World Library  
Flag as Inappropriate
Email this Article

Effect of sun angle on climate

Article Id: WHEBN0003983509
Reproduction Date:

Title: Effect of sun angle on climate  
Author: World Heritage Encyclopedia
Language: English
Subject: Climate, Seasons, Atmospheric radiation, Nordicity, Weather media in the United States
Collection: Atmospheric Radiation, Climate, Seasons
Publisher: World Heritage Encyclopedia

Effect of sun angle on climate

Figure 1
This diagram illustrates how sunlight is spread over a greater area in the polar regions. In addition to the density of incident light, the dissipation of light in the atmosphere is greater when it falls at a shallow angle.

The amount of heat energy received at any location on the globe is a direct effect of sun angle on climate, as the angle at which sunlight strikes the Earth varies by location, time of day, and season due to the Earth's orbit around the Sun and the Earth's rotation around its tilted axis. Seasonal change in the angle of sunlight, caused by the tilt of the Earth's axis, is the basic mechanism that results in warmer weather in summer than in winter.[1][2][3] Change in day length is another factor.[2][3] (See also season.)


  • Geometry of sun angle 1
    • Technical note 1.1
  • See also 2
  • References 3

Geometry of sun angle

Figure 2
One sunbeam one mile wide shines on the ground at a 90° angle, and another at a 30° angle. The one at a shallower angle covers twice as much area with the same amount of light energy.

When sunlight shines on the earth at a lower angle (sun closer to the horizon), the energy of the sunlight is spread over a larger area, and is therefore weaker than if the sun is higher overhead and the energy is concentrated on a smaller area. (See Figure 1.)

Figure 2 depicts a sunbeam one mile (1.6 km) wide falling on the ground from directly overhead, and another hitting the ground at a 30° angle. Trigonometry tells us that the sine of a 30° angle is 1/2, whereas the sine of a 90° angle is 1. Therefore, the sunbeam hitting the ground at a 30° angle spreads the same amount of light over twice as much area (if we imagine the Sun shining from the south at noon, the north-south width doubles; the east-west width does not). Consequently, the amount of light falling on each square mile is only half as much.

Figure 3
This is a diagram of the seasons. Regardless of the time of day (i.e. the Earth's rotation on its axis), the North Pole will be dark, and the South Pole will be illuminated; see also arctic winter.

The Sunbeam entering at the shallower angle must also travel twice as far through the Earth's atmosphere, which reflects some of the energy back into space.

Figure 3 shows the angle of sunlight striking the earth in the Northern and Southern hemispheres when the Earth's northern axis is tilted away from the Sun, when it is winter in the north and summer in the south.

Technical note

Heat energy is not received from the Sun. Rather, radiant energy is received and this results in change in energy level of receiving bodies in Earth's domain. Different materials have different properties for transmitting back received energy in the form of heat energy at different rates.

See also


  1. ^ Windows to the Universe. Earth's Tilt Is the Reason for the Seasons! Retrieved on 2008-06-28.
  2. ^ a b Khavrus, V.; Shelevytsky, I. (2010). "Introduction to solar motion geometry on the basis of a simple model". Physics Education 45 (6): 641.  
  3. ^ a b Khavrus, V.; Shelevytsky, I. (2012). "Geometry and the physics of seasons". Physics Education 47 (6): 680.  
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.