How does insolation change with increasing latitude?

Answer 1

Insolation is the amount of the Sun's energy reaching a unit surface area on

Earth (for example energy per square metre).

Insolation is reduced with increasing latitude, because of the angle at which the Sun's rays hit the surface.

The changing angle at which the energy hits the surface means that the energy is spread over a larger area with increasing latitude, North or South.

That's the main reason the poles are cold and the equator is hot.

In the hemisphere where it's summer, the effect is not so extreme because of the Earth's axial tilt ("towards" the Sun, in that hemisphere).

In the winter time at high latitudes the effect is very significant because the Earth is then "tilted away" from the Sun, in that hemisphere.

Answer 2

The angle of "insolation" is the angle at which the sun's light hits the earth. This varies by the latitude (how far north or south of the equator you are) and by the Sun's declination (the angle of the Sun north or south of the equator). On the Equinoxes, March 20 and September 20, the sun is crossing the equator. At the Summer Solstice, the Sun is 23.5 degrees north of the equator, and on the Winter Solstice (December 20) the Sun is 23.5 degrees south of the equator.

When the Sun is directly overhead, the angle of insolation is 90 degrees.

I live near Sacramento, CA. Our latitude is 38.5 degrees north. On the Summer Solstice, when the Sun is at 23.5 degrees, the angle of insolation (at noon) is 90 - (38.5-23.5) degrees, or 75 degrees. At the Winter Solstice, when the sun is 23.5 degrees south, the angle of insolation is 90 - (38.5+23.5) degrees, or 28 degrees.

Brrr! No WONDER it feels so cold in the winter!