We explain what the stratosphere is, how it is composed, its importance and other characteristics. Also, what is the ozone layer.
What is the stratosphere?
The stratosphere or stratosphere It is one of the lower layers of the atmosphere of planet Earth located between the troposphere and the mesosphere. It is located at a variable altitude between 9 kilometers high (in the polar regions) or 20 kilometers high (in the equatorial region), and 50 kilometers high.
This is the atmospheric stratum in which weather balloons fly, and most commercial flights. Only some species of birds and some aerial bacteria inhabit this region.
On the other hand, in the stratosphere is the ozone layer, so essential for life as we know it. It also contains 19% of total atmospheric gases, and represents 24% of the total mass of the atmosphere.
Before beginning the stratosphere, there is the tropopause, which is the transitional region of the troposphere; similar to the stratopause that marks the end of the stratosphere and the beginning of the mesosphere.
Features of the stratosphere
In the initial portions of the stratosphere, the temperature remains constant, that is, it is isothermal, maintaining the -60 degrees Celsius that usually exists in the tropopause.
However, As altitude increases, temperatures rise, until they reach 0 °C or even 17 °C in some regions of the globe, due to the amount of energy that the ozone molecules in this region absorb and become trapped. Due to all of the above, the stratosphere It is a region with very little humidity margin.
In the stratosphere, the mixing of gases in the air is much faster in horizontal conditions than in vertical conditions, which is why It is composed of fairly homogeneous and identifiable strata. Almost at the end of it is the ozone layer, under conditions of pressure and temperature that allow the formation of these unstable molecules from oxygen (O3).
Composition of the stratosphere
Due to the heat difference between the stratosphere and the layers that precede and succeed it, there is little gas exchange between them. This causes the absence of water vapor in the stratosphere, which translates into the almost total absence of clouds.
The most abundant compound in this entire region is ozone: Almost all of the ozone in the atmosphere is concentrated in its almost 30 kilometers of thickness.
This substance is formed due to the action of ultraviolet rays on atmospheric oxygen. It shares space with other more complex and long-lived compounds, such as chlorofluorocarbons (CFCs) and compounds rich in nitrogen and sulfur, some of which come from ancient volcanic eruptions, and others from the polluting action of human beings.
There is also a certain content of halogen oxides and nitric acid and sulfuric acid in the stratosphere.
Importance of the stratosphere
This atmospheric region is critical to the planet's climatic and biotic stability, supporting an enormous amount of energy that would otherwise be received directly by the surface.
Without the stratosphere, the heat would increase considerably, destabilizing the climate by melting the poles, increasing water evaporation and also bathing all living beings in carcinogenic ultraviolet radiation. In that sense, the stratosphere It acts as a protective shield for the Earth against the Sun.
On the other hand, it is a slightly turbulent layer, which facilitates air transport, especially in its lower layers, since there is no intense mixing of air components.
Ozone layer
Perhaps the most important element of the stratosphere is the ozone layer, which absorbs a significant percentage of solar radiation that enters Earth from space.
Such radiation, if it directly impacts the Earth's surface, would have harmful consequences for life and for the world's climatic stability. Therefore, the presence of this thin envelope of gases (around 3 molecules of ozone per 10 million molecules of air) It is essential for the biotic support of the planet.
The ozone layer, however, has been threatened on several occasions. Many of them as a consequence of volcanic explosions and other similar phenomena that threw tons of materials rich in sulfur and other chemical elements into the atmosphere that react with ozone, reducing its presence.
On other occasions, however, the creation of “holes” in the ozone layer, that is, unprotected regions, was due to humanity's indiscriminate use of chlorofluorocarbon gases (CFCs) in aerosols and refrigeration gases, which, upon escaping upward, are stored in the stratosphere, preventing the formation of ozone.
The latter triggered alarms in the ecological community at the end of the 20th century, to such levels that it was possible to prohibit or limit the use of these substances and thus allow the ozone layer to be replenished naturally.
Since 2000, it is estimated that the presence of these compounds in the atmosphere has decreased at a rate of 1% per year, so there is hope that, by mid-century, the ozone layer will have been almost completely restored. .
Continue in: Ozone Layer
References
- “Stratosphere” on Wikipedia.
- “Characteristics and importance of the stratosphere” in Online Meteorology.
- “Stratosphere” at NASA Space Place (Spanish).
- “What is the stratosphere?” (video) by Simon Clark.
- “Stratosphere” in The Encyclopaedia Britannica.
