Composition of the Atmosphere

Troposphere - the lowest layer of the atmosphere which contains breathable air, and aspects of weather.
Stratosphere - contains a stratified temperature gradient where lower altitudes are cooler. This layer also contains the Ozone Layer.
Mesosphere - the coldest part of the atmosphere.
Thermosphere - the hottest layer of the atmosphere due to the particles here absorbing the Sun’s energy
These layers are separated with breaks called pauses.
The atmosphere is held together due to the Gravity pulling down the gases to Earth and the natural buoyancy of its constituent gases.
- The pull of gravity also explains why higher atmospheric layers contain less particles Lighter gases also exist higher up in the atmosphere .
- This also explains the fact that the higher layers have lower pressures due to having fewer molecules.
The height of the troposphere is influenced by insolation. It is higher near the equator and lower near the poles.

The atmosphere is predominantly made of aerosols which consist of gases, solid particulates, and liquid droplets.
The majority of the atmosphere is Nitrogen and Oxygen.
The solid particulates in the atmosphere primarily consist of dust and salt particles blown by the wind.

The Atmosphere and Insolation

Some atmospheric components can partially reflect incoming insolation. This reflected energy can be returned to space or be contained within the atmosphere.
Some components can absorb energy which increases the temperature of the component.
Some components can scatter atmospheric components which diffuse the energy in various directions.
- The sky is blue because the atmosphere tends to scatter blue light
- The sun appears yellow because the atmosphere tends to allow red and green light through .
- When the sun is at a low angle, the insolation has to pass through more of the atmosphere.. This is why sunrises and sunsets appear red or orange.
The atmospheric layers interact with insolation differently.
- The thermosphere intercepts high energy electromagnetic waves such as X-rays and gamma rays, which causes the layer to warm up at the parts closest to space (although it remains relatively cold because of the sparse number of atoms).
- The stratosphere contains the Ozone Layer which absorbs UV light. Like with the thermosphere, this causes the stratosphere to heat up at higher altitudes.
- The temperature gradient for the other layers can generally be seen as a consequence of the sun heating the surface more, and the surface heating the atmosphere from below.
Clouds also help in intercepting insolation. The amount of energy that is reflected by clouds varies because of their composition, location, and season.

The Ozone Layer contains a recyclable amount of Ozone It is recyclable since sunlight that hits an ozone molecule causes it to disassociate into and . The latter atom can simply recombine with another molecule.
Ozone concentration is typically low over the Equator and in regions with low insolation. The former is because of wind patterns in the stratosphere that are directed to the poles and the latter is because insolation is required for the reformation of Ozone.
- Of note, Antarctica has an ozone hole above it. This is because of circumpolar winds due to being surrounded by water.
- By contrast, the Arctic has high concentrations of Ozone. This is because it is an ocean surrounded by continents which induces the appropriate wind patterns to bring ozone towards the Arctic.
The Ozone layer effectively shields the surface from UV light by acting as a regenerative buffer that can absorb the energy from UV.
Human activity has accelerated the depletion of Ozone. This has caused a hole in the ozone layer.