Weather on a Larger Scale

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Weather on a Larger Scale

• SCI 201

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The Sun and the Earth

• Seasons
• Area of sunlight
• Resulting air masses

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Air Masses
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Jet Stream

• Interaction of the large air masses (high
  altitude)
• Coriolis force (drawing activity - NH/SH)
• Pressure above the poles and equator
• More molecules above equator
• Less molecules above the poles
• Pressure gradient force
• Cancellation and the resulting jet stream
• Polar - higher winds (due to distance and ?T)
• subtropical
• In US, systems follow a general W to E pattern
  ()
• Usually shown P.J.S.
• Cold snaps/warming trends
• winter vs. summer

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Highs/Lows and Precipitation

• High pressure in areas where air is sinking
• Pushes on air below it results in higher P
• Can be high/low T, but few clouds (think cloud in
  a bottle)
• Low pressure in areas where air is rising
• Opposite effect
• If lots of water vapor, clouds can form,
  rain/snow as it rises and cools off
• Rain/Snow showers and clouds around Lows

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Highs/Lows and Winds

• At high altitudes
• In a circle to the left around lows
• In a circle to the right around highs
• Nearer the Earths surface
• Spiral inward around lows
• Spiral outward around highs
• Blowing winds suggest a change from a high to low
  pressure area

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So far

• High and low P areas move across the Earth
• They take winds that circulate around those areas
  with them
• Large scale, cover large portions of the US
• Within and between are smaller regions of cold
  air, warm air, dry air, humid air, and combos

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Fronts

• Pan demo
• Small scale areas come into contact
• Cold front - cold air overtakes warm air
• Warm front - warm air overtakes cold air
• Stationary front - neither displaces the other

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storms

• Depends on DT between cold and warm air and
  humidity of cold and warm air
• If warm air is humid - clouds and possibly rain
  and snow
• When cold air overtakes warm air, warm air rises
  rapidly and cools rapidly, big thunderstorms and
  snowfalls
• When warm air overtakes cold air, the rising is
  more gradual, leads to steady, longlasting
  precipitation