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 is one of the lower layers of the atmosphere of the planet Earth , located between the troposphere and 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.
It is the atmospheric stratum in which the 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, as essential for life as we know it. It also contains 19% of the total atmospheric gases, and represents 24% of the total mass of the atmosphere .
Before the stratosphere begins, the tropopause is found, 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.
In the initial portions of the stratosphere, the temperature remains constant, that is, it is isothermal, holding the -60 degrees Celsius that usually exists in the tropopause.
However, as the height increases the temperatures to rise, reaching 0 ° C or even 17 ° C in some regions of the globe, due to the amount of energy absorbed by the ozone molecules in this region and is trapped. Due to all of the above, the stratosphere is a region with very little moisture margin .
In the stratosphere the mixture of air gases is much faster in horizontal than vertical conditions, so it is composed of fairly homogeneous and identifiable strata . Near the end of it is the ozone layer, under conditions of pressure and temperature that allow the formation of these unstable molecules from oxygen (O 3 ).
Due to the difference in heat between the stratosphere and the layers that precede and happen, 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 at almost 30 kilometers thick.
This substance is formed due to the action of ultraviolet rays on atmospheric oxygen. It shares the space with other more complex and long-lived compounds, such as chlorofluorocarbons (CFCs) and nitrogen and sulfur-rich compounds, some of which come from volcanic eruptions of yesteryear, and others from the contaminating 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 fundamental for the climatic and biotic stability of the planet, since it supports 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 the evaporation of the water and also bathing with carcinogenic ultraviolet radiation to all living beings . In that sense, the stratosphere acts as a protective shield Earth from the sun .
On the other hand, it is a slightly turbulent layer, which facilitates air transport , especially in its lower layers, since it does not give an intense mixture of air components.
Perhaps the most important element of the stratosphere is the ozone layer , which absorbs a significant percentage of the solar radiation that enters Earth from space.
Such radiation, if directly impacted on 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 (about 3 ozone molecules per 10 million air molecules) is essential for the biotic support of the planet .
The ozone layer, however, has been threatened several times . Many of them as a result of volcanic explosions and other similar phenomena that threw tons of sulfur-rich materials and other chemical elements that react with ozone into the atmosphere, decreasing their presence.
On other occasions, however, the creation of “holes” in the ozone layer, that is, of unprotected regions, was due to the indiscriminate use by mankind of chlorofluorocarbonated gases (CFCs) in aerosols and cooling gases, which, when escaping upwards, are stored in the stratosphere preventing the formation of ozone.
The latter unleashed the alarms of the ecological community at the end of the 20th century, at levels such that it was possible to prohibit or limit the use of these substances and thus allow the ozone layer to replenish naturally.
Since 2000, it is estimated that the presence of these compounds in the atmosphere has decreased at an annual rate of 1%, so there is hope that, by mid-century, the ozone layer has been restored almost entirely.