Atmosphere

What Is Atmosphere???

            Atmosphere is a Envelope of gases surrounding the Earth.

Importance of Atmosphere:

The atmosphere is a mixture of nitrogen (78%), oxygen (21%), and other gases (1%) that surrounds Earth. High above the planet, the atmosphere becomes thinner until it gradually reaches space. The atmosphere is an important part of what makes Earth livable. It blocks some of the Sun’s dangerous rays from reaching Earth. It traps heat, making Earth a comfortable temperature. And the oxygen within our atmosphere is essential for life.

Layers of Atmosphere:

The troposphere is the first layer above the surface and contains half of the Earth’s atmosphere. Weather occurs in this layer.

Many jet aircraft fly in the stratosphere because it is very stable. Also, the ozone layer absorbs harmful rays from the Sun.

Meteors or rock fragments burn up in the mesosphere.

The thermosphere is a layer with auroras. It is also where the space shuttle orbits.

The atmosphere merges into space in the extremely thin exosphere. This is the upper limit of our atmosphere.

Layers of Earth Atmosphere:

The hierarchical arrangement of various layers of the Earth’s atmosphere

One of the most important benefits the atmosphere provides is maintaining the Earth’s temperature. On the moon, which has no protective atmosphere, temperatures can range from 121 degrees Celsius in the sun (250 degrees Fahrenheit) to negative 157 degrees Celsius in the shade (negative 250 degrees Fahrenheit). The atmosphere serves as a protective shield against radiation and cosmic rays. The atmosphere also serves an important purpose as a medium for the movement of water. Vapour evaporates out of oceans, condenses as it cools and falls as rain, providing life-giving moisture to otherwise dry areas of the continent

The atmosphere of Earth, commonly known as air, is the layer of gases retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).

NASA photo showing Earth's atmosphere at sunset, with Earth silhouetted

Blue light is scattered more than otherwise wavelengths by the gases in the atmosphere, surrounding Earth in a visibly blue layer when seen from space on board the ISS at an altitude of 335 km (208 mi).[1]

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[2][3]). Numbers are mainly from 2000, with CO2 and methane from 2019, and do not represent any single source.

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.

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

"Air" redirects here. For other uses, see Air (disambiguation).

"Qualities of air" redirects here. Not to be confused with Air quality.

Mean atmospheric water vapor

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 dry air, by mole fraction[8]

Gas Mole fraction(A)

Name Formula in ppm(B) in %

Nitrogen N2 780,840 78.084

Oxygen O2 209,460 20.946

Argon Ar 9,340 0.9340

Neon Ne 18.18 0.001818

Helium He 5.24 0.000524

Methane CH4 1.87 0.00

The average molecular weight of dry air, which can be used to calculate densities or to convert between mole fraction and mass fra ction, 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)

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.[42] 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.[43]

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.[44] 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.

Third Atmosphere:

 

Oxygen content of the atmosphere over the last billion years[46][47]

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.[48] The following time span from 541 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 because oxygen is the high-energy molecule needed to power all complex life-forms.[49] Today's atmosphere contains 21% oxygen, which is great enough for this rapid development of animals.

Air pollution is the introduction into the atmosphere of chemicals, particulate matter or biological materials that cause harm or discomfort to organisms.[51] 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.

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 apparently.

Conclusion: 

Life on the Earth would not be possible without the air .so protect it

                          Thankyou 

Your regards,

Poojavadavelli❤️