La temperatura de la atmósfera terrestre varía con la altitud. La relación entre la altitud y la temperatura es distinta dependiendo de la capa atmosférica considerada: troposfera, estratosfera, mesosfera, termosfera y exosfera. A esto se le llama gradiente térmico atmosférico.

Las divisiones entre una capa y otra se denominan respectivamente tropopausa, estratopausa, mesopausa y termopausa.

Troposphere

Its main features are:

Stratosphere

Its name comes from the fact that it is arranged in more or less horizontal layers (or strata).

It extends between 9 or 18 km up to 50 km in altitude. The stratosphere is the second layer of the Earth's atmosphere. As you go up, the temperature in the stratosphere increases. This increase in temperature is due to the fact that ultraviolet rays transform oxygen into ozone, a process that involves heat: when the air is ionized, it becomes a good conductor of electricity and, therefore, heat. This is why at a certain altitude there is a relative abundance of ozone (ozonosphere), which also implies that the temperature rises to about –3 °C or more. However, it is a very rarefied, very tenuous layer.

The area of ​​the Earth's stratosphere that contains a relatively high concentration of ozone is called the ozone layer, or ozonosphere. This layer, which extends from approximately 15 km to 40 km in altitude, collects 90% of the ozone present in the atmosphere and absorbs 97% to 99% of high-frequency ultraviolet radiation.

Mesosphere

It is the third layer of the Earth's atmosphere. It extends between 50 and 80 km in height, containing only 0.1% of the total air mass. It is the coldest zone of the atmosphere, and can reach –80 °C. It is important because of ionization and the chemical reactions that occur in it. The low density of air in the mesosphere determines the formation of turbulence and atmospheric waves that act on very large spatial and temporal scales.

Thermosphere or ionosphere

In the thermosphere (from 69/90 to 600/800 km), the temperature increases with altitude, hence its name. It practically coincides with the region called the ionosphere. It is the fourth layer of the Earth's atmosphere. It is located above the mesosphere. At this altitude, the air is very thin and the temperature changes with greater or lesser solar radiation both during the day and throughout the year. If the sun is active, temperatures in the thermosphere can reach 1500 °C and even higher. It contains 0.1% of the gases.

In this layer, there is the Kármán Line, which is the limit between atmosphere and outer space, for the purposes of aviation and astronautics.

Exosphere

The last layer of the Earth's atmosphere is the exosphere (600/800-2000/).

It is composed mainly of hydrogen and helium and the particles decrease until they disappear. Due to the low gravitational attraction, some can escape into interplanetary space.

As its name indicates, it is the most distant atmospheric region from the Earth's surface. Its upper limit is at altitudes that reach 1000 and even 10,000 km, being relatively indefinite. It is the transit zone between the Earth's atmosphere and interplanetary space. Its daytime temperature reaches up to 1,500 °C and at night it reaches 0 °C.

Ozonosphere

It is the region of the atmosphere where most of the ozone is concentrated. It is located in the stratosphere, between approximately 15 and 32 km. This layer protects the Earth from ultraviolet radiation from the Sun.

Ionosphere

It is the region ionized by the bombardment produced by solar radiation. The ionization of this layer produces the reflection of the "Wave (physics)") radio waves "Radio (communication medium)") emitted from the Earth's surface, allowing their reception over long distances. It corresponds approximately to the thermosphere.

Magnetosphere

It is the region outside the Earth where the magnetic field, generated by the Earth's core, acts as a protector from the solar winds.

airglow layers

They are layers located near the mesopause, which are characterized by luminescence, even at night, caused by the restructuring of atoms in the form of molecules that had been ionized by sunlight during the day, or by cosmic rays. The main layers are the OH, at about 85 km, and the O, located at about 95 km high, both with an approximate thickness of about 10 km.

A part of Thermodynamics that studies the physical laws and energy flows involved in atmospheric processes is called dynamics of the atmosphere or atmospheric dynamics. These processes present great complexity due to the enormous range of interactions possible both within the atmosphere and with the other parts (solid and liquid) of our planet.

Thermodynamics establishes three laws, in addition to what is known as the zero principle of thermodynamics. These three laws govern the entire physical-natural world and establish the scientific basis of the processes that constitute the field of atmospheric dynamics. Thus, atmospheric dynamics involves all the movements that occur within the Earth's atmosphere and also studies the causes of said movements, their effects and, in general, all the flows of thermal, electrical, physical-chemical, and other types of energy that occur in the air layer that surrounds the Earth.

atmospheric friction

The atmosphere functions as a protective shield against the enormous energy impacts that small space objects can cause when colliding at very high speed against the surface of the planet.

Without an atmosphere, the collision speed of these objects would be the sum of their own inertial space speed (measured from our planet) plus the acceleration caused by the Earth's gravitation.

The kinetic energy of meteorites is transformed into heat by their friction in the air and from the surface we see a meteor "Meteor (astronomy)"), meteorite or also shooting star.

Friction is the macroscopic manifestation of a transfer of kinetic energy, or its transformation into another type of energy, by which one body "loses" movement, giving it to another, either by transferring part of its own movement or by transforming it into molecular movements (heat, sound vibration, etc.).

A body in free fall within the atmosphere can have decreasing velocity, since gravitational attraction produces uniformly accelerated motion only in a vacuum.

If a body begins to fall through the atmosphere, it accelerates until its weight is equal to the friction force produced by the movement through the air. At that moment it stops accelerating, and its speed begins to decrease as the atmosphere increases its density, causing a greater friction force.

It can slow down the rate of fall not only by the density of the atmosphere but also by the variation of the cross-sectional area, which increases friction. Aerial free fall acrobats can vary their fall speed by accelerating or decelerating: if they move upside down they accelerate until their weight balances, and if they open their arms and legs they decelerate.

Biogeochemical cycles

The atmosphere has great importance in biogeochemical cycles. The current composition of the atmosphere is due to the activity of the biosphere (photosynthesis), it controls the climate and the environment in which we live and encompasses two of the three essential elements (nitrogen and carbon); apart from oxygen.

Human activity is modifying its composition, such as the increase in carbon dioxide or methane, causing the greenhouse effect, or nitrogen oxide, causing acid rain.

Solar radiation filter

Harmful solar radiation, such as ultraviolet radiation, is almost 90% absorbed by the ozone layer in the stratosphere. The mutagenic activity of this radiation is very high, causing thymine dimers") that induce the appearance of melanoma in the skin. Without this filter, life outside the protection of water would not be possible.[3]​.

Greenhouse effect

Thanks to the atmosphere, the Earth does not have great thermal contrasts; due to the natural greenhouse effect, which is produced by all the gaseous components of the air, which absorb a large part of the infrared radiation reemitted by the Earth's surface; This heat is retained in the atmosphere instead of being lost in space thanks to two physical characteristics of the air: its compressibility, which compresses the air in contact with the Earth's surface by the own weight of the atmosphere, which, in turn, determines the greater absorption of heat from the air subjected to greater pressure and diathermancy, which means that the atmosphere allows solar radiation to pass through almost without heating (the direct absorption of heat from the sun's rays is very little), while it absorbs a large amount of dark heat ([4]​) forwarded by the terrestrial and, above all, aquatic surface of our planet. This greenhouse effect plays a key role in the planet's mild average temperatures. Thus, taking into account the solar constant (calories that reach the Earth's surface per square centimeter per minute), the average temperature of the planet would be -27 °C, incompatible with life as we know it; On the other hand, its real value is about 15 °C precisely due to the greenhouse effect.[3]​.

La composición de la atmósfera terrestre no ha sido siempre la misma, sino que ha variado a lo largo de la vida del planeta por diversas causas. Además, los elementos ligeros escapan continuamente de la gravedad terrestre; de hecho, en la actualidad se fugan unos tres kilogramos de hidrógeno y 50 gramos de helio cada segundo, cifras que en tiempos geológicos (millones de años) resultan decisivas, aunque compensan, al menos en gran parte, la materia recibida del sol en forma de energía.[5]​ Esta compensación también tiende a equilibrarse en el tiempo, de acuerdo a la mayor o menor energía solar recibida, generando un ciclo complejo, diario, estacional y de ciclos más largos (de acuerdo con la mayor o menor actividad solar) y una respuesta equivalente de la atmósfera en el almacenamiento de dicha energía y su posterior liberación en el espacio. Por ejemplo, la formación del ozono (O) en la capa denominada precisamente, ozonosfera, absorbe la mayor parte de la radiación ultravioleta recibida del sol pero cede esa energía al volverse a transformar durante la noche en oxígeno (O).

Se pueden establecer diferentes etapas evolutivas de la atmósfera según su composición:.

Origin

The atmosphere is derived from various sources, it was and is conditioned by factors such as:

Prebiotic stage

Before life, the atmosphere underwent some important changes:

Microbiological stage

Stage with the appearance of the first anaerobic bacteria (which used H and HS) and photosynthetic bacteria (sulfur bacteria and cyanobacteria):.

Biological stage

Stage with the appearance of eukaryotic organisms with more efficient photosynthesis:.

La variación con la altura de la presión atmosférica con el conocimiento que se tiene del magnetismo o de la densidad atmosférica es lo que se conoce como ley barométrica. La diferencia de presión entre dos capas separadas por un es:.

pues se supone la densidad constante. La ley de la densidad suponiendo el aire como un gas ideal.

aplicada a la superficie de la Tierra resulta una densidad del aire .

En una atmósfera isoterma la presión varía con la altura siguiendo la ley:.

El hecho de que la temperatura varíe sí limita la validez de la fórmula. Por el contrario, la variación de la aceleración de la gravedad es tan mínima que no afecta.

Scale height

The scale height is the height to which one must rise in an atmosphere "Atmosphere (unit)") so that the atmospheric pressure decreases by a factor e = 2.718182. That is, the pressure decrease is 1-1/e = 0.632 (= 63.2%). To calculate it, just put in the Barometric Law it turns out:

For the Earth's atmosphere, the height scale H is about 7.6 km, considering an average temperature of the atmosphere of about 260 K. Depending on the height scale H, the pressure can be expressed:

and similarly for density:.

La temperatura de la atmósfera terrestre varía con la altitud. La relación entre la altitud y la temperatura es distinta dependiendo de la capa atmosférica considerada: troposfera, estratosfera, mesosfera, termosfera y exosfera. A esto se le llama gradiente térmico atmosférico.

Las divisiones entre una capa y otra se denominan respectivamente tropopausa, estratopausa, mesopausa y termopausa.

Troposphere

Its main features are:

Stratosphere

Its name comes from the fact that it is arranged in more or less horizontal layers (or strata).

It extends between 9 or 18 km up to 50 km in altitude. The stratosphere is the second layer of the Earth's atmosphere. As you go up, the temperature in the stratosphere increases. This increase in temperature is due to the fact that ultraviolet rays transform oxygen into ozone, a process that involves heat: when the air is ionized, it becomes a good conductor of electricity and, therefore, heat. This is why at a certain altitude there is a relative abundance of ozone (ozonosphere), which also implies that the temperature rises to about –3 °C or more. However, it is a very rarefied, very tenuous layer.

The area of ​​the Earth's stratosphere that contains a relatively high concentration of ozone is called the ozone layer, or ozonosphere. This layer, which extends from approximately 15 km to 40 km in altitude, collects 90% of the ozone present in the atmosphere and absorbs 97% to 99% of high-frequency ultraviolet radiation.

Mesosphere

It is the third layer of the Earth's atmosphere. It extends between 50 and 80 km in height, containing only 0.1% of the total air mass. It is the coldest zone of the atmosphere, and can reach –80 °C. It is important because of ionization and the chemical reactions that occur in it. The low density of air in the mesosphere determines the formation of turbulence and atmospheric waves that act on very large spatial and temporal scales.

Thermosphere or ionosphere

In the thermosphere (from 69/90 to 600/800 km), the temperature increases with altitude, hence its name. It practically coincides with the region called the ionosphere. It is the fourth layer of the Earth's atmosphere. It is located above the mesosphere. At this altitude, the air is very thin and the temperature changes with greater or lesser solar radiation both during the day and throughout the year. If the sun is active, temperatures in the thermosphere can reach 1500 °C and even higher. It contains 0.1% of the gases.

In this layer, there is the Kármán Line, which is the limit between atmosphere and outer space, for the purposes of aviation and astronautics.

Exosphere

The last layer of the Earth's atmosphere is the exosphere (600/800-2000/).

It is composed mainly of hydrogen and helium and the particles decrease until they disappear. Due to the low gravitational attraction, some can escape into interplanetary space.

As its name indicates, it is the most distant atmospheric region from the Earth's surface. Its upper limit is at altitudes that reach 1000 and even 10,000 km, being relatively indefinite. It is the transit zone between the Earth's atmosphere and interplanetary space. Its daytime temperature reaches up to 1,500 °C and at night it reaches 0 °C.

Ozonosphere

It is the region of the atmosphere where most of the ozone is concentrated. It is located in the stratosphere, between approximately 15 and 32 km. This layer protects the Earth from ultraviolet radiation from the Sun.

Ionosphere

It is the region ionized by the bombardment produced by solar radiation. The ionization of this layer produces the reflection of the "Wave (physics)") radio waves "Radio (communication medium)") emitted from the Earth's surface, allowing their reception over long distances. It corresponds approximately to the thermosphere.

Magnetosphere

It is the region outside the Earth where the magnetic field, generated by the Earth's core, acts as a protector from the solar winds.

airglow layers

They are layers located near the mesopause, which are characterized by luminescence, even at night, caused by the restructuring of atoms in the form of molecules that had been ionized by sunlight during the day, or by cosmic rays. The main layers are the OH, at about 85 km, and the O, located at about 95 km high, both with an approximate thickness of about 10 km.

A part of Thermodynamics that studies the physical laws and energy flows involved in atmospheric processes is called dynamics of the atmosphere or atmospheric dynamics. These processes present great complexity due to the enormous range of interactions possible both within the atmosphere and with the other parts (solid and liquid) of our planet.

Thermodynamics establishes three laws, in addition to what is known as the zero principle of thermodynamics. These three laws govern the entire physical-natural world and establish the scientific basis of the processes that constitute the field of atmospheric dynamics. Thus, atmospheric dynamics involves all the movements that occur within the Earth's atmosphere and also studies the causes of said movements, their effects and, in general, all the flows of thermal, electrical, physical-chemical, and other types of energy that occur in the air layer that surrounds the Earth.

atmospheric friction

The atmosphere functions as a protective shield against the enormous energy impacts that small space objects can cause when colliding at very high speed against the surface of the planet.

Without an atmosphere, the collision speed of these objects would be the sum of their own inertial space speed (measured from our planet) plus the acceleration caused by the Earth's gravitation.

The kinetic energy of meteorites is transformed into heat by their friction in the air and from the surface we see a meteor "Meteor (astronomy)"), meteorite or also shooting star.

Friction is the macroscopic manifestation of a transfer of kinetic energy, or its transformation into another type of energy, by which one body "loses" movement, giving it to another, either by transferring part of its own movement or by transforming it into molecular movements (heat, sound vibration, etc.).

A body in free fall within the atmosphere can have decreasing velocity, since gravitational attraction produces uniformly accelerated motion only in a vacuum.

If a body begins to fall through the atmosphere, it accelerates until its weight is equal to the friction force produced by the movement through the air. At that moment it stops accelerating, and its speed begins to decrease as the atmosphere increases its density, causing a greater friction force.

It can slow down the rate of fall not only by the density of the atmosphere but also by the variation of the cross-sectional area, which increases friction. Aerial free fall acrobats can vary their fall speed by accelerating or decelerating: if they move upside down they accelerate until their weight balances, and if they open their arms and legs they decelerate.

Biogeochemical cycles

The atmosphere has great importance in biogeochemical cycles. The current composition of the atmosphere is due to the activity of the biosphere (photosynthesis), it controls the climate and the environment in which we live and encompasses two of the three essential elements (nitrogen and carbon); apart from oxygen.

Human activity is modifying its composition, such as the increase in carbon dioxide or methane, causing the greenhouse effect, or nitrogen oxide, causing acid rain.

Solar radiation filter

Harmful solar radiation, such as ultraviolet radiation, is almost 90% absorbed by the ozone layer in the stratosphere. The mutagenic activity of this radiation is very high, causing thymine dimers") that induce the appearance of melanoma in the skin. Without this filter, life outside the protection of water would not be possible.[3]​.

Greenhouse effect

Thanks to the atmosphere, the Earth does not have great thermal contrasts; due to the natural greenhouse effect, which is produced by all the gaseous components of the air, which absorb a large part of the infrared radiation reemitted by the Earth's surface; This heat is retained in the atmosphere instead of being lost in space thanks to two physical characteristics of the air: its compressibility, which compresses the air in contact with the Earth's surface by the own weight of the atmosphere, which, in turn, determines the greater absorption of heat from the air subjected to greater pressure and diathermancy, which means that the atmosphere allows solar radiation to pass through almost without heating (the direct absorption of heat from the sun's rays is very little), while it absorbs a large amount of dark heat ([4]​) forwarded by the terrestrial and, above all, aquatic surface of our planet. This greenhouse effect plays a key role in the planet's mild average temperatures. Thus, taking into account the solar constant (calories that reach the Earth's surface per square centimeter per minute), the average temperature of the planet would be -27 °C, incompatible with life as we know it; On the other hand, its real value is about 15 °C precisely due to the greenhouse effect.[3]​.

La composición de la atmósfera terrestre no ha sido siempre la misma, sino que ha variado a lo largo de la vida del planeta por diversas causas. Además, los elementos ligeros escapan continuamente de la gravedad terrestre; de hecho, en la actualidad se fugan unos tres kilogramos de hidrógeno y 50 gramos de helio cada segundo, cifras que en tiempos geológicos (millones de años) resultan decisivas, aunque compensan, al menos en gran parte, la materia recibida del sol en forma de energía.[5]​ Esta compensación también tiende a equilibrarse en el tiempo, de acuerdo a la mayor o menor energía solar recibida, generando un ciclo complejo, diario, estacional y de ciclos más largos (de acuerdo con la mayor o menor actividad solar) y una respuesta equivalente de la atmósfera en el almacenamiento de dicha energía y su posterior liberación en el espacio. Por ejemplo, la formación del ozono (O) en la capa denominada precisamente, ozonosfera, absorbe la mayor parte de la radiación ultravioleta recibida del sol pero cede esa energía al volverse a transformar durante la noche en oxígeno (O).

Se pueden establecer diferentes etapas evolutivas de la atmósfera según su composición:.

Origin

The atmosphere is derived from various sources, it was and is conditioned by factors such as:

Prebiotic stage

Before life, the atmosphere underwent some important changes:

Microbiological stage

Stage with the appearance of the first anaerobic bacteria (which used H and HS) and photosynthetic bacteria (sulfur bacteria and cyanobacteria):.

Biological stage

Stage with the appearance of eukaryotic organisms with more efficient photosynthesis:.