The height of the sun above the horizon: change and measurement. Sunrise in December

How does the height of the Sun above the horizon change throughout the year? To find out, recall the results of your observations of the length of the shadow cast by a gnomon (1 m long pole) at noon. In September the shadow was the same length, in October it became longer, in November it was even longer, and on the 20th of December it was the longest. From the end of December the shadow decreases again. The change in the length of the gno-mon's shadow shows that throughout the year the Sun is at noon at different heights above the horizon (Fig. 88). The higher the Sun is above the horizon, the shorter the shadow. The lower the Sun is above the horizon, the longer the shadow. The Sun rises highest in the Northern Hemisphere on June 22 (on the day of the summer solstice), and its lowest position is on December 22 (on the day of the winter solstice).

Why does surface heating depend on the height of the Sun? From Fig. 89 it is clear that the same amount of light and heat coming from the Sun, with its high position falls on a smaller area, and when low - on a larger one. Which area will heat up more? Of course, smaller, since the rays are concentrated there.

Consequently, the higher the Sun is above the horizon, the more rectilinearly its rays fall, the more it heats up earth's surface, and from it comes the air. Then summer comes (Fig. 90). The lower the Sun is above the horizon, the smaller the angle of incidence of the rays, and the less the surface heats up. Winter is coming.

The greater the angle of incidence of the sun's rays on the earth's surface, the more it is illuminated and heated.

How the Earth's surface heats up. On the surface of the spherical Earth Sun rays, fall at different angles. The greatest angle of incidence of rays is at the equator. Towards the poles it decreases (Fig. 91).

At the greatest angle, almost vertically, the sun's rays fall at the equator. The earth's surface there receives the most heat from the sun, which is why it is hot near the equator all year round and there is no change of seasons.

The further you go north or south from the equator, the smaller the angle of incidence of the sun's rays. As a result, the surface and air heat up less. It becomes cooler than at the equator. The seasons appear: winter, spring, summer, autumn.

In winter, the sun's rays do not reach the poles and subpolar regions at all. The sun does not appear above the horizon for several months, and the day does not come. This phenomenon is called polar night . The surface and air are greatly cooled, so winters there are very harsh. In the same summer, the Sun does not set beyond the horizon for months and shines around the clock (night does not fall) - this polar day . It would seem that if summer lasts so long, then the surface should also heat up. But the Sun is low above the horizon, its rays only glide over the surface of the Earth and almost do not heat it. Therefore, summers near the poles are cold.

Lighting and heating of the surface depend on its location on Earth: the closer to the equator, the greater the angle of incidence of the sun's rays, the more the surface heats up. As we move away from the equator to the poles, the angle of incidence of the rays decreases, and accordingly the surface heats up less and becomes colder.Material from the site

In spring, plants begin to grow rapidly

The importance of light and heat for living nature. Sunlight and warmth are necessary for all living things. In spring and summer, when there is a lot of light and warmth, plants are in bloom. With the arrival of autumn, when the Sun drops above the horizon and the supply of light and heat decreases, plants shed their leaves. With the onset of winter, when the day length is short, nature is at rest, some animals (bears, badgers) even hibernate. When spring comes and the Sun rises higher, the plants begin to actively grow again and come to life. animal world. And all this thanks to the Sun.

Ornamental plants such as monstera, ficus, asparagus, if gradually turned towards the light, grow evenly in all directions. But flowering plants do not tolerate such a change well. Azalea, camellia, geranium, fuchsia, and begonia almost immediately shed their buds and even leaves. Therefore, it is better not to rearrange “sensitive” plants during flowering.

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On this page there is material on the following topics:

• briefly the distribution of light and heat on the globe

Life on our planet depends on the quantity sunlight and warmth. It’s scary to imagine even for a moment what would have happened if there had not been such a star in the sky as the Sun. Every blade of grass, every leaf, every flower needs warmth and light, like people in the air.

The angle of incidence of the sun's rays is equal to the height of the sun above the horizon

The amount of sunlight and heat that reaches the earth's surface is directly proportional to the angle of incidence of the rays. The sun's rays can strike the Earth at an angle of 0 to 90 degrees. The angle of impact of the rays on the earth is different, because our planet is spherical. The larger it is, the lighter and warmer it is.

Thus, if the beam comes at an angle of 0 degrees, it only glides along the surface of the earth without heating it. This angle of incidence occurs in the Northern and South Poles, beyond the Arctic Circle. At right angles, the sun's rays fall on the equator and on the surface between the South and

If the angle of the sun's rays hitting the ground is straight, this indicates that

Thus, the rays on the surface of the earth and the height of the sun above the horizon are equal. They depend on geographical latitude. The closer to zero latitude, the closer the angle of incidence of the rays is to 90 degrees, the higher the sun is above the horizon, the warmer and brighter it is.

How the sun changes its height above the horizon

The height of the sun above the horizon is not constant. On the contrary, it is always changing. The reason for this lies in the continuous movement of the planet Earth around the star Sun, as well as the rotation of the planet Earth around its own axis. As a result, day follows night, and seasons follow each other.

The territory between the tropics receives the most heat and light; here day and night are almost equal in duration, and the sun is at its zenith 2 times a year.

The surface above the Arctic Circle gets everyone less heat and light, there are such concepts as night, which last about six months.

Days of autumn and spring equinox

There are 4 main astrological dates, which are determined by the height of the sun above the horizon. September 23 and March 21 are the days of the autumn and spring equinox. This means that the height of the sun above the horizon in September and March on these days is 90 degrees.

Southern and are equally illuminated by the sun, and the length of the night is equal to the length of the day. When astrological autumn begins in the Northern Hemisphere, it is spring, on the contrary, in the Southern Hemisphere. The same can be said about winter and summer. If it is winter in the Southern Hemisphere, then it is summer in the Northern Hemisphere.

Days of summer and winter solstice

June 22 and December 22 are summer days and December 22 has the shortest day and longest night in the Northern Hemisphere, and the winter sun is at its lowest altitude above the horizon for the entire year.

Above latitude 66.5 degrees, the sun is below the horizon and does not rise. This phenomenon, when the winter sun does not rise to the horizon, is called polar night. The most short night happens at a latitude of 67 degrees and lasts only 2 days, and the longest happens at the poles and lasts 6 months!

December is the month of the entire year when the nights are longest in the Northern Hemisphere. People in Central Russia wake up for work in the dark and also return in the dark. dark time days. This is a difficult month for many, as the lack of sunlight affects people's physical and mental well-being. For this reason, depression may even develop.

In Moscow in 2016, sunrise on December 1st will be at 08.33. In this case, the length of the day will be 7 hours 29 minutes. It will be very early, at 16.03. The night will be 16 hours 31 minutes. Thus, it turns out that the length of the night is 2 times greater than the length of the day!

This year the winter solstice is December 21st. The shortest day will last exactly 7 hours. Then the same situation will last for 2 days. And starting from December 24, the day will start to make a profit, slowly but surely.

On average, one minute of daylight will be added per day. At the end of the month, sunrise in December will be exactly 9 o'clock, which is 27 minutes later than December 1st

June 22 is the summer solstice. Everything happens exactly the opposite. For the entire year, this date is the longest day in duration and the shortest night. This applies to the Northern Hemisphere.

In Yuzhny it’s the other way around. Interesting natural phenomena are associated with this day. A polar day begins above the Arctic Circle; the sun does not set below the horizon at the North Pole for 6 months. Mysterious white nights begin in St. Petersburg in June. They last from about mid-June for two to three weeks.

All these 4 astrological dates can change by 1-2 days, since the solar year does not always coincide with the calendar year. Shifts also occur during leap years.

The height of the sun above the horizon and climatic conditions

The sun is one of the most important climate-forming factors. Depending on how the height of the sun above the horizon over a specific area of ​​the earth's surface changed, climatic conditions and seasons change.

For example, in the Far North, the sun's rays fall at a very small angle and only glide along the surface of the earth, without heating it at all. Due to this factor, the climate here is extremely harsh, there is permafrost, cold winters with freezing winds and snow.

The higher the sun's height above the horizon, the warmer the climate. For example, at the equator it is unusually hot and tropical. Seasonal fluctuations are also practically not felt in the equator region; in these areas there is eternal summer.

Measuring the height of the sun above the horizon

As they say, everything ingenious is simple. So it is here. The device for measuring the height of the sun above the horizon is simply simple. It is a horizontal surface with a pole in the middle 1 meter long. On a sunny day at noon, the pole casts its shortest shadow. With the help of this shortest shadow, calculations and measurements are carried out. You need to measure the angle between the end of the shadow and the segment connecting the end of the pole to the end of the shadow. This angle value will be the angle of the sun above the horizon. This device is called a gnomon.

Gnomon is an ancient astrological tool. There are other instruments for measuring the height of the sun above the horizon, such as the sextant, quadrant, and astrolabe.

Nature gives me a clear answer to this question twice a year: in summer and winter. This is how things are in temperate climate, subtropics and in the subarctic zone, and all other latitudes live either in constant summer conditions or are accustomed to permafrost. To understand this injustice, it is necessary to look at the behavior of the Earth from space.

Reasons for the uneven distribution of solar energy over the Earth's surface

First of all, the reason is hidden in the shape of the globe. If our planet were truly flat, as the first “luminaries” of geography wanted, then every continent would be illuminated like the Equator, and summer would never leave the Earth.

The actual shape of the Earth resembles an ellipsoid, which already excludes the uniform distribution of light over the surface: light rays hit the Equator at right angles, which ensures maximum heating, but not beyond the Arctic Circle most of solar energy hits the Earth and is immediately reflected at an obtuse angle into space.

Balance is an indicator of the reflectivity of the earth's surface. So, equatorial and tropical soils absorb a large number of solar energy and warm up successfully. In northern latitudes, the balance indicator is very high: the sun's rays cannot heat the ground, which is covered by snow caps reflecting the light.

Why is there summer and winter in temperate latitudes?

It is absolutely normal for us to divide the seasons into winter and summer, but if we are guided by what I said above, then the temperate zone lives in conditions of constant spring. This would be so if it were not for one more surprise in the properties of the Earth.

The earth makes the following movements:

• revolves around the Sun;
• rotates around its axis;
• changes its angle of inclination throughout the year.

Thanks to the latter, we can observe the change of seasons in our country. To understand how this works, imagine the Earth as a potato that you decide to fry whole in a frying pan. To give a more or less uniform blush, you will have to constantly unroll it and press the edges.

The most important source from which the Earth's surface and atmosphere receive thermal energy, is the Sun. It sends a colossal amount of radiant energy into cosmic space: thermal, light, ultraviolet. Emitted by the Sun electromagnetic waves propagate at a speed of 300,000 km/s.

The heating of the earth's surface depends on the angle of incidence of the sun's rays. All the sun's rays arrive on the surface of the Earth parallel to each other, but since the Earth is spherical, the sun's rays fall on different parts of its surface at different angles. When the Sun is at its zenith, its rays fall vertically and the Earth heats up more.

The entire set of radiant energy sent by the Sun is called solar radiation, it is usually expressed in calories per unit surface area per year.

Solar radiation determines temperature regime air troposphere of the Earth.

It should be noted that total solar radiation is more than two billion times the amount of energy received by the Earth.

Radiation reaching the earth's surface consists of direct and diffuse.

Radiation that comes to Earth directly from the Sun in the form of direct sunlight under a cloudless sky is called straight. It carries the greatest amount of heat and light. If our planet had no atmosphere, the earth's surface would receive only direct radiation.

However, passing through the atmosphere, approximately a quarter of solar radiation is scattered by gas molecules and impurities and deviates from the direct path. Some of them reach the surface of the Earth, forming scattered solar radiation. Thanks to scattered radiation light also penetrates into places where direct sunlight (direct radiation) does not penetrate. This radiation creates daylight and gives color to the sky.

Total solar radiation

All the sun's rays reaching the Earth are total solar radiation, i.e., the totality of direct and diffuse radiation (Fig. 1).

Rice. 1. Total solar radiation for the year

Distribution of solar radiation over the earth's surface

Solar radiation is distributed unevenly across the earth. It depends:

1. on air density and humidity - the higher they are, the less radiation the earth’s surface receives;

2. depending on the geographic latitude of the area - the amount of radiation increases from the poles to the equator. The amount of direct solar radiation depends on the length of the path that the sun's rays travel through the atmosphere. When the Sun is at its zenith (the angle of incidence of the rays is 90°), its rays hit the Earth through the shortest path and intensively give off their energy to a small area. On Earth, this occurs in the band between 23° N. w. and 23° S. sh., i.e. between the tropics. As you move away from this zone to the south or north, the path length of the sun's rays increases, that is, the angle of their incidence on the earth's surface decreases. The rays begin to fall on the Earth at a smaller angle, as if sliding, approaching the tangent line in the area of ​​the poles. As a result, the same energy flow is distributed across large area, therefore the amount of reflected energy increases. Thus, in the region of the equator, where the sun's rays fall on the earth's surface at an angle of 90°, the amount of direct solar radiation received by the earth's surface is higher, and as we move towards the poles, this amount sharply decreases. In addition, the length of the day depends on the latitude of the area. different times year, which also determines the amount of solar radiation entering the earth's surface;

3. from the annual and daily movement of the Earth - in the middle and high latitudes, the influx of solar radiation varies greatly according to the seasons, which is associated with changes in the midday altitude of the Sun and the length of the day;

4. on the nature of the earth's surface - the lighter the surface, the more sunlight it reflects. The ability of a surface to reflect radiation is called albedo(from Latin whiteness). Snow reflects radiation especially strongly (90%), sand weaker (35%), and black soil even weaker (4%).

Earth's surface absorbing solar radiation (absorbed radiation), heats up and radiates heat into the atmosphere (reflected radiation). The lower layers of the atmosphere largely block terrestrial radiation. The radiation absorbed by the earth's surface is spent on heating the soil, air, and water.

That part of the total radiation that remains after reflection and thermal radiation of the earth's surface is called radiation balance. The radiation balance of the earth's surface varies during the day and according to the seasons of the year, but on average for the year it has a positive value everywhere, with the exception of the ice deserts of Greenland and Antarctica. The radiation balance reaches its maximum values ​​at low latitudes (between 20° N and 20° S) - over 42*10 2 J/m 2 , at a latitude of about 60° in both hemispheres it decreases to 8*10 2 - 13*10 2 J/m 2.

The sun's rays give up to 20% of their energy to the atmosphere, which is distributed throughout the entire thickness of the air, and therefore the heating of the air they cause is relatively small. The sun heats the Earth's surface, which transfers heat atmospheric air due to convection(from lat. convection- delivery), i.e. the vertical movement of air heated at the earth's surface, in place of which colder air descends. This is how the atmosphere receives most of its heat—on average, three times more than directly from the Sun.

Presence in carbon dioxide and water vapor does not allow heat reflected from the earth's surface to freely escape into space. They create Greenhouse effect, thanks to which the temperature difference on Earth during the day does not exceed 15 °C. In the absence of carbon dioxide in the atmosphere, the earth's surface would cool by 40-50 °C overnight.

As a result of the growing scale economic activity people - combustion of coal and oil at thermal power plants, emissions industrial enterprises, increasing automobile emissions - the content of carbon dioxide in the atmosphere increases, which leads to increased greenhouse effect and threatens global climate change.

The sun's rays, having passed through the atmosphere, hit the surface of the Earth and heat it, which, in turn, gives off heat to the atmosphere. This explains characteristic feature troposphere: decrease in air temperature with height. But there are cases when the higher layers of the atmosphere turn out to be warmer than the lower ones. This phenomenon is called temperature inversion(from Latin inversio - turning over).

One of distinctive features human being is curiosity. Probably everyone, as a child, looked at the sky and wondered: “why is the sky blue?” As it turns out, answers to such seemingly simple questions require some knowledge base in the field of physics, and therefore not every parent will be able to correctly explain to their child the reason for this phenomenon.

Let's consider this issue from a scientific point of view.

The wavelength range of electromagnetic radiation covers almost the entire spectrum of electromagnetic radiation, which also includes radiation visible to humans. The image below shows the dependence of the intensity of solar radiation on the wavelength of this radiation.

Analyzing this image, we can note the fact that visible radiation is also represented by uneven intensity for radiation of different wavelengths. Thus, the violet color makes a relatively small contribution to visible radiation, and the largest contribution is made by blue and green colors.

Why the sky is blue?

First of all, this question is prompted by the fact that air is a colorless gas and should not emit blue light. Obviously, the cause of such radiation is our star.

As you know, white light is actually a combination of radiation from all the colors of the visible spectrum. Using a prism, light can be clearly separated into a full range of colors. A similar effect occurs in the sky after rain and forms a rainbow. When sunlight enters the earth's atmosphere, it begins to scatter, i.e. the radiation changes its direction. However, the peculiarity of the composition of air is such that when light enters it, radiation with a short wavelength is scattered more strongly than long-wave radiation. Thus, taking into account the previously depicted spectrum, you can see that red and orange light will practically not change their trajectory when passing through the air, while violet and blue radiation will noticeably change their direction. For this reason, a certain “wandering” short-wave light appears in the air, which is constantly scattered in this environment. As a result of the described phenomenon, short-wave radiation in the visible spectrum (violet, cyan, blue) appears to be emitted from every point in the sky.

The well-known fact of radiation perception is that the human eye can catch, see, radiation only if it directly enters the eye. Then, looking at the sky, you will most likely see shades of that visible radiation, the wavelength of which is the shortest, since it is this that is best scattered in the air.

Why don’t you see a clearly red color when looking at the Sun? Firstly, it is unlikely that a person will be able to carefully examine the Sun, since intense radiation can damage the visual organ. Secondly, despite the existence of such a phenomenon as the scattering of light in the air, most of the light emitted by the Sun reaches the surface of the Earth without being scattered. Therefore, all the colors of the visible spectrum of radiation are combined, forming light with a more pronounced white color.

Let's return to light scattered by air, the color of which, as we have already determined, should have the shortest wavelength. Of visible radiation, violet has the shortest wavelength, followed by blue, and blue has a slightly longer wavelength. Taking into account the uneven intensity of solar radiation, it becomes clear that the contribution purple meager. Therefore, the largest contribution to the radiation scattered by air comes from blue, followed by blue.

Why is the sunset red?

In the case when the Sun hides behind the horizon, we can observe the same long-wave radiation of red-orange color. In this case, light from the Sun must travel a noticeably greater distance in the Earth's atmosphere before reaching the observer's eye. At the point where the sun's radiation begins to interact with the atmosphere, blue and blue are most pronounced. blue colors. However, with distance, short-wave radiation loses its intensity, as it is significantly scattered along the way. While long-wave radiation does an excellent job of covering such long distances. That's why the Sun is red at sunset.

As mentioned earlier, although long-wave radiation is weakly scattered in the air, scattering still takes place. Therefore, being on the horizon, the Sun emits light, from which only radiation of red-orange shades reaches the observer, which has some time to dissipate in the atmosphere, forming the previously mentioned “wandering” light. The latter colors the sky in variegated shades of red and orange.

Why are the clouds white?

Speaking of clouds, we know that they consist of microscopic droplets of liquid that scatter visible light almost uniformly, regardless of the wavelength of the radiation. Then the scattered light, directed in all directions from the droplet, is scattered again on other droplets. In this case, the combination of radiation of all wavelengths is preserved, and the clouds “glow” (reflect) in white.

If the weather is cloudy, then little solar radiation reaches the Earth's surface. In the case of large clouds, or a large number of them, some of the sunlight is absorbed, causing the sky to dim and take on a gray color.