Science With Mr. Milstid

The atmosphere is a layer of gases surrounding the Earth. But, it is also much more.
It is a moving source of life for every creature of the planet. While the atmosphere is mainly composed of nitrogen (N₂), it also contains gases such as oxygen (O₂) and carbon dioxide (CO₂) that plants and animals need to survive.
It has specialized molecules like ozone (O₃) that filter out harmful radiation from space.
The atmosphere also protects us from the vacuum of space. Without the atmosphere, our world would be as barren and dead as the Moon or Mercury, not to mention extremely cold!

 

Atmospheric Composition
The atmosphere is made up of just a few main molecules:

The rest of it is made of things called trace elements like water vapor, ozone, and other particles and molecules floating around.

Layers of the Atmosphere
There are 5 layers in the atmosphere.
From the earth up, they are:

1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
5. Exosphere

Almost all weather occurs in the Troposphere, the lowest layer of the atmosphere, which extends from the surface up to 8 to 16 kilometers above Earth’s surface (lowest toward the poles, highest in the tropics). Earth’s surface captures solar radiation and warms the troposphere from below, allowing it to be habitable.

Temperatures in this layer decrease with elevation/altitude (by about 6.5°C with each kilometer of altitude).

At the top of the troposphere is the Tropopause, a layer of cold air (about -60°C), which forms the top of the troposphere and creates a “cold trap” that causes atmospheric water vapor to condense.

The next atmospheric layer, the Stratosphere, extends upward from the Tropopause to 50 kilometers. In the Stratosphere temperatures increase with altitude because of absorption of sunlight by stratospheric ozone.
(About 90 percent of the ozone in the atmosphere is found in the stratosphere in a section called the Ozone Layer. The Ozone Layer is important because it absorbs harmful UV radiation, preventing it from reaching the surface of the earth.)

At the top of this layer is the Stratopause, where temperatures peak at about -3°C.

In the third atmospheric layer, the Mesosphere, temperatures once again fall with increasing altitude, to a low of about -93°C.

Above this layer is the Thermosphere, where temperatures again warm with altitude, rising higher than 1700°C.

The highest layer of the atmosphere is the Exosphere. This layer is not well defined: it blends into space.

Figure 1 below shows the pattern of temperature fluctuations across layers of the atmosphere.

Figure 1. Structure of the atmosphere

See larger image

Source: © 2006. Steven C. Wofsy, Abbott Lawrence Rotch Professor of Atmospheric and Environmental Science, lecture notes.

Atmospheric pressure in the atmosphere changes with elevation consistently across all layers of the atmosphere: as elevation increases, pressure decreases because the total weight of air above you lowers.
Figure 1 illustrates this trend as well. This fact is what causes pressure changes in your ears while flying in an airplane.

Tags: Atmosphere, Climate, Earth Science
Posted in Earth Science, Weather and Climate