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Weather

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Weather What is Weather to You? 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 ... – PowerPoint PPT presentation

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Title: Weather


1
Weather
  • What is Weather to You?

2
What is weather?
  • Describes the current condition of the
    atmosphere.
  • Factors include- temperature, cloud cover, wind
    speed direction, humidity, and air pressure

3
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

4
  • 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)

5
Clouds
6
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

7
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.
8
Winds
9
Trade Winds
  • Wind flows outward away from the subtropical
    highs. It encounters the Coriolis effect.
  • we find winds blowing from east towards the west.

10
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.

11
Westerlies
  • Above the subtropical highs in the Northern
    Hemisphere, winds blow from the west towards the
    east.

12
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.

13
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

16
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

17
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

18
  • 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

19
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

20
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)

23
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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25
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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27
Cloud types
  • Cirrostratus

28
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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34
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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41
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

42
Anticyclones
  • High pressure centers
  • Winds spiral outward from centers of dry air
  • Spin clockwise in Northern Hemisphere

43
Winds spiral inward towards the low-pressure
center- counterclockwise
Winds spiral outward from the high-pressure
center- clockwise
cyclone
anticyclone
44
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

45
Severe Weather
  • Thunderstorms- cumulonimbus clouds (along cold
    fronts)
  • Lightning- energy flow that occurs between areas
    of opposite electrical charge

46
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

47
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.

48
  • 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.

49
  • 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.

50
Triggered lightning/ "natural" lightning
  • goes from ground to cloud,
  • while "natural" lightning is cloud to ground.

51
  • 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.

52
  • 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.

53
  • 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.

54
  • http//science.howstuffworks.com/nature/natural-di
    sasters/lightning.htm

55
  • 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.

56
  • 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.

57
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.

58
  • 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.

59
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.

60
  • 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.

63
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.

64
A change in wind direction and an increase in
wind speed with increasing height creates an
invisible, horizontal spinning effect in the
lower atmosphere.
65
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.

68
  • 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.

71
Water Cycle
72
Water Cycle
  • http//www.teachertube.com/view_video.php?viewkey
    53bdf2518c53ddf3bce6

73
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.

74
  • 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,

75
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/

78
CONVECTION CURRENTS
http//www.pearsonsuccessnet.com/snpapp/iText/prod
ucts/0-13-370548-X-TR/media/sx02vtlconvect.mov
79
credits
  • http//www.nssl.noaa.gov/
  • www.weatherwizkids.com
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