Atmosphere of Earth

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Blue light is scattered more than other wavelengths by the gases in the atmosphere, surrounding Earth in a visibly blue layer at the stratosphere, above the clouds of the troposphere, when seen from space on board the ISS at an altitude of 335 km (208 mi) (the Moon is visible as a crescent in the far background). Top of Atmosphere.jpg
Blue light is scattered more than other wavelengths by the gases in the atmosphere, surrounding Earth in a visibly blue layer at the stratosphere, above the clouds of the troposphere, when seen from space on board the ISS at an altitude of 335 km (208 mi) (the Moon is visible as a crescent in the far background).

The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth creates pressure, absorbs most meteoroids and ultraviolet solar radiation, warms the surface through heat retention (greenhouse effect), allowing life and liquid water to exist on the Earth's surface, and reduces temperature extremes between day and night (the diurnal temperature variation).

Contents

As of 2023, by mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. [8] Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude. Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere.[ citation needed ]

Earth's early atmosphere consisted of gases in the solar nebula, primarily hydrogen. The atmosphere changed significantly over time, affected by many factors such as volcanism, life, and weathering. Recently, human activity has also contributed to atmospheric changes, such as global warming, ozone depletion and acid deposition.

The atmosphere has a mass of about 5.15×1018 kg, [9] 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 outer space. The Kármán line, at 100 km (62 mi) or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during 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 study of Earth's atmosphere and its processes is called atmospheric science (aerology), and includes multiple subfields, such as climatology and atmospheric physics. Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. [10] The study of historic atmosphere is called paleoclimatology.

Composition

Composition of Earth's atmosphere by molecular count, excluding water vapor. Lower pie represents trace gases that together compose about 0.0434% of the atmosphere (0.0442% at August 2021 concentrations ). Numbers are mainly from 2000, with CO2 and methane from 2019, and do not represent any single source. Atmosphere gas proportions.svg
Composition of Earth's atmosphere by molecular count, excluding water vapor. Lower pie represents trace gases that together compose about 0.0434% of the atmosphere (0.0442% at August 2021 concentrations ). Numbers are mainly from 2000, with CO2 and methane from 2019, and do not represent any single source.

The three major constituents of Earth's atmosphere are nitrogen, oxygen, and argon. Water vapor accounts for roughly 0.25% of the atmosphere by mass. The concentration of water vapor (a greenhouse gas) varies significantly from around 10 ppm by mole fraction in the coldest portions of the atmosphere to as much as 5% by mole fraction in hot, humid air masses, and concentrations of other atmospheric gases are typically quoted in terms of dry air (without water vapor). [11] : 8  The remaining gases are often referred to as trace gases, [12] among which are other greenhouse gases, principally carbon dioxide, methane, nitrous oxide, and ozone. Besides argon, already mentioned, other noble gases, neon, helium, krypton, and xenon are also present. Filtered air includes trace amounts of many other chemical compounds. Many substances of natural origin may be present in locally and seasonally variable small amounts as aerosols in an unfiltered air sample, including dust of mineral and organic composition, pollen and spores, sea spray, and volcanic ash. Various industrial pollutants also may be present as gases or aerosols, such as chlorine (elemental or in compounds), fluorine compounds and elemental mercury vapor. Sulfur compounds such as hydrogen sulfide and sulfur dioxide (SO2) may be derived from natural sources or from industrial air pollution.

Major constituents of air, by mole fraction [8]
Dry air
GasMole fraction(A)
NameFormulain ppm (B)in %
Nitrogen N2780,84078.084
Oxygen O2209,46020.946
Argon Ar9,3400.9340
Carbon dioxide
(April 2022)(C) [13] 		CO24170.0417
Neon Ne18.180.001818
Helium He5.240.000524
Methane CH41.870.000187
Krypton Kr1.140.000114
If air is not dry:
Water vapor (D)H2O0–30,000(D)0–3%(E)
notes:

The average molecular weight of dry air, which can be used to calculate densities or to convert between mole fraction and mass fraction, is about 28.946 [14] or 28.96 [15] [16]  g/mol. This is decreased when the air is humid.

The relative concentration of gases remains constant until about 10,000 m (33,000 ft). [17]

Stratification

Earth's atmosphere. Lower four layers of the atmosphere in three dimensions as seen diagonally from above the exobase. Layers drawn to scale, objects within the layers are not to scale. Aurorae shown here at the bottom of the thermosphere can actually form at any altitude in this atmospheric layer. Earth's atmosphere.svg
Earth's atmosphere. Lower four layers of the atmosphere in three dimensions as seen diagonally from above the exobase. Layers drawn to scale, objects within the layers are not to scale. Aurorae shown here at the bottom of the thermosphere can actually form at any altitude in this atmospheric layer.

In general, air pressure and density decrease with altitude in the atmosphere. However, the temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions (see the temperature section, below). Because the general pattern of the temperature/altitude profile, or lapse rate, is constant and measurable by means of instrumented balloon soundings, the temperature behavior provides a useful metric to distinguish atmospheric layers. In this way, Earth's atmosphere can be divided (called atmospheric stratification) into five main layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere. [18] The altitudes of the five layers are as follows:

Exosphere

The exosphere is the outermost layer of Earth's atmosphere (though it is so tenuous that some scientists consider it to be part of interplanetary space rather than part of the atmosphere). It extends from the thermopause (also known as the "exobase") at the top of the thermosphere to a poorly defined boundary with the solar wind and interplanetary medium. The altitude of the exobase varies from about 500 kilometres (310 mi; 1,600,000 ft) to about 1,000 kilometres (620 mi) in times of higher incoming solar radiation. [22]

The upper limit varies depending on the definition. Various authorities consider it to end at about 10,000 kilometres (6,200 mi) [23] or about 190,000 kilometres (120,000 mi)—about halfway to the moon, where the influence of Earth's gravity is about the same as radiation pressure from sunlight. [22] The geocorona visible in the far ultraviolet (caused by neutral hydrogen) extends to at least 100,000 kilometres (62,000 mi). [22]

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 kilometres 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 follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind. Every second, the Earth loses about 3 kg of hydrogen, 50 g of helium, and much smaller amounts of other constituents. [24]

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 occur in the lower part of the exosphere, where they overlap into the thermosphere. The exosphere contains many of the artificial satellites that orbit Earth.

Thermosphere

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 thermopause at an altitude range of 500–1000 km (310–620 mi; 1,600,000–3,300,000 ft). The height of the thermopause varies considerably due to changes in solar activity. [20] Because the thermopause lies at the lower boundary of the exosphere, it is also referred to as the exobase. The lower part 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. [25] 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 conduct 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 this layer where many of the satellites orbiting the Earth are present.

Mesosphere

Afterglow of the troposphere (orange), the stratosphere (blue) and the mesosphere (dark) at which atmospheric entry begins, leaving smoke trails, such as in this case of a spacecraft reentry. ISS-46 Soyuz TMA-17M reentry.jpg
Afterglow of the troposphere (orange), the stratosphere (blue) and the mesosphere (dark) at which atmospheric entry begins, leaving smoke trails, such as in this case of a spacecraft reentry.

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 mesopause that marks the top of this middle layer of the atmosphere. It is the coldest place on Earth and has an average temperature around −85  °C (−120  °F ; 190  K ). [26] [27]

Just below the mesopause, the air is so cold that even the very scarce water vapor at this altitude can condense into polar-mesospheric noctilucent clouds of ice particles. These are the highest clouds in the atmosphere and may be visible to the naked eye if sunlight reflects off them about an hour or two after sunset or similarly before sunrise. They are most readily visible when the Sun is around 4 to 16 degrees below the horizon. Lightning-induced discharges known 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.

Stratosphere

The stratosphere is the second-lowest layer of Earth's atmosphere. It lies above the troposphere and is separated from it by the tropopause. This layer extends from the top of the troposphere at roughly 12 km (7.5 mi; 39,000 ft) above Earth's surface to 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) 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. [28]

The stratospheric temperature profile creates very stable atmospheric 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.

Troposphere

A picture of Earth's troposphere with its different cloud types of low to high altitudes casting shadows. Sunlight is reflected off the ocean, after it was filtered into a redish light by passing through much of the troposphere at sunset. The above lying stratosphere can be seen at the horizon as a band of its characteristic glow of blue scattered sunlight. ISS-47 Islands In The Sky, Indonesia.jpg
A picture of Earth's troposphere with its different cloud types of low to high altitudes casting shadows. Sunlight is reflected off the ocean, after it was filtered into a redish light by passing through much of the troposphere at sunset. The above lying stratosphere can be seen at the horizon as a band of its characteristic glow of blue scattered sunlight.

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 altitude varies from about 9 km (5.6 mi; 30,000 ft) at the geographic poles to 17 km (11 mi; 56,000 ft) at the Equator, [21] 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. [29] [30]

Although variations do 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 section 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. [31] 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 total 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 types 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 accessible by propeller-driven aircraft.

Other layers

The volume fraction of the main gases in Earth's atmosphere according to height. The boundary between the homosphere (left) and heterosphere (right) is at about 100 km. The outermost layer of the exosphere (off the chart) is dominated by hydrogen. Msis atmospheric composition by height.svg
The volume fraction of the main gases in Earth's atmosphere according to height. The boundary between the homosphere (left) and heterosphere (right) is at about 100 km. The outermost layer of the exosphere (off the chart) is dominated by hydrogen.

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

Above this altitude lies the heterosphere, which includes the exosphere and most of the thermosphere. Here, the chemical composition varies with altitude. This is because the distance that particles can move without colliding with one another is large compared with the size of motions that cause mixing. This allows the gases to stratify by molecular weight, with the heavier ones, such as oxygen and nitrogen, present only near the bottom of the heterosphere. The upper part of the heterosphere is composed almost completely of hydrogen, the lightest element. [32]

The average temperature of the atmosphere at Earth's surface is 14 °C (57 °F; 287 K) [34] or 15 °C (59 °F; 288 K), [35] depending on the reference. [36] [37] [38]

Physical properties

Comparison of the 1962 US Standard Atmosphere graph of geometric altitude against air density, pressure, the speed of sound and temperature with approximate altitudes of various objects. Comparison US standard atmosphere 1962.svg
Comparison of the 1962 US Standard Atmosphere graph of geometric altitude against air density, pressure, the speed of sound and temperature with approximate altitudes of various objects.

Pressure and thickness

The average atmospheric pressure at sea level is defined by the International Standard Atmosphere as 101325 pascals (760.00  Torr ; 14.6959  psi ; 760.00  mmHg ). This is sometimes referred to as a unit of standard atmospheres (atm). Total atmospheric mass is 5.1480×1018 kg (1.135×1019 lb), [40] about 2.5% less than would be inferred from the average sea level pressure and Earth's area of 51007.2 megahectares, this portion being displaced by Earth's mountainous terrain. Atmospheric pressure is the total weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and weather.

If the entire mass of the atmosphere had a uniform density equal to sea level density (about 1.2 kg per m3) from sea level upwards, it would terminate abruptly at an altitude of 8.50 km (27,900 ft).

Air pressure actually decreases exponentially with altitude, dropping by half every 5.6 km (18,000 ft) or by a factor of 1/e (0.368) every 7.64 km (25,100 ft), (this is called the scale height) -- for altitudes out to around 70 km (43 mi; 230,000 ft). However, the atmosphere is more accurately modeled with a customized equation for each layer that takes gradients of temperature, molecular composition, solar radiation and gravity into account. At heights over 100 km, an atmosphere may no longer be well mixed. Then each chemical species has its own scale height.

In summary, the mass of Earth's atmosphere is distributed approximately as follows: [41]

By comparison, the summit of Mount Everest is at 8,848 m (29,029 ft); commercial airliners typically cruise between 10 and 13 km (33,000 and 43,000 ft) where the lower density and temperature of the air improve fuel economy; weather balloons reach 30.4 km (100,000 ft) and above; and the highest X-15 flight in 1963 reached 108.0 km (354,300 ft).

Even above the Kármán line, significant atmospheric effects such as auroras still occur. Meteors begin to glow in this region, though the larger ones may not burn up until they penetrate more deeply. The various layers of Earth's ionosphere, important to HF radio propagation, begin below 100 km and extend beyond 500 km. By comparison, the International Space Station and Space Shuttle typically orbit at 350–400 km, within the F-layer of the ionosphere where they encounter enough atmospheric drag to require reboosts every few months, otherwise, orbital decay will occur resulting in a return to Earth. Depending on solar activity, satellites can experience noticeable atmospheric drag at altitudes as high as 700–800 km.

Temperature

Temperature trends in two thick layers of the atmosphere as measured between January 1979 and December 2005 by microwave sounding units and advanced microwave sounding units on NOAA weather satellites. The instruments record microwaves emitted from oxygen molecules in the atmosphere. Source: Atmospheric Temperature Trend.jpg
Temperature trends in two thick layers of the atmosphere as measured between January 1979 and December 2005 by microwave sounding units and advanced microwave sounding units on NOAA weather satellites. The instruments record microwaves emitted from oxygen molecules in the atmosphere. Source:

The division of the atmosphere into layers mostly by reference to temperature is discussed above. Temperature decreases with altitude starting at sea level, but variations in this trend begin above 11 km, where the temperature stabilizes over a large vertical distance through the rest of the troposphere. In the stratosphere, starting above about 20 km, the temperature increases with height, due to heating within the ozone layer caused by the capture of significant ultraviolet radiation from the Sun by the dioxygen and ozone gas in this region. Still another region of increasing temperature with altitude occurs at very high altitudes, in the aptly-named thermosphere above 90 km.

Speed of sound

Because in an ideal gas of constant composition the speed of sound depends only on temperature and not on pressure or density, the speed of sound in the atmosphere with altitude takes on the form of the complicated temperature profile (see illustration to the right), and does not mirror altitudinal changes in density or pressure.

Density and mass

Temperature and mass density against altitude from the NRLMSISE-00 standard atmosphere model (the eight dotted lines in each "decade" are at the eight cubes 8, 27, 64, ..., 729) Atmosphere model.png
Temperature and mass density against altitude from the NRLMSISE-00 standard atmosphere model (the eight dotted lines in each "decade" are at the eight cubes 8, 27, 64, ..., 729)

The density of air at sea level is about 1.2 kg/m3 (1.2 g/L, 0.0012 g/cm3). Density is not measured directly but is calculated from measurements of temperature, pressure and humidity using the equation of state for air (a form of the ideal gas law). Atmospheric density decreases as the altitude increases. This variation can be approximately modeled using the barometric formula. More sophisticated models are used to predict the orbital decay of satellites.

The average mass of the atmosphere is about 5 quadrillion (5×1015) tonnes or 1/1,200,000 the mass of Earth. According to the American National Center for Atmospheric Research, "The total mean mass of the atmosphere is 5.1480×1018 kg with an annual range due to water vapor of 1.2 or 1.5×1015 kg, depending on whether surface pressure or water vapor data are used; somewhat smaller than the previous estimate. The mean mass of water vapor is estimated as 1.27×1016 kg and the dry air mass as 5.1352 ±0.0003×1018 kg."

Tabulated properties

Table of physical and thermal properties of air at atmospheric pressure: [43] [44]

Temperature (K)Density (kg/m^3 )Specific heat (J/kg °C)Dynamic viscosity (kg/m s)Kinematic viscosity (m^2/s)Thermal conductivity (W/m °C)Thermal diffusivity (m^2/s)Prandtl NumberBulk modulus (K^-1 )
1003.6011026.66.92E-061.92E-060.0009252.50E-060.770.01
1502.36751009.91.03E-054.34E-060.0137355.75E-060.7530.006667
2001.76841006.11.33E-057.49E-060.018091.02E-050.7380.005
2501.41281005.31.60E-051.13E-050.022271.57E-050.7220.004
3001.17741005.71.85E-051.57E-050.026242.22E-050.7080.003333
3500.99810092.08E-052.08E-050.030032.98E-050.6970.002857
4000.882610142.29E-052.59E-050.033653.76E-050.6890.0025
4500.78331020.72.48E-053.17E-050.037074.22E-050.6830.002222
5000.70481029.52.67E-053.79E-050.040385.56E-050.680.002
5500.64231039.22.85E-054.43E-050.04366.53E-050.680.001818
6000.58791055.13.02E-055.13E-050.046597.51E-050.680.001667
6500.5431063.53.18E-055.85E-050.049538.58E-050.6820.001538
7000.5031075.23.33E-056.63E-050.05239.67E-050.6840.001429
7500.47091085.63.48E-057.39E-050.055091.08E-040.6860.001333
8000.44051097.83.63E-058.23E-050.057791.20E-040.6890.00125
8500.41491109.53.77E-059.08E-050.060281.31E-040.6920.001176
9000.39251121.23.90E-059.93E-050.062791.43E-040.6960.001111
9500.37161132.14.02E-051.08E-040.065251.55E-040.6990.001053
10000.35241141.74.15E-051.18E-040.067531.68E-040.7020.001
11000.320411604.44E-051.39E-040.07321.97E-040.7040.000909
12000.294711794.69E-051.59E-040.07822.25E-040.7070.000833
13000.270711974.93E-051.82E-040.08372.58E-040.7050.000769
14000.251512145.17E-052.06E-040.08912.92E-040.7050.000714
15000.235512300.0000542.29E-040.09463.26E-040.7050.000667
16000.221112485.63E-052.55E-040.13.61E-040.7050.000625
17000.208212675.85E-052.81E-040.1053.98E-040.7050.000588
18000.19712876.07E-053.08E-040.1114.38E-040.7040.000556
19000.185813096.29E-053.39E-040.1174.81E-040.7040.000526
20000.176213380.0000653.69E-040.1245.26E-040.7020.0005
21000.168213726.72E-054.00E-040.1315.72E-040.70.000476
22000.160214196.93E-054.33E-040.1396.12E-040.7070.000455
23000.153814827.14E-054.64E-040.1496.54E-040.710.000435
24000.145815747.35E-055.04E-040.1617.02E-040.7180.000417
25000.139416887.57E-055.44E-040.1757.44E-040.730.0004
30000.11352.7269.55E-058.41E-040.4861.57E-030.5360.0003333333333

Optical properties

Solar radiation (or sunlight) is the energy Earth receives from the Sun. Earth also emits radiation back into space, but at longer wavelengths that humans cannot see. Part of the incoming and emitted radiation is absorbed or reflected by the atmosphere. [45] [46] In May 2017, glints of light, seen as twinkling from an orbiting satellite a million miles away, were found to be reflected light from ice crystals in the atmosphere. [47] [48]

Scattering

When light passes through Earth's atmosphere, photons interact with it through scattering. If the light does not interact with the atmosphere, it is called direct radiation and is what you see if you were to look directly at the Sun. Indirect radiation is light that has been scattered in the atmosphere. For example, on an overcast day when you cannot see your shadow, there is no direct radiation reaching you, it has all been scattered. As another example, due to a phenomenon called Rayleigh scattering, shorter (blue) wavelengths scatter more easily than longer (red) wavelengths. This is why the sky looks blue; you are seeing scattered blue light. This is also why sunsets are red. Because the Sun is close to the horizon, the Sun's rays pass through more atmosphere than normal before reaching your eye. Much of the blue light has been scattered out, leaving the red light in a sunset.

Absorption

Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including visible light. Atmospheric electromagnetic opacity.svg
Rough plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including visible light.

Different molecules absorb different wavelengths of radiation. For example, O2 and O3 absorb almost all radiation with wavelengths shorter than 300 nanometres. Water (H2O) absorbs at many wavelengths above 700 nm. When a molecule absorbs a photon, it increases the energy of the molecule. This heats the atmosphere, but the atmosphere also cools by emitting radiation, as discussed below.

The combined absorption spectra of the gases in the atmosphere leave "windows" of low opacity, allowing the transmission of only certain bands of light. The optical window runs from around 300 nm (ultraviolet-C) up into the range humans can see, the visible spectrum (commonly called light), at roughly 400–700 nm and continues to the infrared to around 1100 nm. There are also infrared and radio windows that transmit some infrared and radio waves at longer wavelengths. For example, the radio window runs from about one centimetre to about eleven-metre waves.

Emission

Emission is the opposite of absorption, it is when an object emits radiation. Objects tend to emit amounts and wavelengths of radiation depending on their "black body" emission curves, therefore hotter objects tend to emit more radiation, with shorter wavelengths. Colder objects emit less radiation, with longer wavelengths. For example, the Sun is approximately 6,000  K (5,730  °C ; 10,340  °F ), its radiation peaks near 500 nm, and is visible to the human eye. Earth is approximately 290 K (17 °C; 62 °F), so its radiation peaks near 10,000 nm, and is much too long to be visible to humans.

Because of its temperature, the atmosphere emits infrared radiation. For example, on clear nights Earth's surface cools down faster than on cloudy nights. This is because clouds (H2O) are strong absorbers and emitters of infrared radiation. This is also why it becomes colder at night at higher elevations.

The greenhouse effect is directly related to this absorption and emission effect. Some gases in the atmosphere absorb and emit infrared radiation, but do not interact with sunlight in the visible spectrum. Common examples of these are CO2 and H2O.

Refractive index

Distortive effect of atmospheric refraction upon the shape of the sun at the horizon. SB DouglasPreserve SunAtmosphericEffects 2017 3 cropped.jpg
Distortive effect of atmospheric refraction upon the shape of the sun at the horizon.

The refractive index of air is close to, but just greater than 1. Systematic variations in the refractive index can lead to the bending of light rays over long optical paths. One example is that, under some circumstances, observers on board ships can see other vessels just over the horizon because light is refracted in the same direction as the curvature of Earth's surface.

The refractive index of air depends on temperature, [49] giving rise to refraction effects when the temperature gradient is large. An example of such effects is the mirage.

Circulation

An idealised view of three pairs of large circulation cells. AtmosphCirc2.png
An idealised view of three pairs of large circulation cells.

Atmospheric circulation is the large-scale movement of air through the troposphere, and the means (with ocean circulation) by which heat is distributed around Earth. The large-scale structure of the atmospheric circulation varies from year to year, but the basic structure remains fairly constant because it is determined by Earth's rotation rate and the difference in solar radiation between the equator and poles.

Evolution of Earth's atmosphere

Earliest atmosphere

The first atmosphere consisted of gases in the solar nebula, primarily hydrogen. There were probably simple hydrides such as those now found in the gas giants (Jupiter and Saturn), notably water vapor, methane and ammonia. [50]

Second atmosphere

Outgassing from volcanism, supplemented by gases produced during the late heavy bombardment of Earth by huge asteroids, produced the next atmosphere, consisting largely of nitrogen plus carbon dioxide and inert gases. [50] A major part of carbon-dioxide emissions dissolved in water and reacted with metals such as calcium and magnesium during weathering of crustal rocks to form carbonates that were deposited as sediments. Water-related sediments have been found that date from as early as 3.8 billion years ago. [51]

About 3.4 billion years ago, nitrogen formed the major part of the then stable "second atmosphere". The influence of life has to be taken into account rather soon in the history of the atmosphere because hints of early life-forms appear as early as 3.5 billion years ago. [52] How Earth at that time maintained a climate warm enough for liquid water and life, if the early Sun put out 30% lower solar radiance than today, is a puzzle known as the "faint young Sun paradox".

The geological record however shows a continuous relatively warm surface during the complete early temperature record of Earth – with the exception of one cold glacial phase about 2.4 billion years ago. In the late Archean Eon an oxygen-containing atmosphere began to develop, apparently produced by photosynthesizing cyanobacteria (see Great Oxygenation Event), which have been found as stromatolite fossils from 2.7 billion years ago. The early basic carbon isotopy (isotope ratio proportions) strongly suggests conditions similar to the current, and that the fundamental features of the carbon cycle became established as early as 4 billion years ago.

Ancient sediments in the Gabon dating from between about 2.15 and 2.08 billion years ago provide a record of Earth's dynamic oxygenation evolution. These fluctuations in oxygenation were likely driven by the Lomagundi carbon isotope excursion. [53]

Third atmosphere

Oxygen content of the atmosphere over the last billion years Sauerstoffgehalt-1000mj2.png
Oxygen content of the atmosphere over the last billion years

The constant re-arrangement of continents by plate tectonics influences the long-term evolution of the atmosphere by transferring carbon dioxide to and from large continental carbonate stores. Free oxygen did not exist in the atmosphere until about 2.4 billion years ago during the Great Oxygenation Event and its appearance is indicated by the end of the banded iron formations.

Before this time, any oxygen produced by photosynthesis was consumed by the oxidation of reduced materials, notably iron. Free oxygen molecules did not start to accumulate in the atmosphere until the rate of production of oxygen began to exceed the availability of reducing materials that removed oxygen. This point signifies a shift from a reducing atmosphere to an oxidizing atmosphere. O2 showed major variations until reaching a steady state of more than 15% by the end of the Precambrian. [56] The following time span from 539 million years ago to the present day is the Phanerozoic Eon, during the earliest period of which, the Cambrian, oxygen-requiring metazoan life forms began to appear.

The amount of oxygen in the atmosphere has fluctuated over the last 600 million years, reaching a peak of about 30% around 280 million years ago, significantly higher than today's 21%. Two main processes govern changes in the atmosphere: Plants using carbon dioxide from the atmosphere and releasing oxygen, and then plants using some oxygen at night by the process of photorespiration while the remaining oxygen is used to break down organic material. Breakdown of pyrite and volcanic eruptions release sulfur into the atmosphere, which reacts with oxygen and hence reduces its amount in the atmosphere. However, volcanic eruptions also release carbon dioxide, which plants can convert to oxygen. The cause of the variation of the amount of oxygen in the atmosphere is not known. Periods with much oxygen in the atmosphere are associated with the rapid development of animals.

Air pollution

Air pollution is the introduction into the atmosphere of chemicals, particulate matter or biological materials that cause harm or discomfort to organisms. [57] Stratospheric ozone depletion is caused by air pollution, chiefly from chlorofluorocarbons and other ozone-depleting substances.

Since 1750, human activity has increased the concentrations various greenhouse gases, most importantly carbon dioxide, methane and nitrous oxide. This increase has caused an observed rise in global temperatures. Global average surface temperatures were 1.1 °C higher in the 2011–2020 decade than they were in 1850. [58]

Animation shows the buildup of tropospheric CO2 in the Northern Hemisphere with a maximum around May. The maximum in the vegetation cycle follows in the late summer. Following the peak in vegetation, the drawdown of atmospheric CO2 due to photosynthesis is apparent, particularly over the boreal forests.

Images from space

On October 19, 2015, NASA started a website containing daily images of the full sunlit side of Earth at https://epic.gsfc.nasa.gov/. The images are taken from the Deep Space Climate Observatory (DSCOVR) and show Earth as it rotates during a day. [59]

See also

Related Research Articles

<span class="mw-page-title-main">Troposphere</span> Lowest layer of Earths atmosphere

The troposphere is the lowest layer of the atmosphere of Earth. It contains 75% of the total mass of the planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the planetary surface of the Earth, the average height of the troposphere is 18 km in the tropics; 17 km in the middle latitudes; and 6 km in the high latitudes of the polar regions in winter; thus the average height of the troposphere is 13 km.

<span class="mw-page-title-main">Stratosphere</span> Layer of the atmosphere above the troposphere

The stratosphere is the second layer of the atmosphere of Earth, located above the troposphere and below the mesosphere. The stratosphere is an atmospheric layer composed of stratified temperature layers, with the warm layers of air high in the sky and the cool layers of air in the low sky, close to the planetary surface of the Earth. The increase of temperature with altitude is a result of the absorption of the Sun's ultraviolet (UV) radiation by the ozone layer. The temperature inversion is in contrast to the troposphere, near the Earth's surface, where temperature decreases with altitude.

<span class="mw-page-title-main">Mesosphere</span> Layer of the atmosphere directly above the stratosphere and below the thermosphere

The mesosphere is the third layer of the atmosphere, directly above the stratosphere and directly below the thermosphere. In the mesosphere, temperature decreases as altitude increases. This characteristic is used to define limits: it begins at the top of the stratosphere, and ends at the mesopause, which is the coldest part of Earth's atmosphere, with temperatures below −143 °C. The exact upper and lower boundaries of the mesosphere vary with latitude and with season, but the lower boundary is usually located at altitudes from 47 to 51 km above sea level, and the upper boundary is usually from 85 to 100 km.

<span class="mw-page-title-main">Thermosphere</span> Layer of the Earths atmosphere above the mesosphere and below the exosphere

The thermosphere is the layer in the Earth's atmosphere directly above the mesosphere and below the exosphere. Within this layer of the atmosphere, ultraviolet radiation causes photoionization/photodissociation of molecules, creating ions; the thermosphere thus constitutes the larger part of the ionosphere. Taking its name from the Greek θερμός meaning heat, the thermosphere begins at about 80 km (50 mi) above sea level. At these high altitudes, the residual atmospheric gases sort into strata according to molecular mass. Thermospheric temperatures increase with altitude due to absorption of highly energetic solar radiation. Temperatures are highly dependent on solar activity, and can rise to 2,000 °C (3,630 °F) or more. Radiation causes the atmospheric particles in this layer to become electrically charged, enabling radio waves to be refracted and thus be received beyond the horizon. In the exosphere, beginning at about 600 km (375 mi) above sea level, the atmosphere turns into space, although, by the judging criteria set for the definition of the Kármán line (100 km), most of the thermosphere is part of space. The border between the thermosphere and exosphere is known as the thermopause.

Altitude or height is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context. Although the term altitude is commonly used to mean the height above sea level of a location, in geography the term elevation is often preferred for this usage.

The exosphere is a thin, atmosphere-like volume surrounding a planet or natural satellite where molecules are gravitationally bound to that body, but where the density is so low that the molecules are essentially collision-less. In the case of bodies with substantial atmospheres, such as Earth's atmosphere, the exosphere is the uppermost layer, where the atmosphere thins out and merges with outer space. It is located directly above the thermosphere. Very little is known about it due to a lack of research. Mercury, the Moon, Ceres, Europa, and Ganymede have surface boundary exospheres, which are exospheres without a denser atmosphere underneath. The Earth's exosphere is mostly hydrogen and helium, with some heavier atoms and molecules near the base.

<span class="mw-page-title-main">Tropopause</span> The boundary of the atmosphere between the troposphere and stratosphere

The tropopause is the atmospheric boundary that demarcates the troposphere from the stratosphere, which are the lowest two of the five layers of the atmosphere of Earth. The tropopause is a thermodynamic gradient-stratification layer that marks the end of the troposphere, and is approximately 17 kilometres (11 mi) above the equatorial regions, and approximately 9 kilometres (5.6 mi) above the polar regions.

<span class="mw-page-title-main">Atmosphere</span> Layer of gases surrounding an astronomical body held by gravity

An atmosphere is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosphere is the outer region of a star, which includes the layers above the opaque photosphere; stars of low temperature might have outer atmospheres containing compound molecules.

<span class="mw-page-title-main">Natural environment</span> Living and non-living things on Earth

The natural environment or natural world encompasses all living and non-living things occurring naturally, meaning in this case not artificial. The term is most often applied to Earth or some parts of Earth. This environment encompasses the interaction of all living species, climate, weather and natural resources that affect human survival and economic activity. The concept of the natural environment can be distinguished as components:

<span class="mw-page-title-main">Ozone–oxygen cycle</span> Biogeochemical cycle

The ozone–oxygen cycle is the process by which ozone is continually regenerated in Earth's stratosphere, converting ultraviolet radiation (UV) into heat. In 1930 Sydney Chapman resolved the chemistry involved. The process is commonly called the Chapman cycle by atmospheric scientists.

<span class="mw-page-title-main">Upper Atmosphere Research Satellite</span> NASA-operated orbital observatory (1991-2011)

The Upper Atmosphere Research Satellite (UARS) was a NASA-operated orbital observatory whose mission was to study the Earth's atmosphere, particularly the protective ozone layer. The 5,900-kilogram (13,000 lb) satellite was deployed from Space Shuttle Discovery during the STS-48 mission on 15 September 1991. It entered Earth orbit at an operational altitude of 600 kilometers (370 mi), with an orbital inclination of 57 degrees.

<span class="mw-page-title-main">TIMED</span> American Weather Satellite

The TIMED mission is dedicated to study the influences energetics and dynamics of the Sun and humans on the least explored and understood region of Earth's atmosphere – the Mesosphere and Lower Thermosphere / Ionosphere (MLTI). The mission was launched from Vandenberg Air Force Base in California on 7 December 2001 aboard a Delta II rocket launch vehicle. The project is sponsored and managed by NASA, while the spacecraft was designed and assembled by the Applied Physics Laboratory at Johns Hopkins University. The mission has been extended several times, and has now collected data over an entire solar cycle, which helps in its goal to differentiate the Sun's effects on the atmosphere from other effects. It shared its Delta II launch vehicle with the Jason-1 oceanography mission.

<span class="mw-page-title-main">Index of meteorology articles</span>

This is a list of meteorology topics. The terms relate to meteorology, the interdisciplinary scientific study of the atmosphere that focuses on weather processes and forecasting.

<span class="mw-page-title-main">Outline of Earth sciences</span> Hierarchical outline list of articles related to Earth sciences

The following outline is provided as an overview of and topical guide to Earth science:

The homosphere is the layer of an atmosphere where the bulk gases are homogeneously mixed due to turbulent mixing or eddy diffusion. The bulk composition of the air is mostly uniform so the concentrations of molecules are the same throughout the homosphere. The top of the homosphere is called the homopause, also known as the turbopause. Above the homopause is the heterosphere, where diffusion is faster than mixing, and heavy gases decrease in density with altitude more rapidly than lighter gases.

<span class="mw-page-title-main">Atmosphere of Venus</span> Gas layer surrounding Venus

The atmosphere of Venus is primarily of supercritical carbon dioxide and is much denser and hotter than that of Earth. The temperature at the surface is 740 K, and the pressure is 93 bar (1,350 psi), roughly the pressure found 900 m (3,000 ft) underwater on Earth. The Venusian atmosphere supports opaque clouds of sulfuric acid, making optical Earth-based and orbital observation of the surface impossible. Information about the topography has been obtained exclusively by radar imaging. Aside from carbon dioxide, the other main component is nitrogen. Other chemical compounds are present only in trace amounts.

<span class="mw-page-title-main">Atmospheric chemistry observational databases</span> Aspect of atmospheric sciences

Over the last two centuries many environmental chemical observations have been made from a variety of ground-based, airborne, and orbital platforms and deposited in databases. Many of these databases are publicly available. All of the instruments mentioned in this article give online public access to their data. These observations are critical in developing our understanding of the Earth's atmosphere and issues such as climate change, ozone depletion and air quality. Some of the external links provide repositories of many of these datasets in one place. For example, the Cambridge Atmospheric Chemical Database, is a large database in a uniform ASCII format. Each observation is augmented with the meteorological conditions such as the temperature, potential temperature, geopotential height, and equivalent PV latitude.

<span class="mw-page-title-main">Atmosphere of Uranus</span> Layer of gases surrounding the planet Uranus

The atmosphere of Uranus is composed primarily of hydrogen and helium. At depth it is significantly enriched in volatiles such as water, ammonia and methane. The opposite is true for the upper atmosphere, which contains very few gases heavier than hydrogen and helium due to its low temperature. Uranus's atmosphere is the coldest of all the planets, with its temperature reaching as low as 49 K.

<span class="mw-page-title-main">Solar Mesosphere Explorer</span> NASA satellite of the Explorer program

The Solar Mesosphere Explorer was a NASA spacecraft to investigate the processes that create and destroy ozone in Earth's upper of the atmosphere of Earth. The mesosphere is a layer of the atmosphere extending from the top of the stratosphere to an altitude of about 80 km (50 mi). The spacecraft carried five instruments to measure ozone, water vapor, and incoming solar radiation.

<span class="mw-page-title-main">Atmospheric temperature</span> Physical quantity that expresses hot and cold in the atmosphere

Atmospheric temperature is a measure of temperature at different levels of the Earth's atmosphere. It is governed by many factors, including incoming solar radiation, humidity and altitude. When discussing surface air temperature, the annual atmospheric temperature range at any geographical location depends largely upon the type of biome, as measured by the Köppen climate classification

References

  1. ↑ "Gateway to Astonaut Photos of Earth". NASA. Retrieved 2018-01-29.
  2. ↑ Cox, Arthur N., ed. (2000), Allen's Astrophysical Quantities (Fourth ed.), AIP Press, pp. 258–259, ISBN   0-387-98746-0 , which rounds N2 and O2 to four significant digits without affecting the total because 0.004% was removed from N2 and added to O2. It includes 20 constituents.
  3. 1 2 Haynes, H. M., ed. (2016–2017), CRC Handbook of Chemistry and Physics (97th ed.), CRC Press, p. 14-3, ISBN   978-1-4987-5428-6 , which cites Allen's Astrophysical Quantities but includes only ten of its largest constituents.
  4. 1 2 "Trends in Atmospheric Carbon Dioxide", Global Greenhouse Gas Reference Network, NOAA, 2019, retrieved 2019-05-31
  5. 1 2 "Trends in Atmospheric Methane", Global Greenhouse Gas Reference Network, NOAA, 2019, retrieved 2019-05-31
  6. ↑ National Aeronautics and Space Administration (1976), U.S. Standard Atmosphere, 1976 (PDF), p. 3
  7. ↑ Allen, C. W. (1976), Astrophysical Quantities (Third ed.), Athlone Press, p. 119, ISBN   0-485-11150-0
  8. 1 2 Two recent reliable sources cited here have total atmospheric compositions, including trace molecules, that exceed 100%. They are Allen's Astrophysical Quantities [2] (2000, 100.001241343%) and CRC Handbook of Chemistry and Physics [3] (2016–2017, 100.004667%), which cites Allen's Astrophysical Quantities. Both are used as references in this article. Both exceed 100% because their CO2 values were increased to 345 ppmv, without changing their other constituents to compensate. This is made worse by the April 2019 CO2 value, which is 413.32 ppmv. [4] Although minor, the January 2019 value for CH4 is 1866.1 ppbv (parts per billion). [5] Two older reliable sources have dry atmospheric compositions, including trace molecules, that total less than 100%: U.S. Standard Atmosphere, 1976 [6] (99.9997147%); and Astrophysical Quantities [7] (1976, 99.9999357%).
  9. ↑ Lide, David R. Handbook of Chemistry and Physics. Boca Raton, FL: CRC, 1996: 14–17
  10. ↑ Vázquez, M.; Hanslmeier, A. (2006). "Historical Introduction". Ultraviolet Radiation in the Solar System. Astrophysics and Space Science Library. Vol. 331. Springer Science & Business Media. p. 17. Bibcode:2005ASSL..331.....V. doi:10.1007/1-4020-3730-9_1. ISBN   978-1-4020-3730-6.
  11. 1 2 Wallace, John M. and Peter V. Hobbs. Atmospheric Science: An Introductory Survey Archived 2018-07-28 at the Wayback Machine . Elsevier. Second Edition, 2006. ISBN   978-0-12-732951-2. Chapter 1
  12. ↑ "Trace Gases". Ace.mmu.ac.uk. Archived from the original on 9 October 2010. Retrieved 2010-10-16.
  13. ↑ "Vital signs: Carbon Dioxide". NASA Climate. April 2022. Retrieved 16 May 2022.
  14. ↑ Detlev Möller: Luft: Chemie, Physik, Biologie, Reinhaltung, Recht. Walter de Gruyter, 2003, ISBN   3-11-016431-0, S. 173. (View in Google Books).
  15. ↑ Yunus Çengel. Termodinamica e trasmissione del calore.
  16. ↑ "Air - Molecular Weight and Composition". www.engineeringtoolbox.com. Retrieved 2021-04-27.
  17. ↑ "Air Composition". The Engineering ToolBox. Retrieved 2017-07-04. The composition of air is unchanged until elevation of approximately 10.000 m
  18. ↑ Zell, Holly (2015-03-02). "Earth's Upper Atmosphere". NASA. Retrieved 2017-02-20.
  19. ↑ "Exosphere - overview". UCAR. 2011. Archived from the original on 17 May 2017. Retrieved April 19, 2015.
  20. 1 2 Randy Russell (2008). "The Thermosphere" . Retrieved 2013-10-18.
  21. 1 2 "The height of the tropopause". Das.uwyo.edu. Retrieved 2012-04-18.
  22. 1 2 3 "Exosphere - overview". UCAR. 2011. Archived from the original on 17 May 2017. Retrieved April 19, 2015.
  23. ↑ "Earth's Atmospheric Layers". January 22, 2013.
  24. ↑ David C. Catling and Kevin J. Zahnle, The Planetary Air Leak, Scientific American, May 2009, p. 26 (accessed 25 July 2012)
  25. ↑ Ahrens, C. Donald. Essentials of Meteorology. Published by Thomson Brooks/Cole, 2005.
  26. ↑ States, Robert J.; Gardner, Chester S. (January 2000). "Thermal Structure of the Mesopause Region (80–105 km) at 40°N Latitude. Part I: Seasonal Variations". Journal of the Atmospheric Sciences. 57 (1): 66–77. Bibcode:2000JAtS...57...66S. doi: 10.1175/1520-0469(2000)057<0066:TSOTMR>2.0.CO;2 .
  27. ↑ Joe Buchdahl. "Atmosphere, Climate & Environment Information Programme". Ace.mmu.ac.uk. Archived from the original on 2010-07-01. Retrieved 2012-04-18.
  28. ↑ Journal of the Atmospheric Sciences (1993). "stratopause". Archived from the original on 2013-10-19. Retrieved 2013-10-18.
  29. ↑ Barry, R.G.; Chorley, R.J. (1971). Atmosphere, Weather and Climate . London: Menthuen & Co Ltd. p.  65. ISBN   9780416079401.
  30. ↑ Tyson, P.D.; Preston-Whyte, R.A. (2013). The Weather and Climate of Southern Africa (2nd ed.). Oxford: Oxford University Press. p. 4.
  31. ↑ "Troposphere". Concise Encyclopedia of Science & Technology. McGraw-Hill. 1984. It contains about four-fifths of the mass of the whole atmosphere.
  32. 1 2 Anne Marie Helmenstine, PhD (June 16, 2018). "The 4 Most Abundant Gases in Earth's Atmosphere".
  33. ↑ "homosphere – AMS Glossary". Amsglossary.allenpress.com. Archived from the original on 14 September 2010. Retrieved 2010-10-16.
  34. ↑ "Earth's Atmosphere". Archived from the original on 2009-06-14.
  35. ↑ "NASA – Earth Fact Sheet". Nssdc.gsfc.nasa.gov. Archived from the original on 30 October 2010. Retrieved 2010-10-16.
  36. ↑ "Global Surface Temperature Anomalies". Archived from the original on 2009-03-03.
  37. ↑ "Earth's Radiation Balance and Oceanic Heat Fluxes". Archived from the original on 2005-03-03.
  38. ↑ "Coupled Model Intercomparison Project Control Run" (PDF). Archived from the original (PDF) on 2008-05-28.
  39. ↑ Geometric altitude vs. temperature, pressure, density, and the speed of sound derived from the 1962 U.S. Standard Atmosphere.
  40. ↑ Trenberth, Kevin E.; Smith, Lesley (1970-01-01). "The Mass of the Atmosphere: A Constraint on Global Analyses". Journal of Climate. 18 (6): 864. Bibcode:2005JCli...18..864T. CiteSeerX   10.1.1.727.6573 . doi:10.1175/JCLI-3299.1. S2CID   16754900.
  41. ↑ Lutgens, Frederick K. and Edward J. Tarbuck (1995) The Atmosphere, Prentice Hall, 6th ed., pp. 14–17, ISBN   0-13-350612-6
  42. ↑ "Atmospheric Temperature Trends, 1979–2005 : Image of the Day". Earthobservatory.nasa.gov. 2000-01-01. Retrieved 2014-06-10.
  43. ↑ Holman, Jack P. (2002). Heat transfer (9th ed.). New York, NY: McGraw-Hill Companies, Inc. pp. 600–606. ISBN   9780072406559. OCLC   46959719.
  44. ↑ Incropera 1 Dewitt 2 Bergman 3 Lavigne 4, Frank P. 1 David P. 2 Theodore L. 3 Adrienne S. 4 (2007). Fundamentals of heat and mass transfer (6th ed.). Hoboken, NJ: John Wiley and Sons, Inc. pp. 941–950. ISBN   9780471457282. OCLC   62532755.
  45. ↑ "Absorption / reflection of sunlight". Understanding Global Change. Retrieved 2023-06-13.
  46. ↑ "The Atmospheric Window". National Oceanic and Atmospheric Administration. Retrieved 2023-06-13.
  47. ↑ St. Fleur, Nicholas (19 May 2017). "Spotting Mysterious Twinkles on Earth From a Million Miles Away". The New York Times . Retrieved 20 May 2017.
  48. ↑ Marshak, Alexander; Várnai, Tamás; Kostinski, Alexander (15 May 2017). "Terrestrial glint seen from deep space: oriented ice crystals detected from the Lagrangian point". Geophysical Research Letters . 44 (10): 5197. Bibcode:2017GeoRL..44.5197M. doi:10.1002/2017GL073248. S2CID   109930589.
  49. ↑ Edlén, Bengt (1966). "The refractive index of air". Metrologia. 2 (2): 71–80. Bibcode:1966Metro...2...71E. doi:10.1088/0026-1394/2/2/002.
  50. 1 2 Zahnle, K.; Schaefer, L.; Fegley, B. (2010). "Earth's Earliest Atmospheres". Cold Spring Harbor Perspectives in Biology. 2 (10): a004895. doi:10.1101/cshperspect.a004895. PMC   2944365 . PMID   20573713.
  51. ↑ B. Windley: The Evolving Continents. Wiley Press, New York 1984
  52. ↑ J. Schopf: Earth's Earliest Biosphere: Its Origin and Evolution. Princeton University Press, Princeton, N.J., 1983
  53. ↑ Timothy W. Lyons, Christopher T. Reinhard & Noah J. Planavsky (2014). "Atmospheric oxygenation three billion years ago". Nature. 506 (7488): 307–15. Bibcode:2014Natur.506..307L. doi:10.1038/nature13068. PMID   24553238. S2CID   4443958.
  54. ↑ Martin, Daniel; McKenna, Helen; Livina, Valerie (2016). "The human physiological impact of global deoxygenation". The Journal of Physiological Sciences. 67 (1): 97–106. doi:10.1007/s12576-016-0501-0. ISSN   1880-6546. PMC   5138252 . PMID   27848144.
  55. ↑ Graph: Atmospheric Oxygen and CO2 vs Time
  56. ↑ Christopher R. Scotese, Back to Earth History : Summary Chart for the Precambrian, Paleomar Project
  57. ↑ Starting from Pollution – Definition from the Merriam-Webster Online Dictionary
  58. ↑ IPCC (2021). "Summary for Policymakers" (PDF). IPCC AR6 WG1. pp. 4–5. Archived from the original (PDF) on 2021-08-11. Retrieved 2021-11-20.
  59. ↑ Northon, Karen (2015-10-19). "Daily Views of Earth Available on New NASA Website". NASA. Retrieved 2015-10-21.
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