Review Question 1When is the subsolar point directly over 20°N latitude?
A) Never
B) Between the summer solstice and the fall equinox
C) Between the spring equinox and the summer solstice
D) B and C
Review Question 2Why is Pluto no longer considered a planet?
A) Because it is square
B) Because it is a thermonuclear reactor
C) Because it shares its orbit with another planet
D) Because it is 3 billion light years from the sun
Chapter 3Earth’s Modern Atmosphere
Geosystems 6eAn Introduction to Physical Geography
Robert W. ChristophersonCharles E. Thomsen
The AtmosphereAtmosphereAtmosphere: an envelop of gaseous mixture (also containing suspended solid and liquid particles and clouds) that encircles a planet
Earth’s Modern Atmosphere
The atmosphere is absolutely essential for life on Earth
Earth’s atmosphere exists in a series of spheres or layers that grade into one another
Composition, temperature, and function
Atmospheric Profile Our atmosphere extends to roughly 32,000 km (20,000 mi) from surface
The top of the atmosphere has no clear boundary
Gravity holds our atmosphere in place
Top of Thermosphere is at 480 km (300 mi) = top of the principle atmosphere
Exosphere
Atmospheric Composition
Two broad regions:Heterosphere – outer atmosphere
80 km (50 mi) outwards, to top of thermosphere Layers of gases sorted by gravity
Homosphere – inner atmosphere Surface to 80 km (50 mi)Gases evenly blendedOzone layer
Atmospheric Pressure
Figure 3.3
Atmospheric Temperature
TroposphereSurface to 18 km (11 mi)
90% mass of atmosphere
Normal lapse rate – average cooling at rate of 6.4 C °/ km (3.5 F°/1000 ft)
Tropopause
Atmospheric Temperature
Temperature Profile
Figure 3.5
Atmospheric Temperature
Stratosphere18 to 50 km (11 to 31 mi)
Temperatures increase with altitude
Ozone layer
Stratopause
Atmospheric Temperature
MesosphereTemperatures decrease with altitude
Mesopause
Atmospheric Temperature
ThermosphereRoughly same as heterosphere
80 km (50 mi) outwards
Altitude of thermopause varies
Temperatures increase with altitude, but little actual heat
Atmospheric Function
IonosphereAbsorbs cosmic rays, gamma rays, X-rays, some UV rays
OzonospherePart of stratosphere
Ozone (O3) absorbs UV energy and converts it to heat energy
Protective Atmosphere
Figure 3.6
Four Principal Components of AtmosphereNitrogen from volcanic sources
Oxygen from photosynthesis
Argon through radioactive decay of isotopes
Carbon dioxide byproduct of life processes
Composition of the AtmosphereComposition of the Atmosphere
Atmospheric gasesAtmospheric gases
Permanent gasesPermanent gases Variable gasesVariable gases
Nitrogen (~78% of vol.)
Oxygen (~21% of vol.)
Argon (~1% of vol.)
…
Water vapor (0-4% of vol.)
Carbon dioxide (0.037% of vol.)
Ozone (0.000007% of vol.)
Methane (0.00017% of vol.)
...
Water VaporWater Vapor
The most abundant variable gas (0.25% of total atmospheric
mass).
Added and removed from the atmosphere through the
hydrologic cycle.
A major contributor to Earth’s energy balance and many
important atmospheric processes.
Carbon DioxideCarbon Dioxide
A trace gas accounting for only 0.037% of the atmosphere.
Added to the atmosphere through biologic respiration and
decay, volcanic eruptions, and natural and human-related
combustion.
Anthropogenically related increases in recent decades have
led to great concern with regard to global “greenhouse
warming”.
Removed from the atmosphere by photosynthesis (go to
biosphere).
Carbon DioxideCarbon Dioxide
The steady increase of atmospheric CO2.
Question: the seasonal variation?the seasonal variation?
MethaneMethane
1.7 ppm; increase 0.01 ppm/yr.
An extremely effective
absorber of thermal
radiation emitted by
Earth’s surface; hence
related in the warming of
the atmosphere.
Released to the atmosphere through fossil fuel activities,
livestock digestion, and agriculture cultivation (especially rice).
CarbonCarbon Sequestration – removing carbon in the form of carbon dioxide from the atmosphere and storing it in the terrestrial biosphere
Carbon stored in biomass of plants
Soil organic carbon is carbon retained by the soil in humus form
The Carbon Cycle- source of atmospheric
carbon dioxideHuman acitivities release 7.1 GtC/yr (gigatons of Carbon per year).2 GtC/yr absorbed by oceans.1.9 GtC unaccounted for.3.2 GtC remain in atmosphere.
Carbon BanksCarbon bank – program that enables organizations to keep track of a stock or supply of greenhouse gases in secure fashion for future use in the trading market
www.icbe.com
