Summer Solstice Sunrise over Stonehenge

Ok, this post is about our atmosphere, which is key in our survival.

What is Earth’s atmosphere made up of? If you said oxygen then you are partially correct. Our atmosphere is a complex system that is composed of many different gases, not just oxygen. In all reality, oxygen only makes up roughly 20% of our atmosphere. Nitrogen is the most abundant gas in the atmosphere, making up roughly 79%. Other gases include: Argon (.93%), Carbon dioxide (.038%), Neon (.0018%), Helium (.00052%), Methane (.00017%), Krypton (.00011%), Hydrogen (.000055%), Nitrous oxide (.000030%), and so on and so forth.(If you want to know more about the gases from the perspective of chemistry then ask Mitchell Peters. If you want to know more about the gases from an atmospheric point of view, then read on for a general explanation of them. Depending on what you want, I might write something on atmospheric chemistry later on.)The interactions between these different gases help sustain life on our lovely planet. Aside from enabling you and I to exist, the interaction of these gases allows the atmosphere to absorb most of the ultraviolet solar radiation rays to the point that exposure to them is not lethal (by this I mean a short exposure, not long periods of time.  By exposing yourself to the UV rays, especially without skin protection, you can harm your body and increase your risk for skin cancer). The atmosphere also helps to regulate the temperature of the Earth, which makes it so we do not burst into flames during the summer from the sun or freeze instantly during the winter from the lack of sun. It also regulates the weather and different climates of the world.

So, how is the atmosphere structured?

The atmosphere is composed of four main layers with three boundaries that separate the different layers. The four layers are called the troposphere, stratosphere, mesosphere, and the thermosphere. The boundaries that separate the layers are called the tropopause, stratopause, and the mesopause.

Troposphere:

The troposphere is the bottom layer of the atmosphere that begins at ground level and extends to roughly 5 to 10 miles (8 to 16 kilometers) in the air. Its height is lowest at the poles and highest at the equator.The troposphere is where all of our weather takes place: clouds, storms, winds, etc. It is very rare for clouds to penetrate the troposphere and mix in with the stratosphere but this can occur with particularly violent storms where the top of the cloud or system is strong enough to develop a cap and punch through the layer. But a majority of the time the atmosphere is stable enough where this does not occur. As you go further into the troposphere both pressure and temperature will drop. I am more focused on the temperature fluctuations and not so much on the pressure but just so you know, the pressure at the top of the troposphere is 1/10 of the pressure at ground level. Now, obviously temperatures at ground level will vary with your location and elevation but as you go higher up into the troposphere, there is a roughly 4 degrees Fahrenheit drop in temperature for every 1000 feet (7 degrees Celsius per kilometer). Depending on your location, the top of the troposphere can drop to temperatures ranging from roughly -49 degrees Fahrenheit (-45 degrees Celsius) at the poles where the troposphere is thinner, to roughly -105 degrees Fahrenheit (-75 degrees Celsius) at the equator. Additionally, the troposphere can divided into six zonal flow regions that are called cells and are the cause for atmospheric circulation which create the prevailing winds. Basically, here is what you should know about the atmosphere: it extends from the ground to roughly 5 to 10 miles (8 to 16 kilometers), as you go higher in the troposphere the temperature decreases, and this is where all weather phenomena occurs.

Tropopause:

This is the boundary that separates that troposphere and the stratosphere. Basically,  at this point the temperature stops dropping. The temperatures here are still very low and reach -70 degrees Fahrenheit (-58 degrees Celsius).

Stratosphere:

This is the layer that is above the troposphere. It extends roughly 30 miles (50 kilometers) above the surface of the Earth. Unlike the troposphere, the temperature actually increases with height, with the the maximum temperature reaching roughly 40 degrees Fahrenheit (4 degrees Celsius). This is because there are many interactions between many atmospheric chemicals and the stratospheric ozone absorbs much of the ultraviolet radiation. Additionally, the oxygen content is lower in this layer than in the troposphere. Another interesting thing about the stratosphere is that a secondary circulation is generated that is crucial in the movement of such things as ozone and water vapor. This circulation is called quasi-Biennial Oscillation and is located above tropical regions. Gravitation waves that are generated by convection in the troposphere help to create and move the QBO.

Stratopause:

This is a boundary that separates the stratosphere from the mesosphere. In this boundary, the temperatures still increase, much like the stratosphere.

Mesosphere:

This layer is what follows the stratosphere and reaches a height of 50 miles (80 kilometers). Temperature decreases as the you go higher in the mesosphere and can drop as low as -99 to -130 degrees Fahrenheit (-73 to -90 degrees Celsius) depending on your location and the season. The mesosphere helps to prevent a very large majority of the meteors that hurtle towards us from actually hitting us. So many meteors are burned up in this layer because they collide with the billions of chemical particles that causes enough heat to burn up the meteors, among other things that are trapped by Earth’s gravitational field. Fun fact: Noctilucent clouds occur in the mesosphere. Not much is known about these clouds except that it is primarily composed of water particles and is thought to be associated with climate change. They are very difficult to see; they are best seen when illuminated by the sun from below the horizon.

Mesopause:

This is yet another boundary in the atmosphere. It separates the mesosphere from the thermosphere. At this point, the temperature stops decreasing.

Thermosphere:

This layer reaches a height of roughly 120 miles (190 kilometers) above the Earth. Temperatures increase as altitude increases in the thermosphere. Actually, the temperatures can reach roughly 2,700 degrees Fahrenheit (1,480 degrees Celsius). This is because there is such a high amount of solar radiation present and so little oxygen in this layer. This radiation electrically charges particles which allows many radio waves to be bounced off and can be received elsewhere.

Exosphere:

This is the outermost layer of Earth’s atmosphere. This layer can extend to 600 miles (960 kilometers) above the Earth. Temperatures are still very hot in this layer but they are still lower than those in the thermosphere. Because there is a large lack of gravity, many gaseous particles are able to escape into space. Also, satellites orbit here.