Weather

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Weather

• What is Weather to You?

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What is weather?

• Describes the current condition of the
  atmosphere.
• Factors include- temperature, cloud cover, wind
  speed direction, humidity, and air pressure

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What is weather?

• Temperature-
• Measures how fast air molecules are moving
• Rapid-warm/slow-cold
• Use a thermometer to measure

• Atmospheric Pressure
• Air has weight, and the weight exerts pressure
• When air is heated molecules move faster and air
  expands, making air less dense. This is why it is
  moved upward
• Warm rises/cool sinks
• Use a barometer to measure

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• Humidity-
• amount of water vapor in the atmosphere
• Warmer more evaporation occurs thus more water
  vapor
• Dew point- temperature at which condensation can
  occur. when the air is saturated (holds all the
  vapor it can) condensation can occur
• Measured with pshychrometer or hygrometer

• Energy Transfer
• Fast moving molecules transfers to slow moving,
  transfer of energy when molecules collide is
  conduction
• Warm air rising cool air sinking is convection
  (main way heat is transferred in atmosphere)

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Clouds
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Clouds
A cloud is a large collection of very tiny
droplets of water or ice crystals. The droplets
are so small and light that they can float in the
air.

• Middle Clouds
• Altocumulus
• Altostratus

• Low clouds
• Stratus
• Nimbostratus
• Cumulonimbus
• Stratocumulus
• Cumulus

• High and vertical clouds
• Cirrus
• Cirrocumulus
• Cirrostratus

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Wind

• Measuring Wind-
• Direction is measured by wind vane.
• An ANEMOMETER measures wind speed. The cups catch
  the wind, turning a dial attached to the
  instrument. The dial shows the wind speed. .

Wind is the horizontal movement of air from high
to low pressures. Described by their direction
and their speed. Name tells you where it is
coming from.
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Winds
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Trade Winds

• Wind flows outward away from the subtropical
  highs. It encounters the Coriolis effect.
• we find winds blowing from east towards the west.

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Coriolis effect

• This force causes the winds in the Northern
  Hemisphere to move from the east towards the west
  below the subtropical high, and from the west
  towards the east above the subtropical high.

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Westerlies

• Above the subtropical highs in the Northern
  Hemisphere, winds blow from the west towards the
  east.

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Sea Breezes

• During the day, land gets heated by the Sun much
  quicker than does water. As the land becomes
  warmer, it heats the air in the atmosphere above
  it. This causes the air to expand, becoming less
  dense, and thus creating a low pressure.

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Land Breeze

• In the night, land cools down much quicker than
  does the waters of the ocean. As the land becomes
  cooler, so does the air above it. This results in
  air becoming more dense, forming a high pressure,
  causing winds to blow outward towards the sea.
  This is known as a land breeze.

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Animation of sea land breeze

• http//www.classzone.com/books/earth_science/terc/
  content/visualizations/es1903/es1903page01.cfm

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Air masses

• Air masses move due to wind
• Dry (continental) or moist (maritime) and warm
  (tropical) or cool (polar), depending on where it
  begins.
• Mass of air that remains over a region for a few
  days and takes on the characteristics of the area
  it occurs
• When air masses of different temperature meet, a
  boundary is formed called a front

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Air Masses

• A large body of air with similar temperature and
  moisture.
• Air masses form over large land or water masses
  and are named by where the formover
  land-continental or over water-maritime and also
  named for where they originate from-near the
  tropic-tropical and from near the poles-polar

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• Dry (continental)- comes from land masses
• Humid (maritime)- comes from water
• Warm (tropical)- warm air coming up from the
  equator
• Cold (polar)- cool air coming down from the poles
• Pg 598 in book

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Description of air masses

• Continental polar (cP)- cool and dry
• Continental arctic-type of continental polar mass
  that is much colder-forms in the arctic circle
• Continental tropical (cT)- warm (hot) and dry
• Maritime polar (mP)- humid (wet) and cold
  unstable
• Maritime tropical (mT)- humid (wet) and warm
  unstable

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cP continental polar cold, dry, stable
cT continental tropical hot, dry, stable air aloft--unstable surface air
mP maritime polar cool, moist, and unstable
mT maritime tropical warm, moist, usually unstable
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Fronts

• Warm-
• less dense (warm) slides up and over cold air
• high cirrus clouds first and then stratus
• Long periods of slow precip.
• Warm air in Temperature rises

• Cold-
• Cold air pushes under warm air pushing it up,
• Cumulus cumulonimbus brings
• narrow band of precipitation can occur (short
  period of heavy precip.)
• cold air in (temp drops)

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Fronts

• Cold-
• Cold fronts move faster than warm fronts.
• The weather activity in a cold front is often
  violent and happens directly at the front.
• Cold fronts have sudden gusty winds high in the
  air creating turbulence .
• Shown on a weather map by a blue line with
  triangles pointing the direction in which the
  cool air (front) is moving.

• Warm-
• The weather activity in a warm front generally
  happens before the front passes through an area.
• In a warm front the cloud formation is very low
  often creating situations of poor visibility.
• Shown on a weather map by a red line with half
  circles pointing the direction in which the warm
  air (front) is moving.

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Fronts

• Warm-
• less dense (warm) slides up and over cold air
• high cirrus clouds first and then stratus
• Long periods of slow precip.
• Temperature rises

• Cold-
• pushes under warm air pushing it up,
• Cumulus cumulonimbus brings
• narrow band of precipitation can occur (short
  period of heavy precip.)
• cold air in (temp drops)

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Cloud types

• Cirrostratus

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Fronts

• Stationary
• Warm air cold air meet and neither advances
• Remains in same location for days
• Cloudiness and precip. may occur

• Occluded
• -When a warm front is trapped by (between) two
  cold fronts.
• -Shown on a weather map by a purple line with
  alternating triangles and half circles pointing
  the direction the front is moving.
• -may produce cloudy with precip.

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Fronts

• Stationary
• Warm air cold air meet and neither advances
• Remains in same location for days
• Cloudiness and precip. may occur

• Occluded
• When a warm front is trapped by (between) two
  cold fronts.
• -Shown on a weather map by a purple line with
  alternating triangles and half circles pointing
  the direction the front is moving.
• -may produce cloudy with precip.

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High and low pressure centers

• Moves from high to low areas
• High pressure areas air sinks
• Moves from high to low
• Air moves clockwise due to Coriolis
• Usually dry with few clouds
• High air pressure is associated with cold fronts
  which means sunny and fair weather.

• Low pressure area- air rises and cools
• Air circulates in counterclockwise
• Air reaches dew point water vapor condenses
  forming clouds and precipitation
• Low pressure is associated with warm fronts which
  means cloudy, overcast, drizzly, and possibly
  rainy weather.

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Cyclones

• Cyclones- swirling center of low air pressure
• Warm air at the center rises and air pressure
  decreases. Cooler air blows from areas nearby.
• Spins counterclockwise in Northern Hemisphere

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Anticyclones

• High pressure centers
• Winds spiral outward from centers of dry air
• Spin clockwise in Northern Hemisphere

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Winds spiral inward towards the low-pressure
center- counterclockwise
Winds spiral outward from the high-pressure
center- clockwise
cyclone
anticyclone
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Cyclones
Anticyclones

• Decreasing air pressure
• Marked as Lows on weather maps
• Counterclockwise
• Associated with clouds, wind, and precipitation

• High pressure centers
• Marked as High on weather maps
• Clockwise
• Associated with dry, clear weather

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Severe Weather

• Thunderstorms- cumulonimbus clouds (along cold
  fronts)
• Lightning- energy flow that occurs between areas
  of opposite electrical charge

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Thunder

• Thunder- what causes?
• Lightning 5-6 times hotter than suns surface
  (54,000 degrees Fahrenheit.) -causes air to
  expand quickly, then cools quickly and contracts
  producing rapid movement of molecules
• Sound due to expansion and contraction of the
  heated air

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Thunder Exp.

• EXPLANATION
• Hitting the bag causes the air inside the bag to
  compress so quickly that the pressure breaks the
  bag. The air rushes out and pushes the air
  outside away from the bag. The air continues to
  move forward in a wave. When the moving air
  reaches your ear, you hear a sound. Thunder is
  produced in a similar way. As lightning strikes,
  energy is given off that heat the air through
  which it passes. This heated air quickly expands
  producing energetic waves of air resulting in a
  sound called thunder.

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• What color is lightning?Lightning seems to be
  clear or a white-yellow color, but it really
  depends on the background.
• If your hair stands on end or your skin starts to
  tingle, lightning maybe about to strike. Get down
  on your hands and knees and keep your head tucked
  in. Do not lay flat, because it can give
  lightning a better chance of strike you.

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• What is cloud-to-ground lightning?
• All lightning is dangerous, but cloud-to-ground
  lightning is the most dangerous type of
  lightning. Most cloud-to-ground lightning strikes
  come from the negatively charged bottom of the
  cloud traveling to the positively charged ground
  below.Cloud-to-ground lightning bolts strike
  the tall objects, like trees and buildings. These
  lightning strikes can cause fire and property
  damage. If you're the tallest object, then
  lighting can strike you.
• Lightning is the second weather related killed.

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Triggered lightning/ "natural" lightning

• goes from ground to cloud,
• while "natural" lightning is cloud to ground.

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• Lightning happens when the negative charges
  (electrons) in the bottom of the cloud (and your
  finger) are attracted to the positive charges
  (protons) in the ground.

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• The accumulation of electric charges has to be
  great enough to overcome the insulating
  properties of air. When this happens, a stream of
  negative charges pours down towards a high point
  where positive charges have clustered due to the
  pull of the thunderhead.

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• The connection is made and the protons rush up to
  meet the electrons. It is at that point that we
  see lightning. A bolt of lightning heats the air
  along its path causing it to expand rapidly.
  Thunder is the sound caused by rapidly expanding
  air.

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• http//science.howstuffworks.com/nature/natural-di
  sasters/lightning.htm

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• What is intracloud lightning?
• Intracloud lightning is the most common type of
  lightning. This occurs when there are both
  positive and negative charges within the same
  cloud. Usually, the process takes place within
  the cloud and looks like a bright flash of light
  which flickers.

• What is intercloud lightning?
• Intercloud lightning is less common. It's when a
  lightning strike occurs when there are positive
  and negative charges within different clouds and
  the strike travels in the air between them.

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• What is forked lightning?
• Forked lighting appears as jagged lines of light.
  They can have several branches. Forked lightning
  can be seen shooting from the clouds to the
  ground, from one cloud to another cloud, or from
  a cloud out into the air. This lightning can
  strike up to 10 miles away from a thunderstorm.

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What is heat lightning?

• Heat lightning is a term used to describe
  lightning flashes that are too far away from you
  to hear the thunder.
• The reason that it is called heat lightning is
  that it appears most often on a hot summer day
  when the sky is clear overhead.

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• Outdoor Lightning Safety
• Seek shelter indoors or in a car.
• Stay away from single tall objects (such as a
  tree) and metal objects (fences, pipes, rails).
• Don't hold golf clubs, fishing poles.
• Remove backpacks with metal frames.
• It is not safe to be riding bicycles, motor
  scooters, motorcycles, or golf carts.
• If you are out in the open and cannot get to
  shelter, stand in a low spot under a group of
  trees (not under a lone tree)
• or crouch down on the balls of your feetdo not
  lie flat on the ground. If you are swimming or
  boating, get out of the water.

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Can you tell how far away?

• If You Can Hear It, Clear It If You Can See It,
  Flee It This saying means that you should take
  shelter if the time between a lightning flash and
  the thunder is 30 seconds or less, which means
  that the lightning is about 5 miles away. Don't
  resume activities until 30 minutes after you hear
  the last thunder.

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• Can you tell how far away a storm is?
• Yes, you can use thunder to tell how far away a
  storm is. Next time you see a storm, count the
  number of seconds between when you see the
  lightning and hear the thunder. Take the number
  of seconds and divide by 5 and that will tell you
  how far away the storm is in miles. For example
  If you counted 10 seconds between the lightning
  and the thunder, the lightning is 2 miles away!

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Tornadoes

• A tornado is a violent rotating column of air
  extending from a thunderstorm to the ground.
• The most violent tornadoes are capable of
  tremendous destruction with wind speeds of up to
  300 mph.
• They can destroy large buildings, uproot trees
  and hurl vehicles hundreds of yards. They can
  also drive straw into trees. Damage paths can be
  in excess of one mile wide to 50 miles long. In
  an average year, 1000 tornadoes are reported
  nationwide.

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How do tornadoes form?

• Most tornadoes form from thunderstorms.
• You need warm, moist air from the Gulf of Mexico
  and cool, dry air from Canada. When these two air
  masses meet, they create instability in the
  atmosphere.

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A change in wind direction and an increase in
wind speed with increasing height creates an
invisible, horizontal spinning effect in the
lower atmosphere.
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Rising air within the updraft tilts the rotating
air from horizontal to vertical. An area of
rotation, 2-6 miles wide, now extends through
much of the storm.
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What is a hurricane?

• A hurricane is a huge storm!
• It can be up to 600 miles across and have strong
  winds spiraling inward and upward at speeds of 75
  to 200 mph.
• Each hurricane usually lasts for over a week,
  moving 10-20 miles per hour over the open ocean.

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• Hurricanes gather heat and energy through contact
  with warm ocean waters.
• Evaporation from the seawater increases their
  power.
• Hurricanes rotate in a counter-clockwise
  direction around an "eye" in the Northern
  Hemisphere and clockwise direction in the
  Southern Hemisphere.
• The center of the storm or "eye" is the calmest
  part. It has only light winds and fair weather.
  When they come onto land, the heavy rain, strong
  winds and large waves can damage buildings, trees
  and cars.

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What is the difference between a hurricane and a
typhoon?

• Nothing except geography.
• Tropical storms occur in several of the world's
  oceans, and except for their names, they are
  essentially the same type of storm.
• In the Atlantic Ocean, Gulf of Mexico, and the
  Eastern Pacific Ocean, they are called
  hurricanes.
• In the Western Pacific Ocean, they are called
  typhoons.
• In the Indian Ocean, the Bay of Bengal, and
  Australia, these types of storms are called
  cyclones.

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Water Cycle
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Water Cycle

• http//www.teachertube.com/view_video.php?viewkey
  53bdf2518c53ddf3bce6

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Atmosphere

• The envelope of gases that surround the planet.
• a buffer that keeps us from being peppered by
  meteorites,
• a screen against deadly radiation,
• and the reason radio waves can be bounced for
  long distances around the planet.

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• It is roughly
• 78 nitrogen (N2), (Nitrogen is "fixed" from the
  atmosphere by bacteria in the roots of certain
  plants-nitrogen cycle)
• 21 oxygen (O2) ,
• with trace amounts of water (H2O), argon (Ar),
  carbon dioxide (CO2) and other gases.
• Nowhere else in the solar system can one find an
  atmosphere loaded with free oxygen,

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Atmosphere

• Levels
• Troposphere-
• Stratosphere
• Mesosphere
• Thermosphere
• Exosphere

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Clouds

• http//ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/c
  ldtyp/home.rxml

• http//vortex.plymouth.edu/clouds.html/

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CONVECTION CURRENTS
http//www.pearsonsuccessnet.com/snpapp/iText/prod
ucts/0-13-370548-X-TR/media/sx02vtlconvect.mov
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credits

• http//www.nssl.noaa.gov/
• www.weatherwizkids.com