10.15: Solar Energy and Latitude

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This is Antarctica. What season is this?

The Sun is always up, even in the middle of the night. That's the photo on the left. In the day, the Sun never gets too high in the sky. That's the photo on the right. So, this is summer. In the winter, it's just dark in Antarctica.

Energy and Latitude

Different parts of Earth’s surface receive different amounts of sunlight (Figure below). The Sun’s rays strike Earth’s surface most directly at the Equator. This focuses the rays on a small area. Near the poles, the Sun’s rays strike the surface at a slant. This spreads the rays over a wide area. The more focused the rays are, the more energy an area receives, and the warmer it is.

Diagram of latitude and energy received

The lowest latitudes get the most energy from the Sun. The highest latitudes get the least.

The difference in solar energy received at different latitudes drives atmospheric circulation. Places that get more solar energy have more heat. Places that get less solar energy have less heat. Warm air rises, and cool air sinks. These principles mean that air moves around the planet. The heat moves around the globe in certain ways. This determines the way the atmosphere moves.

Summary

A lot of the solar energy that reaches Earth hits the Equator.
Much less solar energy gets to the poles.
The difference in the amount of solar energy drives atmospheric circulation.

Review

The North Pole receives sunlight 24 hours a day in the summer. Why does it receive less solar radiation than the Equator?
What part of Earth receives the most solar radiation in a year? Why?
What makes the atmosphere move the way it does?