Atmosphere is a Greek word means Vapor Sphere.
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth’s gravity.
The study of Earth’s atmosphere and its processes is called atmospheric science or aerology. Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann.
The earth’s atmosphere conist 78.084% Nitrogen(N2), 20.946% Oxygen(O2), 0.94340% Argon(Ar), 0.0397% of Carbon DiOxide(CO2).
Roughly 0.25% have local water vapor.
The density of air at sea level is about 1.2 kg/m3 (1.2 g/L).
The principle layers:
Exosphere: >700 km (>440 miles)
Thermosphere: 80 to 700 km (50 to 440 miles)
Mesosphere: 50 to 80 km (31 to 50 miles)
Stratosphere: 12 to 50 km (7 to 31 miles)
Troposphere: 0 to 12 km (0 to 7 miles)
Troposphere: The troposphere is the lowest layer of Earth’s atmosphere. It extends from Earth’s surface to an average height of about 12 km, although this altitude actually varies from about 9 km (30,000 ft) at the poles to 17 km (56,000 ft) at the equator.
The troposphere is bounded above by the tropopause, a boundary marked by stable temperatures.
It has basically all the weather-associated cloud genus types generated by active wind circulation.
Most conventional aviation activity takes place in the troposphere, and it is the only layer that can be accessed by propeller-driven 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 ozone layer is contained within the stratosphere. In this layer ozone concentrations are about 2 to 8 parts per million, which is much higher than in the lower atmosphere but still very small compared to the main components of the atmosphere. It is mainly located in the lower portion of the stratosphere from about 15–35 km (9.3–21.7 mi; 49,000–115,000 ft), though the thickness varies seasonally and geographically. About 90% of the ozone in our atmosphere is contained in the stratosphere.
Only polar stratospheric or nacreous clouds are occasionally seen in the lower part of this layer of the atmosphere where the air is coldest. This is the highest layer that can be accessed by jet-powered aircraft.
Mesosphere: 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).
Just below the mesopause, the air is so cold that even the very scarce water vapor at this altitude can be sublimated into polar-mesospheric noctilucent clouds. These are 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 a similar length of time before sunrise.
A type of lightning referred to as either sprites or ELVES, occasionally form far above tropospheric thunderclouds. The mesosphere is also the layer where most meteors burn up upon atmospheric entrance.
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 500–1,000 km (310–620 mi; 1,600,000–3,300,000 ft). The height of the thermopause varies considerably due to changes in solar activity
Since 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 km above Earth’s surface, contains the ionosphere.
The International Space Station orbits in this layer, between 320 and 380 km (200 and 240 mi).
Exosphere: The exosphere is the outermost layer of Earth’s atmosphere (i.e. the upper limit of the atmosphere). It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km (6,200 mi; 33,000,000 ft). The exosphere merges with the emptiness of outer space, where there is no atmosphere.
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