Stratosphere

The air has many layers.

One layer is high up. It is called the stratosphere.

This layer has a special shield. It is made of ozone. The sun sends bright light down. The ozone catches this light. This makes the air warmer as you go up.

The air here is very dry. It is also very still. This helps planes fly smoothly.

Pilots like to fly in this layer. It is a very calm place to be.

The stratosphere is the second layer of our air.

It sits above the troposphere. It sits below the mesosphere. This layer is very dry. It is also very still. This stillness helps planes fly smoothly. Most jets fly here to avoid bumpy weather.

A special part of this layer is the ozone layer. Ozone is a gas that acts like a shield. It blocks harmful UV radiation from the sun. This radiation can damage life on Earth. The ozone layer makes heat when it works. It catches sunlight and turns it into warmth. This creates a temperature inversion. In this layer, the air gets warmer as you go higher. This is the opposite of the layer below it.

Scientists found this layer by using balloons. In 1902, two men studied the air. They found a layer where the heat stayed the same. This was the base of the stratosphere. Even in this high place, some things happen. For example, blue jet lightning can reach into this layer.

The stratosphere is the second layer of our atmosphere. It sits right above the troposphere and below the mesosphere.

This layer is very important because it is very stable. Unlike the layer below it, the stratosphere does not have much vertical mixing. This means the air does not move up and down very easily. Instead, the air stays in layers, which is why we call it stratified. This stability makes the stratosphere a very different place from the weather we see on the ground.

One of the most amazing things here is the ozone layer. Ozone is a gas made of three oxygen atoms. This layer works like a shield for our planet. It catches harmful ultraviolet radiation, or UV radiation, from the sun. When ozone absorbs this sunlight, it undergoes a process called photolysis. This means the light breaks the ozone apart into oxygen. Then, those pieces join back together to form ozone again. This cycle releases heat, which warms the air. This creates a temperature inversion, where the air gets warmer as you go higher.

People first discovered this special layer using instrumented balloons. In 1902, Léon Teisserenc de Bort from France and Richard Assmann from Germany both studied the air. They worked separately but published their findings at the same time.

They found a layer where the temperature stayed the same. This area was about 11 to 14 kilometers above the Earth. This discovery showed scientists that the atmosphere has very distinct parts. Later, in 1930, a mathematician named Sydney Chapman explained how the ozone cycle works.

There are many specific facts about this high place. Near the equator, the bottom of the stratosphere is 18 kilometers high. At the poles, it is only about 8 kilometers high. The temperature at the very top can reach about 270 Kelvin, which is about -3 degrees Celsius.

The winds here can be very strong too. In the Southern polar vortex, winds can reach speeds near 100 kilometers per hour. Even in this dry place, some life exists. In 2001, scientists found dust at 41 kilometers high that contained bacteria.

You might interact with the stratosphere without even knowing it. Many commercial airplanes fly in the lower stratosphere.

They fly there to stay above the bumpy weather and turbulence found below. Flying in the thin, stable air also helps them use less fuel. Some very fast planes, like the Concorde, have even flown much higher. High-altitude balloons also reach into this layer. In 2014, Alan Eustace set a record by reaching 41 kilometers with a manned balloon.

The stratosphere is the second major layer of Earth's atmosphere. It sits directly above the troposphere and below the mesosphere.

This layer is vital because it contains the ozone layer. This layer protects life on Earth by absorbing harmful solar ultraviolet (UV) radiation. Without this protection, life would struggle to exist outside of the oceans. The stratosphere is also characterized by being highly stratified. This means the air is organized into distinct layers based on temperature.

In the troposphere, temperature typically decreases as you go higher. However, the stratosphere experiences a temperature inversion. This means the air actually gets warmer as altitude increases. This warming happens because of the ozone layer. The ozone layer absorbs high-energy UV radiation from the sun. This process is called exothermic photolysis. In this cycle, ozone molecules are broken apart into oxygen. These pieces then recombine to reform ozone, releasing heat in the process. This cycle is known as the Chapman cycle. It was first described by the British mathematician Sydney Chapman in 1930.

Because of this temperature inversion, the stratosphere is dynamically stable. There is very little regular convection or turbulence here. This stability prevents the rapid vertical mixing seen in the lower atmosphere. Most air movement in the stratosphere is horizontal rather than vertical. However, extreme events can occasionally push air upward. Volcanic eruption columns or severe supercell thunderstorms can carry convection into the stratosphere. These events are usually local and temporary.

Scientists first identified this layer at the turn of the 20th century. In 1902, Léon Teisserenc de Bort from France and Richard Assmann from Germany made a major discovery. They used instrumented balloons to measure temperature profiles. They both published findings about an isothermal layer at around 11 to 14 kilometers. This layer marked the base of the lower stratosphere. Later, researchers like Paul J. Crutzen, Mario J. Molina, and F. Sherwood Rowland studied ozone more deeply. Their work on ozone formation and decomposition earned them the Nobel Prize in Chemistry in 1995.

The stratosphere has very specific physical boundaries and measurements. The lower edge varies depending on your location on Earth. Near the equator, the stratosphere starts at about 18 kilometers high. At mid-latitudes, it starts around 15 kilometers. At the poles, it is much lower, starting at about 8 kilometers. The top of the layer is called the stratopause. At the stratopause, temperatures reach about 270 K, which is -3 degrees Celsius.

The air is also incredibly dry because rising air is freeze-dried at the tropopause.

Humans interact with the stratosphere frequently through aviation. Many commercial airliners cruise in the lower stratosphere. They do this to avoid the turbulent weather found in the troposphere. Flying in the stratosphere also improves fuel efficiency. The air is much thinner, which reduces parasitic drag on the plane. This allows aircraft to fly faster while maintaining lift. Some specialized aircraft fly even higher. The Concorde cruised at about 18,000 meters. The SR-71 reached altitudes of 25,750 meters.

Global circulation patterns also move air through this layer. This movement is called the Brewer-Dobson circulation. It involves air rising in the tropics and sinking in the extra-tropics. This circulation is driven by waves, such as Rossby waves. Another feature is the quasi-biennial oscillation, or QBO, in tropical latitudes. This oscillation is important for transporting tracers like ozone and water vapor. Even in this harsh environment, life is present. In 2001, scientists found bacteria on dust particles at 41 kilometers high.