudes does not descend beyond the horizon around the clock.
Closer to the pole, the duration of the polar day increases and reaches $ 189 $ days at the North Pole, at the South Pole, due to the unequal speed of the Earth's motion, the duration is somewhat shorter. On the parallel of $ 68 $ degrees - this is the polar circle - a day lasts about $ 40 $ a day.
Definition 3
polar night- This is the period during which the Sun does not rise above the horizon at high latitudes.
This phenomenon is opposite to the polar day and is also observed in the Northern and Southern Hemispheres. The polar night is in fact always shorter than the polar day. Dividing the planet into such large light belts does not satisfy practical needs. Determining the height of the Sun and the length of daylight hours is quite simple. Let's look at an example.
Example 1
In St. Petersburg, for example, whose latitude is $ 60 degrees at noon, $ 21 in March and $ 23 in September, the Sun will be at an altitude of $ 90-60 = $ 30 degrees. When the Sun is in the tropics, its height at noon will increase by $ 23 $ degrees $ 27 $ minutes. Then the length of the day in St. Petersburg $ 21 $ in June will be $ 90-60 + 23.27 = $ 53 degrees $ 27 $ minutes, which is $ 18.5 hours. In winter, the Sun moves to the Southern Hemisphere, its height naturally decreases and reaches its minimum mark on the days of the solstices. In this case, it decreases by $ 23.27 degrees. For St. Petersburg, $ 22 December, the Sun will be at an altitude of $ 90-60-23.27 = $ 6.33 degrees. The duration of daylight hours at such an altitude of the Sun will be only $ 5.5 $ hours.
Of all the zones of illumination that exist on Earth, the most comfortable conditions for humans are noted in temperate zones closer to hot ones. Cold belts are of little use for life. There is an excess of energy in hot zones.
Illumination of the Earth's surface and health
Daylight plays a very important role in people's lives. It not only provides visual perception, but also affects the basic life processes, regulating metabolism and resistance to adverse environmental factors. Nature established the rhythm of life by the alternation of day and night. Natural light, as shown by numerous experiments, is an element of time in a person's internal clock. The atmosphere created by lighting affects people's mood and their performance.
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