1. THERMAL STRUCTURE OF
EARTHS ATMOSPHERE
NEETHA SUSAN JOSE
PHYSICAL SCIENCE
13350020
2. What is an Atmosphere?
• An atmosphere is a layer
of gases that may surround a material
body of sufficient mass by
the gravity of the body.
From Greek, Atmos -----”vapor”
sphaira------”sphere”
3. Composition of Earth’s Atmosphere
Nitrogen 78.0842%
Oxygen 20.9463%
Water Vapor about 1%
Argon 0.9342%
Carbon Dioxide 0.0384%
Other gases 0.0020%
4. Earth’s Atmosphere: Composition
• The Earth’s atmosphere differs from those of the other terrestrial
planets in its chemical composition, temperature profile and
circulation pattern
• Composition of present-day: 78% Nitrogen, 21% Oxygen
and 1% water vapor and carbon dioxide (greenhouse gas)
• The composition of atmosphere has evolved with time due to
presence of living organisms
5. The atmosphere consists of many gases which below the
homopause (near 105 km on Earth) are well mixed due to
small scale turbulence and larger scale winds:
6. Atmospheric layers
• 8 layers are defined by
constant trends in average
air temperature (which
changes with pressure and
radiation).
1. Troposphere
2. Tropopause
3. Stratosphere
4. Stratopause
5. Mesosphere
6. Mesopause
7. Thermosphere
8. Exosphere
7. TROPOSPHERE
• Lowest and thinnest layer
—16 km at equator, 8 km at poles
• 90% of the atmosphere’s mass
• Temperature decreases with
altitude
—6°C per kilometer
—Top of troposphere averages –50°C
• Where weather occurs
• Boundary between the troposphere, and
the stratosphere is called the tropopause
8. STRATOSPHERE
• Extends from 10 km to 50 km above
the ground
• Less dense (less water vapor)
• Temperature increases with altitude
• Almost no weather occurrence
• Contains high level of ozone
> ozone layer
Upper boundary is called stratopause
9. MESOSPHERE
• Extends to almost
80 km high
• Gases are less dense.
• Temperature
decreases as altitude
increases.
Gases in this layer
absorb very little UV
radiation.
10. THERMOSPHERE
• above the mesosphere
and extends to almost
600 km high
• temperature increases
with altitude
• readily absorbs solar
radiation
• Temperature can go as
high as 1,500 °C
• reflects radio waves
12. Measurement of atmospheric pressure with
the mercury barometer:
P P
gh
B A Hg
5
Atmospheric pressure =
= 1.013x10 Pa
1013hPa
= 1013 mb
= 1 atm
= 760 mm Hg (torr)
vacuum
A B
h
ATMOSPHERIC PRESSURE
