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Weather
Factfile |
 Weather |
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The Power of the Sun |
There are a number of reasons why the Sun does not heat the surface of the Earth evenly.
Firstly, the radiation from the Sun travels to the surface of the Earth in straight lines. Because the Earth's surface is curved, the rays (radiation) hit different parts of the Earth at different angles. This process divides the world into specific climate zones, each with its own typical weather. (The word climate describes a pattern of weather that is roughly the same every year in a particular place). The climate of an area will affect the type of plants and animal life that can live there.
If you look at our drawing of the Earth, you will see that the Sun's rays hit the surface near the Equator full on. Here the heat is concentrated over a short area with a heating effect that is at its strongest when in the middle of the day. However, If you look at areas away from the Equator, you will see that the Sun's rays hit the surface at shallow angle, so that the heat is spread out over a wider area. One of the reasons why Antarctica is so cold is because the Sun's rays are spread over a great angle because the Sun is always either low in the sky or below the horizon. When the Sun is low in the sky, its rays have to heat more atmosphere and a greater area of ground than when it is high in the sky.
Another explanation comes from the surface of the Earth itself. Some types of surfaces absorb more heat from the Sun than others. Bare dark coloured soil for example, absorbs more heat than deep water or land covered with forests. In the case of Antarctica, snow-covered ice reflects 80% of the Sun's radiation, which helps to explain why Antarctica remains cold, even in the long daylight periods of summer.
Photograph Courtesy of British Antarctic Survey
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