Weather

1
Weather

• Chapters 7-9 in your review book

2
Origin of the atmosphere

• Early atmosphere very different than today.
• Mostly made of water vapor, carbon dioxide, and
  nitrogen from the out-gassing of volcanoes.
• Water vapor went into oceans.
• Carbon dioxide was used by early organisms that
  performed photosynthesis.
• Other percentages of CO2 are tied up in rock
  deposits like limestone.

3
Why the atmosphere is important today

• Holds the oxygen.
• Moderates temperatures on Earth.
• Provides protection from asteroids, etc.
• (think of moon surface.)
• Protects us from dangerous forms of
  electromagnetic energy.

4
Air pressure

• Caused by the weight of the atmosphere.
• Pressure is generally greatest at the surface,
  and decreases as you gain altitude.
• Use a barometer to measure it.
• Differences in air pressure cause winds.
• Also, differences in air pressure is the main way
  to predict weather.

5
Factors that affect air pressure

• Altitude Air becomes less dense with increasing
  altitude.
• Temperature Colder air is more dense, therefore
  it is at a higher air pressure.
• Humidity Usually, air pressure decreases as
  humidity increases.

6
Winds

• Caused by the heat flow through the atmosphere
  (convection).
• Winds are a result of the uneven heating of the
  earths surface.
• Fastest winds occur when there is a large
  gradient (change) in pressure over a small
  distance.

7
Local winds

• Land breeze is a wind that blows from the land
  towards the sea.
• Sea breeze is a wind that blows from the sea
  towards the land, usually occurs during the
  afternoon as land heats up.

8
The coriolis effect

• Apparent curvature of winds (or ocean currents
  etc.) over long distances along the earths
  surface.
• Due to the rotation of the earth.
• In the northern hemisphere, winds curve to the
  RIGHT.
• Southern hemisphere is opposite.

9
Jet streams

• Very fast currents of air in the upper
  atmosphere.
• Where we live, the jet stream flows from west to
  east.
• This knowledge helps us to predict weather.
• Meaning, we will most likely experience the
  weather that is to the west of us.

10
RecapBe able to discuss the following

• How did the atmosphere form, and what is its
  current structure?
• What is air pressure?
• What are winds and what causes the strongest
  winds?
• What is the coriolis effect?