Mountain Effect

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Mountain Effect
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Take a look at the next three slides and try to
answer the following

• Try to decide why each city has the climate it
  does.
• Why does it rain more in certain places than
  others?

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Seattle, WA
Boston, MA
Las Vegas, NV
Memphis, TN
Jacksonville, FL
Austin, TX
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Seattle, WA
Average Monthly Temperature
Annual Amount of Precipitation Inches
37.07 Days 155
January April July October 40.9
50.2 65.3 52.7
Annual Snowfall 11.4''
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Jacksonville, FL
Average Monthly Temperature
Annual Amount of Precipitation Inches
52.34 Days 116
January April July October 53.1
66.6 81.6 52.3
Annual Snowfall Trace
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Why does it rain more in certain places than
others?

• Mountains near the ocean hold part of the answer.
• When water evaporates from the ocean, it becomes
  water vapor in the air.
• The warm, moist air rises and moves over land.

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• Air that meets mountains is forced to go higher,
  where temperatures are colder.
• Clouds form that can drop rain or snow on one
  side of the mountain.
• This side is called the windward side (closest to
  the ocean/ wind).
• Some of the wettest places on Earth are on the
  windward side of mountains.

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After the clouds have dissipated, the air finally
crosses to the other side of the mountain. There
is usually very little moisture left.

• Because there is not much moisture left, clouds
  are not likely to form. This leaves the back
  side of the mountains often dry and desert-like.
  

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Sierra Nevada Mountain Range
The Sierra Nevada Mountains span 400 miles
across CA.
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The windward side (eastern side) of the Sierra
Nevada Mountains receive much precipitation and
are lush with vegetation.
The leeward side (western side), however, is a
very dry desert region.
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Whats the reason for this?
Its all about the Mountain Effect!
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• Why is there little moisture left in the air by
  the time it reaches the leeward side of a
  mountain?

Most of the moisture has already fallen as
precipitation.
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• Why does more rain and snow fall at the top of a
  mountain than at its base?

At the base of a mountain, the air is warmer. The
air needs to cool to form clouds that drop
precipitation.
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• If you chose G, you are correct!
• The air on the leeward (backside) of the mountain
  is drier than on the windward (front) side of the
  mountain.

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• If you chose J, you are correct!
• The air cools as it rises, causing fog to form.

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Notes

• Water evaporates from the ocean, and it becomes
  water vapor.
• This warm, moist air rises and moves over land.
• Clouds form that can drop rain or snow on one
  side of the mountain.
• The clouds dissipate, and the air crosses to the
  other side of the mountain. There is usually very
  little moisture left.
• In your notes, draw a diagram of a mountain
  and the mountain effect.

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Review
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If you chose J, you are correct. The land on the
leeward side of the mountain receives air with
the least amount of moisture, making it hotter.
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The correct answer is G. The air is drier at Y
than at X. There is more moisture in the air at
point X, on the top of the mountain. All of the
moisture will be lost on the mountain, making the
air at Y drier.