Review Question 1In your own words, what is Geography?

BAD answer:The science that studies the relationships between natural and cultural systems and the interdependence of the two over space and time

These are not YOUR words!

Review Question 2Why are sunspots darker than the rest of the sun?

A) Because they are hotter than the surrounding surface

B) Because they are cooler than the surrounding surface

C) Because of solar wind

D) Because there is no sunlight on them

Review Question 3When 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 & C

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

Stratopause

Ozone layer

Atmospheric Temperature

MesosphereTemperatures decrease with altitude

Mesopause

Atmospheric Temperature

ThermosphereRoughly same as heterosphere

80 km (50 mi) outwards

Altitude 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).

Variable Atmospheric Components  

Natural Factors That Affect Air Pollution  Winds – gather and move pollutants

Landscape – mountains and hills can form barriers to air movement or can direct pollutants

Temperature inversions – trap pollutants and do not allow them to be diluted by the atmosphere

Wildfires

Figure 3.7

Temperature Inversion

Figure 3.9

Pollution Sources

Figure 3.10

Antarctic Ozone Hole

Figure FS 3.1.1

Ozone HoleOzone losses in the midlatitudes 6-8% per decade

Alters atmospheric chemistry, biological systems, ocean phytoplankton, fisheries, crop yields, human eye and skin tissue, and human immunity

Ozone hole is not caused by global warming

CFCsSynthetic molecules of chlorine, fluorine, and carbon

Released by aerosol sprays, propellants, and refrigerants

Do not break down naturally or dissolve in water

CFCsWhen CFCs reach the stratosphere, they are split by UV light

The freed chlorine atom breaks apart ozone atoms creating ClO and O2

O2 is transparent to UV radiation

ClO and O3

Figure FS 3.1.2