Chapter 17 Notes: The Atmosphere
What is the Atmosphere?
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The atmosphere can be defined as the
portion of planet earth that contains gas.
Weather can be defined as the current state of
the atmosphere at any given time or place.
Climate can be defined as the average
weather conditions of a given area.
What is the Composition of the
Earth's Atmosphere?
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About 99% of air is Nitrogen and Oxygen.
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About 0.93% of air is Argon.
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About 0.039% of air is Carbon Dioxide.
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Water vapor is also an important component of
the atmosphere.
One form of oxygen in the atmosphere is
ozone. Ozone protects living organisms from
harmful ultraviolet radiation from the sun.
Composition of the Atmosphere
How does air pressure and
temperature change with altitude?
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As altitude increases, air pressure decreases.
Air pressure is simply the pressure of air created by
the weight of the air above it.
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Increasing air pressure increases kinetic energy.
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Increasing kinetic energy increases temperatures.
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As a general rule, the higher the altitude, the lower
the air pressure will become, the lower the air
pressure, the colder the temperature.
Air Pressure
How does air pressure and
temperature change with altitude?
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However, not all of the earth's layers of the
atmosphere get colder with height.
The earth's atmosphere can be divided into
four layers based on changing temperatures.
The first layer which starts at the earth's
surface and goes up to about the height of 510 miles, is called the troposphere.
The troposphere gets colder with height.
How does air pressure and
temperature change with altitude?
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The next layer is called the stratosphere.
The stratosphere remains a constant
temperature until about 15 miles above sea
level, where it reaches the ozone layer.
Once the stratosphere reaches the ozone
layer it heats up until it reaches the next layer,
which is the mesosphere.
Troposphere and Stratosphere
Troposphere and Stratosphere
How does air pressure and
temperature change with altitude?
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The mesosphere begins about 30 miles high.
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The mesosphere gets colder with height.
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The last and final layer is the thermosphere
which begins about 50-60 miles high.
Includes the ionosphere and exosphere.
Only a small percentage of the atmosphere's
mass is in the thermosphere.
Increased solar radiation causes the
temperature in the thermosphere to increase.
Mesosphere and Thermosphere
Layers of the Atmosphere
Aurora Borealis is Produced in
the Thermosphere
What causes the seasons of the earth?
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The earth rotates on its axis every day.
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The earth revolves around the sun every year.
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The earth's axis is not perpendicular to the orbit or
the path that it takes around the sun.
The earth has a tilted axis.
The earth is tilted 23.5 degrees from a line that is
perpendicular to the earth's orbit around the sun.
Earth's Tilted Axis
What causes the earth's seasons?
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It is this 23.5 degree tilted axis that causes the earth
to experience seasonal changes in the weather
across the earth.
In places like the equator, the sun's full force is
experienced nearly year round.
In places like the north and south pole, daylight and
darkness can last for months at a time.
Places in between have four distinct seasons.
Earth's Tilted Axis and the
Seasons
When are the solstices and equinoxes?
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In the Northern Hemisphere, the summer solstice or
longest day of the year is on June 21 or 22.
In the Northern Hemisphere, the winter solstice or
shortest day of the year is on December 21 or 22.
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September 22 or 23 is the autumnal equinox.
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March 21 or 22 is the spring equinox.
The Seasons
Heat in the Atmosphere
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The definition of heat is the thermal energy
that is transferred from one object to another.
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The definition of temperature is a measure
of the average kinetic energy of the atoms or
molecules of an object or substance.
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Heat always flows from areas of high
temperatures to areas of low temperatures.
Energy Transfer as Heat
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There are three different ways that thermal
energy or heat can be transferred.
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Conduction – the transfer of heat through
matter by molecular activity. The energy of
molecules is transferred by collisions from
one molecule to another.
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The transfer of heat through metal objects is
a good example of conduction.
Conduction
Energy Transfer as Heat
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Convection – The transfer of heat by mass
movement or circulation within a substance.
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Convection usually occurs in fluids, like the
oceans and air, where the atoms and
molecules are free to move around.
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The earth's mantle is also believed to move
by convection currents.
Convection
Convection
Energy Transfer as Heat
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Radiation – The transfer of energy (heat)
through space by electromagnetic waves.
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Unlike conduction or convection, radiation
does not need a substance to travel through.
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Radiation can travel through a vacuum or
empty space without a medium or any
substance containing matter.
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The Sun’s warmth reaches Earth by radiation.
Radiation
Radiation
What happens to Solar Radiation
that comes into the Atmosphere?
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Some solar radiation gets absorbed by
atmospheric gases and the earth's surface.
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Some solar radiation is transmitted through
transparent objects like water and air.
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When solar radiation is transmitted through
objects, sometimes it is scattered.
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Some solar radiation is reflected off of
clouds and the surface of the earth.
Earth's Radiation Budget
What are some factors that affect
temperatures on the earth?
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Factors that affect the temperature of the Earth
include latitude, proximity to land and water,
altitude, cloud cover, and wind and ocean currents.
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Water moderates temperature changes. If a
geographic location lies close to a large body of
water, the region will experience cooler summers
and warmer winters compared to regions located
farther away from a large body of water.
Factors influencing Temperatures
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When cloud cover is high, the sun's solar
radiation is reflected back into space,
causing cooler daytime temperatures.
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At night, the cloud cover reflects the radiation
of the earth under the clouds back to the
Earth. This keeps the nighttime
temperatures a little warmer.
What are Isotherms?
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Isotherms are lines drawn on a map
connecting areas of equal temperatures.
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They are similar to contour lines, but instead
of connecting lines of equal elevation they
are connecting areas of equal temperatures.
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They are useful for determining weather
patterns and factors affecting temperature.
Isotherms
Isotherms