Atmosphere and Climate
Gasses surrounding the planet vs. weather’s effect on regions of the planet
Atmosphere Composition
Dry Air mass:
99% Nitrogen and Oxygen
1% mix of other gasses
Wet Air mass
up to 4% of nitrogen/oxygen portion is water vapor
Density of wet vs. dry air masses
Water has a mass of 18 amu per atom (H2O)
Oxygen has a mass of 32 amu per molecule (O2)
Nitrogen has a mass of 28 amu per molecule (N2)
Which has a greater density, a dry air mass or a wet air mass?
What is the other 1%?
Aerosols are part of this 1%
Sources vary (sea salt, dust, ash , smog etc)
Gives water vapor place to condense and create clouds
Absorbs/reflects solar radiation
Scatters light (sunrise and sunsets)
Pollutants are often aerosols
Primary…directly emitted into the atmosphere
Volcanic ash, CO, SO2,
Secondary…converts into a pollutant
Primary Pollutants
Directly emitted into atmosphere
Volcanic ash, CO, SO2, salt, dust….
Secondary Pollutants
Converted in the atmosphere due to chemical reactions
H2SO4
NO2
Ozone (O3)
DEQ (Dept of Environmental Quality)
6 major components to pollution
CO, SO2, NO2, Particulates, ozone and now CO2
Measured by air quality index
Clean Air Act
Purpose to provide clean/healthy air to all citizens
Established in 1970
Updated 1990, 2004
Cause of Pollution?
Ozone…what is it?
Oxygen molecule--> O2
Ozone molecule--> O3
Ozone can be both good and bad--> HOW?
Good Ozone
Naturally < 1part/100 million in lower atmosphere
Concentrated between 10-50 km up
photochemical disassociation of O2
O and O2 combine through catalyst and get O3
right conditions at 10-50 Km for this to happen
Absorbs UV radiation
good protection for planet and life
Bad Ozone
Occurs in lower atmosphere due to pollution
Very reactive and corrosive
Causes respiratory problems
Causes photosynthesis problems
Low concentrations are toxic to life
Often major problem in summer. Why?
Internal combustion engines creates Nitrogen oxides which react with
hydrocarbons to produce ozone.
Summer has more intense radiation to drive bonding process which creates ozone
Depletion of Ozone in Upper Atmosphere
Why is this a problem?
NOT PART OF GLOBAL WARMING
Where is this happening?
Antarctica
30-60 degrees N latitude
Chemistry that drive reaction?
Secondary Pollution:
CFC’s (chloroflurocarbons)
Stable, nontoxic non-corrosive chemicals at surface
In upper atmosphere break into Cl, F, Br & C
Cl, F, & Br atoms combine with O3 and remove it to create ClO, BrO and O2
Montreal Protocol (1987)
Enacted when ozone problem found in ‘85
Global agreement
Stopped using or producing CFC’S by 2000
Includes freon, hairspray propellants, cleaning solvents
CFCs are still accumulating in atmosphere but at a slower rate now.
Expect ozone layer to recover by 2050
Thin spot or hole in Ozone layer is found above Antarctic
Biggest in spring (October)
Regions of the Atmosphere
Increase elevation what happens to temperature
Increase elevation what happens to air pressure
What is air pressure
Troposphere
0-10 km from surface
Decreasing temperature with height
Decreasing pressure with height
Vertical mixing of the air (tropo means to turn over)
Most weather systems occur here
Thickness of the troposphere varies with latitude and season
Tropopause
Transition between the troposphere and the stratosphere
Stratosphere
10-46 km from surface
constant temperature to ~20 km then warms
Why?
Stratopause
boundary between stratosphere and thermosphere
Mesosphere and Mesopause
50 -85 km
Temperature decreases
Thermosphere
85 km and up
increasing temperature with elevation
absorption of short wave energy waves by atoms of O and N
Temperature is high but region feels cold
why?
How does the atmosphere heat?
Sun is primary energy source
Reacts with atmosphere
Scattering (refraction)
Reflection
Absorption
Heats earth which causes heating of atmosphere
Variations in atmospheric heating
Latitude
Amount of energy/surface area varies based on latitude
High latitudes--> energy is spread out
Low latitudes more intense
Seasonal angle of sun to point on earth
Winter in Oregon--> sun is low in sky
More atmosphere energy passes through, more absorption occurs
Variations in atmospheric heating cont…
Differential heating
Rock type, soil type, snow, water etc...
Elevation
Geographic location
Near water? Near Mountains? Wind?
Clouds
Latent heat
Latent Heat
Hidden heat
created by phase changes of water
Evaporation, condensation, melting, freezing, sublimation…
All of these add or take energy from surrounding atmosphere.
Variations in Temperature create many of the weather features we see on earth
Cloud formation
Wind
Thunderstorms
Tornadoes
Pressure systems
….more in a bit.