Chapter 04: Atmosphere and Surface Energy Balance. Energy Essentials Energy Balance in the Troposphere Energy Balance at Earth s Surface

Transcription

1 Chapter 04: Atmosphere and Surface Energy Balance Energy Essentials Energy Balance in the Troposphere Energy Balance at Earth s Surface

2 Energy Essentials Energy Pathways and Principles

3 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

4 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 ( W/m 2 ); Low-latitude desert areas has the great annual insolation ( W/m 2 ). Why? Because cloudless skies occurs so often in deserts! Fig. 4.2, p. 91

5 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

6 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

7 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)

8 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

9 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

10 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 /fall04/atmo336/lectures/sec3/energybudget.html

11 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

12 Energy Balance in the Troposphere The Greenhouse Effect and Atmospheric Warming Clouds and Earth s Greenhouse Earth Atmosphere Radiation Balance

13 The Greenhouse Effect and Atmospheric Warming

14 Clouds and Greenhouse Forcing Figure 4.11

15 Earth Atmosphere Radiation Balance Figure 4.12

16 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

17 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)--

18 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

19 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

20 Global NET R Figure 4.17 Global and local net budgets are important for managing the solar energy collection and concentration

21 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

22 The Urban Environment Figure 4.21

23 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

24 End of Chapter 4 Robert W. Christopherson Charles E. Thomsen