Wind and Water

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Wind and Water

• Objectives
• Describe the water cycle
• Relate temperature and humidity
• Classify clouds
• Discuss the sources of winds

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Processes in the Water Cycle

• Evaporation
• Mainly from the oceans
• Transpiration
• Plants lose moisture through pores in leaves
• Condensation
• Formation of clouds
• Precipitation
• Rain, snow, hail, sleet
• Run-off

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Wheres the Water?

• 97.5 in the oceans (salt)
• 2.5 on land (freshwater)
• 0.001 in the atmosphere

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Where does the water go?

• The flow in to each box equals the flow out of
  the box
• Precipitation gt 30X the amount of water in the
  atmosphere
• Lots of rain!

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63
77
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Energy and the Water Cycle
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Pollutants Spread through Ground Water and Runoff
to the Oceans

• Disease-carrying pollutants
• Inorganic pollutants/chemical waste
• Fertilizers
• Sediments
• Oxygen demanding wastes (sewage)
• Nuclear waste
• Thermal pollution (hot water)

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Humidity

• At warmer temperatures the air can hold more
  water vapor
• Relative humidity is the ratio of how much water
  is in the air to the maximum (saturated) amount
  at a given temperature

Saturated Vapor Pressure
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Relative Humidity Map
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Relative Humidity and Dew Point
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Dew Point

• Temperature at which water vapor will condense
  and begin to form liquid
• Dew point can never be greater than the current
  temperature
• The higher the humidity, the higher the dew point
• The further away the dew point, the lower the
  humidity

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Dew Point Map
PLOT
Temp
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Cloud Formation

• Warm, moist air rises
• Temperature falls below the dew point at a given
  altitude
• Water condenses out onto dust particles (seeds)
  or already formed drops
• If cold enough, ice crystals form

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Clouds are Named by Height and Shape
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Types of Clouds

• Cirrus
• Thin, wispy
• High altitudes, strong winds
• Formed of ice crystals
• When they thicken, can indicate rain is coming
• Stratus
• Grey cloud sheet-like with flat base
• Forms at low altitudes
• Large air miss lifted into place, produces rain
• Cumulus
• Cottonballs with flat bottoms
• Form when warm air is rising
• Fair weather clouds, but can form thunderstorms

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Cloud Names

• Cirro high altitude
• Alto mid altitude
• Strato low altitude
• Cumulus heaps
• Stratus layers
• Nimbo able to produce rain
• Use to form combinations
• cumulonimbushuge tall rain clouds

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Can it rain if it is less than 100 relative
humidity?

• Yeswhat counts is the relative humidity at the
  height of the clouds

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What is Atmospheric Pressure?

• The pressure due to the weight of the atmosphere
• Column of air extending from the top of the
  thermosphere to the altitude of the measurement
• Also called barometric pressure
• 14.7 lbs/in2 at sea level or 1013.25 millibars

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Measuring Air Pressure
760 mm
Aneroid Barometer Pressure deforms thin-walled
partially evacuated can moving pointer
Mercury Barometer pressure on pool pushes column
higher
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High Pressure Usually Means Nicer Weather

• Isobars connect points with the same pressure
• Low pressure is purple
• High pressure is orange
• Cold air is usually at higher pressure because it
  is more dense

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Wind

• Need difference in air pressure or pressure
  gradient
• Wind moves air from regions of high pressure to
  regions of low pressure
• The closer together the isobars, the higher the
  wind speed
• Which way are the winds blowing on the map?

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Wind

• Wind is named by the direction it is blowing from

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Coriolis Effect Earths Rotation Affects the
Winds

• Earth is rotating left to right, fastest at the
  equator. (Must cover larger circumference in a
  day.)
• Cannonball moves E to W at Earths rate from
  point it was shot (Inertia).
• Cannonball path curves because it is moving
  faster E to W than the earth beneath it

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The Wind Belts Combinations of Pressure
Variations and Coriolis Effect

• Loops are called cells
• 3 loops in northern hemisphere, 3 in southern
  hemisphere