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J. Air
Pressure: The
measure of the force of the air pressing down on the Earth's
surface. Air pressure can vary from one point to
another on the Earth's surface. The air pressure at
any particular point on the Earth depends on the density of
the air.
The
denser the air, the more air pressure that pushes down on
the Earth.
What affects air pressure?
1. Temperature
2. Water Vapor
3. Elevation
Remember..............
warm are rises. Therefore warmer temperatures have
less dense air. Cooler temperatures have more dense
air.
Moist air is less dense than dry air. This is because
a water molecule (H2O) has less mass than either a nitrogen
(N2) or an oxygen (O2) molecule. Dry air has more
pressure because it has greater density.
The farther you go down
in the ocean, the greater the
air pressure. The higher you go in a plane, the less
air pressure.
K.
Measuring Air Pressure: Barometer-
an instrument used to measure air pressure.
2
types:
1.
Mercury barometer is filled with mercury.
As the air pressure increases the mercury rises.
2.
Aneroid barometer (used in our homes and offices).
A change in air pressure causes a needle to move along a
dial, which indicates the new air pressure.
L. Air
Pressure and Weather:
High
Pressure usually
means fair or good weather.
Low Pressure usually
means cloudy, rainy, weather.
END OF SECTION 1-2 NOTES!!!
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