Transcript The Atmosphere

The Atmosphere
and is its importance to the Earth
• The atmosphere
what is it?
– A thin
envelope of
gases that
surrounds the
Earth
• What does it do?
– Controls the weather, hydrologic cycle,
and the climate of the Earth.
– Allows for life to exist on Earth
Atmospheric Composition
Ancient Atmosphere
• Composition
–
–
–
–
Carbon Dioxide
Sulfur Dioxide
Water vapor
Nitrogen
• What is the source of
the atmosphere?
• Could not support life
– no oxygen
• Conditions changed 3.8 Ga
(billion years before present)
• Water could condense
(precipitation occurred)
• Life was generated (amino acids
- aquatic microorganisms)
• CO2 dissolves in water and is
used by MO – tied up in rocks
• Oxygen enters atmosphere
• Nitrogen remains – does not
react with other chemicals
Layers of the Atmosphere
• Temperature
stratifies the
atmosphere
• Troposphere
– Lowest layer – 0 to 15 km
– Contains 80% of the mass of the
atmosphere.
– Layer where weather occurs.
– Temperature decreases with
height.
• Stratosphere
– Occurs between 15 and 50 km
above the surface.
– Temperature increases with
height.
– Contains ozone (O3) that shields
the surface from ultraviolet (UV)
Energy Balance
Water Vapor
• Water content in the
atmosphere is called the:
humidity
• Composition varies as a
function of temperature.
– Warm air holds > 40 g H2O/Kg
air
– Cold air holds < 5 g H2O/Kg
air
• Addition/removal of water to
the atmosphere
requires/generates energy.
• Importance to climate
– water vapor transfers
heat from warmer to
colder regions
• Latent heat – heat
released or absorbed
when matter changes
state.
Latent
Heat Cycle
Pressure
• Air Pressure – the weight of the overlying air
– Measured in atm or bars (1 bar = 0.986 atm)
– 1 atm is the weight of the atmosphere at sea level ~
1,035 g/cm2
• Mixture of gases in the atmosphere is not uniform
– Air pressure decreases as one moves away from the
Earth’s surface
• As the pressure increases the density of the air
increases
Air Density
Energy and the Atmosphere:
Pressure, Water Vapor, & Weather
• What drives energy within the Atmosphere?
Is the distribution of solar energy equal on the Earth’s surface?
Uneven Heating of Earth Surface
• Solar energy is a function of both
• Location
• Time of year
June 1998 Mean Surface Temperature
Daily Question
• Describe what would happen to a parcel of
air that rises from the land surface up into
the atmosphere. Your answer should
discuss the density of the air, the
temperature of the air, and the humidity of
the air as it moves up. A sketch may be
helpful in showing what is happening to the
parcel of air at different altitudes.
What happens to hot air?
• Warm air rises
• As air rises it enters a
lower pressure area and
expands
• Expansion cools the air –
the cold air can hold less
water
• Condensation occurs –
clouds form (latent heat)
Which is more dense cold air or
warm air?
Mechanism that lift air
• Density Lifting
• Frontal lifting
• Orographic lifting
• Convergence Lifting
Daily Assignment
• Draw a circle to represent the Earth (label the
tropics (300 N and S), equator, and polar circles
(600 N and S)
• Based upon what you know of air movement –
indicate the direction of vertical movement at the
labeled locations (keep in mind a balance of what
goes up must come down)
• Indicate how the air moves from one region to
another (horizontal lines either at the surface or
higher in the atmosphere)
Global Air
Circulation
Where Will
Precipitation and
Evaporation
Occur?
The Atmosphere in Motion
Air masses move
from high
pressure areas to
low pressure
areas
Coriolis Effect
Air Circulation Around a Pressure Low
Low and High Pressure Systems
•
•
•
•
Low Pressure
Air moves up
Weather cloudy
Usually associated
with a cold front
• High Pressure
• Air descending
• Little to no clouds –
sunny
Wave-cyclones & Mid-Latitude
Storms