Chapter 4 Atmosphere and Surface Energy Balances

1. Chapter 4Atmosphere and Surface Energy Balances Robert W. Christopherson Charlie Thomsen

2. Energy Essentials  • Energy and matter make up the universe. • E=mc2 • Matter: the “stuff” we see, smell and touch. • Energy: exists in various forms  • Energy from the Sun (electromagnetic radiation) • Energy in Food (chemical) • The heat we feel • Energy can convert from one form to other forms (e.g?) • Definition: The capacity to do work

3. Forms of Energy   • Kinetic Energy: • Energy associated with an object by virtue of its motion. • e.g. Kinetic energy of a moving hammer can drive in a nail. The bigger the hammer and the fast the swing, the higher the kinetic energy. • Kinetic energy at atomic level is significant as atoms and molecules are continually vibrating. • Potential Energy: • To potential to do work • e.g. suspended hailstone possess potential energy.

4. Solar Radiation Passing Atmosphere • Scattering: Air particles alter direction of light, without altering its wavelengths. • Raleigh Scattering • scattering by atmospheric molecules (scattering particle’s diameter smaller than wavelength) • Selective: scattering strongly • Mie Scattering • Scattering by aerosols (scattering particle’s diameter equal or greater than wavelength. • Non-selective. • Reflection: • Deflection of photons from the objects that radiation falls upon. • Clouds reflect solar radiation, cooling the Earth. • Absorption • Selective, not all • Both atmospheric molecules and aerosols absorb solar radiation.

5. Refraction Figure 4.4

6. Energy Pathways Figure 4.1

7. Insolation at Earth’s Surface Figure 4.2

8. Daily Net Radiation at TOA Figure 2.11

9. Albedo Figure 4.5

10. July and January Albedos Satellite Measurements Figure 4.6

11. Clouds and Albedo Figure 4.7

12. Atmospheric Aerosols Figure 4.8

13. Heat Transfer • Definition: • the amount of internal energy of matter transferred between two objects due to temperature difference. • Air is a poor conductor of heat • Conduction • Molecule-to-molecule transfer • Convection • Energy transferred by vertical movement of substance • Advection • Horizontally dominant movement of substance • Radiation • Energy traveling through air or space without medium • Blackbody emits radiation according three radiation laws introduced early.

14. Heat Transfer Figure 4.9

15. The Greenhouse Effect and Atmospheric Warming • Atmosphere absorbs heat energy • A real greenhouse traps heat inside • Atmosphere delays transfer of heat from Earth into space

16. Clouds and Forcing Figure 4.10

17. Energy Budget by Latitude Figure 4.13

18. Shortwave and Longwave Energy Figure 4.11

19. Radiation Balance Equation Radiation Balance Equation: Rn = Qsun(1-α) + Lair-Learth • Every term on the right hand side is radiation. This is the net energy available for all other biophysical processes. Many environmental problems can be explain with this equation. • Snow melting at high latitudes: lowers α, thus warms the planet. • Increase CO2, increase Lair, warms the planet. Figure 4.15

20. Surface Energy Balance Equation • Radiation balance equation tells us how much energy is available, these energy can be converted into various forms depending on usage: • The evaporate water, storage in water vapor as latent heat (LE) . • Heat the ground surface and then passing to the surrounding air through convection (H) . • Heat the ground surface and then passing to lower layer through conduction (G). • Used by plants in photosynthesis and store energy in chemical bonds (A). Energy Balance Equation: Rn = LE + H +G +A On an daily or longer time basis Rn = LE + H Figure 4.15

21. Earth–Atmosphere Radiation/Energy Balance Figure 4.12

22. Energy Balance at Earth’s Surface • Daily Radiation Patterns   • Simplified Surface Energy Balance   • The Urban Environment

23. Systems View of Daily Surface Energy Reservoir: Total Energy Storage Nearly Ground Inflows: Shortwave Radiation from the sun longwave from atmosphere Outflow: Shortwave reflected Longwave outgoing Relationship: R(t)=R(t-1)+ inflows -outflow Inflows outflow Figure 4.14

24. Daily Radiation Curves Figure 4.14

25. Simplified Surface Energy Balance • NET R = +SW (insolation) –SW (reflection) +LW (infrared) –LW (infrared) Figure 4.16

26. Global NET R Figure 4.17

27. Global Latent Heat Figure 4.18

28. Global Sensible Heat Figure 4.19

29. El Mirage, CA Radiation Budgets Pitt Meadows, BC Figure 4.20

30. The Urban Environment Figure 4.21

31. Urban Heat Island Figure 4.22

32. Urban Heat IslandPilotProject Figure 4.23

33. End of Chapter 4 Geosystems 7e An Introduction to Physical Geography