HMH Unit 6.2 Day Two

If you step outside on a sunny day, you can feel the warmth of the sun’s light. Earth’s cycles and the processes associated with them rely on the sun’s energy. 

The sun’s energy moves outward in all directions. A tiny part of the sun’s total energy affects Earth’s spheres.

At some locations, the sun's rays do not hit Earth straight on.

They strike at an angle.

In these places, the energy is spread out over a bigger area.

These areas are cooler.

Near the equator, the sun's rays strike Earth at a 90 degree angle.

The energy does not spread out.

These areas are warmer because more energy is focused on a smaller area.

The sun has an essential role in the water cycle

Recall that evaporation occurs due to energy from the sun.

But not all of the sun's energy that moves toward Earth strikes the Earth's surface.

About 9% of the sun's energy is reflected by particles in the atmosphere; another 23% is reflected by clouds.

2% of the sun's energy reaches Earth's surface but then is reflected by features such as ice and snow.

About 47% of the sun's energy is absorbed by Earth's surface. About 19% is absorbed by the atmosphere and clouds

When the sun’s energy heats Earth, it provides the energy that powers the water cycle. 

Winds also affect the water cycle. Wind over a body of water can increase evaporation and lead to precipitation.

Warm air near the equator rises in the atmosphere. Cool air from areas closer to the poles flows toward the equator to fill the void left by the rising warm air.

The movement of air is wind.

Wind also forms because of temperature differences over land and water.

Land heats up and cools down more quickly than water.

On a sunny day, air over the land warms and rises, and cooler air over the water flows inaldn, creating a "sea breeze"