The Atmospheric Layers
Lesson objectives :
- By the end of this lesson, the student must be able to:
1-Know the concept of atmospheric pressure.
2- Interpret the change of atmospheric pressure with changing height above sea level.
3- Understand the change of atmospheric pressure with changing height above sea level
4- Appreciate the importance of instruments that measure atmospheric pressure.
5-Mention the importance of altimeter.
6-Know atmospheric layers.
7- Mention the characteristics of atmospheric layers.
8-Compare among the characteristics of atmospheric layers.
8-Determine the importance of each layer of the atmosphere.
Atmospheric pressure
- The Earth is surrounded by a gas envelope that rotates with it about its axis, and extends 1000 km above sea level. It is known as atmosphere
- The weight of air column of an atmospheric height on a unite area is called air pressure or atmospheric pressure.
- It is measured in a unit called a bar. The bar equals
1000 millibar (mbar).
- Normal atmospheric pressure at sea level equals 1013.25 millibar.
- In airplanes, an altimeter is used to determine the elevation of the navigation based on the atmospheric
pressure at this level.
- The possible day’s weather can be estimated directly with an instrument known as aneroid measure atmospheric pressure.
- for more in formation about troposphere , please visit these link:
Atmospheric layers
1-First layer : Troposphere
Characteristics and importance of the troposphere:
1-It extends 13 km above sea level to the tropopause.
As we go up, the temperature decreases by
a rate of 6.5 ºC per 1 km until it reaches the lowest
value of about (-60 ºC) at troposphere.
2-Atmospheric pressures decreases as we go higher,
where it reaches about 0.1 bar of the normal pressu re
at sea level.
3-It contains about 75% of the atmosphere mass.
This explains why all atmospheric phenomena like
the weather conditions ,and consequently up the climate climate, occurs in this layer and affects the
activities of living organisms.
4-It contains about 99% of the atmospheric water vapor,which organize the temperature of earth.
- for more in formation about troposphere , please visit these link:
2- Second layer: Stratosphere
Characteristics and importance of the stratosphere:
1-It extends from troposphere (13 km above sea level) to the stratosphere (50 km) with thickness of 37 km.
2-At the lower part, the temperature is constant and measure (– 60º C), then increases gradually until it
reaches 0º C at the end of the layer. This is due to the absorption of ultraviolet radiation ( emitted from the
Sun) by the ozone layer that is present in the upper
part of the layer.
3-The atmospheric pressure decreases on going higher where it reaches the smallest value ( .oo1 bar f the
normal pressure at sea level) at the
end of the layer.
4-It contains most of the atmospheric ozone which is
concentrated between 20 - 40 km above sea level.
The lower part does not contain clouds or suffer
from any weather disturbances.
5-The air moves in this layer horizontally.
- for more in formation about troposphere , please visit these link:
3-Third layer: Mesosphere
Characteristics and importance of the mesosphere:
1- It is extended from the stratopause (50 km above sea
level) to the mesopause (85 km) with thickness of
about 35 km.
2-Temperature decreases with height rate until
reaches (– 90º C) at its end.
3-This layer is much vacuumed as it contains only
a limited amount of helium and hydrogen gases.
Meteors are formed in this layer and burnt due to friction
- for more in formation about troposphere , please visit these link:
4-Fourth layer: Thermosphere
- Thermosphere is the fourth atmospheric layer. It means the heated layer as it is the hottest layer of the atmosphere.
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