THERMAL STRUCTURE OF EARTHS ATMOSPHERE

NEETHA SUSAN JOSEPHYSICAL SCIENCE

13350020

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”

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%

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

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:

Atmospheric layers

• 8 layers are defined by constant trends in average air temperature (which changes with pressure and radiation).

1. Troposphere2. Tropopause3. Stratosphere4. Stratopause5. Mesosphere6. Mesopause7. Thermosphere8. Exosphere

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

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

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.

THERMOSPHERE• above the mesosphere

and extends to almost 600 km high

• temperature increaseswith altitude

• readily absorbs solar radiation

• Temperature can go as high as 1,500 °C

• reflects radio waves

Atmospheric Pressure

Measurement of atmospheric pressure with the mercury barometer:

Hg

5

Atmospheric pressure =

= 1.013x10 Pa 1013hPa

= 1013 mb

= 1 atm

B AP P gh

= 760 mm Hg (torr)

vacuum

A Bh

ATMOSPHERIC PRESSURE

Air Density

Air Density and height

THANK YOU

NEETHA SUSAN JOSE