Chapter 04: Atmosphere and Surface Energy Balance Energy Essentials Energy Balance in the Troposphere Energy Balance at Earth s Surface
Energy Essentials Energy Pathways and Principles
Energy Pathways and Principles Transmission: Passage of energy through atmosphere or water Atmosphere Energy Inputs: Shortwave energy in from the Sun Ultraviolet light, visible light, near-infrared wavelengths Longwave Radiation Outputs: thermal infrared radiation Atmospheric Energy Budget: Inputs + Outputs Fig. 2.8, p. 48
Energy Pathways and Principles 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). Insolation decreases poleward from 25 latitude in both hemispheres; Equatorial and tropic latitudes high insolation (180-220 W/m 2 ); Low-latitude desert areas has the great annual insolation (240-280 W/m 2 ). Why? Because cloudless skies occurs so often in deserts! Fig. 4.2, p. 91
Energy Pathways and Principles Scattering (Diffuse Radiation): Changing direction of light s movement, without altering its wavelengths Gas molecules, dust particles, pollutants, ice, cloud droplets, water vapor, etc. Scattering represents about 7% of Earth s reflectivity, or albedo. Rayleigh Scattering: Different sizes of molecules or particles causes scattering of different wavelengths The shorter the wavelength, the grater the scattering; The longer the wavelength, the less the scattering Fig. 4.1, p. 90
Why sunsets and sunrises are often red? At sunsets and sunrises, lights needs to travel longer; More shorter waves from the sun get reflected and scattered; Only longer wavelengths reach you: that s RED Fig. 2.6, p. 47
Energy Pathways and Principles 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.) - Spoon in a cup filled with water - Rainbow (light refracted by myriad raindrops)
Energy Pathways and Principles 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 (light surfaces are more reflective than dark surfaces) Albedo R I Fig. 4.5, p. 93
Energy Pathways and Principles Cloud- albedo forcing: increase in albedo caused by clouds. Outcome: reflect insolation and cool Earth s surface Fig. 4.7, p. 95 Cloud- greenhouse forcing: clouds acts as insulation, trapping longwave radiation emitted by Earth Outcome: increase in greenhouse warming
Energy Principles -- Absorption Absorption: Assimilation of radiation by molecules of matter and its conversion from one form of energy to another Outcome: Energy delivered to the matter or transferred to chemical energy (e.g., photosynthesis). Once absorbed, the radiation no longer exists http://www.atmo.arizona.edu/students/courselinks /fall04/atmo336/lectures/sec3/energybudget.html
Heat Transfer Figure 4.10 Conduction Molecule to molecule transfer (diffuses through a substance) Convection Energy transferred by movement (involves a strong vertical motion) Advection Energy transferred by movement (involves a predominantly horizontal motion) Radiation Energy traveling through air or space
Energy Balance in the Troposphere The Greenhouse Effect and Atmospheric Warming Clouds and Earth s Greenhouse Earth Atmosphere Radiation Balance
The Greenhouse Effect and Atmospheric Warming http://www.environment.sa.gov.au/sustainability/images
Clouds and Greenhouse Forcing Figure 4.11
Earth Atmosphere Radiation Balance Figure 4.12
Energy Budget by Latitude Outcome: 1. Between the tropics, energy surpluses dominate; 2. In polar regions, energy deficits prevail; 3. Around ~36 latitude, a balance exists; 4. The imbalance of net radiation from tropic surpluses to polar deficits drives global circulation of both energy and mass: Winds, ocean currents, dynamic weather systems Figure 4.13
Energy Balance at Earth s s Surface Simplified Surface Energy Balance NET Radiation = +SW (insolation) SW (reflection) +LW (infrared) LW (infrared) The Net Radiation (R) depends on the local surface conditions (e.g., a park, a front yard, or a place on campus)--
Energy Balance at Earth s s Surface Daily Radiation Patterns Figure 4.14 The daily temperature lag The annual temperature lags: similar to daily lags In N. Hemisphere, Jan. is the coldest after December Solstice
Simplified Surface Energy Balance NET R = SW (insolation( insolation) SW (reflection) +LW (infrared) LW (infrared) Not a perfect balance at zero, but for a longer time, the earth s surface balances the incoming and outgoing energy
Global NET R Figure 4.17 Global and local net budgets are important for managing the solar energy collection and concentration
Energy Balance at Earth s s Surface The Urban Environment Trees and grass land are important for Urban environments The central park in NY City has daytime temperature 5-10 C cooler than outside the park
The Urban Environment Figure 4.21
End of Chapter 4 1. Energy Essentials: Transmission; Energy Inputs; Radiation Outputs; Diffuse Radiation (Scattering); Refraction; Reflection; Albedo; Cloud- albedo forcing; Cloud- greenhouse forcing; Absorption; Heat Transfer. 2. Energy Balance in the Troposphere: The Greenhouse Effect; Earth Atmosphere Radiation Balance; Energy Budget by Latitude and outcome. Daily Radiation Patterns; Simplified Surface Energy Balance (Net( Radiation); The daily temperature lag; The annual temperature lags; The urban environment (heat island) 3. Energy Balance at Earth s Surface: Daily Radiation
End of Chapter 4 Robert W. Christopherson Charles E. Thomsen