Download WeatherReview - Northview Middle School

Weather
Atmosphere and Air Temperature
insolation – the amount of the Sun’s energy
that reaches Earth at a given time and place
 When the sun is directly overhead its shadow
is shortest. As the angle decreases, the
shadow lengthens.
 The angle of insolation affects
temperature.
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It takes more heat to raise the temperature
of water than it takes to raise the
temperature of land.

In winter, warm water warms the air and
in the summer, the cooler water cools the
air.
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atmosphere – the blanket
of gases that surround the
earth
Troposphere – the layer
of the atmosphere that is
closest to the Earth’s
surface
The higher the altitude,
the colder the air
temperature!
air pressure – the force put on a given
area by the weight of the air above it
 Air has weight.
 As altitude increases, air pressure
decreases.

weather – what the
lower atmosphere is
like at any given place
and time
 Weather includes a number of conditions at
any one time
 barometer – a device for
measuring air pressure
 Barometers help to predict
the weather

 Example:
When air pressure falls, rain is likely
Water in the Air
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water vapor – water in the form of gas
humidity – the amount of water vapor
in the air
evaporation – the changing of a
liquid into a gas
Evaporation requires heat and
in places where evaporation
takes place become cooler as
a result.
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relative humidity – a comparison between the
actual amount of water vapor in the air and the
amount the air an hold at a
given temperature.
condensation – the changing of
a gas into a liquid
Molecules in water vapor move
more quickly than molecules in
cold water.
Heat causes water to change to
water vapor.
 How
can warm air become cool?
 Warm
air can be pushed upward by
winds
 Warm air can be pushed
up by cool air
 Warm air can cool by rising and
expanding
Clouds of Water and Ice
Stratus Clouds

stratus clouds – a cloud that forms in a blanket
like layer
Cumulus Clouds

cumulus cloud – a puffy cloud that appears to
rise up from a flat bottom
Cirrus Clouds

cirrus cloud – a high
altitude cloud with a
featherlike shape, made of
ice crystals
Fog

fog – a cloud that forms at ground level
Precipitation

precipitation – any form of water particles that falls
from the atmosphere and reaches the ground

The larger the cloud the more water it holds, so it
may produce more precipitation.
The Water Cycle

water cycle – the continuous movement of water
between Earth’s surface and the air, changing from
liquid to gas to liquid.
Air Pressure and Wind
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Warming molecules speed up and spread out. This
lowers air pressure.
Molecules of water vapor weigh less than oxygen
and nitrogen in the air, and thus exert less pressure.
The direction a barometer is changing can be a clue
to future weather.
 A falling barometer may be a sign that a storm is
on its way
 A rising barometer may be a sign that fair
weather is approaching
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wind – air that moves horizontally
updraft – air that rises
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downdraft – air that sinks
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Air that is warmed rises
Air moves down when air pressure above is higher
and the moves down to an area of lower pressure
convection cell – part of
the atmosphere where air
moves in a circular pattern
because of unequal heating
and cooling.
Air moves from an area with higher
pressure to an area of lower
pressure
 sea breeze – wind that blows from sea
to land

 When
the air over the land gets hotter than the
air over the water

land breeze – wind that blows from land to
sea
 When
the air pressure over the sea is higher than
the air pressure over the land.
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Coriolis effect – the
curving of the path of
a moving object
caused by Earth’s
rotating.
If the Earth did not
rotate, air would
travel away from the
equator towards the
poles. At the poles,
the air would move
back towards the
equator.
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air mass – a large region of the atmosphere
where the air has similar properties throughout
front – a boundary between air masses with
different temperatures
Cold Front

cold front - cold air
moves in under a warm
air mass
What kind of weather
would you expect a cold
front to produce?
Cold fronts can produce
short, heavy rains, often
thunderstorms with
heavy winds, followed by
clear skies and cooler,
drier weather.
Warm Front

warm front – warm air
moves in over a cold air
mass
What kind of weather
does a warm front
produce?
A warm front can cause
steady rain or snow that
may last for days and
light winds, followed by
warmer and more humid
weather.
Occluded Front

occluded front – a front
formed where a warm
front and cold front
meet
Stationary Front

stationary front – an
unmoving front where a
cold air mass and a
warm air mass meet
What Do Fronts Look Like from
Space?
Satellites show
large weather
patterns, such
as fronts and
storms which
help weather
scientists.
Thunderstorm

thunderstorm – the
most common severe
storm, formed in
cumulonimbus clouds
What causes
lightning?
Air from updrafts
rubs against air from
downdrafts, creating
static electricity.
The static electricity
builds up, until
lightning sparks.
Tornado
tornado – a violent whirling wind that moves
across the ground in a narrow path
Hurricane
hurricane – a very large, swirling storm with very low
pressure at the center
Hurricane Fran
Storm Surge

storm surge – a great
rise of the sea along a
shore caused by low
pressure
A steeper continental shelf
(below) will not see as much of
a storm surge.
A shallow slope off the coast
(above) will allow a greater storm
surge.
Doppler Radar
Doppler radar bounces sound waves off the storm clouds.
Doppler radar can tell if raindrops are moving toward or
away from observers, and it can spot spinning
movements in clouds. This helps scientists predict
which way storms will travel.
Climate

climate – the average
weather pattern of a
region
Factors That Affect Temperature

Distance from the equator
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Air pressure and winds
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Altitude
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Distribution of water
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radiative balance – a balance between energy
lost and energy gained

The Earth is constantly radiating energy into the
atmosphere, which lowers temperature.
Greenhouse Effect

greenhouse
effect – the
ability of the
atmosphere to let
in sunlight but to
not let heat
escape
What causes climate change?

The Sun (sunspots)
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Ocean Currents
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Volcanoes
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isobar – a line on a weather map connecting
places with equal air pressure

Show patterns better than numbers
wind vane – a device that
indicates wind direction
 anemometer – a device
that measures wind speed
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Exploring Weather – The
Atmosphere In Motion