Layers of the Atmosphere
Discover Where Weather Happens and How Climate is Affected
Scientists define the atmosphere as the thin envelope or clouds of gases surrounding the Earth (National Weather Service, 2008). This atmosphere becomes thinner the further it is from the Earth's surface. The atmosphere processes the sun's energy into various forms. Half of the sun's energy is absorbed at the surface, with 20 percent absorbed by clouds and atmosphere. The remaining energy is reflected and scattered back into space. Ninety-nine percent of the atmosphere we know and weather occurs between the layer of the troposhere and below the top of the stratosphere.
Layers of the Atmosphere
There are five layers of the atmosphere:
Troposphere
The troposhere is the layer of the atmosphere where the weather happens. Lying just above Earth, this layer extends from the surface to 10 miles above. The gases thin and temperatures drop as altitude increases. This layer contains half of the gases in the atmosphere and they are generally well blended. This layer is heated from the ground.
Stratosphere
The stratosphere extends from 10 to 30 miles above the surface of the Earth. This layer is known as the middle atmosphere. Aircraft fly in this layer as the gases are stable and slow. Weather balloons penetrate the stratosphere, relaying pertinent information to scientists.
Mesosphere
The Mesosphere layer lies from 30 to 50 miles above the Earth. Meteors leave trails when hitting this layer of atmosphere, as the thick gases slow them down and they eventually burn up.
Thermosphere
The thermosphere occurs from 50 to 80 miles from the surface of the Earth. This atmospheric layer is called the upper atmosphere. The thermosphere contains thin layers of gases, which absorb the sun's ultraviolet radiation. This causes the thermosphere to be significantly warmer temperatures than other layers. Auroras occur and the space shuttle orbits in this layer of the atmosphere.
Exosphere
This outermost layer of the atmosphere is the closest to space. In the exosphere, molecules and atoms escape into space. This layer is also where satellites orbit the Earth.
Important Gases to Weather
Over 78 percent of the atmosphere is made up of nitrogen, according to the National Weather Service. The rest consists of mainly oxygen and a small amount or trace amount of other gases such as helium, hydrogen, carbon dioxide, xenon, ammonia, water vapor, methane, nitrous oxide, ozone, CFCs (chlorofluorocarbons) and particles like dust. Some of these gases have an important effect on weather and climate including:
- Oxygen combines with hydrogen to form water. Water makes up precipitation and all of the hydrologic cycle.
- Ozone is a form of oxygen that is important in filtering ultraviolet radiation from the sun. This beneficial ozone is found in the upper atmosphere. Harmful ozone occurs near the Earth, as a manmade pollutant and results in smog.
- Water vapor is involved in most weather we know. Water vapor forms cloud, precipitation, the hydrologic cycle and is also important to the greenhouse effect, without which there would be no life on Earth.
- Carbon dioxide is also an imporant part of the greenhouse effect. This gas has more effect on climate than on weather. Increasing amounts of carbon dioxide, those from industrial emissions, are a main culprit of global warming.
- Particles or aerosols derived from natural sources and human sources like fires and volcanic eruptions can change weather. Human effects have caused an increase in acid rain.
Reference:
Cox, John D. Weather For Dummies. 2000. Wiley Publishing, Inc. Indianapolis, Indiana.
National Weather Service
