15.3 Energy in the Atmosphere
Lesson Objectives
- Describe how energy is transmitted.
- Describe the Earth’s heat budget and what happens to the Sun’s energy.
- Discuss the importance of convection in the atmosphere.
- Describe how a planet’s heat budget can be balanced.
- Describe the greenhouse effect and why it is so important for life on Earth.
Introduction
Wind and precipitation, warming and cooling depend on how much energy is in the at-
mosphere and where that energy is located. Much more energy from the Sun reaches low
latitudes (nearer the equator) than high latitudes (nearer the poles). These energy differ-
ences cause the winds, affect climate, and even drive ocean currents. Heat is held in the
atmosphere by greenhouse gases.
Energy, Temperature, and Heat
Every material hasenergy:All the molecules within it vibrate. Gas molecules contain more
energy than an equal number of liquid molecules (under the same temperature and pressure
conditions) and move freely. Liquid molecules contain more energy than solids and move
more freely than solids.
Energy travels through space or material. You know this because you can stand near a fire
and feel the warmth. In this situation, energy is being transferred as invisible waves that can
travel through air, glass, and even the vacuum of outer space. These waves have electrical
and magnetic properties, so they are calledelectromagnetic waves. The transfer of energy
from one object to another through electromagnetic waves is known asradiation. Different
types of electromagnetic waves have different wavelengths. A wavelength is the horizontal
distance from trough-to-trough or crest-to-crest of adjacent waves (Figure15.9).
Humans are able to see some wavelengths of light, the wavelengths known as ’visible light.’
These wavelengths appear to us as the colors of the rainbow (Figure15.10). The longest
wavelengths of visible light appear red and the shortest wavelengths appear violet. Wave-
lengths that are longer than visible red are infrared. Snakes can see infrared energy. We can
record this with special equipment. Wavelengths that are shorter than violet are ultraviolet.
Infrared and ultraviolet wavelengths of energy are just as important as the wavelengths in
visible light; we just can’t see them.
Some objects radiate electromagnetic waves in the visible light spectrum. Two familiar