Transcript The Atmosphere

The Atmosphere
• Atmosphere- A thin layer of
gases that surrounds the Earth
–78% nitrogen
–21% oxygen
–1% water vapor, argon, carbon
dioxide, neon, helium and other
gases
The Atmosphere
• Life on Earth would not exist
without the atmosphere
–Blocks UV rays
–Provides Oxygen and Carbon
Dioxide for living things
–Allows light to reach the surface
–Keeps the Earth warm
The Atmosphere
• Early Earth
–Contained no oxygen
–Bacteria started to
photosynthesize about 4 billion
years ago
• Added oxygen to the atmosphere
and conditions for other living
things improved
The Atmosphere
• Layers of the atmosphere
–Troposphere- Surface to 10 km
above the surface
• Contains 90% of the gases of the
atmosphere
• Most weather occurs here
The Atmosphere
–Stratosphere- 10 km to 50 km
above the Earth
• Air is less dense
• Contains the ozone layer
• Planes fly in the stratosphere
The Atmosphere
–Mesosphere- 50 km to 80 km
–Thermosphere- 80 km- 500km
–Exosphere- 500 km to space
• Air is very thin in these three
layers
Assignment
• P. 175 1-4
• Keep this and add the next
assignment to it
Climate
• Weather- The local conditions
in an area at a given time
• Climate- The long term
average conditions in an area
Climate
• Consists of:
–Precipitation
–Temperature
–Humidity
–Winds
Climate
• What determines climate?
–Latitude
–Air circulation
–Proximity to oceans
–Air circulation
–Geography
Latitude
• How far from the equator a
location lies
–Sun angle decreases as you
move from the equator
Atmospheric Circulation Patterns
• Air is heated at the equator,
rises and then cold air replaces
it from the poles
–This causes winds and
precipitation to form in the
tropics
Atmospheric Circulation Patterns
• Cool air from the tropics moves
away toward the poles and
sinks at 300 latitude.
–This causes the air to become
dry and deserts form
Atmospheric Circulation Patterns
• Air that sinks at
0
at 60 .
0
30
rises again
–This causes precipitation in the
temperate regions of the Earth
Atmospheric Circulation Patterns
• The air that rises at
the poles
0
60
sinks at
–This causes the air there to be
very dry and cold
Ocean Circulation Patterns
• Ocean currents have a great
effect on climate
–Warm currents warm areas that
would normally be and cold
currents cool areas that would
normally be warm
• Ex. London is relatively warm due
to the Gulf Stream
Ocean Circulation Patterns
• Oceans moderate
temperatures in areas causing
them to have cool summers
and warm winters
–Ex. Los Angeles
Local Geography
• Elevation has a large impact on
climate
–High elevations are cooler that
low elevations
• Ex. It snows regularly in Hawaii on
top of a 20,000 ft volcano
–Every 1000m the temperature drops
110 F
Local Geography
• Mountains also influence
precipitation patterns
–As moist air is forced up a
mountain it loses the ability to
hold moisture.
–This squeezes most of the
moisture from the air
Local Geography
–This is called the orographic
effect
–Rainforests occur on one side of
a range and rain shadow deserts
form on the other side of a
mountain range
Local Geography
Seasonal Changes in Climate
• Seasons are caused by the
orbit of the Earth around the
sun
–The Earth is tilted on its axis and
this causes the sun angle to
change throughout the year
Assignment
• P. 179 1-4
Greenhouse Earth
• The Earths atmosphere acts as
the glass of a greenhouse
–As sunlight enters the Earths
atmosphere some of its energy
is trapped by the gases
• This keeps the Earth warm and
hospitable for life
Greenhouse Gases
• Water Vapor
• Carbon Dioxide
• Chlorofluorocarbons
• Methane
• Nitrous Oxide
Greenhouse Effect
• It is suspected that increases in
greenhouse gases are causing
the Earth to heat up above its
normal temperature
–Burning of fossil fuels has
caused levels of greenhouse
gases to rise
Greenhouse Effect
• Some scientists believe that the
Earth is heating up due to
increased greenhouse gas
production while others do not
agree.
Global Warming
• The average temperature of the
Earth has risen very slightly
over the past 100 years
–Is this due to greenhouse gases
or is it due to natural events?
Global Warming
• We only have records back to 150
years ago
–We do know that the climate has
changed drastically in the past (ice
age etc.)
–We don’t know if the current change
is due to man or if it is a result of
changes that occur naturally
Global Warming
• Many people want to reduce
emissions of carbon dioxide in
order to combat climate change
–Smaller cars
–Energy efficient homes
–Recycling
–Conservation
Assignment
• P. 185 1-4
Ozone Layer
• Three oxygen atoms that are
chemically combined
–Absorbs UV radiation from the
sun
• Harmful to living things
Ozone Layer
• CFC’s have been accused of
destroying the ozone layer
–An ozone hole developed over
Antarctica
–It has since become smaller
since CFC’s were banned
Ozone Hole
• Effects of ozone depletion
–It damages DNA in organisms
–UV radiation causes skin cancer
–Kills phytoplankton in the oceans
which are the base of the food
chain
Assignment
• P. 188 1-4