1. Chapter 4 Atmosphere and Surface Energy Balances Geosystems 6e An Introduction to Physical Geography Robert W. Christopherson Charles E. Thomsen

2. Why do we have to learn about energy? Energy powers the biosphere, hydrosphere, and atmosphere. Energy deficits are created by the earth’s curved surface—solar insolation varies with latitude. To compensate for energy deficits, ocean currents, global winds, and weather systems move energy around the globe. This is why we have weather and climate.

3. Energy Essentials Energy Pathways and Principles Shortwave energy in from the Sun Longwave energy out from Earth Transmission Passage of energy through atmosphere or water Refers to shortwave radiation that goes straight through the atmosphere to the surface

4. Energy Pathways Figure 4.1

5. Energy Pathways Insolation input All radiation received at Earth’s surface – direct and indirect Scattering (diffuse radiation) Changing direction of radiation’s movement, without altering its wavelengths Pollutants, ice, and water vapor increase scattering Why is diffuse radiation important? Because it colors the sky

6. Energy Pathways Scattering (diffuse radiation) Rayleigh Principle – the shorter the wavelength, the greater the scattering; the longer the wavelength, the less the scattering Shorter wavelengths of visible light (blues and violets) scatter the most and dominate the lower atmosphere More blue present in sunlight, so the sky is blue If we had NO atmosphere, what color would the sky be?

7. Energy Pathways Sunrise/Sunset When the sun is low on the horizon, its rays must travel through more atmosphere This increases scattering of shorter wavelengths (blues) so that only the longer wavelengths color the sky (oranges, reds)

8. Refraction – change in speed and direction of light When a form of radiation moves from one medium to another (air to water, space to atmosphere), its speed and direction change The wavelengths of radiation are bent into different angles, separating the light into its component colors Rainbows – created when visible light passes through raindrops, is refracted, and reflected showing all colors Energy Pathways

9. Figure 4.3 Refraction

10. Mirage – an image that appears near the horizon where light waves are refracted by layers of air at different temperatures and densities on a hot day When the sun is low in the sky, its light must penetrate through more air – its refracted by layers of air at different temperatures and densities creating a mirage

11. Refraction Figure 4.4

12. Energy Essentials Albedo - % of insolation an object reflects Darker colors have lower albedos (they absorb more insolation) Lighter colors have higher albedos (they reflect more insolation) During the day, clouds reflect radiation back to space At night, clouds reflect longwave radiation back to Earth’s surface

13. Energy Essentials Aerosols Volcanic origin Decrease atmospheric albedos Leads to cooling of almost 1°F Insolation reflected by dirty sky

14. Albedo Figure 4.5

15. Energy Balance in the Troposphere Greenhouse Effect – where gases (carbon dioxide, water vapor, methane, and CFCs) absorb insolation and reradiate it back to Earth in longer wavelengths thereby warming the lower troposphere The Greenhouse Effect and Atmospheric Warming Atmosphere absorbs heat energy Atmosphere delays transfer of heat from Earth into space

16. Energy Budget by Latitude Figure 4.13

17. Daily Radiation Patterns Figure 4.14

18. Global NET R Figure 4.17

19. Global NET R Non-vegetated surfaces lose heat in one of 3 ways: Latent heat of evaporation – energy released as water changes state Sensible heat – heat you can feel and measure; convection and conduction Ground heating and cooling – energy stored during warm periods and released during cool periods

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

21. The Urban Environment Figure 4.21

22. Urban Heat Island Figure 4.22