Download Weather and the water cycle

Chapter 8
What Causes
Weather?
 Earth
is surrounded by a
blanket of air called the
atmosphere.
 The atmosphere is thin,
compared to the size of Earth.
 The atmosphere is made up of
several layers.
 Each layer has a different
temperature.

Troposphere






layer closest to earth
surface.
It is about 8 miles thick.
All Earth’s landforms are
located here.
Contains 90% of the gases
in the entire atmosphere.
Contains water, dust and
other tiny particles.
Most weather occurs here.
More air pressure, because
air molecules higher up in
the atmosphere press
down on all the air
molecules below them.
 Stratosphere




Layer above the troposphere
Where the ozone is located
Air is very dry
Few clouds
Less air pressure, because air
molecules higher up in the
atmosphere press down on all
the air molecules below
them.
 The
ozone is a gas that
protects earth from the
sun’s harmful UV rays.
 is
the weight of the
atmosphere pressing down on
Earth.
 Is greatest at sea level
 Becomes less, the higher you
go.
 Is affected by temperature


Cold air is more dense, and is
heavier.
Warm air is less dense, and is
lighter.
 Air
around you is always moving
and changing.
 When the sun’s energy reaches
Earth:


some of the energy bounces off
objects such as clouds.
Earth absorbs the rest of the
energy.
 Different
types of surfaces
absorb different amounts of
energy.
Water can absorb more heat
than an equal amount of soil.
 Therefore, the soil gets
hotter quicker.


Sand at the beach would:


be hotter than the water.
give off more heat than the
water.
Because the sand is hotter, the
air over the beach will be
hotter.
 The water would:



absorb more heat, it will stay
cooler.
the air over the water is cooler.
 Cool


air-
Is denser than warm air
Is heavy, so it sinks
 Warm


air-
Is less dense
Is lighter, so it’s pushed
up
 This
sinking and rising of
air causes wind.
 Wind is the result of
uneven heating of the
atmosphere.

Winds




Result from air moving
from areas of high air
pressure to areas of low
air pressure.
Move short distances
Can blow in any
direction.
Blows from cooler
places toward warmer
places.
Happens because the
cold air is heavier then
the hot air and is able
to push it.

Local windsWind that results form a
local difference in
temperature.
 Often occur on lakeshores or
seashores.
 During the day, land gets hot
quicker, so the cool air from
the sea moves toward the
air. This is known as a sea
breeze.
 At night, the land loses heat
faster than the sea, so the
cool air from the land moves
toward the sea. This is
known as a land breeze.

 Constant
winds.
 Are global winds that
always blow in the
same direction.
 Is caused by:
 uneven heating of
large areas of Earth’s
surface.
 Earth’s rotation.
Air
moves in
curved paths.
The curving is due
to Earth’s
rotation.
This rotation
causes the
prevailing winds
to blow mainly
from the east or
from the west.
P.291
What Conditions Affect the
Water Cycle?



Water moving continuously
from Earth’s surface to the
atmosphere and back to the
Earth.
Includes three states: liquid,
gas, and solid.
Is changed by three
processes: evaporation,
condensation, precipitation.
 Process
in which
liquid water changes
to a gas (water vapor)
 Is caused by heating
water particles
 Water remains a gas
as long as the air is
warm
 Process
in which
water changes from
a gas (water vapor)
back to a liquid.
 Occurs when air
cools.
 Causes cloud
formation.
 When
water drops are
too heavy to stay in the
atmosphere, they fall
from the clouds
 Has 4 forms:

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
Rain
Snow
Sleet
Hail
 When
rain falls,
the water runs into
streams, rivers,
and lakes.
 Some is soaked
into the ground.
 Water underground
(GROUNDWATER),
also flows back to
the , streams,
rivers, oceans.
 Rivers carry water
back to the ocean.
 Amount
of water vapor in
the air.
 Is limited by air temp.
 Warm air has more water
vapor than cold air.
 Some areas of the
atmosphere have more
water vapor than other
areas.
 Water vapor doesn’t
always form precipitation,
(dew and frost)
How close the location is to the Earth’s
poles.
1.
1.
2.
The closer you are, the colder it is.
The colder it is, the greater chance you will get
snow or sleet.
The shape of the land
2.
1.
2.
3.
Air must move over landforms like mountains.
When the air pushes up it cools.
This causes rain to fall on one side of the
mountain and snow on the other.
4.
5.
6.
7.
Coastlines
also affect
the water
cycle
Sea breezes
carry humid
air.
As the air
rises over
land, clouds
form.
Clouds cause
rain.
How Can Patterns
in Weather Be
Observed?
 Tools:
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Thermometer-measures air
temp.
Hygrometer-measures
humidity.
Barometer-measures air
pressure.
Anemometer-measures wind
speed.
Wind Stocks and Wind Vanes
measure wind direction.
 Air
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
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Mass:
is a large body of air that has the same temp
and humidity throughout.
move from west to east, in the US.
can be warm or cold, humid or dry.
takes on the characteristics of the region over
which it forms.


If it forms over the Caribbean Sea, it will be humid
and warm.
If it forms over northern Canada, it will be dry and
cold.
4
1.
2.
3.
4.
kinds in US
Continental polar air
masses (cP)- cool, dry
weather.
Continental tropical air
masses (cT)- hot, dry
weather.
Maritime polar air masses
(mP)- cold, humid
weather.
Maritime Tropical air
masses (mT)-warm, humid
weather.
 When
the weather
changes in an
area, it means
that the air mass
over the area has
changed.
 The current air
mass is being
replaced by a
different air
mass.
 Where
2 air
masses meet.
 Where weather
changes.
 Usually contains
precipitation.
 2 main kinds:
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Cold fronts
Warm fronts
 Most
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weather occurs in patterns:
Wind
Temp.
Seasonal
Etc.
 The
pattern of weather an area experiences
over a long time is climate.
 Weather-condition
of the atmosphere
at a particular
time.
 Climate-average
of weather
conditions over
many years.
P.309
P.314-315