There are five layers of the atmosphere and several secondary layers. The dividing points between these layers are altitude and temperature. Here is the list of the layers of the atmosphere, their altitudes, temperatures, and other properties.
- The atmosphere is the layer of gases that surround Earth.
- The five layers of the atmosphere, in order from the ground up, are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
- The atmosphere extends to roughly 100 km or 62 miles. This is the Kármán line, which marks the beginning of space. The atmosphere gradually thins and does not abruptly end. Note that part of the thermosphere and all of the exosphere are beyond this mark.
The 5 Layers of the Atmosphere
The five main layers are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. Mainly, temperature determines the altitude of these layers. The atmosphere is fluid and changes according to season, day/night cycle, and other factors, so the lower and upper limits of each layer shift.
Main Features of the Atmospheric Layers
| Layer | Main Characteristic |
|---|---|
| Troposphere | Weather and clouds |
| Stratosphere | Ozone layer |
| Mesosphere | Meteors burn up |
| Thermosphere | Auroras and ISS |
| Exosphere | Transition into space |
Troposphere
The troposphere is the layer of the atmosphere that contacts the Earth’s surface. Its average height is 12 km (7.5 mi; 39,000 ft), but it is thickest at the equator and also varies according to weather.
The troposphere contains most of the air and water vapor in the atmosphere. Hence, most clouds and weather occur here. Mostly, temperature decreases with increasing altitude. This is because heat comes from the surface.
The tropopause is the layer separating the troposphere from the stratosphere.
Stratosphere
The stratosphere is the layer bounded by the tropopause at its base (12 km; 7.5 mi; 39,000 ft) up to the stratopause (55 km; 31 to 34 mi; 164,000 to 180,000 ft). Air pressure within the stratosphere is only about 1/1000 of the pressure at sea level.
Temperature rises with increasing altitude, mainly from the absorption of ultraviolet radiation by the ozone layer. The stratosphere contains few clouds. Most commercial aircraft stay within the troposphere, but some fly in the lower stratosphere.
Mesosphere
The mesosphere is the atmospheric layer between the stratosphere and thermosphere. It is bounded by the stratopause (55 km; 31 to 34 mi; 164,000 to 180,000 ft) and mesopause (80–85 km; 50–53 mi; 260,000–280,000 ft).
The mesosphere is the coldest part of the atmosphere, with an average temperature of −85 °C (−120 °F; 190 K). Noctilucent clouds form in this layer. The mesosphere is also where many meteors begin glowing as they encounter increasing friction with atmospheric gases. Although the atmosphere extends far beyond this layer, the mesosphere marks the transition to extremely thin air and near-space conditions.
Thermosphere
The thermosphere is the region of the atmosphere between the mesopause (80–85 km; 50–53 mi; 260,000–280,000 ft) and thermopause or exobase (500–1000 km; 310–620 mi; 1,600,000–3,300,000 ft). Its height depends on solar activity. The ionosphere roughly coincides with the lower thermosphere.
The layer gets its name because temperatures can exceed 1500 °C (2700 °F), although the extremely low density means the heat content is very low. Gas atoms and molecules are far apart from one another. The aurora mainly occurs in the thermosphere. Many satellites and the International Space Station (ISS) are in this layer.
By international convention, outer space begins at the Kármán line, which lies within the thermosphere at an altitude of 100 km (62 mi). While part of Earth’s atmosphere actually extends beyond this point, it is where objects start experiencing friction from air.
Exosphere
The exosphere is the outer layer of the Earth’s atmosphere. It extends from the thermopause or exobase (500–1000 km; 310–620 mi; 1,600,000–3,300,000 ft) to around 100,000 km (6,200 mi; 33,000,000 ft). At this point, the atmosphere merges into the solar wind. Atoms and molecules are hundreds of kilometers apart and can escape into space.
The aurora sometimes extends into the lower exosphere. Many artificial satellites orbit within this layer, too.
Space actually starts within the atmosphere, where objects start to experience friction from air.
Atmospheric Layers Table
This table sums up the key features of the layers of the atmosphere:
| Layer | Altitude | Temperature | Contains? | Features |
|---|---|---|---|---|
| Troposphere | 0-12 km 0 to 7 miles | −56 °C to 15 °C (−69 °F to 59 °F) | most clouds most water vapor weather balloons, aircraft | 80% of the total atmosphere |
| Stratosphere | 12-50 km 7-31 miles | −56 °C to -2.5 °C (−69 °F to 37 °F) | ozone layer few clouds highest altitude jets fly | pressure 1/1000 that of sea level |
| Mesosphere | 50-80 km 31-50 miles | average: −85 °C (−120 °F) | noctilucent clouds transient luminous events (TLEs) meteors burn up | thin atmosphere water vapor turns into ice crystals |
| Thermosphere | 80-700 km 50-440 miles | up to 1500 °C (2700 °F) | aurora International Space Station (ISS) satellites | low density gases, including singlet oxygen |
| Exosphere | 700-10,000 km 440-6,200 miles | ~1200 °C (2200 °F) | satellites aurora (lower portion) | low density atoms and molecules hydrogen, helium, nitrogen, oxygen, carbon dioxide |
Other Atmospheric Layers
Temperature determines the five main layers, but the atmosphere contains other layers, too.
- Ozone Layer: The ozone layer is within the lower stratosphere. In this region, ozone concentration ranges from 2 to 8 parts per million. The layer’s altitude is from 15–35 km (9.3–21.7 mi), although its thickness varies geographically and seasonally. It is thinnest near the poles.
- Ionosphere: The ionosphere ranges in altitude from 50 to 1,000 km (31 to 621 mi). It includes the mesosphere, thermosphere, and part of the exosphere. This is the region where solar radiation ionizes atmospheric gases. The aurora borealis and aurora australis form in the ionosphere.
- Homosphere and Heterosphere: Another way of defining the atmosphere is according to whether the gases are well-mixed and homogeneous (homosphere) or layered (heterosphere). The homosphere includes the troposphere, stratosphere, mesosphere, and lower thermosphere. Most of the thermosphere together with all of the exosphere make up the heterosphere. Here, gases layer by molecular weight. Oxygen and nitrogen are near the bottom of the layer, with hydrogen and helium at the top.
Composition of Earth’s Atmosphere
Earth’s atmosphere consists primarily of nitrogen (78%) and oxygen (21%), along with argon, carbon dioxide, water vapor, and trace gases. Water vapor concentration varies widely depending on location and weather conditions. Although carbon dioxide makes up only about 0.04% of the atmosphere, it plays an important role in climate and the greenhouse effect.
| Gas | Approximate Percentage |
|---|---|
| Nitrogen | 78% |
| Oxygen | 21% |
| Argon | 0.93% |
| Carbon Dioxide | 0.04% |
| Other Gases | Trace amounts |
How Air Pressure Changes With Altitude
Air pressure and density decrease rapidly with increasing altitude because gravity pulls most atmospheric gases close to Earth’s surface. About 50% of the atmosphere’s mass lies below an altitude of 5.5 km (3.4 mi), while approximately 99% lies below 32 km (20 mi). The decrease in pressure affects weather, aircraft performance, and human physiology.
As altitude increases, the atmosphere becomes thinner and contains fewer gas molecules per unit volume. This is why high-altitude climbers and pilots may require supplemental oxygen.
Atmosphere and the Greenhouse Effect
Earth’s atmosphere helps regulate planetary temperature through the greenhouse effect. Gases such as water vapor, carbon dioxide, methane, and nitrous oxide absorb and re-radiate infrared energy emitted by Earth’s surface. Without the natural greenhouse effect, Earth’s average temperature would be far below freezing and life as we know it could not exist.
Human activities that increase greenhouse gas concentrations contribute to global climate change by trapping additional heat within the atmosphere.
Why Atmospheric Temperature Changes With Altitude
Atmospheric temperature does not steadily decrease with altitude. Instead, temperatures alternate between cooling and warming because different layers absorb solar energy differently.
For example, temperatures rise in the stratosphere because ozone absorbs ultraviolet radiation from the Sun. Temperatures decrease again in the mesosphere before increasing sharply in the thermosphere due to the absorption of high-energy solar radiation.
Why Earth’s Atmosphere Is Important
Earth’s atmosphere makes life possible by supplying oxygen, regulating temperature, and protecting the planet from harmful solar radiation. The atmosphere also burns up many meteoroids before they reach the surface and helps distribute heat and moisture around the globe.
Without the atmosphere, Earth would experience extreme temperature swings between day and night, liquid water would not persist on the surface, and life could not survive.
Atmospheric Layers on Other Planets
Other planets also have layered atmospheres, although their compositions and temperature structures differ from Earth’s atmosphere. Venus has a dense carbon dioxide atmosphere with sulfuric acid clouds and an intense greenhouse effect. Mars has a thin atmosphere composed mainly of carbon dioxide. The giant planets, including Jupiter and Saturn, possess extremely deep atmospheres made mostly of hydrogen and helium.
Studying planetary atmospheres helps scientists understand weather, climate, and the potential habitability of other worlds.
FAQs
What are the five layers of the atmosphere?
The five main atmospheric layers are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
Which atmospheric layer contains weather?
Most weather occurs in the troposphere because it contains most of the atmosphere’s water vapor and clouds.
Which atmospheric layer contains the ozone layer?
The ozone layer is mainly located within the stratosphere.
What is the coldest layer of the atmosphere?
The mesosphere is the coldest atmospheric layer, with temperatures near −85 °C (−120 °F).
Where does outer space begin?
By international convention, outer space begins at the Kármán line, located 100 km (62 mi) above Earth’s surface.
References
- Barry, R.G.; Chorley, R.J. (1971). Atmosphere, Weather and Climate. London: Menthuen & Co Ltd. ISBN 9780416079401.
- Lutgens, Frederick K.; Edward J. Tarbuck (1995). The Atmosphere (6th ed.). Prentice Hall. ISBN 0-13-350612-6.
- States, Robert J.; Gardner, Chester S. (2000). “Thermal Structure of the Mesopause Region (80–105 km) at 40°N Latitude. Part I: Seasonal Variations”. Journal of the Atmospheric Sciences. 57 (1): 66–77. doi:10.1175/1520-0469(2000)057<0066:TSOTMR>2.0.CO;2