Structure of the Atmosphere

Study Notes

The Earth's atmosphere is divided into four main layers: troposphere, stratosphere, mesosphere, and thermosphere.
The exosphere is the uppermost layer, gradually fading away into space.

The troposphere is the layer closest to the Earth's surface, extending up to 7.5 miles (12 kilometers) in height.
Its height is lower at the poles and highest at the Equator.
The troposphere holds the air necessary for breathing and photosynthesis.
It contains a mix of nitrogen, oxygen, and carbon dioxide.
The air temperature decreases with elevation due to the transfer of energy from the Earth's surface.
Most of the Earth's weather is generated within the troposphere.
The clouds around the Earth are also within the troposphere, except for some thunderous cumulonimbus clouds.

The stratosphere is the layer above the troposphere, extending up to 31 miles (50 kilometers) above the Earth's surface.
It's a narrow layer that can be passed through in about 5 seconds.
The stratosphere has virtually no clouds and weather.
The temperature rises with elevation due to UV radiation.
It's home to the Earth's ozone layer, which protects the Earth from harmful UV radiation.
The ozone layer has a balance between formulation and natural depletion, but human activity can deplete it.

The mesosphere is the last noticeable layer of the atmosphere, existing between 31 and 50 miles (50 to 80 kilometers) above the Earth's surface.
It's the coldest layer, with temperatures averaging around -120°F (-84°C).
The highest clouds above the Earth's surface form in this layer due to scarce water vapor.
The mesosphere contains the ionosphere, which is home to Earth-orbiting satellites.
The ionosphere reflects and modifies radio waves, allowing for communication with satellites.

The thermosphere is the last layer of the atmosphere, beginning about 62 miles above the Earth.
It's very thin and gives way to the far depths of space.
The thermosphere is home to the International Space Station and other orbiting satellites, including part of the ionosphere.