Structure and Composition of Atmosphere

STRUCTURE AND COMPOSITION OF THE ATMOSPHERE

ATMOSPHERE: Is a layer of gases containing numerous small suspended solid and liquid particles.

STRUCTURE OF ATMOSPHERE

The atmosphere is divided into regions based on its thermal (temperature changes) characteristics, chemical, composition, movement and density.

LAYERS OF ATMOSPHERE

i)       Troposphere

ii)     Stratosphere

iii)   Mesosphere

iv)   Thermosphere

v)      Exosphere

TROPOSPHERE

Is the layer (region) nearest to the Earth, it extends to an altitude of up to 10km above the poles and

20km, above the equator

  

PROPERTIES OF TROPOSPHERE

i)  Has the most density. Is the region of the most density part of the atmosphere.

ii)  It contains most of the atmosphere’s water – vapour.

iii)  The temperature decreases with the increase of altitude at an average rate of 6°C/km.

iv) Most weather phenomenon occurs in the troposphere.

v)  Clouds and rain are formed within this region.

NOTE:

The boundary which separates the troposphere and the stratosphere is called “Tropopause”.

Temperature at the Tropopause remains constant.

STRATOSPHERE

The stratosphere starts from the tropopause and extends to 50km high.

PROPERTIES OF STRATOSPHERE

i)   It is drier and less dense than the troposphere.

ii) Temperature increase as altitude increase due to presence of the ozone layer which absorbs ultraviolet rays from the sun.

iii) It plays the important role of absorbing ultraviolet radiations which otherwise reach the Earth’s surface.

iv) The stable air of the stratosphere prevents large storms from extending much beyond the tropopause.

v)  Planes fly in the stratosphere because it has strong steady horizontal winds, which are above the stormy weather of the troposphere.

NOTE:

The boundary which separates the stratosphere and the Mesosphere is called “stratosphere”

MESOSPHERE

The mesosphere starts just above the stratosphere and extends to 85km high.

PROPERTIES MESOSPHERE

i)  The temperature decrease with the increase of altitude. The lowest temperature of atmosphere (-90°c) occur in this region.

ii)  It plays a great role in most meteors burn while entering the earth’s atmosphere.

NOTE:

The layer (boundary) which separates the Mesosphere and the thermosphere is called “Mesopause”

  

THERMOSPHERE

Is the layer starts just above the Mesosphere and extends up to 690km high.

PROPERTIES OF MESOSPHERE

i)  The temperature increase as the increase of altitude due to the suns heat

ii)  The temperature can rise as high as 1720°C.

iii)  Chemical reactions occur much faster than on the Earth surface. It is sometimes called “upper atmosphere.

IONOSPHERE

Is the region (layer) containing a high concentration of charged particles called Ions and free- electrons.

The large number of free electrons allows the propagation of electromagnetic waves.

PROPERTIES OF IONOSSPHERE

i) It exists at the lower part of the thermosphere and upper part of Mesosphere. It extends from 80km to 530km above the Earth’s surface.

ii) It plays an important role in absorption of dangerous radiations. The dangerous radiations include hard and support X – rays, and extreme ultraviolet (EUV).

iii) Also plays important role in communications. Radio waves can be reflected off the ionosphere allowing radio communications over long distances.

EXOSPHERE

Is the outer most region of the atmosphere.

PROPERTIES OF EXOSPHERE

i)  The atmospheric gas pressure is very low.

ii)  Light atoms such as hydrogen and Helium may acquire sufficient energy to escape the earth’s gravitation pull.

NOTE:

The upper part of the Exosphere is called ²Magnetosphere²

This is the layer (region) where satellites orbit the Earth.

IMPORTANCE OF ATMOSPHERE

i)  The troposphere controls the climate and ultimately determines the quality of life on the Earth.

ii) The troposphere is important for life on the Earth. Contain gases such as oxygen and carbon dioxide for animal respiration and plant photosynthesis respectively. Also nitrogen which provide inactive environment for many chemical process to occur (Take place),

iii)  The stratosphere prevents harmful ultraviolet radiation from reaching the earth.

iv) The mesosphere, thermosphere and exosphere prevent harmful radiation such cosmic rays from reaching the earth’s surface.

v)   Ionosphere help in radio Communication