Weather and Climate

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Chapter 15 16

• Weather and Climate

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15.1 What is weather?

• What is weather and what are the factors that
  affect it?
• Weather
• The present daily atmospheric conditions
• Factors that affect weather
• Air pressure, wind, temperature, and air moisture

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15.1 What is weather?

• Describe humidity and how it is affected by
  different temperatures.
• Humidity
• The amount of moisture in the atmosphere
• The warmer the temperature the more moisture

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15.1 What is weather?

• Describe relative humidity
• The amount of water vapor in the air at a
  temperature compared to the amount the air can
  hold

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15.1 What is weather?

• How does relative humidity affect the dew point?
• The dew point is the point in which the air is
  saturated with water vapor and begins to condense
  to liquid water
• The higher the relative humidity, the more likely
  dew or frost will form.

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15.1 What is weather?

• How do clouds form?
• Warm air is forced upwards and the water vapor
  begins to condense as it cools on tiny dust
  particles
• When millions of water droplets collect in an
  area a cloud forms.

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15.1 What is weather?

• How are clouds classified?
• Clouds are classified by the shape and height of
  the cloud base above the ground.

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15.1 What is weather?

• Describe the three shapes of clouds and the type
  of weather associated with them.
• Stratus
• Layers of clouds that are smooth and sheet-like
• Associated with fair weather and precipitation
• Near the ground they form fog

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• Cumulus
• Puffy white clouds that have a flat base (cotton
  balls)
• Associated with fair weather and thunderstorms
• Cirrus
• Fibrous or curly and thin
• Associated with fair weather, but may indicate
  approaching storms

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15.1 What is weather?

• Describe the name of clouds associated with the
  height of the cloud and give the heights in which
  they can be found.
• Cirro- means high clouds with a base above 6,000m
• Alto- means middle clouds with a base between
  2,000-6,000m
• Strato means low clouds with a base below
  2,000m

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15.1 What is weather?

• Describe how a hailstone forms.
• Rising air pushes water droplets above the
  freezing point of the atmosphere
• The water droplet freezes and begins to fall
• The ice pellet falls below the freezing point and
  is coated with a layer of water.
• The coated ice pellet is again pushed up above
  the freezing point
• The process occurs again and again until the ice
  pellet becomes so large the rising air cant
  support it and it falls to the ground

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15.2 Weather Patterns

• What is a front and how do they move along
  Earths surface?
• A front is the boundary between two air masses of
  different temperatures
• A front moves from areas of high pressure to
  areas of low pressure

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15.2 Weather Patterns

• Describe the structure and the weather associated
  with a warm, a cold, and occluded, and a
  stationary front.
• Warm
• Develops when warm air masses is pushed up over a
  departing cold air masses
• Precipitation occurs over large areas

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• Cold front
• Results from cold air masses push under warm air
  masses causing the warm air to rise
• Causes a narrow band of violent storms
• Occluded front
• Results from two cool air masses merging and
  forcing warm air upwards
• Causes strong winds and precipitation
• Stationary front
• Results from pressure differences cause a warm
  front or cold front to stop moving
• Causes light wind and rain across the whole front

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15.2 Weather Patterns

• Describe what causes lightning and thunder during
  a thunderstorm.
• Lightning
• Occurs when a rapid uplift of air build up
  electric charges in the clouds and there is flow
  of current between the regions of positive areas
  and negative areas
• Can be cloud-cloud, cloud-ground, or ground-cloud
• Thunder
• The rapid expansion of air due to the rapid
  warming of the air caused by lightning then it
  cools rapidly making a noise

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15.2 Weather Patterns

• Explain how a tornado forms.
• Wind shear occurs, which is wind at different
  altitudes blow in opposite directions and at
  different speeds
• A strong updraft causes the wind shear to tilt,
  which causes rotation
• If the rotation gets fast enough the funnel will
  reach the ground, which is then a tornado

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15.2 Weather Patterns

• Describe how a hurricane forms.
• SE trade winds meet with the NE trade winds
  causing a low pressure system to form
• Air masses begin to rotate counterclockwise in
  the northern hemisphere around 5-20 north
  latitude
• Warm air rises and water vapor condenses
• The longer the low pressure system is over warm
  water the stronger the hurricane

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16.1 What is Climate

• Define climate and list what is used to determine
  climate.
• Climate is the weather averages over several
  years in a given area
• Temperature, precipitation, air pressure,
  humidity, and days of sunshine

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16.1 What is climate?

• List and describe the factors that affect
  climate.
• Latitude determines the amount of direct
  sunlight
• Topography mountain windward side receives more
  rain due to the warm air rising and cooling
• Location of lakes and oceans water warms and
  cools faster than land
• Availability of moisture the more moisture in
  the air the wetter the area remains
• Global wind patterns does the wind blow onto
  land or out to sea (onto land wet out to sea
  dry)

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• Ocean currents warm oceans cause warmer
  climates cooler oceans cause cooler climates
• Location of air masses large cities heat up the
  air more than surrounding areas and cause the
  climate to be different

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16.3 Climatic Changes

• Explain how seasons occur.
• The Earth is tilted 23.5 on its axis
• As the Earth revolves around the sun the angle of
  the suns rays striking Earth changes.
• Northern hemisphere tilted towards the sun causes
  summer and the southern hemisphere is opposite
  even though we are the farthest from the sun.
• Northern hemisphere tilted away from the sun
  causes winter and the southern hemisphere is
  opposite even though we are the closest to the
  sun

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• Northern hemisphere when not tilted toward or
  away from the sun results in spring or fall
• In the southern hemisphere it is spring, when it
  is fall in the northern hemisphere
• In the southern hemisphere it is fall, when it is
  spring in the northern hemisphere

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16.3 Climatic Changes

• Describe how the greenhouse effect could change
  the climate around the world.
• Heat is trapped in the Earths atmosphere by
  carbon dioxide
• Does help life exist on Earth, but too much
  carbon dioxide causes a slow increase in the
  average global temperature

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16.4 How can global warming be slowed?

• Describe how humans have increased the amount of
  carbon dioxide in the atmosphere.
• Burning fossil fuels releases more carbon dioxide
• Reducing the number of trees decreases the amount
  of carbon dioxide used by plants
• Increases carbon dioxide and decreases oxygen

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16.4 How can global warming be slowed?

• What measures humans can take to decrease the
  amount of carbon dioxide in the atmosphere.
• Find alternative fuels
• Find ways to reduce the amount of fossil fuels
  used
• Car pool, use solar and wind energy
• Increase the amount of plant vegetation by
  planting trees.