And now'the weather

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And now.the weather!
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This unit is concerned with the measurement of
current weather conditions. Students will learn
about each condition and then learn how to build
a device in order to measure that weather
condition. Students will measure weather
conditions in science and use that information to
perform mathematical calculations. Then, in
Language Arts class, the students will learn
about the career of the Meteorologist.
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Winds
Winds are a very important part of the weather.
The winds bring us our weather. For example,
when the winds are out of the south, you usually
can expect the weather to be warmer. If it is
raining today to the west of you and the winds
are out of the west, you can expect it to be
raining tomorrow.
Winds are named for the direction in which they
come from. This means a westerly wind is coming
out of the west. Knowing the direction the wind
is blowing from is an important part of the
information a meteorologist uses to make the
weather forcast.
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What Makes the Wind Blow?
A discussion of what makes the wind blow usually
starts at the beach where the land is much warmer
than the water. Air over the warm beach is
warmed and rises. This air moves out to sea
where it cools and becomes heavy and starts to
sink. Sinking air over water moves in toward
the beach to replace the rising air. This is
called a seabreeze and is a simple wind.
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Global Winds
Like the beach, the equator is a region of warm,
rising winds. This warm air moves away from the
equator, cools and sinks at latitude 30º causing
high pressure there. Some of this sinking air
flows back to the equator as the Tropical
Easterlies, sometimes called the Trade Winds.
These winds blow constantly. The rest of the
sinking air moves towards the poles as the
Prevailing Westerlies.
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Global Winds
At latitude 60º, the air is pushed up by air
coming from the poles. This rising air causes an
area of low pressure called the Subpolar Low.
Some of this rising air moves toward the poles
forming constant winds called the Polar
Easterlies. The remaining air flows back to
latitude 30º and sinks to help form the high
pressure found there.
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Coriolis Force
These global movements of air are caused to
curve to the right in the northern hemisphere by
the Coriolis Force. In the southern hemisphere,
the Coriolis Force causes the winds to curve to
the left. This makes the winds blow out of the
east or the west.
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Measuring Wind Direction
Nothing beats a good old fashioned weather vane
for finding the direction from which the wind is
blowing. It is simple to make your own weather
vane out of simple materials.
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Air Pressure
Air has force and weight. At the surface, air
presses down on you with a weight of 14 pounds
per inch. We can measure the pressure with a
barometer as 29.92 inches or 1013 milibars. On
days when the pressure is higher than normal, the
weather usually is clear and sunny. On days when
the pressure is lower than normal, the weather is
cloudy and rainy.
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Measuring Air Pressure
The barometer was invented in 1643 by
Evangelista Torricelli, a secretary of the noted
astronomer and inventor, Galileo.
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Measuring Air Pressure
In this unit, the student will learn how to
assemble a simple barometer. The student will
use this simple barometer to make observations of
the weather. Rising air pressure usually means
that the weather tomorrow will be nice. Falling
air pressure means the weather tomorrow will be
wet.
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Humidity
Humidity affects how you feel! A warm, humid
day makes you feel worse than on a warm, dry day.
A cool, dry house in winter is not as
comfortable as a cool house with average
humidity. This is why new furnaces come with
humidifiers!
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What is Humidity?
In any weather report, humidity is mentioned as
a percentage. While up to three percent of the
atmosphere can be water vapor, the amount depends
on the temperature. Warmer temperatures allow
the atmosphere to hold more water vapor.
Relative Humidity is a measure of how much
water vapor the atmosphere contains as compared
to how much it is capable of containing at that
temperature. A relative humidity of 50 means
that the atmosphere at the current temperature
contains only half the water vapor that is could
hold.
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Humidity and Dew Point
When you watch the weather on the weather
channel, you hear about something called the Dew
Point temperature. This is the temperature at
which water condenses from the atmosphere and dew
is deposited on the ground. It is also the
temperature at which relative humidity is at
100. Usually this happens during rain
storms. The Dew Point temperature is also a
measure of how much moisture and energy is in the
atmosphere. A Dew Point in the 70s in the
summer means there is a lot of moisture in the
air for a thunderstorm to liberate. Dew Points
more than 20 degrees lower than current air
temperature mean the air is pretty dry. There is
not much energy for thunderstorms, nor much
likelihood.
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How to Measure Humidity
It is relatively easy to make a hydrometer (also
called a psychrometer) to measure the current
relative humidity. All you need is a pair of
thermometers, a way to make one of them wet, and
a Table of numbers to look up the relative
humidity.
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How to Use Your Instruments
After three weeks of daily observations, you
will have these data tables filled with
information about the weather.
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From the gang at Hamilton JHS in Parkersburg,
WV Bob Wharton - C.A.T.S. Science 8
Sara Little
- Language Arts 8 / Developmental Reading /
Careers Vicki Ruble - Mathematics 8
The End