Water and Weather
• Humidity
• Clouds
• Precipitation
Weather is affected by the amount of water in the air.
Don’t forget
transpiration.
Humidity
•
•
the amount of water vapor (moisture) in the air
warm air can hold more moisture
Relative Humidity
• Relative Humidity (%)=amount of moisture in the
air compared to how much moisture the air can
hold (100%=saturated)
• evaporational cooling
• use psychrometer and chart
• 2 thing affect RH
– amount of water vapor
– temperature—RH decreases as the
temperature rises and RH increases as
temperature drops
EX: If the dry bulb reads 10°C,
& the difference between the wet
& dry-bulb thermometers is 8°C,
what is the RH? ____%
Condensation
• gas (water vapor) COOLS and
becomes a liquid
• air must be saturated
(RH=100%)
• Dew Point (measure as class
activity—using jar, water, ice
and thermometer)
– temperature where
condensation occurs
– this is the temperature that
dew and frost forms and the
temperature where
fog/clouds form
Cloud Formation
• Cloud droplets are made of LIQUID water
droplets and/or ice crystals
• in order for clouds to form you need
– 1. moisture (water vapor)
– 2. cooling (to dew point)
– 3. particles---condensation nuclei
(smoke, dust, etc)
Cloud types (classified by height and appearance)
E-activity: Types of Clouds
Face in the clouds (website)
3 main types of clouds— classified
according to shape and height
• Cumulus
– puffy with flat bottom
– form when warm air
rises
– can result in showers
– may develop into
cumulonimbus clouds
(CB)= T-storm
• Cirrus
– thin, wispy, feathery,
white clouds
– form at top of
troposphere (so icy)
3 main types of clouds
• Stratus
– form in smooth, flat layers
– blanket a large area of the
sky (usually gray)
– called nimbostratus if
precipitating (long periods of
drizzle or snow)
– called fog if formed at/near
the ground
• other clouds
– nimbo means producing
precipitation
– alto- means middle
altitudes
– contrails=make by
airplanes’ exhaust
Websites
•
•
a. Types of clouds (with pictures)
b. Cloud pictures:
•
•
c. More cloud pictures (as time permits):
d. Cloud matching game --if time permits:
Precipitation
• 5 types of precipitation
– Rain/drizzle
– Snow
– Sleet (also called ice pellets)
– Hail
– Freezing rain/freezing drizzle
SNOW
•
•
water vapor
changes directly
to a solid
(sublimation)
SNOW was
NEVER rain
HAIL
•
•
•
balls of ice that fall from
thunderstorms
each trip up and down is
a layer
hail forming (animated website)
•
Sleet/ice pellets —
forms when rain falls
through a thick layer of
freezing air
•
Freezing rain— rain
freezes right when it hits
(layer of ice)—VERY
dangerous
Measuring
precipitation
• rain gauge
• ruler for snow
Did you know…
• About 78% of all precipitation falls over Earth’s
oceans (WHY?). Of the 22% that falls on land,
about 65% returns to the air by evaporation.
• The largest hailstone ever recorded fell in
Bangladesh in 1986. It weighed over 1 kg.
• *Arica, Chile has an average rainfall of less than
1 mm a year (.76 mm)
• Kauai, Hawaii has average rainfall of 12 meters
a year (keep in mind that Atlanta gets an
average of 1.3 meters per year).
Funny??
• What is a king’s favorite kind
of precipitation?
• ...............HAIL
• What do you get when you
cross a snowman with a
vampire?
• ...........frostbite
• What do you call it when it
rains chickens and ducks?
• ....... Foul weather
Websites
• Weather Maker simulation
• Cloud Tutorial PowerPt (about 10 min—needs
sound): if time permits
• Weather Eye Simulation (optional)