# § 30. The distribution of sunlight and heat on Earth (textbook)

§ 30. Distribution sunlight and heat on Earth

1. Remember why on Earth there is a change of day and nights and seasons.

2. What is called the orbit of the Earth?

Change height of the Sun above the horizon throughout the year. To understand why, during the year in the midday sun is at different height above the horizon, remember the lessons of natural features of the Earth around the sun.

On the globe shows that the earth has a tilt axis. During of the Earth around the sun angle does not change. This Land Sun returns to more then North, the southern hemisphere. From this changing the angle of sunlight on the Earth's surface. Correspondingly, more lights and then heated one thing hemisphere.

If the Earth axis was not tilted, and perpendicular to the plane of Earth's orbit, the amount of solar heat on each parallel within a year without changing to. Then would their observations by high midday sun, you have recorded all year round the same length gnomon shadow. This would indicate that the length of day throughout the year always equal night. Then the surface would be heated equally throughout the year and then year would not exist.

Lighting and heating the surface of the Earth during the year. On the spherical surface of the Earth solar heat and light are distributed unevenly. This is because the angle of rays at different latitudes different.

You already know that Earth's axis is inclined to the plane inclination angle. His northern end of it directed toward the Polar star. The sun always illuminates half of the Earth. It covered more then North hemisphere (and the day lasts longer than the other hemisphere), then, on the contrary, South. Twice a year the two hemispheres are illuminated equally (if and length of day in both hemispheres is the same).

When the Earth facing the Sun North Pole, then it is more light and heat the Northern Hemisphere. The days become longer than nights. There comes a warm time of year - summer. At the pole and polar part sun shines clock  and does not go beyond the horizon (Night is attained). This phenomenon is called the polar day. At the pole, he takes 180 days (six months), but farther south, the duration is reduced to one day on the parallels 66.50 пн. sh. This called parallel Arctic range. South of this line is sun descends over the horizon and change of day and nights are for us in the usual order - every day. June 22 solar rays fall sheer (at the largest angle - 900) On parallel 23.5 пн. sh. This will be the longest day and night the shortest of the year. This is called parallel Northern TropicAnd the day June 22 - summer solstice.

At this time the South Pole away from the Sun and less than it illuminates and warms the Southern Hemisphere. There winter. At the pole and polar part of sunlight during the day does not fall. Sun does not appear from the horizon and the day is reached. This phenomenon is called the polar night. At the pole it lasts 180 days, and the farther north, the more it becomes shorter one day to the parallel 66.50 AP. sh. This parallel called Southern polar circle.North of it there is sun on the horizon and change of day and night happens every day. June 22 is the shortest day of the year. For South Hemisphere it is winter solstice.

Three months later, September 23, Earth will take this position relative to the sun when the sun's rays are the same as osvitlyuvatymut Northern and Southern Hemisphere. The sheer sunlight falling on equator. The whole earth except the poles, a day equals the night (12 h). This day is called Happy Autumnal Equinox.

In three months, December 22, the Sun will return to South hemisphere. There will come summer. This will be the longest day and night - the shortest. In polar region polar day will come. Rays of the Sun sheer fall 23.5 in parallel0 AP. sh. Instead, in the Northern Hemisphere winter will be. This will be the shortest day and longest night. Parallel 23.50 AP. sh. called Southern tropicsand on 22 December - winter solstice.

In three months, March 21, again both Hemisphere will be equally illuminated, the day is equal night. Rays of sunshine sheer fall on the equator. This day is called spring Equinox.

In Ukraine, the greatest height of the sun at noon  – 61–690 (June 22) and the lowest - 14-220 (22 December).

Interesting geography

WordsSlavic printing god Sun

The ancient Slavic god of light and the sun called Dazhboh. In a famous literary work "The Tale Igor" ancestors - called Rus Dazhboh grandchildren. Along with other gods set by Prince Vladimir in Kiev, stood Dazhboh. According to ancient myths it is accompanied by three sunny skies Twin: Jari - God of the vernal equinox, Semyyarylo - God of the summer solstice and Christmas carol - God winter solstice. Happy birthday young Sun was considered the day of winter solstice. Patron of the top three was considered the god of Light Troyan - Bishop of heaven, earth and otherworldly kingdom.

Fig. The annual movement of the Earth around the Sun

Heat zones of the Earth. Uneven heating of Earth's surface causes different temperatures at different latitudes. Band pulse with certain Temperature called heat belts. Belts differ in the amount of heat coming from the Sun. They reach depending on the temperature distribution is well illustrated isotherm (From the Greek "iso" - The same "Thermal- Heat). This line on the map that connecting points of equal temperature.

Torrid zone placed on both sides of the equator, between the North and Southern tropics. He is limited on both sides of the isotherm 20 0S. Interestingly, the zone boundaries coincide with the boundaries of the spread of palm trees on land and corals in the ocean. Here the surface receives the most solar heat. Twice a year (22 December and 22 June) at noon the sun's rays fall almost sheer (angle 900). The air from the surface gets very hot. Therefore, there is hot during the year.

Temperature zones (In both hemispheres) adjacent to the hot zone. They stretched in both hemispheres between the Arctic Circle and Tropic. Sun there fall to the Earth's surface with some tilt. And, the north, the greater slope. Because the sun heats the lower surface. As a result less heated and air. Therefore, in temperate zones colder than hot. The sun never there in the heyday. Distinct seasons: winter, Spring, summer, autumn. Thus, the closer to the Arctic Circle, the winter is longer and colder. The closer to the Tropic, the longer and warmer summers. Temperature zones from the poles limits the isotherm warmest month 10 0С.  It is the limit distribution of forests.

Cold zone (North and south) between both hemispheres are isotherms 10 0C and 0 0C warmest month. There in the winter sun for several months does not appear over the horizon. In summer, although it does not go the horizon for months, but is very low over horizon. Its rays just slip the Earth's surface and heat it slightly. Ground not only heats and cools and air. Because there are low temperature. Winter cold and harsh and summers short and cool.

Two Zones eternal cold (north and south) okonturyuyutsya isotherm with temperature all months below 0 0C. This is an everlasting kingdom cnihiv and ice.

Thus, heating and lighting of each locality depends on the situation in the thermal zone, that is - of latitude. What closer to the equator, the greater the angle of sunlight, the stronger heated surface and higher temperatures. Conversely, with the distance from equator to the poles angle rays decreases, respectively temperature air decreases.

It is important to remember that line the tropics and polar circles beyond the thermal zones are accepted conditionally. Since in reality the temperature air is determined and a number of other conditions.

Fig. Heat Zones Earth

1. Why the height of the sun varies throughout the year?

2. Which hemisphere will be given the Earth to the Sun, when in Ukraine: a) north 22 June; b) December 22 noon?

3. Where the average annual temperature will be higher: in Singapore or Paris?

4. Why average annual temperatures decrease from the equator to the poles?

5. What are thermal zones continents Africa, Australia, Antarctica, North America, Eurasia?

6. In a thermal zone is located in Ukraine?

7. Find the city on the map hemispheres, knowing that it is at 430 зх. D. and December 22 at noon sun is over there head.