GEOG101: Physical Geography

Lecture 06: Monday, Feb. 2, 2009

Topics
1. Energy Essentials
2. Energy Balance in the Troposphere
3. Energy Balance at Earth's Surface

Energy Essentials
• Energy pathways: Insolation input, Transmission, Scattering, Refraction
    Insolation Input: The single energy input driving the Earth-Atmosphere system, including all the radiation that arrives at the Earth's surface, both direct and diffuse (scattered by the atmosphere).
    Transmission: Passage of energy through atmosphere or water;
    Scattering (Diffuse Radiation): Changing direction of light's movement, without altering its wavelengths;
    Answer the questions such as 1) Why Earth's sky is blue? 2) Why sunrises and sunsets are often red?
    Refraction: Change in speed and direction of light (when light entering a different medium; e.g., from empty space to atmospheric gases, or from air to water; etc.);
    Answer the questions such as 1) why a spoon is 'bended' in a cup filled with water? 2) How does the rainbow form? and 3) How does the mirage of the sun form?

• Energy Principles: Albedo and reflection, cloud's albedo effects, Absorption
     Reflection: Arriving energy bounces directly back into space without being absorbed or performing any work;
    Albedo: The reflectivity quality, or intrinsic brightness, of a surface;
     Comparing the ice-covered antarctic and the pacific ocean, which area would have a higher albedo?
    Cloud-albedo forcing: increase in albedo caused by clouds. Outcome: reflect insolation and cool Earth's surface;
    Cloud-greenhouse forcing: clouds acts as insulation, trapping longwave radiation from Earth; Outcome: increase in greenhouse warming;
    Absorption: Assimilation of radiation by molecules of matter and its conversion from one form of energy to another;

• Heat Transfer: Conduction, Convection, Advection, Radiation
    Conduction: Molecule to molecule transfer;
    Convection: Energy transferred by movement that involves a strong vertical motion;
    Advection: Energy transferred by movement that involves a predominantly horizontal motion;
    Radiation: Energy traveling through air or space

Energy Balance in the Troposphere
• The Greenhouse Effect and Atmospheric Warming: what effects do the high coluds and low clouds have to the global temperature changes?
• Earth-Atmosphere Radiation Balance: Read Fig. 4.12, understand the 'positive' and 'negative' radiation parameters in Earth-Atmosphere energy budget;
• Energy Budget by Latitude: their influence to Winds, ocean currents, dynamic weather systems, etc. (read Fig. 4.13)

Energy Balance at Earth's Surface
• Daily Radiation Patterns: Read Fig. 4.14, notice the the daily temperature lag in the afternoon;
• The annual temperature lags: similar to daily lags. In the northern hemisphere, January is the coldest after December Solstice (a cold temperature lag); July and August are possibly the hottest time after the June solstice (a hot temperature lag);
• Energy Balance at Earth's Surface: NET R = +SW (insolation) -SW (reflection) +LW (infrared) -LW (infrared) = A simplified Surface Energy Balance
• The Net surface energy Radiation is NOT a perfect balance at zero, but for a longer time, the earth's surface balances the incoming and outgoing energy;
• Global and local net budgets are important for managing the solar energy collection and concentration;
• The Urban Environment: Urban heat island;
• The Urban Environment: Trees and grass lands are important for Urban micro-environments;
    The central park in NY City has daytime temperature 5-10 degree C cooler than outside the park;
     A smaller planter with trees outside a shopping mall can be 16 degree C cooler;