Download Science 4 weather and clouds

What are they?
 Air
mass: a body of air that has similar temperature &
humidity throughout
 Humidity:

the amount of water vapor in the air
An air mass can form over water or land

An air mass over polar areas will be cold or cool
 An air mass over tropical areas will be warm or hot
 Air
masses have water
vapor in them
 How does the water get
there?
 Which would have more
humidity: an air mass
formed over water or an
air mass formed over
land?
 When
an air mass moves,
it takes its temperature &
humidity along with it to
another place
 Movement
of air masses
helps them predict the
weather
 They
track:
 Where
the air mass is
moving
 What other air masses it will
meet
 How it will meet them
A
front is the area where
two air masses meet
 These can be either cold
or warm
 Winds
over North America
usually blow from west to
east
 A cold front forms when a
moving cold air mass
bumps into a warm air
mass
 The
cold air sinks under
the warm air and the
warm air rises
 The warm air cools
 The water vapor in the
warm air condenses and
forms clouds
 This type of front usually
brings strong winds &
heavy precipitation
A
warm front forms when
a warm air mass bumps
into a cold air mass that is
moving more slowly
 The warm air slides over
the cooler air
 As it rises, it cools
 Water vapor condenses
into clouds
 This
type of front usually
brings steady, long-lasting
precipitation
Cumulus clouds
 These
are thick, white & puffy
Stratus clouds
 These
are flat layers of clouds
that form close to Earth’s
surface
Cirrus clouds
 These
are feathery clouds that
form high in the atmosphere
when water vapor turns to tiny
crystals of ice
 Temperature
 Pressure
 Moisture