Heat balance of the Earth
Liou, Kuo-Nan Department of Atmospheric Sciences, University of California, Los Angeles, California.
Last reviewed:November 2019
- Related Primary Literature
- Additional Reading
The balance of various types of energy in the atmosphere and at the Earth's surface. Essentially all the energy that the Earth–atmosphere system receives comes from the Sun. This energy is conventionally referred to as the solar constant, and is defined as the flux of solar energy (energy per time) available on 1 square meter facing the Sun at the top of the atmosphere when the Earth is at its mean distance from the Sun. On the basis of recent satellite observations, a value of about 1336 watts per square meter (W/m2) has been suggested. Because the area of the spherical Earth is four times that of its cross section facing the parallel solar beam, the top of the Earth's atmosphere receives an average of about 342 W/m2. Based on analysis of the observed data from satellite radiation budget experiments in the last 40 years, about 30% of this is reflected back to space and is referred to as the global albedo. The reflecting power of the Earth–atmosphere system includes the scattering of molecules, aerosols, and clouds, as well as reflection of different types of surfaces. As a consequence of this global albedo, only about 70% of the incoming solar flux (that is, about 239 W/m2) is available on average to warm the Earth–atmosphere system. For this system to be in thermodynamic equilibrium or balance so that an equilibrium temperature can be defined, it must radiate the same amount of energy (239 W/m2) back to space. The emitted (or outgoing) terrestrial radiation from the Earth and the atmosphere having an equilibrium temperature of about 254 K (−2.5°F) is in the infrared portion of the electromagnetic spectrum and is called the thermal infrared radiation or longwave radiation. This is differentiated from the solar radiation or shortwave radiation from the Sun, which has an effective temperature of about 5800 K (10,000°F). See also: Albedo; Atmosphere; Heat balance; Solar constant; Solar energy; Terrestrial radiation
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 10,000 highly qualified scientists and 46 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information