Transcript Chapter 9 - MsFascianella

An air mass is a large region of the
atmosphere where the air has similar
properties throughout
 Gets its properties from the region it is
from
 Are named for the region they come
from
 When an air mass moves it brings the
conditions with them
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4 types:
1. Continental polar: cold, dry air
2. Maritime polar: cool, moist air
3. Continental tropical: hot, dry air
4. Maritime tropical: warm, moist air
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When 2 air masses meet, they form a
boundary called a front
Weather changes rapidly at fronts
because you are passing from one kind
of air mass into another
4 types:
1. Cold Front
 Cold air moves in under a warm air
mass
 Brings brief, heavy storms
 Can cause strong winds and
thunderstorms
 After the storm, the weather is cooler
and drier
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2.
Warm Front
Warm air moves in over a cold air mass
 It brings light, steady rain or snow
 Precipitation can last for days
 Can bring fog
 After the rain, the weather is warmer
and more humid
3. Occluded Front
 Occurs when a cold front and warm
front meet
 2 ways this can happen
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2.
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Cold front occlusion
Air behind the front is cold
Air ahead of the warm front is cool
Cold air is moving in on cool air and the
warm is pushed up in between them
Weather is like that of a cold front
Warm front occlusion
Air behind front is cool not cold
Air ahead of warm front is cold
Weather is like that of a warm front
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Stationary Front
Stays over an area for days without
moving
Have calm weather
Most common kind of severe storm
 Form in cumulonimbus clouds called
thunderheads
 Usually have heavy rains, strong winds,
thunder and lightning
 Some can even produce hail
 There are 3 stages during a
thunderstorm
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2.
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First Stage
Intense heat causes air to rise very
quickly
Updrafts form and the cloud grows
bigger and bigger
Water droplets and ice crystals grow
larger too
Second Stage
When the rain starts falling air moves
downward
Static electricity forms from the rubbing
of upward air and downward air
Lightning occurs when static electricity
builds up
 Lightning is unpredictable
3. Third Stage
 The storm dies when the downdraft
becomes stronger than the updraft
 Heavy rains subside and finally stop
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Thunderstorms usually form in the
warm air just ahead of a cold front
A tornado is a violent whirling wind
that moves across the ground in a
narrow path
 Form when dry, cold air masses mix
with warm, moist air masses.
 When the updraft is really strong air
rushes in from all sides causing the air
to curve into a spin
 This spin lowers the air pressure even
more, causing air to rush in even faster
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As the tornado gets stronger a funnel
forms that touches the ground
 Winds can reach up to 300 mph in the
center of a tornado
 The direction of a tornado can
continually change
 Most tornadoes occur in the Midwest of
the United States
 They mostly likely occur where there
are big differences in the air masses
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Are very large, swirling storms with very
low pressure at their center
 They form over tropical oceans
 Strong heating and lots of evaporation
cause a large low pressure center to
form
 The Coriolis effect causes winds to
spiral counterclockwise and clusters of
thunderstorms are pulled into the spiral
 The thunderstorms merge forming the
storm
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The lower the pressure, the stronger the
winds blow
 In order for the storm to be considered a
hurricane, the winds need to reach 75
mph or higher
 Hurricanes have an eye at the center of
the storm
 The eye is an area of light winds and
clear skies
 Hurricanes can grow 400 miles in
diameter
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Hurricane winds cause large waves in
the ocean
 These waves pound the shore for days
before the hurricane hits
 The storm surge causes the most
damage
 Storm surges are caused by low air
pressure
 It causes the sea to rise, along with
heavy rain from the hurricane
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Storm surges cause flooding, which
destroys homes and wears away
beaches
Hurricanes begin to die when they
move onto land because it has no
water to replace what falls as rain
Doppler radar is used to find storms as
they form
 Radar stands for radio detection and
ranging
 Radar sends out radio waves and records
their echoes
 The change in echoes gives scientists
clues
 It is used to track storms because radio
waves reflect off storm clouds
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With the radar, scientists can tell if
rain is moving toward or away from an
area, and spot spinning motions of
clouds
 Spotting motions of clouds can help
warn scientists of tornadoes or
hurricanes
 Doppler radar helps scientists find and
track thunderstorms, tornadoes and
hurricanes
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Is the average weather pattern of a region
 Climate can be described by the following
factors: temperature, precipitation,
winds, distance from coast, mountain
ranges and ocean currents
 We can also describe climate by the
plants that live their b/c plants require
their own conditions for growth, such as
amount of sunlight, precipitation and
temperature
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Examples:
1. Alaska has a climate of long, cold
winters and short cool summers
2. Florida has a climate of long, hot
summers and short, cool winters
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Latitude
is the measure of how far north or
south a place is from the equator
Temperatures are different at different
latitudes due to the angle of insolation
3 different zones:
Tropical Zone
Temperate Zone
Polar Zone
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Bodies of Water
Most of Earth is covered with water
Land and water cool and heat at
different rates
Land heats up faster in sunlight and
cools off faster
Air temperatures over land are warmer
in the summer and cooler in the winter
than over oceans at the same latitude
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Winds and Ocean Currents
The westerlies blow in the middle
latitudes
They bring warm, moist air to the west
coast and push air masses and fronts
Ocean Currents are also moved by
winds
Gulf stream is a warm current that flows
up the east coast
California current is a cool current that
moves down along the west coast
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Altitude
Is the measure of how high a place is
above sea level
The higher a place the cooler it is
Earth absorbs heat from the sun
 It also gives off heat into space
 Radiative balance is when the amount of
energy gained equals the energy lost
 Average temperature of Earth = 59˚F
 The atmosphere protects Earth from
getting too hot or too cold
 Only about ½ of incoming sunlight
reaches Earth
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30% reflects off of particles and clouds
back to space
 The atmosphere absorbs 15- 20% of the
heat
 This keeps temperatures from rising too
high
 At night clouds aid in keeping the night
from getting too cold
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The atmosphere keeps Earth warmer than
it would be
 Earth’s atmosphere acts like the glass in
a greenhouse by letting in sunlight, but
not letting heat escape
 2 main greenhouse gases are water vapor
and CO2
 Methane, nitrous oxide and
chlorofluorocarbons (CFC’s) have a small
effect
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These greenhouse gases are increasing
due to human activity
 With this increase Earth’s climate can
change and make our planet warmer
 The increase in these gases have a great
effect on our environment
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Over time Earth has undergone changes,
which caused periods of cooling and
heating
 Shifts in the radiative balance is caused
by changes in sunlight, currents and
landmasses and volcanoes
1. Sunlight
 the amount of energy the sun sends
out changes
 These changes are due to sunspots
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Sunspots are dark areas that appear on
the surface of the sun
 These spots are cooler than other parts
of the sun
 They are not permanent
 Sunspot maximum-large count of
sunspots, which happens about every 11
years
 Around the time of a sunspot maximum,
earth’s temperature goes up
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Ocean Currents
They move heat from the equator to
the poles
Change in speed and direction of
currents can explain sudden and long
term climate changes
Landmasses
Continents have changed positions and
continue to move
climate will change with their locations
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Volcanoes
Eruption of volcanoes send dust and
gases into the atmosphere
The dust and gases could block out the
sun and cause cooling
In the past volcanic eruptions were very
common and could have caused the ice
ages
They are less common today, but still
cause cooling, just not long term
changes