What is the Stratosphere? 5 Facts About Stratosphere!
Above the troposphere and below the mesosphere is the stratosphere. “Strat” stands for layer. This layer of our atmosphere also has its own lower layers. There are no storms or turbulence to stir the air here, so it’s cold, heavy air below; At the top there is a warm, light air. This is the opposite of how layers work in the troposphere, where we live. If you were to climb a mountain in the stratosphere, instead of dressing as we are used to, you would have to take off your thick clothes as you approach the top.
This layer is 35 kilometers thick. The stratosphere is where the very important ozone layer is located. The ozone layer helps protect us from ultraviolet rays (UV) from the Sun. In fact, the ozone layer absorbs most of the UV rays that the Sun sends us. Life would not be possible without this layer of protection.
Ozone, an unusual type of oxygen molecule that is relatively abundant in the stratosphere, heats this layer as it absorbs energy from ultraviolet radiation from the Sun. As you go up in the stratosphere, temperatures rise. This is the opposite of the behavior in the troposphere we live in, where the temperature drops as it rises.
Because of this temperature stratification, there is very little convection and mixing in the stratosphere, so the air layers there are quite stable. Commercial jet aircraft fly in the lower stratosphere to avoid the turbulence prevalent in the troposphere below.
The stratosphere is very dry air and contains very little water vapour. Therefore, very few clouds are found in this layer, and almost all clouds are located in the lower, more humid troposphere. Polar stratospheric clouds (PSCs) are the exception. PSCs occur in the lower stratosphere near the poles in winter. They are found at altitudes of 15 to 25 km and only form when temperatures at these altitudes drop below -78°C.
Stratospheres and Planes
The air at the top of the stratosphere is roughly a thousand times thinner than at sea level. Therefore, jet aircraft and weather balloons reach their maximum operational altitudes within the stratosphere.
Since there is no vertical convection in the stratosphere, substances entering the stratosphere can stay there for a long time. This is the case for ozone-destroying chemicals called CFCs (chlorofluorocarbons). Large volcanic eruptions and massive meteorite impacts can hurl aerosol particles into the stratosphere, where they can linger for months or years and sometimes change Earth’s global climate. Rocket launches inject exhaust gases into the stratosphere, leading to ambiguous results.
Various waves and tides in the atmosphere affect the stratosphere. Some of these waves and tides carry energy from the troposphere to the stratosphere, while others carry energy from the stratosphere to the mesosphere. Waves and tides affect airflow in the stratosphere and can also cause regional warming of this layer of the atmosphere.
A rare lightning-like electrical discharge occurs in the stratosphere. These “blue jets” appear above thunderstorms and extend below the stratosphere to an altitude of 40 or 50 km.
Frequented by commercial airlines, the stratosphere is the second lowest level in Earth’s atmosphere. A bastion of ozone gas and fast winds, a place where clouds are few but life goes on.
Five Facts About Stratosphere
1. Limited to the Tropopause
When you get to the bottom of it, we’re all creatures of the troposphere. This atmospheric layer is where almost all weather-related events on planet Earth occur. Although the troposphere begins at the surface of our planet, its upper limit is less consistent. Depending on your latitude and the season you are in, the top of the layer can be anywhere from 7 to 12 kilometers above.
Above the troposphere, respectively; stratosphere, mesosphere, thermosphere and exosphere. Let’s go back and talk about the first two levels.
The troposphere-stratosphere boundary, or tropopause, separates two areas with opposite temperature trends. Inside the troposphere, the global average temperature decreases with altitude. There is a different story in the stratosphere, where everything heats up as it rises. You will reach the ceiling of the stratosphere in about 50 kilometers. From this point on, things start to turn around; because the temperature in the mesosphere begins to drop.
2. The Ozone Layer Is Mostly Limited To The Stratosphere
Ozone gas protects this planet from the extreme ultraviolet (UV) radiation sent by the sun. Composed of oxygen atoms, ozone absorbs UV light – like most sunscreens. Without this critical service, entire ecosystems would fail. Our atmosphere’s gas supply is mostly limited by the famous ozone layer, and about 90 percent of this layer is contained within the stratosphere.
On a related note, ozone explains why stratospheric temperatures rise at higher altitudes. It not only absorbs the Sun’s UV rays, but also absorbs infrared radiation from the troposphere. The result is a glowing stratosphere for miles.
3. Stratospheric Clouds Are Rare
The troposphere is the cloud city. You need water droplets and/or ice crystals to form clouds like cirrus, stratus or cumulonimbus. So the relatively humid troposphere is a great environment for them. But it cannot be said to be so for the stratosphere. Generally too dry to facilitate cloud formation.
Not having a cloud isn’t a bad thing, though. The stratosphere combines (largely) cloudless skies with limited turbulence, making it attractive to airline pilots. Indeed, most commercial aircraft maintain cruising altitudes in the lower stratosphere.
Stratospheric clouds sometimes form when ice mixes with volcanic dust. Also, polar regions see stratosphere-level clouds during the winter months.
4. Stratospheric Polar Vortices Are Major Players in Earth’s Climate
The term “polar vortex” is used a lot these days. But what you might not realize is that the Arctic region has witnessed two different types of polar vortices. The tropospheric polar vortex, rotating all year round, surrounds the North Pole; Its borders are usually located between 40 and 50 degrees north latitude. Traveling from west to east, this jet stream helps separate the cold arctic air and the warm southern currents.
Higher up is the stratospheric polar vortex. Like its counterpart below, this one also moves counterclockwise. But the vortex of the stratosphere is seasonal, collapsing every spring and then forming again in winter.
Winds are strongest when there is a large temperature difference between the North Pole and regions at lower latitudes. But the Arctic is warming rapidly. Some scientists argue that climate change has weakened the stratospheric polar vortex, allowing the extremely cold winds it normally captures to head south. Maybe the same temperature rise is destroying the tropospheric jet.
We would be negligent if we did not acknowledge the Southern Hemisphere’s polar vortex. Located above Antarctica, this vortex is stronger than its northern counterpart.
5. Bacteria Can Survive There
Participants of a study published in the journal Frontiers in Microbiology in August 2018 designed an air-capturing probe placed on a NASA aircraft. The device detected bacteria floating above the local tropopause at an altitude of 12 kilometers.
UV radiation and extreme temperatures make the stratosphere a challenging place for life. Some bacteria will need sun-blocking pigments and protective outer shells to survive there. Rapid DNA repair is another life-saving trick.
Hitchhiking in storms and volcanic eruptions, microbes use the stratosphere as an atmospheric highway. Here, the winds carry them between the continents at great speed, allowing the microbes to disperse. The ability of life to endure our stratosphere, even for limited periods, could profoundly affect its prey for Martian organisms.