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Name: Kimberly Nicole S.
Status: Other
Age: 14
Location: N/A
Country: N/A
Date: October 4, 2003


Question:
How do different colors on the earth's surface affect the amount of solar radiation absorbed?



Replies:
Dark colors absorb energy from the sun while light colors reflect energy from the sun. As an example, on very hot days during the summer it us recommended that people wear light colored clothing to help them stay cooler.

Steven Miller


Kimberly,

It is true that lighter colored surfaces (white, light green, etc.) tend to absorb less and reflect more solar energy, while darker colored surfaces (brown, black, etc.) tend to absorb more and reflect less solar energy.

However, the composition of the surface is also important. Conductive objects (such as metal or concrete), can absorb more solar energy than can wood (like trees), which is a better insulator. The characteristics of a material determine its absorptivity.

The angle at which the Sun's rays strike an object are also important, as reflection occurs more readily when the object is tilted to the Sun's rays (like randomly tilted tree leaves). The transmitivity of the surface (how well the Sun's rays can penetrate) is another important factor. Water, particularly clear water, has a high transmittivity, allowing the Sun to penetrate into the water and warm it at greater depths than it can the soil, for instance. However, water tends to reflect solar energy well also, reducing the amount of Sunlight that has a chance to penetrate the water.

You can see that absorption can be quite complicated.

David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory



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