1. Local Winds

2. What causes local winds?
Local winds: change daily, flow within a small area, typically flow in a regular pattern
How would this local wind pattern change at night?
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Local Winds
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Science Starter:
Two barometers are placed one kilometer apart. One shows higher pressure than the other. What will happen to the air between them?
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5. Global Winds

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Global Winds
Global winds: Travel thousands of kilometers in steady patterns. Global winds are caused by uneven heating between equator & N/S poles.
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7. Calm Regions & Global Wind Belts
(1) Doldrums: Low pressure equator
Warm air rises & spreads toward poles
Rising moist air -->clouds & heavy rain
(2) Horse Latitudes:
High pressure 30˚ N/S
Warm air from equator cools & sinks
Clear & dry weather
Air usually stays calm in high/low pressure zones. Winds are light & often change direction.
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Global Winds
Global winds: Travel thousands of kilometers in steady patterns. Global winds are caused by uneven heating between equator & N/S poles.
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Global Wind Belts:
Trade Winds:
Blow East from Horse latitudes to Equator
Strong & steady. Die out as they reach equator
Westerlies: (blow from the West)
Blow from Horse latitudes to poles
Bring storms across U.S.
Dense air (in horse latitudes & other high pressure zones) moves toward low pressure zones (like the doldrums)
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Global Winds
Global winds: Travel thousands of kilometers in steady patterns. Global winds are caused by uneven heating between equator & N/S poles.
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Easterlies: (blow from East)
Blow from polar regions to mid-latitudes
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Global Winds
Global winds: Travel thousands of kilometers in steady patterns. Global winds are caused by uneven heating between equator & N/S poles.
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13. Science Starter: Calm Areas and Wind Belts
Name
Characteristics
(1)
A low-pressure zone near the equator.
(2)
High-pressure zone at about 30° N and 30° S of the equator.
(3)
Winds that blow from the East from the horse latitudes to the equator.
(4)
Winds that blow from the West from the horse latitudes to the poles.
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14. Jet Streams Flow Near the Top of the Troposphere
Jet Stream: Long distance wind that flows in the upper Troposphere.
Not all long distance winds Earth’s surface.
Jet Streams: Flow in a wavy pattern, move from W -->E, can pull cold air down into US, pull warm air up into Canada, flow faster than surface winds
Each hemisphere has 2 jet streams: (1) Polar jet stream (2) Subtropical jet stream
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Air Masses (2 words)
Air mass takes on characteristics of where it formed:
1. First Word: moisture
Continental (land)
Maritime (water)
2. Second Word: temperature
Tropical (warm)
Polar (cold)
Continental
p. 80 (in text)
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Fronts
A front is the boundary separating air masses of different densities
Fronts extend both vertically and horizontally in the atmosphere
p. 83 (in textbook)
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Fronts:
1. Cold Front: The zone where cold air is replacing warmer air
In U.S., cold fronts usually move from northwest to southeast
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18. As the warm air meets the cold air, it condenses into clouds.
Cold fronts produce cumulonimbus clouds and precipitation.
Brief, heavy storms are likely.
After the storms, the air is cool and often very clear.

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Fronts:
2. Warm Front: The zone where warm air is replacing colder air
In U.S., warm fronts usually move from southwest to northeast
Air gets more humid after a warm front moves through
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20. Warm fronts move more slowly than cold fronts.
The warm air gradually moves up and over the cold air mass.
The clouds form slowly along the front producing cloud covered skies.
A warm front may bring hours of steady rain or snow.
After the front passes, the air is warmer.

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Fronts:
3. Stationary Front: When either a cold or warm front stops moving
When the front starts moving again it returns to either being a cold or warm front
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22. When cold and warm fronts stop moving.
The air in each mass can still move sideways along the front or upwards..
The upward motion produces clouds.
The clouds may stay in the sky for days at a time.

26. Create Front Flip Chart here.

27. High and Low Pressure Systems
The “H” or the “L” on the map mark the highest or lowest pressure in the area.
The highs and lows cause a whole weather system to develop in the region.

28. High Pressure Centers
In a high pressure area, air slowly sinks and spreads out to lower pressure areas.
In the northern hemisphere the Coriolis Effect causes the air to move clockwise.
The air has to move all the way around the center before it can be a pressure center.

29. When the high pressure system stays in one place for some time, it may become an air mass.
It generally brings warm air, clear skies and gentle breezes.
It happens because as the air sinks it starts to warm up.
Clouds often disappear.

32. Low Pressure Centers
These can also form as air moves inward in a counter-clockwise motion.
It then moves upward to higher altitudes.
As the air moves up, the pressure lowers and the air moves faster.
Rising air produces stormy weather.

33. One place low pressure centers often form is near a stationary front.
The cold front moves one way, the warm front moves the other way.
The low pressure center is formed where the two boundaries meet.