Layers of

Atmosphe

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ATMOSPHERE

An atmosphere (New Latin atmosphaera , created in the 17th

century from Greek ἀτμός [atmos] "vapor" [1] and σφα ῖρα

[sphaira] "sphere" [2]) is a layer ofgases that may surround a

material body of sufficient mass, [3] and that is held in place

by the gravity of the body. An atmosphere may be retained for

a longer duration, if the gravity is high and the atmosphere's

temperature is low. Some planets consist mainly of various

gases, but only their outer layer is their atmosphere.

ATMOSPHERE

The Troposphere

The troposphere is where all weather takes place; it is the

region of rising and falling packets of air. The air pressure at

the top of the troposphere is only 10% of that at sea level (0.1

atmospheres). There is a thin buffer zone between the

troposphere and the next layer called the tropopause .

LAYERS OF ATMOSPHERE

The Stratosphere and Ozone Layer

Above the troposphere is the stratosphere , where air flow is mostly horizontal. The thin ozone layer in the upper stratosphere has a high concentration of ozone, a particularly reactive form of oxygen. This layer is primarily responsible for absorbing the ultraviolet radiation from the Sun. The formation of this layer is a delicate matter, since only when oxygen is produced in the atmosphere can an ozone layer form and prevent an intense flux of ultraviolet radiation from reaching the surface, where it is quite hazardous to the evolution of l ife. There is considerable recent concern that manmade flourocarbon compounds may be depleting the ozone layer, with dire future consequences for l ife on the Earth

STRATOSPHERE

The mesosphere (/ m̍ɛsoʊsfɪər / ; from Greek mesos = middle and sphaira = bal l) is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. In the mesosphere temperature decreases with increasing height. The upper boundary of the mesosphere is the mesopause, which can be the coldest natural ly occurring place on Earth with temperatures below 130 K. The exact upper and lower boundaries of the mesosphere vary with lat i tude and with season, but the lower boundary of the mesosphere is usual ly located at heights of about 50 km above the Earth's surface and the mesopause is usual ly at heights near 100 km, except at middle and high lat i tudes in summer where i t descends to heights of about 85 km.

The stratosphere, mesosphere and lowest part of the thermosphere are col lect ively referred to as the "middle atmosphere", which spans heights from approximately 10 to 100 km. The mesopause, at an alt i tude of 80–90 km (50–56 mi), separates the mesosphere from thethermosphere— the second-outermost layer of the Earth's atmosphere. This is also around the same alt i tude as the turbopause, below which different chemical species are wel l mixed due to turbulent eddies. Above this level the atmosphere becomes non-uni form; the scale heights of di fferent chemical species differ by their molecular masses.

MESOSPHERE

The ionosphere is a part of the upper atmosphere, from

about 85 km (53 mi) to 600 km (370 mi) altitude, comprising

portions of the mesosphere, thermosphere and exosphere,

distinguished because it is ionized by solar radiation. It

plays an important part in atmospheric electricity and forms

the inner edge of the magnetosphere. It has practical

importance because, among other functions, it

influences radio propagation to distant places on

the Earth. [1]

IONOSPHERE

LAYERS OF ATMOSPHERE