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14.1. Solar energy on Earth

Solar energy on Earth

The geological processes internal are responsible for the formation of the relief (mountains, ocean ridgesvolcanoes, ...), while the geological processes external are responsible for destroying it, tending to level the earth 's surface .

The energy that the Earth constantly receives in the form of solar radiation is what determines the climate of each area of ​​the planet and the action of the relief modeling agents (liquid watericewind ,…).

The atmosphere absorbs part of the radiation that reaches the Earth, the ozone layer filters ultraviolet rays to prevent them from reaching the surface, clouds reflect another part (an effect called albedo), and the part of visible light reaches the surface. The radiation that reaches Earth is what allows life to exist on our planet.

When the Earth heats up and emits infrared radiation, the greenhouse effect causes part of this radiation to reflect back into the atmosphere and return to the Earth's surface, increasing its temperature.

The same amount of solar radiation does not reach all parts of the Earth. It depends on several factors:

  • As the Earth is approximately spherical, the rays strike more perpendicularly at the Equator than in the polar zones , so the equatorial zones accumulate more thermal energy than the poles, since the rays have to pass through a much smaller thickness of air .
  • As the Earth's axis of rotation is tilted, the seasons of the year are generated . In summer there are more hours of solar radiation than in winter. Also, because the axis is tilted, the equator is not as hot and the poles are not as cold as they would be if the axis of rotation were vertical.
  • If there are clouds, the solar radiation is reflected more, modifying the albedo .

The air is heated by solar radiation, and being less dense, it rises by convection currents. This air contains water vapor, but as it rises, its temperature drops and the water vapor condenses to form clouds. Later it will precipitate accumulating in lakes, glaciers , rivers , underground waters, circulating by gravity, towards the sea.

Sea water heats up less than Earth, although they absorb the same amount of energy, and it also cools less when it loses it. For this reason, the temperature of the coastal areas is milder than that of the continental areas.

There is a balance between the amount of solar energy that reaches the Earth and that which is lost, in such a way that winds and marine currents are generated that carry the energy from the equatorial to the polar areas.

For all this, the solar radiation that reaches the Earth is responsible for the atmospheric dynamics and the hydrosphere. Air movements, together with humidity and atmospheric pressure, are the cause of atmospheric phenomena.

The convection currents of the atmosphere originate different air masses that generate regions with characteristic climates, the so-called climatic zones.

Answer in your notebook

14.1.- Why in the northern hemisphere, in summer, it is hotter if we are further away from the Sun?