The atmosphere and its functions on planet earth
The atmosphere: it is the layer of gases that is around the Earth, avoiding that the rays of the sun cross it, giving rise to the life. The atmosphere is also involved in the rain, allowing the plants to grow, and provide us with oxygen to breathe.
The atmosphere protects life on Earth by absorbing a large part of the ultraviolet solar radiation in the ozone layer. In addition, acts as a protective shield against meteorites, which are crushed into dust because of the friction they suffer when making contact with air.
For millions of years, life has transformed the composition of the atmosphere over and over again.
For example, its considerable amount of free oxygen is possible thanks to life forms, such as plants, which convert carbon dioxide into oxygen, which is respirable, in turn, by other forms of life, such as human beings and animals in general. Likewise, next to the hydrosphere, it constitutes the system of superficial fluid layers of the planet, whose dynamic movements are closely related.
The air currents drastically reduce the temperature differences between day and night, distributing heat throughout the planet's surface.
It has a thickness of approximately 1000 kilometers and in turn is divided into several successive concentric layers, which extend from the surface of the planet to outer space. Based on a classification based on the temperature distribution, we can divide it into troposphere, stratosphere, mesosphere and thermosphere.
The following describes the classification of the layers of the atmosphere based on the distribution of temperatures and as a function of height. In this way we can distinguish those indicated below.
The lower or troposphere layer extends from the surface to about 10-15 km altitude (lower at the poles and higher at the equator). It contains approximately 75% of the mass of total gases that make up the atmosphere.
In this layer the temperature decreases with altitude. Each 100 m ascent decreases the temperature 0.64 ºC.
Tropospheric temperature
In general, we can consider that the troposphere has a homogeneous composition, since there is a continuous mixture of gases due to differences in pressures, which cause a global circulation of large masses of air on Earth. Also at the local level, depending on the relief and meteorology of the area movements and mixtures of air masses are produced.
In this layer, where important vertical and horizontal movements of air masses (winds) occur, most of the pollutants are dispersed and this is where the meteorological phenomena take place.
At the upper end of the troposphere is the tropopause, an ideal surface that marks the beginning of the stratosphere, at a height where the temperature reaches approximately -57ºC.
The stratosphere extends from the tropopause (15 km altitude) to the stratopause (50 km altitude). In it we can distinguish two parts: the lower stratosphere, in which the temperature remains constant, and the upper stratosphere, in which the temperature increases as we ascend can reach 60C at its highest point, coinciding with the stratopause.
The temperature increase in the stratosphere is due to the presence of ozone (O3). This is located approximately at a height range of 20 to 40 kilometers and has the property of absorbing a large part of the ultraviolet radiation (with a λ less than 360 nm) that come from the sun, in this way this heating effect occurs.
Above the stratopause is the mesosphere, this layer extends over 50 kilometers, here the temperature drops again to a minimum of 85ºC at a height of 80 kilometers. The mesopause is located on the mesosphere.
Next, we find the thermosphere, or ionosphere. Ultraviolet radiation plays a fundamental role in this layer, due to its ability to dissociate existing nitrogen and oxygen molecules. The temperature rises again reaching temperatures of up to approximately 1,500ºC due to the absorption of these high energy radiations.
The gases are strongly ionized, this ionization increases with height and reaches several maximums called layers: layer D, base of the ionosphere; E layer of Kennelly-Heavyside, 120 km; F layer or Appleton, 160 km and the Fr layer from 260 to 350 km.
These ionized layers are conductive of electricity and reflect the hertzian waves, mainly the short wave.
From 600 to 800 km, begins the outer layer or exosphere, which only contains 1% of the total mass of the atmosphere. Their gases are in the atomic state and can extend up to 1200 km.
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