Atmosphere of Earth

The atmosphere of Earth, ordinarily known as air, is a layer of liquid water to equal on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention greenhouse effect, as well as reducing temperature extremes between day as well as night the diurnal temperature variation.

By carbon dioxide, together with small amounts of other gases. Air also contains a variable amount of ]

Earth's early atmosphere consisted of gases in the atmospheric changes, such(a) as global warming, ozone depletion and acid deposition.

The atmosphere has a mass of approximately 5.15×10^{18 kg, three quarters of which is within about 11 km 6.8 mi; 36,000 ft of the surface. The atmosphere becomes thinner with increasing altitude, with no definite boundary between the atmosphere and atmospheric reentry of spacecraft at an altitude of around 120 km 75 mi. Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition.}

The explore of Earth's atmosphere and its processes is called atmospheric science aerology, and includes multinational subfields, such(a) as climatology and atmospheric physics. Early pioneers in the field put Léon Teisserenc de Bort and Richard Assmann. The explore of historic atmosphere is called paleoclimatology.

Stratification

In general, air pressure and density decrease with altitude in the atmosphere. However, the temperature has a more complicated design with altitude, and may remain relatively fixed or even increase with altitude in some regions see the temperature section, below. Because the general sample of the temperature/altitude profile, or lapse rate, is fixed and measurable by means of instrumented balloon soundings, the temperature behavior helps a useful metric to distinguish atmospheric layers. In this way, Earth's atmosphere can be dual-lane up called atmospheric stratification into five main layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere. The altitudes of the five layers are as follows:

The exosphere is the outermost layer of Earth's atmosphere i.e. the upper limit of the atmosphere. It extends from the solar wind.

This layer is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen and carbon dioxide closer to the exobase. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another. Thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles undertake ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind.

The exosphere is too far above Earth for meteorological phenomena to be possible. However, Earth's auroras—the aurora borealis northern lights and aurora australis southern lights—sometimes arise in the lower part of the exosphere, where they overlap into the thermosphere. The exosphere contains numerous of the artificial satellites that orbit Earth.

The thermosphere is the second-highest layer of Earth's atmosphere. It extends from the mesopause which separates it from the mesosphere at an altitude of about 80 km 50 mi; 260,000 ft up to the exobase. The lower component of the thermosphere, from 80 to 550 kilometres 50 to 342 mi above Earth's surface, contains the ionosphere.

The temperature of the thermosphere gradually increases with height and can rise as high as 1500 °C 2700 °F, though the gas molecules are so far apart that its temperature in the usual sense is not very meaningful. The air is so rarefied that an individual molecule of oxygen, for example travels an average of 1 kilometre 0.62 mi; 3300 ft between collisions with other molecules. Although the thermosphere has a high proportion of molecules with high energy, it would not feel hot to a human in direct contact, because its density is too low to extend a significant amount of energy to or from the skin.

This layer is completely cloudless and free of water vapor. However, non-hydrometeorological phenomena such as the aurora borealis and aurora australis are occasionally seen in the thermosphere. The International Space Station orbits in this layer, between 350 and 420 km 220 and 260 mi. it is for this layer where numerous of the satellites orbiting the earth are present.

The mesosphere is the third highest layer of Earth's atmosphere, occupying the region above the stratosphere and below the thermosphere. It extends from the stratopause at an altitude of about 50 km 31 mi; 160,000 ft to the mesopause at 80–85 km 50–53 mi; 260,000–280,000 ft above sea level.

Temperatures drop with increasing altitude to the °C −120 K.

Just below the mesopause, the air is so cold that even the very scarce water vapor at this altitude can sublimate into polar-mesospheric noctilucent clouds of ice particles. These are the highest clouds in the atmosphere and may be visible to the naked eye whether sunlight reflects off them about an hour or two after sunset or similarly ago sunrise. They are near readily visible when the Sun is around 4 to 16 degrees below the horizon. Lightning-induced discharges asked as transient luminous events TLEs occasionally form in the mesosphere above tropospheric thunderclouds. The mesosphere is also the layer where most meteors burn up upon atmospheric entrance. it is too high above Earth to be accessible to jet-powered aircraft and balloons, and too low to permit orbital spacecraft. The mesosphere is mainly accessed by sounding rockets and rocket-powered aircraft.

The stratosphere is the second-lowest layer of Earth's atmosphere. It lies above the troposphere and is separated from it by the stratopause at an altitude of about 50 to 55 km 31 to 34 mi; 164,000 to 180,000 ft.

The atmospheric pressure at the top of the stratosphere is roughly 1/1000 the pressure at sea level. It contains the ozone layer, which is the part of Earth's atmosphere that contains relatively high concentrations of that gas. The stratosphere defines a layer in which temperatures rise with increasing altitude. This rise in temperature is caused by the absorption of ultraviolet radiation UV radiation from the Sun by the ozone layer, which restricts turbulence and mixing. Although the temperature may be −60 °C −76 °F; 210 K at the tropopause, the top of the stratosphere is much warmer, and may be near 0 °C.

The stratospheric temperature array creates veryatmospheric conditions, so the stratosphere lacks the weather-producing air turbulence that is so prevalent in the troposphere. Consequently, the stratosphere is almost completely free of clouds and other forms of weather. However, polar stratospheric or nacreous clouds are occasionally seen in the lower part of this layer of the atmosphere where the air is coldest. The stratosphere is the highest layer that can be accessed by jet-powered aircraft.

The troposphere is the lowest layer of Earth's atmosphere. It extends from Earth's surface to an average height of about 12 km 7.5 mi; 39,000 ft, although this geographic poles to 17 km 11 mi; 56,000 ft at the Equator, with some variation due to weather. The troposphere is bounded above by the tropopause, a boundary marked in most places by a temperature inversion i.e. a layer of relatively warm air above a colder one, and in others by a zone that is isothermal with height.

Although variations defecate occur, the temperature usually declines with increasing altitude in the troposphere because the troposphere is mostly heated through energy transfer from the surface. Thus, the lowest part of the troposphere i.e. Earth's surface is typically the warmest piece of the troposphere. This promotes vertical mixing hence, the origin of its name in the Greek word τρόπος, tropos, meaning "turn". The troposphere contains roughly 80% of the mass of Earth's atmosphere. The troposphere is denser than all its overlying layers because a larger atmospheric weight sits on top of the troposphere and causes it to be most severely compressed. Fifty percent of the or situation. mass of the atmosphere is located in the lower 5.6 km 3.5 mi; 18,000 ft of the troposphere.

Nearly all atmospheric water vapor or moisture is found in the troposphere, so it is the layer where most of Earth's weather takes place. It has basically all the weather-associated cloud genus classification generated by active wind circulation, although very tall cumulonimbus thunder clouds can penetrate the tropopause from below and rise into the lower part of the stratosphere. Most conventional aviation activity takes place in the troposphere, and it is the only layer that can be accessed by propeller-driven aircraft.

Within the five principal layers above, which are largely determined by temperature, several secondary layers may be distinguished by other properties:

The average temperature of the atmosphere at Earth's surface is 14 °C 57 °F; 287 K or 15 °C 59 °F; 288 K, depending on the reference.