Www.soran.edu.iq Earth Atmosphere Chapter 3 Meteorology \ Dr. Mazin sherzad.

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Earth AtmosphereChapter 3

Meteorology \ Dr. Mazin sherzad

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Earth Atmosphere

1) Composition of the atmosphere

2) Structure of the atmosphere

-Principle layers

3) Air Pressure, Density, and Temperature

Structure


Chapter 3

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Atmosphere

• The atmosphere is a thin layer of gases that surround the Earth.


The atmosphere protects life on Earth by

absorbing ultraviolet solar radiation, warming the

surface through heat retention and reducing temperature

extremes between day and night.

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How did the atmosphere change?

• Methane is made up carbon and hydrogen.

• Ammonia, is composed of nitrogen and hydrogen.

• Sunlight caused chemical reaction among the methane, ammonia and water in the air.

• New materials, nitrogen, hydrogen and carbon dioxide, were formed as the methane and ammonia broke down.


Methane is an important gas in “global warming”

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Solid Particles

• Tiny particles of dust, smoke dirt and salt float in the air.

• Dust in the air comes from the eruption of volcanoes.

• Dirt and smoke comes from people as they burn fuels and drive cars.


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Today’s Atmosphere

• 600 million years ago the amounts of oxygen and carbon dioxide in the atmosphere began to level off.

• Since that time, the composition of the atmosphere has remained fairly constant.


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Composition of Atmosphere


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Layers of the Atmosphere

• The atmosphere is divided into layers according to the major changes in its temperature. Layers with thinner particles can hold less heat.


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Air Pressure

• The layers of air that surround the Earth are held close to it by the force of gravity.

• Because of gravity, the layers of air push down on the Earth’s surface. This is called air pressure.

• The upper layers push down on the lower layers so the air pressure near the surface is greater than the air pressure further away.


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Structure of the atmosphere


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The Troposphere

• This is the layer closest to the Earth.• Weather occurs in this layer. Life occurs in the

troposphere.

• Temperature decreases with height because the troposphere is heated by the surface and not directly by sunlight.

• 80% of the atmosphere’s mass


This layer contains 99% of the water vapor.

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The Stratosphere

• The stratosphere extends from the troposphere to an altitude of about 50 km.

• temperature increases with height

• The ozone layer, which protects against harmful UV radiations, is here.


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The Mesosphere• In the mesosphere, 50-90km above the earth, the

temperature begins to decrease to –100 degrees C.

• The upper region is the coldest. If water vapor is present thin clouds of ice form

• Most meteors burn up in this layer • The mesosphere protects the Earth from meteoroids.


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The Thermosphere

• The air is very thin. The density of the atmosphere and the air pressure are one ten-millionth of what they are at the Earth’s surface.

• The temperature is very high in this layer because the rays from the sun are absorbed in this layer.

• This layer contains the ionosphereionosphere, which

causes the reflection of radio waves.


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The Exosphere

• The upper thermosphere is called the exosphere.

• The exosphere extends from 550 km above the surface for thousands of km. The air is very thin.

• Artificial satellites orbit in the exosphere.


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Temperature in the Layers

• The sun is the source of energy for Earth. As the sun’s light passes through the layers some layers contain gases that absorb the energy.

• The troposphere is warmed mainly by heat from the ground.

• The air temperature decreases 6.5º every kilometer you climb up.


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Temperature of Layers


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Ozone Layer

• Most of the ozone in the atmosphere is found between 16 km and 60 km about the surface of the Earth.

• Ozone molecules absorb much of the het and Ultraviolet (UV) rays from the sun..


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Ozone Layer

• The oxygen that was left behind joined together, in sets of three, to form a gas known as ozone.

• The ozone layer absorbs harmful ultraviolet radiation from space.


O2 + hν → O + O

O + O2 + M → OO33 + M

O2 + hν → O + O

O + O2 + M → OO33 + M

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Ionosphere

• Within the mesosphere and the thermosphere is a layer of electrically charged particles called the Ionosphere. It allows radio waves to travel around the earth.



Hole in the Ozone Layer• The destruction of ozone

molecules by CFCs seems to cause a seasonal reduction in ozone over Antarctica called the Ozone hole.


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Atmospheric Layers• The layers are identified based on how

temperature changes with height

Troposphere – temperature decreases with

height

Stratosphere – temperature increases with

height

Mesosphere – temperature decreases with

height

Thermosphere – temperature increases with

heightMeteorology \ Dr. Mazin sherzad

www.soran.edu.iqMeteorology \ Dr. Mazin sherzad

Layer Temperature Special Qualities

Troposphere 0 to 15 km

Decreases as you climb. On average from 17oC to -52oC

Weather occurs in this layer, as does the greenhouse effect. Contains 75% of the atmosphere by mass and 90% of the water vapor in the atmosphere.

Stratosphere 15 to 50 km

Increases as you climb. The top of the layer is about -3oC.

Planes cruise near the bottom of the stratosphere. The ozone layer, which protects against harmful UV radiations, is here. Contains 20% of the atmosphere by mass.

Mesosphere 50 to 85 km

Decreases as you climb. Temperatures as low as -90oC.

Coldest layer. Most meteors burn up in this layer. Contains very few molecules of atmosphere.

Thermosphere 85 to 1,000 km

Increases as you go up. Temperatures as high as 2,000oC!

This layer contains the ionosphere, which causes the northern lights and the reflection of radio waves. Contains very few molecules of atmosphere.

Layers of the AtmosphereLayers of the Atmosphere


3) Air Pressure, Density, and Temperature Structure

4) Atmosphere Hazards

Www.soran.edu.iq Earth Atmosphere Chapter 3 Meteorology \ Dr. Mazin sherzad.

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