Physical Geography: GEOG 1301

Spring 2005

Chapter Three: Earth’s Modern Atmosphere

 

Pay close attention to the maps, charts and graphs in all chapters- they are important learning tools.

 

Modern atmosphere: 4th in earth's history, 5 billion years old, 300 miles (exosphere up to 20,000 miles), bound to planet by gravity

 

Air: mixture of gasses

Exosphere- outer space

 

Function of the Atmosphere: 1) sustains, 2) protects and 3) filters (protective membrane)

 

Atmosphere- series of “shells” of air and gas, bound to the planet by gravity. (Remember- that gravity exerts a pull on air molecules- therefore air has weight and mass.)

 

Where does the atmosphere end and outer space begin?

(the geocorona at 1,000 kilometers from earth

 


Explanation of this image at: http://image.gsfc.nasa.gov/poetry/ask/q2136.html

 

 

Profile of the Modern Atmosphere- Figure 3.2 Page 67

 

Air pressure- under force of gravity, air molecules exert pressure on any surface in contact with the air (includes our skin and bodies.)  (Our bodies must be strong enough to push out against the pressure pushing in.)

 

Air pressure is denser at earth’s surface- thinner at higher altitudes.

 

Definition and Function of Atmospheric Criteria (Composition, Temperature and Function)  All but 0.1% exists below 31 miles

 

Destination Earth (NASA web site):

http://earth.nasa.gov/flash_top.html

http://science.hq.nasa.gov/

 

Composition: Uses chemical composition as the criteria

 

Heterosphere: (50-300 miles, sorted by gravity w/ hydrogen/helium lightest and oxygen/nitrogen heavier)

Homosphere: (surface to 50 miles, uniformily mixed except ozonsphere, 500 million years old, every breath and plant respiration)

 

Composition of gases in the homosphere: nitrogen (78%), oxygen (21%), argon (.9%), carbon dioxide (.037%)  Oxygen forms compounds that make up 1/2 earth's crust, C02 maintains global temperature- sensitive to human influence

 

Project Learn- Introduction to the Atmosphere:

http://www.ucar.edu/learn/1_1_1.htm

 

Temperature: Criteria of distinct temperature zones

 

Temperature and heat are not the same- temperature shows kinetic energy (energy of motion) of vibrating molecules) while heat is the flow of kinetic energy between bodies due to a temperature difference.

 

Thermosphere (like heterosphere- high temperatures- 2200 F) - upper limit is called Thermopause.

Mesosphere (coldest- -130 F)- 30 – 50 miles above surface

Stratosphere- 11 – 31 miles, temperatures increase with altitude

Troposphere - (biosphere, weather, 90% of atmosphere)

Normal Lapse Rate- 3.5 degrees per 1,000 feet, temperature decrease with increasing altitude.

Environmental Lapse Rate- adjusted rate for local conditions

 

Function: Removes most harmful wavelengths of insolation,

 

Ionosphere- outer layers, absorbs cosmic rays, gamma rays, x-rays and short, ultraviolet radiation

Ozonosphere- (absorbs UV and radiates as infrared) Filters radiation and safeguards life on earth.

 

Value and problem of ozonosphere- page 73

 

Air Pollution- Variable Atmospheric Components

 

Troposphere contains natural and anthropogenic (human-caused) types of gases, particles and other chemicals. 

 

Sources of natural air pollution- greatest cause of air pollution.  Includes nitrogen oxide, carbon monoxide, hydro-carbons and carbon dioxide.  Amounts are greater than human produced sources.

 

Natural factors that affect air pollution-

1.      Wind

2.      Local landscape

3.      Temperature inversion (when a normal lapse rate is reversed and temperature increase, trapping air underneath)

 

Anthropogenic pollution- human-caused, half of the world’s people live in cities- creating and coming into contact with more forms of air pollution than ever.  Main problem is one of concentration.

 

Describe sources and effects of anthropogenic pollution-

 

1.      60% of US air pollution from automobiles (SUVs are bad!)

http://www.suv.org/environ.html

http://www.sierraclub.org/globalwarming/suvreport/

http://www.columbia.edu/~sc2033/SUVs.htm

(These are one sided discussions!!- sorry for the lack of objectivity.  I ride my bike to work most days…)

 

2.      Urban pollutants concentrate and effect most people.

3.      Sources are described on pages 79-86

 

Acid Deposition- acid rain that carries tiny aerosol droplets that damage plants, animals and soils.