The atmosphere, the layer of air around the Earth, does not simply get colder all the way up; its temperature falls, then rises, then falls and rises again.
So it is divided by how the temperature changes with height into four layers, from the bottom: the troposphere, stratosphere, mesosphere and thermosphere.
Clouds, rain and other weather happen only in the troposphere, where there is plenty of water vapor and air mixes up and down, and the stratosphere holds the ozone layer that absorbs harmful ultraviolet light.
Move the altitude from 0 km to 120 km and see which layer you are in and the average temperature at that height, along with a point on the temperature graph.
The Atmosphere Around the Earth
🌍 The Air Around the Earth
①The atmosphere is the layer of air around the Earth; it reaches up to about 1000 km, but most of the air is packed into the lowest few tens of kilometers.
②The air gets thinner with height, which is why climbing a high mountain leaves you short of breath.
③Each layer changes temperature with height in its own way, so the atmosphere is divided into the troposphere, stratosphere, mesosphere and thermosphere.
8 km
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The four layers of the atmosphere: troposphere, stratosphere, mesosphere, thermosphere
Temperature Change with Height
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Average temperature with height (approximate standard atmosphere)
🌡️ Different Temperature Changes in Each Layer
①Troposphere (surface to about 11 km): air warmed by the ground cools as it rises, about 0.65 °C per 100 m.
②Stratosphere (about 11 to 50 km): the ozone layer absorbs ultraviolet light, so it gets warmer with height.
③Mesosphere (about 50 to 80 km): it gets colder with height again, and its top is the coldest place in the atmosphere (about −90 °C).
④Thermosphere (above about 80 km): it absorbs solar energy directly and gets much hotter with height.
⑤Even in the troposphere, on clear nights when the ground cools fast, a temperature inversion can briefly make the lower air colder.
Summary
Troposphere
surface to about 11 km: the layer where weather happens
Temperature falls with height, so convection is active, and water vapor forms clouds, rain and snow.
Stratosphere
about 11 to 50 km: the layer with the ozone layer
Temperature rises with height, so there is no convection and the air is stable; long-haul planes fly in its lower part.
Mesosphere and thermosphere
about 50 to 80 km / above about 80 km
The mesosphere has convection but almost no water vapor, so no weather, and meteors burn up there; the thermosphere has very thin air and auroras.
🎯 Exam Points
①Troposphere: weather, convection, colder with height.
②Stratosphere: ozone layer, stable, warmer with height.
③Mesosphere: where meteors burn up; the lowest temperatures in the atmosphere.
④Thermosphere: auroras, very thin air, much hotter with height.
⑤Convection happens in both the troposphere and mesosphere, but only the troposphere has the water vapor to make weather.
Examples and Unit Test
Example 1
List the layers of the atmosphere from lowest to highest, and explain how temperature changes with height in the troposphere and the stratosphere.
1
From the bottom: troposphere (surface to about 11 km) → stratosphere (about 11 to 50 km) → mesosphere (about 50 to 80 km) → thermosphere (above about 80 km).
2
In the troposphere temperature falls with height; in the stratosphere the ozone layer absorbs ultraviolet light, so temperature rises with height.
▸ Troposphere → stratosphere → mesosphere → thermosphere / troposphere: colder with height; stratosphere: warmer with height
Layers that cool and layers that warm take turns; the bends in the graph are the boundaries between layers.
Example 2
In which layer does weather such as clouds and rain happen, and why is the stratosphere stable?
1
The troposphere gets colder with height, so warmed air from below rises in active convection, and with plenty of water vapor, clouds and rain form.
2
The stratosphere gets warmer with height, so cold air below does not rise into it; the air does not mix and stays stable.
▸ Weather: troposphere (active convection and water vapor) / stratosphere: warmer on top, so no convection and stable
Cold air is heavy and sinks, warm air is light and rises; if the warm air is already on top, there is nothing to stir it.
Unit Test
Which statement about the atmosphere is correct?
①In the troposphere temperature rises with height
②The ozone layer is in the mesosphere
③Weather events occur in the troposphere
④The thermosphere has the lowest temperature in the atmosphere
⑤Meteors mostly burn up in the stratosphere
▸ ③ Weather events occur in the troposphere
1
In the troposphere temperature falls with height (①), and the ozone layer is in the stratosphere (②).
2
The thermosphere gets much hotter with height (④), and meteors burn up in the mesosphere (⑤). Weather happens in the troposphere, which has water vapor and convection, so ③ is correct.