The Earth’s atmosphere consists of five layers, each with its own distinct characteristics. The stratosphere is the second layer, situated above the troposphere. We take a closer look at this layer and its defining features.

It is easy and understandable to view our atmosphere as a continuous layer of air. However, it is made up of five different layers: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. This article focuses on the stratosphere, Earth’s second layer.

It not only examines what the stratosphere is but also looks at the characteristics or facts that define it.

Before we look at specific facts about the stratosphere and its defining characteristics, we first need to establish exactly what the stratosphere is:

Stratosphere Definition

The stratosphere is the second of Earth’s five atmospheric layers, situated above the troposphere and below the mesosphere. It begins at an altitude of approximately 10 km (6 miles) and extends up to about 50 km (30 miles). It is the only layer where temperature inversion occurs and the region where the ozone layer is located.

The stratosphere contains very few of the elements found in the troposphere. The majority is broken down by sunlight or deposited back to the planet’s surface via rain.

Temperature inversion takes place between the troposphere and the stratosphere. (An increase in temperature with height.) This also contributes to making the exchange of air between the two layers virtually impossible.

By far the most important element present is ozone. The stratosphere contains the highest concentration of ozone of all the layers.

Air is extremely dry in the stratosphere, as water contained in the air and clouds is trapped in the troposphere. (With almost no air exchange between the two layers, as already mentioned.) This means basically no form of precipitation takes place from the stratosphere.

The air continues to get less dense as height increases, leading to the air in the stratosphere being about 1 000 times thinner than at sea level.

The stratosphere starts at a height just above the troposphere and reaches as high as 50 km (30 miles) above the surface of the Earth.

Almost no weather occurs in the stratosphere, although big storm clouds (in the form of supercells containing cumulonimbus clouds) occasionally punch through the tropopause and reach lower parts of the stratosphere.

One of the main characteristics of the stratosphere is an occurrence called temperature inversion.

Temperature inversion occurs when the temperature rises as the height above the Earth’s surface increases. (This is the direct opposite of what occurs with the air temperature in the troposphere.)

Starting with an average temperature of -51° Celsius (-60° Fahrenheit) just above the troposphere, it starts to increase in temperature, reaching an average of -15° Celsius (5° Fahrenheit) close to the mesosphere. 

One of the most important functions of the stratosphere, though, is the presence of the ozone layer within it. This layer of ozone protects the Earth from the harmful ultraviolet rays of the sun.

A very simple way of explaining how the ozone layer protects us is to see the ozone layer as a gigantic filter. It allows the less harmful longwave UVA radiation through while absorbing the more dangerous shortwave UVB and UVC radiation. This is done through a process called the “ozone-oxygen cycle.”

The ozone layer gained fame and came to the forefront a few decades ago when a hole in the layer was discovered over Antarctica. Through a process called ozone depletion, large amounts of ozone were reduced in the stratosphere.

It was mainly caused by CFC gases, commonly used in refrigerators and air conditioners at the time. An international ban on the use of CFC gases was issued, and since then, the ozone layer has made a significant recovery. 

(On an interesting note, as necessary as the ozone layer is for protecting the Earth from the Sun’s harmful UV radiation, it is actually quite harmful to us humans. It can cause a variety of respiratory problems and permanently damage your lungs when inhaled.)

Since almost all weather activity is limited to the troposphere and almost no water vapor is present in the stratosphere, Polar Stratospheric Clouds are the only visual meteorological phenomenon that can be observed in the stratosphere.

Also known as Nacreous Clouds, these unique clouds develop near the poles at an altitude of 15 – 25 kilometers (9 – 15 miles) during the winter months. They are a combination of supercooled water and nitric acid that develop at very low temperatures.

(Learn more about Nacreous or Polar Stratospheric Clouds in this article.)

By far the most important attribute of the stratosphere is the fact that it contains the ozone layer, which is so vital to all life on Earth. (It has already been discussed and explained, so no need to explain its importance again.) The state of the ozone layer is so important that weather balloons are sent up on a regular basis to measure ozone levels. Weather balloons are capable of reaching the stratosphere and can also be launched from various regions worldwide.

The readings of the ozone layer in Arctic regions are especially important. The reason is that the hole in the ozone layer was first discovered over Antarctica. The stratosphere is also at its lowest altitude over the polar regions. The stratosphere also acts as a barrier or containment layer. It confines the important elements in the air, including water vapor, to the troposphere.

Jet airliners make good use of some of the attributes of the stratosphere. They fly at cruising altitudes in the lower stratosphere for two reasons.

The fact that almost all weather is restricted to the troposphere allows aircraft to fly above the weather in the stratosphere, avoiding turbulence and potential damage in the process.

In the lower stratosphere, the air is also much thinner than in the troposphere, allowing airliners to fly through air with much less resistance. In the process, it saves a significant amount of fuel, which can also extend the range of the airplane.

A thin layer, called the stratopause, forms the border between the stratosphere and the mesosphere. Interestingly, it is within this thin layer that a maximum in temperature occurs. The combination of warm and very dry air makes cloud formation (and any form of weather, for that matter) practically impossible within the stratopause.

The following list highlights the characteristics and facts about the stratosphere in more detail.

1. 1. The stratosphere is the second layer of the atmosphere (above the troposphere)
   2. It extends from a height of approximately 10 km (6 miles) to 50 km (30 miles) above the Earth’s surface.
   3. It borders the troposphere below through a thin transitional space called the tropopause.
   4. It borders the mesosphere above through a thin transitional space called the stratopause.
   5. It is the only layer of the atmosphere where temperature inversion occurs (an increase in temperature as altitude increases)
   6. The air in the stratosphere is about 1 000 times thinner than the air at sea level in the troposphere.
   7. The ozone layer is situated within this layer.
   8. Commercial airliners fly in the lower stratosphere to avoid the weather, travel faster, and save fuel.
   9. Polar Stratospheric Clouds develop in this layer near the poles at an altitude of 15 – 25 kilometers (9 – 15 miles) during the winter.
   10. Brewer-Dobson Circulation occurs in the stratosphere.
   11. The layer is approximately 35 kilometers (22 miles) thick.
   12. Certain swans, cranes, and vultures can fly in the lower stratosphere. 

This list does not contain all the data available about the stratosphere, but highlights the key facts and characteristics of this layer.

As this article clearly illustrates, the stratosphere has a crucial role to play in maintaining the atmosphere and all life in it.

This sets it apart from the other atmospheric layers, as temperature rises instead of dropping as altitude increases, a process called temperature inversion.

The importance of the stratosphere is highlighted by the presence of the ozone layer, without which no life on Earth would be possible.

If you are interested in the complete structure and make-up of the atmosphere, this article covers all five atmospheric layers and their relation to each other in more detail.

Until next time, keep your eye on the weather!