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•Humidity- is
the measure
of water
vapor in the
air
•Warm air
can hold
more water
vapor than
cooler air.
• Relative humidity
is a ratio of how
much water vapor
the air is holding
to how much
water vapor it is
capable of
holding at a given
temperature
• Study the graph.
• The same amount of
water vapor is in the air.
• The air is shown at
different temperatures.
• As the temperature
increases, what happens
to the percent of relative
humidity? Does it
increase or decrease?
•A hygrometer
measures
relative
humidity.
• A psychrometer
is made of 2
thermometers.
One is normal
(dry bulb). One
has a wet wick
on the end (wet
bulb).
• Evaporation is when
liquid water becomes
water vapor.
• Water changes from
liquid to gas.
Condensation is
when water vapor
becomes liquid
water.
Water changes from
gas to liquid.
When air becomes cooler,
it may reach a
temperature where the air
can no longer hold its
water in vapor form. At
that point condensation
occurs.
That temperature is called
the dew point.
• …when the
relative
humidity is
100%.
• If the air
continues to
cool,
condensation
occurs.
• Air in direct contact
with your cold glass of
ice water
• Air during the
night can cool
below
saturation and
reach its dew
point.
• Condensation
on small
particles of
dust in the
atmosphere
forms clouds.
• Contrails are
caused by water
condensing on
particles from
the exhaust of
jets.
• Warm moist air rises and
cools.
• Condensation in the
atmosphere forms clouds.
• Eventually the
condensation becomes
too heavy to cling to dust
particles in the air.
• Rain, snow or sleet is the
result.
• A barometer measures
air pressure.
• When air pressure
drops, warmer air is
rising and precipitation is
predicted.
• Look at current weather conditions in
your area.
• Find the
•Temperature
•Relative humidity
•Dew point
•Barometric pressure (air pressure)