• Some Notes about Earth Atmosphere

    (Atmosphere layers from ground)

    1 : Troposphere from Greek word tropos meaning mixing , which contains almost all of earth's weather . the troposphere has two defining characteristics : firstly in troposphere with gaining height the temperature would deacrese . secondly the troposphere contains over 70% of total mass of atmmosphere .

    2 : Tropopause which is the upper limit of the troposphere and difine as the point where temperature no longer decreases with height . the height of tropopause varies from 16 km over the Equator to 8 km over the Poles so the average height of that is 11 km at 45 degree of latitude .

    3 : Stratosphere is next layer after tropopause and unlike troposhpere is characterised by the lack of any significant change in temperature with height . this absence of any significant temperature variation within the lower stratosphere gives the air of the stratosphere stability in other words vertical movment of air within the stratosphere is severely restricted .

    4 : Stratopause which is upper boundary of stratosphere and above that temperature begins to increase with height again . stratopause is usually found around 50 km above surface .

    There is some other layers above stratopause such as mesosphere , mesopause , thermosphere , ionosphere , exosphere which thay have little practical influence over weather .

    (Composition of Earth's atmosphere)

    The atmosphere consist of 78% nitrogen , 21% oxygen and 1% other gases which argon is 0.95% of that 1% and the other 0.05% are carbon dioxide and trace gases (carbon monoxide , helium , ozone , hydrogen and methane) .

    Note : water vapour can make up between 0% and 7% of the atmosphere but water vapour has the greatest effect on our weather .


    ISA or international standard atmosphere assumes that at mean sea_level air temperature is +15 degree of celsius , air pressure is 1013.25 mb = 760 mm.hg = 76 cm.hg = 29.92 in.hg , air density is 1.225kg/m3 = 1225 g/m3 , from mean sea leve to 11 km temperature decreases by 1.98 degree of celsius per 1000ft ,from 11 km to 20 km temperature remains constant at -56.5 degree of celsius and from 20 km to 32 km temperature rises by 0.3 degree of celsius per 1000ft , air pressure from mean sea level to 10000ft decreases 1 mb per 27ft , from 10000ft to 18000ft air pressure decreases 1 mb per 36ft , from 18000 ft to 30000ft air pressure decreases 1 mb per 50ft and finally form 30000ft to more than that air pressure decreases 1 mb per 73ft . (so interesting!!!)

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