Geography 101: The Atmosphere Notes

Definition: The atmosphere is the gaseous envelope that surrounds the Earth, composed of a mixture of gases along with suspended liquids and solids (aerosols).
Non-variable Gases (constant composition):
- Nitrogen (N2): 78.08%
- Oxygen (O2): 20.95%
- Argon (Ar): 0.93%
- Neon (Ne): 0.002%
- Others (He, Kr): 0.001%
Variable Gases (variable composition):
- Water Vapor (H2O): 0.1 to 4.0%
- Carbon Dioxide (CO2): 0.040%
- Ozone (O3): 0.0006%
- Other Gases (CH4): 0.0015%, CFC: trace amounts

As altitude increases, both density and pressure decrease:
- Density: Mass per unit volume decreases with height.
- Pressure: The weight of overlying atmospheric components decreases with altitude.
The atmosphere is divided into layers based on temperature:
- Troposphere: 0 to ~17-18 km (equatorial) and 0 to ~8-10 km (polar).
- Contains 80% of the mass of the atmosphere; temperatures decrease with height.
- Turbulent and well-mixed layer; rapid transfers of water vapor occur.
- Stratosphere: ~15 to 50 km, characterized by the ozone layer where temperature increases with altitude. Limited circulation with the troposphere.
- Mesosphere: 50 to 80 km, where temperatures decrease with height.
- Thermosphere: Very low density and temperature increases beyond 80 km.

Acid Deposition: Refers to the settling of acidic pollutants from the atmosphere to the earth's surface.
Stratospheric Ozone Depletion: Leads to increased UV radiation reaching the earth's surface, which can cause harm to biological systems.
Air Pollution:
- Smog: Historically significant examples include London in 1952 and Beijing in 2017.
- Photochemical Smog: Results from vehicle exhaust reacting with atmospheric compounds, producing harmful substances like ozone and nitric acid.
- Conditions:
  - Hot sunny weather
  - Light winds
  - Temperature inversions influenced by topography.
- Industrial Smog: Results from emissions of sulfur oxides and particulate matter, often from industries or coal plants.
- Sulfur dioxide can form sulfuric acid in the air; fine particulates can penetrate lungs.
Air Quality Monitoring: Improvements seen in North America; however, poor air quality persists. Monitor daily AQI (Air Quality Index) values to track air quality (e.g., 0-50 = Good, 301-500 = Hazardous).

Q1: Solar radiation reflected off of the Earth’s surface back to space is called:
- a. Outgoing Shortwave
- b. Incoming Longwave
- c. Incoming Shortwave
- d. Outgoing Longwave
Q2: Net Radiation (Q*):
- a. is always positive in the polar regions
- b. is the balance between incoming and outgoing radiation
- c. does not influence surface temperature
- d. is lowest in the equatorial region
Q3: The Earth's atmosphere selectively absorbs radiation emitted from the Earth's surface in which group of wavelengths?
- a. Ultraviolet
- b. Thermal infra-red
- c. X-ray
- d. Microwave