Clouds, Precipitation, Air Pressure, and Wind

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Clouds, Precipitation, Air Pressure, and Wind

• Listen up and pay attention..write this stuff
  down!

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What are clouds and how do they form?

• Clouds are just collections of tiny water
  droplets
• They form when air rises and cools

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Cloud droplet vs. rain droplet
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Condensation Level

• As air rises it cools
• When the air gets cold enough condensation will
  form
• This altitude is the condensation level

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Cloud Types

• Cirrus
• High clouds
• Light and feathery looking
• Made of Ice crystals
• Can signal approaching warm front

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• Cumulus
• puffy looking
• Like Mr. England
• Form vertically
• Fairly low level

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• Stratus
• Layered clouds
• Low level

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• Cumulonimbus
• Huge!
• Go up to the top of the troposphere
• Massive updrafts of air
• Huge thunderstorms
• Form at the front of cold fronts

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Precipitation
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How it forms

• When cloud droplets collide they get bigger
• When they get too heavy to stay aloft they will
  fall to the ground

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TYPES

• Rain
• Liquid water falling from the sky

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• Snow
• -Frozen water falling from the sky
• -Crystallized (snow flakes)

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• Sleet
• Raindrops that fall through freezing air
• Turns to ice on the way down

• Freezing Rain
• Rain freezes AFTER it hits the ground.

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• Hail
• Massive upward movement of air in cumulonimbus
  clouds carries hailstones to top of troposphere.
• More ice layers added on each time.
• Falls to Earth when it is too heavy.

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• Hail Formation

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• Why are areas of sinking air dry?
• Sinking air warms and compresses when it sinks
• Water droplets will evaporate and form water
  vapor
• Remember the cloud in the bottle! (when I
  squeezed the bottle the cloud went away)

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Atmospheric Pressure and Wind

• Air pressure is the weight of the atmosphere at a
  given altitude.
• A barometer is used to measure air pressure

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• Atmospheric pressure usually
• DECREASES as altitude
• INCREASES!!!!!

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• The jet stream can create different pressure
  systems.

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• High Pressure Systems
• When the jet stream bends upward a ridge of high
  pressure is created.
• The air spins clockwise and sinks

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• Weather associated with a HIGH
• Because the air is sinking there will be no
  clouds.
• CALM WINDS
• WARMER TEMPERATURES
• DRY CONDITIONS (NO RAIN)

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• Low Pressure Systems
• When the jet stream bends downward a trough of
  low is created.
• Air rises and spins counter-clockwise

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• Weather associated with a LOW
• Because the air is rising and cooling it will
  form clouds
• Stormy conditions
• Rain/clouds
• Wind
• Cooler temperatures

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On a weather map they look like this
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• Notice air rushes into a LOW and away from a HIGH

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• What makes the wind blow?
• Remember air travels from HIGH to LOW pressure.
• ..so..
• air moving from HIGH to LOW is