Earth's Atmosphere

The Atmosphere

• Without its atmosphere, Earth would be a very different planet. Gases in the atmosphere allow plants to photosynthesize and animals and plants to engage in respiration.
• Water vapor, which is an atmospheric gas, is an essential part of the water cycle.
• All weather takes place in the atmosphere.
• While the amount of gases do not vary relative to each other in the atmosphere, there is one exception: the ozone layer. Ozone in the upper atmosphere protects life from the Sun's high-energy ultraviolet radiation.
• Air pressure varies with altitude, temperature and location.

Atmospheric Layers

• Different temperature gradients create different layers within the atmosphere. The lowest layer is the troposphere, where most of the atmospheric gases and all of the planet's weather are located.
• The troposphere gets its heat from the ground, and so temperature decreases with altitude. Warm air rises and cool air sinks and so the troposphere is unstable.
• In the stratosphere, temperature increases with altitude. The stratosphere contains the ozone layer, which protects the planet from the Sun's harmful UV. The higher layers contain few gas molecules and are very cold.

Energy in the Atmosphere

• All materials contain energy, which can radiate through space as electromagnetic waves. The wavelengths of energy that come from the Sun include visible light, which appears white but can be broken up into many colors.
• Ultraviolet waves are very high energy. The highest energy UV, UVC and some UVB, gets filtered out of incoming sunlight by ozone.
• More solar energy reaches the low latitudes and the redistribution of heat by convection drives the planet's air currents.

Air Movement

• Winds blow from high pressure zones to low pressure zones. The pressure zones are created when air near the ground becomes warmer or colder than the air nearby.
• Local winds may be found in a mountain valley or near a coast.
• Global wind patterns are long term, steady winds that prevail around a large portion of the planet.
• The location of the global wind belts has a great deal of influence on the weather and climate of an area.