Assignment Task:
Task:
The atmosphere is an integral part of the earth surrounding it from all sides, extending up to about 1600 kilometers from the earth’s surface. It is divided into a series of vertical layers. The division of these vertical layers is based on temperature and pressure. In that context, this assignment will describe the structure of the atmosphere, clearly bringing out the various layers that form the atmosphere.
Petersen. J (2011) the layer closest to the earth is called troposphere above it is the stratosphere, followed by the mesosphere, above the mesosphere is the ionosphere, then exosphere. There are upper boundaries between the first three layers and they are known as the tropopause, the stratopause, and the mesopause respectively.
The troposphere extends about 8 to 16 kilometers the surface making it the lowest layer, temperatures in this layer decreases with altitude, The rate at which temperature decreases with increased altitude is called the environmental lapse or normal lapse rate, All-weather phenomena are present in the troposphere because it contains about 75 percent of the mass of the atmospheric air, the troposphere organises the Earth’s temperature because it contains 99% of atmospheric water vapour. Weather phenomena such as rains, wind and clouds take place in this layer, the troposphere forms weather conditions and consequently up the climate, which affect the activities of living organisms because it contains about 75 percent of the mass of the atmospheric envelope. The air never remains static in this layer, it is for this reason that the troposphere is also known as the changing sphere. The upper limit of the troposphere is called the tropopause a transitional boundary the separates the troposphere from the stratosphere the next layer of the atmosphere (Petersen. J, 2011).
Spreading an average of about 40 to 50 kilometers from the surface of the earth, the stratosphere is the second layer in the atmospheric envelope, temperatures remain almost the same in the lower part of the stratosphere up to a height of 20 kilometers after which it increases slowly with height, this is because the ozone layer which is found in the stratosphere the ozone layer absorbs ultra-violet radiation and this absorbed energy causes the release of heat resulting an increase in temperature in the upper parts of the stratosphere. The lower part of this layer is very important for life-forms in the biospheric ecosystem height of 15-30 km. It acts as a protective cover because it absorbs almost all of the ultra-violet rays of solar radiation and thus protects the earth’s surface from becoming too hot. The stratosphere is considered to be ideal for flying aircraft because weather related incidences do not take place in this layer. (Gabler, 2007)
Mesosphere is the third and middle layer extending about 80 kilometers from the earth’s surface the mesosphere has extremely low density air, resulting in very low air pressure. Unlike the stratosphere below, it absorbs very little solar radiation. This layer is incredibly cold, going from freezing at the bottom to about -90°C extremely cold, at its top, the mesosphere layer contains limited quantities of helium and hydrogen gases only, So, It is highly rarefied. The mesosphere layer protects the planet Earth from the celestial rocky masses that enter the atmospheric envelope of the Earth, where they burn as a result of their friction with the air molecules and forming luminous meteors also known as shooting stars., temperature in the mesosphere decreases with increasing height, due to decreasing absorption of solar radiation by the rarefied atmosphere and increasing cooling by Carbon dioxide radiative emission, the top of the mesosphere layer, called the mesopause, a transitional boundary and is the coldest part of Earth’s atmosphere, varying according to the latitude and the season.
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