The Atmosphere

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The Atmosphere
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What is the atmosphere?

• Atmosphere a thin layer of gases that surrounds
  the Earth.
• 5 layers
• The most important layers (and the only ones I
  will ask you remember) are troposphere and
  stratosphere

Troposphere

• This is the atmosphere we breathe
• Where most weather occurs
• Extends to about 10 km above the earth

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Stratosphere

• Where the ozone layer is
• Air is less dense here than in the troposphere
• Extends from about 10 km to 50 km
• About 90 of the atmospheric gases are contained
  in the troposphere and stratosphere together.

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How our air came to be

• Air - the mixture of gases that make up the
  atmosphere
• 4 billion years ago the Earths atmosphere had
  little oxygen
• Living organisms began to appear and started to
  photosynthesize
• Early photosynthetic organisms made life as we
  know it possible by greatly increasing the amount
  of oxygen in our atmosphere.
• Current Atmospheric Gases
• Nitrogen 78
• Oxygen 21
• Other gases 1
• Argon, water vapor, carbon dioxide (0.03), neon,
  helium, ozone
• Some gases can cause pollution while others are
  very useful!

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PHOTOSYNTHESIS AND RESPIRATION

• Photosynthesis uses carbon dioxide gas and
  produces oxygen gas
• Respiration does the opposite- uses oxygen and
  produces carbon dioxide.
• These two processes keep the amounts of carbon
  dioxide and oxygen relatively stable in our
  atmosphere.
• This balance is key to maintaining the life that
  we know on this planet!

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• What layer of the atmosphere do we live in?
• Ozone layer
• Statosphere
• Troposphere
• thermosphere

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• Today, 99 of our atmosphere is made up of
• Hydrogen and oxygen
• Nitrogen and methane
• Oxygen and carbon dioxide
• Oxygen and nitrogen

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• The Earths early atmosphere probably contained
  little
• hydrogen
• oxygen
• methane
• ammonia

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What if we had more oxygen? Less oxygen?

• Too much oxygen and things would burn
  spontaneously.
• Oxygen is a flammable gas and too much of it can
  be a bad thing.
• Too little and we could not breath. Without
  enough oxygen our brain cannot function and can
  hallucinate.
• Nitrogen is an inert (non-reactive) gas that
  helps balance the highly reactive oxygen!

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MORE CARBON DIOXIDE? LESS CARBON DIOXIDE?

• Carbon dioxide is a greenhouse gas
• It traps heat in the atmosphere and helps warm
  the planet.
• Too much carbon dioxide and our planet will warm
  up - we will talk more about this later
• Too little carbon dioxide and we cannot maintain
  a warm enough climate to live in
• Of course other greenhouse gases (for example
  water vapor) can help with the temperature
  regulation of Earth.

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What would we expect to see if photosynthesis
increased to 5x its normal rate but cell
respiration stayed the same?

1. Things would catch on fire due to large amounts
   of oxygen.
2. Things would catch on fire due to large amounts
   of carbon dioxide.
3. The planet would begin to cool down because of
   large amounts of carbon dioxide
4. The plant would begin to cool down because of
   large amounts of oxygen

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Climate and Seasons
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Weather vs Climate

• Weather what is happening in the atmosphere at
  a particular place at a particular moment.
• Climate is the average weather in an area over
  a long period of time.
• Climate is determined by a variety of factors
• Latitude
• Air circulation
• Ocean currents
• Local geography

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Latitude

• Latitude is the most important factor of
  climate!!
• Affects the amount of solar energy (heat) an area
  receives.

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Air Circulation

• Cold air sinks and warms as it sinks
• Warm air rises and cools as it rises
• Warm air can hold more moisture than cold air.

Solar energy warms the air closest to Earths
surface causing it to rise. The rising air is
replaced by cooler air flowing from the north.
Circulation cell!
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Ocean Currents

• Remember water
• holds a lot of heat!
• The currents redistribute warm and cool masses of
  water.
• Oceans make the coastal climates more moderate.
• Local Geography
• Mountains and elevation changes can alter the
  climate at a given location.
• Temperatures decrease as you go higher in
  elevation
• Mountains also influence precipitation patters
  and air has to rise and thus cool and lose
  precipitation to pass over a mountain.

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• Which of these factors MOST influence a regions
  climate?
• Number of forests
• Distance from an ocean
• Number of mountain ranges
• Distance from the equator

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Thermal Inversion

• Normal higher air is cooler
• Thermal inversion occurs when the air above is
  warmer than the surface air.
• This can trap pollutants near the Earths
  surface!
• Cities in a valley have a greater chance of
  experiencing this!

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• Thermal inversion is
• like a sponge soaking up pollutants.
• like a giant fan, causing pollutants to disperse.
• like a ceiling, preventing pollutants from moving
  upward.
• something that happens only in Los Angeles.

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Seasons

• Seasons are a result of Earths tilt as it
  rotates around the Sun.
• The tilt affects the angle that the
• sun hits the
• Earth.

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• Which of the following is NOT an adverse effect
  of high levels of UV light?
• Increased incidence of skin cancer
• Increased photosynthesis
• Disruption of food chains
• Increased amount of atmospheric carbon dioxide

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1. Increased photosynthesis in the winter months.
2. Increased photosynthesis during summer months.
3. Increased cellular respiration during summer
   months
4. More births and thus more people during winter
   months.

• On the graph above what is casing the rapid
  fluctuations each year? Look at the annual cycle
  inset.