The atmosphere and winds

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The atmosphere and winds

• The Hadley cell.
• Geostrophic winds.
• Fronts and weather.
• Local scale weather.

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A non-rotating Earth
High pressure at poles.
Low pressure At equator
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Polar Front
Inter- Tropical Convergence
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It is most accurate at high elevations
Winds blow clockwise around high pressures and
counterclockwise around low pressures (in the no
rthern hemisphere)
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At low elevations, friction comes into play and
Air spirals into low pressure areas and out from
high pressure areas.
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The actual path of the westerlies is a wave
pattern
That migrates to the east.
L
L
H
H
H
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When the wind blows, the packets of air carry
many of their properties such as moisture
(humidity), temperature, pollutants
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Cumulus clouds forming as warm moist air rises
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Saturation of water as a function of temperature
Warm air can hold more water vaper,
when air cools water precipitates.
Saturated
Unsaturated
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When water precipitates it releases a lot of
energy in the form of heat, which will heat up th
e air.
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A mature storm is generating its own heat, which
Sucks in more moist air, and releases more rain
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Storm dissipates as cool downdrafts
overcome the rising moist air
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Tornados form when there are localized rotations
about very low Pressure zones. The winds in torn
ados can be approximated by A balance between the
pressure forces and the inertia (centrifugal)
Forces. They are not geostrophic.
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Tropical cyclonesCategorized by maximum
sustained (1 minute) measured 10 meters above the
ground.

• Tropical depression. 38 mph
• Tropical storm.38-73 mph
• Hurricane..74 mph

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Low Pressure eye
Geostrophic Winds
Hurricanes can be approximated as a geostrophic
balance. They get Their energy the same way tha
t thunderstorms do.
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The Safir-Simpson Damage Potential Scale
Category Central Pressure
Winds Surge
1 -- Minimal greater than 980 mb 7
4 - 95 mph 4 to 5 ft 2 -- Moderate
965 to 979 mb 96 - 110 mph
6 to 8 ft 3 -- Extensive 945 to 964 mb
111 - 130 mph 9 to 12 ft
4 -- Extreme 920 to 944 mb 131
- 155 mph 13 to 18 ft 5 -- Catastrophic
155 mph 18 feet