GEO101: Physical Geography

Lecture 05: Wednesday, January 28, 2009

Topics
1. The Modern Atmosphere
2. Atmospheric Pressure
3. Variable Atmospheric Components

The Modern Atmosphere
• From lecture 4 we have learned that the solar radiation includes 8% of X-ray, Gamma-ray, and ultraviolet wavelengths, 47% of visible light wavelengths, and 45% of infrared wavelengths. We now know that the Earth's atmosphere is protecting us from the harmful short wavelengths (X-ray, Gamma-Ray, and Ultraviolet);
• The Earth's atmosphere extends from the Earth surface to 32,000 km, but we commonly consider the top of the atmosphere to be around 480 km. Beyong 480 km, it's nearly a vacuum containing scarce lightweight hydrogen and helium atoms and is called the exosphere;
• The modern atmosphere can be divided into different layers according to three criteria: composition, temperature, and function;
• Heterosphere and Homosphere are compositional layers. Homosphere contains > 99.99% of the total atmosphere mass and its gases are evenly blended;
      If you dive in the heterosphere, would you expect to hear a lot of noises and feel the real speed? Why?
• What are the three most abundant gases in the homosphere? Is the CO2 content in the homosphere higher than Argon (Ar) ?
• Thermosphere, Mesophere, Stratosphere and Troposphere are the four atmosphere layers divided by the temperatures. Which one has the lowest average temperature? Which one has the average temperature decrease of 6.4 degree (C) per kilometer that is called the 'normal lapse rate'? Which layer do the Noctilucent clouds commonly occur?
• Ionosphere and Ozonosphere are the atmospheric layers divided according to their functions. What does the Ionosphere do for the solar radiation? What does the Ozonosphere do for the solar radiation?
• Why and how does the stratospheric Ozone Loss happen and what effects would it have to human health?

• Understand the UV index in weather forecasts;

Atmospheric Pressure
• What is the atmospheric pressure at the sea level (in millibars)? What is the human body pressure ?
• When the airplane is taking off, you feel on a pressure change on your eardrum, Why? How about the landing ?

Variable Atmospheric Components
• What are the common Natural Factors That Affect Air Pollution?
• What is the 'Temperature Inversion'?
• What are the common Anthropogenic Pollutions ? Understand the basics on their negative effects to human health and to the ecosystems.
• Why are anthropogenic gases more significant to human health than are those produced from natural sources?
• Do you think the 'Clear Air Act' has been effective and should be continued?