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Chapter 3
Weather
Lesson 2
How do the ocean and Water Cycle
affect weather?
 current
 weather
 humidity
 precipitation
Current
Water on the ocean surface is pushed
forward by winds. The result is a current or
a stream of water that flows like a river
through the ocean.
Ocean Affect Weather
The oceans help keep Earth’s weather
mild. The temperature on Earth would
be much more extreme without oceans.
Ocean Affect Weather
During the summer, the
oceans absorb much
heat from the sun. This
absorption keeps the
air over the ocean
cooler.
In the winter, the
ocean release heat into
the air above them,
causing the planet to
be warmer.
Water Cycle
The constant movement of water from the
Earth’s surface to the atmosphere and back to
the earth’s surface.
Weather
Weather is the condition of the atmosphere
at a certain time and place. What you may
call weather is the water cycle at work.
Humidity
Some areas of the atmosphere have more water vapor than
others. The amount of water vapor in the air is called
humidity.
Humidity
 A large amount of water vapor is high humidity. A
small amount of water vapor is low humidity.
Humidity depends on partly the airs’ temperature.
This is a hygrometer. It measure
the amount of water vapor, or
humidity in the air.
Warm air has more water vapor in the air in it than
cold air. High humidity usually means its about to
rain.
Georgia Humidity Map
Cloud Formation
Clouds form in air that is high in humidity, or
water vapor. As warm air is forced up, it
cools.
Some of the water vapor begins to condense
on bits of dust and other particles in the air.
As more and more water condenses, a cloud
forms.
Types of Clouds
Cumulus
 very puffy
 fair or good
weather,
 if they are gray
at the bottom,
rain may come.
Stratus
 form low in
atmosphere.
 look long and flat
 Usually mean some
rainfall or snow is
coming.
Cirrus
 form high in
atmosphere where
the air is very cold.
 Made mostly of ice
crystals.
Cloud Formation
What type of clouds are in the
pictures above?
Precipitation
Rain
Sleet
Snow
Hail
Let’s Review
 How does the ocean affect temperature and




weather?
What causes clouds to form?
Describe each type of cloud.
What is a current?
What does humidity tell you about the
weather?
Lesson 3
How is weather predicted?
Vocabulary
meteorology
barometer
anemometer
hygrometer
Air mass
front
climate
Meteorology
The study of weather is meteorology. To study
weather, scientist must first measure it.
Meteorologist, scientist who study weather, use
many measuring instruments.
Weather Instruments
Thermometer
Barometer
 Measures air pressure which
 Measures air temperature.
 If the air cools down during
the day or warms up in the
evening, this change may
mean rain is coming.
is also called barometric
pressure.
 A change in the air pressure
often means the weather is
about to change.
Weather Instruments
Anemometer
Hygrometer
 Measures humidity, or water
 Measures the wind speed.
 A change in wind speed may
mean the weather is about
to change.
vapor.
 An increase in humidity
often means its about to
rain.
Air Mass

An air mass is a large body of air that has the
same temperature and humidity throughout.
 Air masses can be warm, cold, humid, or dry.
 The type of air mass is based on the region
where it forms.
Types of Air Mass
There are four kinds of air masses that
affect weather in the United States.
Continental Polar (cP)
 bring cool and dry weather.
Maritime Polar (mP)
 bring cold and humid weather.
Continental Tropical (cT)
 bring hot and dry weather.
Maritime Tropical (mT)
 bring warm and humid weather.
Types of Air Mass
Fronts
 The border where two air masses meet is called a
front. The two main kinds of fronts are cold
fronts and warm fronts.
Warm Fronts
 A warm front forms where a
warm air mass moves over a
cold air mass.
 It get warmer and more
humid after a warm front
passes.
 It brings rain or snow that
last for hours.
Cold Fronts
 A cold front forms when a
cold air mass moves under a
warm air mass.
 It gets cooler and drier
after a cold front passes.
 It brings heavy rain or snow
that will pass quickly.
Weather Maps
 A weather map gives you information about what
the weather is like in an area.
Weather Map Symbols
Rainy Weather
Sunny Weather
Partly Cloudy
H
High Pressure
L
Low Pressure
Cold
Front
Warm Front
Let’s Review
 How can weather be predicted?
 Name and describe each type of weather
instrument.
 What is the difference between air mass
and a front?
 What kind of information is given on a
weather map?
 Identify following symbols from a weather
map.
L
H