Precipitation

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Section 1
The Water Cycle
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The Water (Hydrologic) Cycle

• A Cycle consisting of water entering the
  atmosphere through evaporation and returning
  through condensation and precipitation

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Terms for the Hydrologic cycle

• Transpiration -
• Evaporation -
• Evapotranspiration -
• Condensation -
• Ground Water -

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Transpiration . . . . .

• The loss of water into the atmosphere through the
  leaves of plants (sometimes referred to as plant
  sweat)

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Evaporation . . . .

• The change of liquid water to gaseous water vapor

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Evapotranspiration . . . .

• The combined effects of transpiration and
  evaporation.

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Condensation

• The change of gaseous water vapor back into the
  liquid phase

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Ground Water . . .

• Water which is stored and moves through the ground

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Part 2 Precipitation
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Precipitation requires..

• Relatively warm moist air
• Some agent to cause the warm moist air to rise
  ..
• Expansion of the air due to lower air pressure
  above it..
• Causing the air to cool down below the dew
  point

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Precipitation terms...

• Capacity - The amount of water vapor the air can
  hold at a given temperature
• (Warm air can hold more moisture than cold air)
• Absolute humidity - The amount of water vapor
  actually in the air at a given time
• Relative humidity - A comparison of the absolute
  humidity to the capacity

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Water will evaporate into dry air leading to a
saturated condition such as is seen in the last
flask.
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As the temperature falls, the capacity of the air
in the flask decreases and the water condenses
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In order for clouds to form,3 basic ingredients
must exist.

• There must be warm moist air
• There must be cooling temperatures
• There must be dust particles around which the
  water vapor can condense to form cloud droplets.

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As air rises, it expands and cools. This lowers
the capacity of the air and causes condensation
(cloud formation) to occur.
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As Cloud droplets strike one another, they
coalesce (stick together) until they are heavy
enough to fall through the rising column of air.
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Mountains can block moving parcels of air and
force them upwards, cooling them by expansion.

• Such cooling by expansion is called Adiabatic
  Cooling

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III. Factors which affect climate
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A. Latitude

• 1. Areas of low latitude (near the equator)
  receive high angles of insolation (AOI) and are
  therefore warmer.

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2. Areas of high latitude (near the poles)
receive low angles of insolation and are
therefore cooler.
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3. The average AOI is equal to the compliment of
the latitude. AOI 90 - latitude
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II. Altitude

• 1. As Altitude increases, the average daily
  temperature decreases.
• a. The thinner blanket of air at higher
  altitudes holds in less heat radiating from the
  earth back into the atmosphere than does a
  thicker layer at lower altitudes.
• b. Due to cooler temperatures, snow is often
  found at the highest altitudes, making
  temperatures even colder since white reflects
  rather than absorbs heat.

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C Orographic Effects

• Mountains barriers force warm moist air to rise,
  making the windward sides of mountain ranges cool
  and wet and the leeward sides warmer and drier
  (deserts).

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D. Proximity to large bodies of water

• 1. Since large bodies of water heat up and
  radiate heat more slowly than land, they temper
  the climate. Regions close to large bodies of
  water tend to have cooler summers and warmer
  winters.
• 2. Inland areas tend to have more severe
  temperature ranges with frigid winters and hot
  summers.

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The Badlands of interior U.S. show evidence of
extremes
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The Pacific Northwest is close to the ocean is
more temperate
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E. Ocean Currents

• 1. Eastern coasts of continents tend to be
  warmed by currents coming up from the equator
  (driven by the Coriolis Effect)
• 2. Western coasts of continents tend to be
  cooler due to the ocean currents flowing down
  from the polar regions.

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F. Planetary Wind Belts
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