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Meteorology Unit (Atmosphere and air pressure)
• Weather: Condition of the atmosphere at a
certain place and time.
• Atmosphere: a mixture of gases that
surrounds Earth and acts like a protective
blanket
– Contains oxygen
– Protects from sun
Layers of the Atmosphere
• Troposphere: all weather happens here
• Stratosphere: ozone layer-protects us
• Mesosphere: middle layer (protects us for
meteors)
• Thermosphere
What do you think is the most abundant gas in
our atmosphere? ____________
Atmosphere
Composition of the atmosphere
• Nitrogen=78%
• Oxygen=21%
• Other 1%=water vapor,
CO2 and other gases
Atmosphere/Air Pressure
• Atmosphere held in place by gravity
• Air Pressure is strongest at the surface
because there is more air above you.
• As altitude increases, air pressure decreases
– Think of a stack of books or a cheerleading
pyramid
Air pressure- the measure of the force
with which air molecules push on a
surface.
Air Pressure
As air pressure decreases, so
does density.
presses
The weight of the atmosphere ________
down on every part of the Earth’s surface.
The pressure exerted by the Earth’s
atmosphere at any given location is called
the atmospheric
___________ pressure or __________
barometric
pressure.
TRY THIS TO DEMONSTATE AIR PRESSURE:
1) Fill a plastic bottle with heated water.
2) Leave the water for a couple of minutes.
3) Pour water out and immediately screw on the cap.
4) Roll the bottle in ice.
5) Explain the results.
dense
In high pressure areas, air is more ________
than in areas of lower pressure. The high
rising and
pressure keeps water vapor from ______
forming rain clouds. The air is ________.
sinking High
pressure areas, or highs, are shown by “H”
symbols.
High barometric
pressure supports
sunny, clear, and
favorable weather
conditions.
dense than
In low pressure areas, air is less _______
in areas of higher pressure. The low pressure
rise Moist water vapor can rise
allows air to _____.
and form _____________.
storm clouds Low pressure areas,
or lows, are shown by “L” symbols.
Low barometric
pressure supports
unstable, and
sometimes stormy
weather conditions.
Identify the areas of high and low pressure on the
map. Notice what type of weather is indicated by
radar in these areas.
higher pressure into
Air travels from areas of ______
areas of _______
lower pressure. As winds blow
into a lower pressure region, the air moves
clouds
up. The upward flow of air can cause _______
and precipitation to form.
A __________
barometer is an instrument used to measure
atmospheric pressure. There are two types of
aneroid barometer. It
barometers. The first is the ________
consists of a box in which the air has been __________.
removed
Changes in the air pressure cause the sides to bulge in
or out moving the pointer.
1)
2)
3)
4)
Make a homemade barometer.
Cut off the end of a balloon. Place the balloon over the top of a
can or jar, pull tightly and secure with a rubber band.
Cut the tip of the straw to create a pointer. Tape one end of the
straw horizontally to the center of the balloon so that the other
end hangs past the end of the can.
Hold an index card up so that the straw points somewhere close
to the middle of the card. Mark the spot. Draw five lines above
and below this mark.
Watch the barometer and
record results daily.
The other type of
barometer is the
mercurial
_________
barometer. A tube
is filled with rising
and falling
mercury Higher
________.
pressure causes
the mercury to
rise in the tube.
____
How does a mercurial barometer measure atmospheric
pressure?
1) Fill a glass barometer tube (closed at one end) with colored
water.
2) Fill a beaker with colored water.
3) Cover the open end of the tube with your finger and invert
the tube. Lower the tube carefully into the beaker.
4) Clamp the tube upright on the stand.
5) Mark a scale of centimeters on cardboard and label it from 60
– 90 cm.
6) Measure the actual height of the colored water over the next
several days. (Keep out of the sunlight).
Look at the map. Which part of the United
States is having clear weather? Which part is
most likely having stormy conditions?