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Keseimbangan energi di bumi
- 1. Introducing Physical Geography Alan Strahler Chapter 2 TheEarth’s Global Energy Balance Return Copyright © 2011 by John Wiley & Sons, Inc. to Main Slide
- 2. The Earth’s GlobalEnergy Balance Chapter 2 2 Return to Main Slide
- 3. Chapter Outline 1. ElectromagneticRadiation Ozone Layer 2. Insolation over the Globe 3. Composition of the Atmosphere 4. Sensible Heat & Latent Heat Transfer 5. The Global Energy System CERES – Clouds & Earth’s Radiant Energy Systems 6. Net Radiation, Latitude, & Energy Balance 3 Click Section Return to go to Main contentSlide
- 4. 1. Electromagnetic Radiation RADIATIONAND TEMPERATURE SOLAR RADIATION CHARACTERISTICS OF SOLAR ENERGY LONGWAVE RADIATION FROM THE EARTH THE GLOBAL RADIATION BALANCE Return 4 to Main Slide
- 5. 1. Electromagnetic Radiation Allsurfaces emit radiation. •Hot objects - radiation in the form of light •Cooler objects - emit heat radiation. Earth emits exactly as much energy as it absorbs from the sun - energy balance Electromagnetic Radiation collection of waves, wide range of wavelengths, travel away from the surface of an object. Wavelength is the distance separating one wave crest from the next wave crest 5 Return to Main Slide
- 6. 1. Electromagnetic Radiation Gammarays and X rays – short wavelength, high energies, hazardous to health. Ultraviolet - 10 nm to 0.4 μm. Can damage living tissues. Visible light - 0.4 to 0.7 μm. from violet blue, green, yellow, orange, to red. Near-infrared - 0.7 to 1.2 μm. Similar to visible light. From the Sun. Cannot be seen because eyes not sensitive to radiation beyond 0.7 μm. Shortwave infrared - 1.2 and 3.0 μm. From the sun Middle-infrared - 3.0 μm to 6 μm. From Sun or hot sources on Earth (forest fires, gas well flames) Thermal infrared – 6 μm to 300 μm. Given off by bodies at temperatures found at the Earth’s surface. 6 Return to Main Slide
- 7. 1. Electromagnetic Radiation 7 Return toMain Slide
- 8. RADIATION AND TEMPERATURE Hot objectsradiate more energy that cool Hotter object, shorter wavelength Suburban scene at night. Black and violet tones - lower temperatures Yellow and red tones – higher temperatures. Ground and sky - coldest, windows of the heated homes warmest. 1. Electromagnetic Radiation 8 Return to Main Slide
- 9. SOLAR RADIATION Sun -ball of constantly churning gases heated by continuous nuclear reactions (hydrogen to helium at high temperatures and pressures) •Surface temperature 6000°C (11,000°F) •Rays of solar radiation spread apart as they move away from the Sun •Rate of incoming energy, solar constant about 1367 W/m2 •Intensity of received (or emitted) radiation = power of the radiation and the surface area being hit by (or giving off) energy 1. Electromagnetic Radiation Intensity of solar radiation is greatest in the visible portion of the spectrum. Most of the solar radiation in the visible spectrum penetrates the Earth’s atmosphere to reach the surface. 9 Return to Main Slide
- 10. CHARACTERISTICS OF SOLAR ENERGY Sunemits shortwave radiation (ultraviolet, visible and shortwave infrared) Earth emits longwave radiation (infrared) - much is absorbed by the Earth’s atmosphere before it leaves (e.g. by carbon dioxide) Radiation intensity is shown on a logarithmic scale. 1. Electromagnetic Radiation 10 Return to Main Slide
- 11. LONGWAVE RADIATION FROM THEEARTH Earth radiates less energy that the sun •Energy radiated by Earth is Longwave •Wavelengths are absorbed by gases in the atmosphere, such as water vapor and carbon dioxide 1. Electromagnetic Radiation 11 Return to Main Slide
- 12. THE GLOBAL RADIATION BALANCE Shortwaveradiation from the Sun transmitted through space, intercepted by the Earth. Absorbed radiation is then emitted as Longwave radiation to outer space. 1. 1. Electromagnetic Radiation 12 Return to Main Slide
- 13. THE GLOBAL RADIATION BALANCE Incomingsolar radiation is either: • reflected (scattered) back to space, or • absorbed by the atmosphere or surface 1. Electromagnetic Radiation 13 Return to Main Slide
- 14. THE GLOBAL RADIATION BALANCE Absorptionof shortwave radiation by the Earth and atmosphere provides energy that the Earth – atmosphere system radiates away in all directions. 1. Electromagnetic Radiation Return to Main Slide
- 15. 2. Insolation overthe Globe DAILY INSOLATION THROUGH THE YEAR ANNUAL INSOLATION BY LATITUDE WORLD LATITUDE ZONES 15 Return to Main Slide
- 16. 2. Insolation overthe Globe Insolation – the flow rate of incoming solar radiation. It is high when the Sun is high in the sky. • Angle of the solar beam striking the Earth varies with latitude • Insolation is strongest near the equator and weakest near the poles. • The intensity of the solar beam depends on the angle between the beam and the surface. 16 Return to Main Slide
- 17. 2. Insolation overthe Globe • Most intense when the beam is vertical. • Beam at an angle of 45° covers a larger surface, less intense. • At 30° beam covers greater surface, even weaker. 17 Return to Main Slide
- 18. DAILY INSOLATION THROUGH THEYEAR Daily insolation depends on: 1) Angle that the sun’s rays strike 2) How long a place is exposed to those rays Midlatitude, mid summer – days are long, sun’s position is high – maximum heating 2. Insolation over the Globe 18 Return to Main Slide
- 19. DAILY INSOLATION THROUGH THEYEAR 2. Insolation over the Globe 19 Return to Main Slide
- 20. DAILY INSOLATION THROUGH THEYEAR Equator - Sun’s path across the sky varies in position and height above the horizon. Sun is always in the sky for 12 hours, but its noon angle varies through the year. 2. Insolation over the Globe 20 Return to Main Slide
- 21. DAILY INSOLATION THROUGH THEYEAR North Pole Sun moves in a circle in the sky at an elevation that changes with the seasons. 2. Insolation over the Globe 21 Return to Main Slide
- 22. DAILY INSOLATION THROUGH THEYEAR Tropic of Capricorn the Sun is in the sky longest and reaches its highest elevations at the December solstice. 2. Insolation over the Globe 22 Return to Main Slide
- 23. ANNUAL INSOLATION BY LATITUDE TiltedAxis • Annual insolation varies smoothly from equator to pole • Insolation greater at lower latitudes • High latitudes receive flow of solar Energy • Insolation at poles 40 percent of equator. 2. Insolation over the Globe Axis Perpendicular • No seasons • Annual insolation high at the Equator, Sun directly overhead at noon every day throughout year • Annual insolation zero at the poles, • Sun’s below horizon. Tilt redistributes significant portion of insolation from equator to poles. 23 to Main Slide
- 24. WORLD LATITUDE ZONES Globedivided into broad latitude zones based on the seasonal patterns of daily insolation observed globally 2. Insolation over the Globe 24 Return to Main Slide
- 25. 3. Composition ofthe Atmosphere Constant gases in the Troposphere Nitrogen 78% (converted by bacteria into a useful form in soils) Oxygen 21% (produced by green plants in photosynthesis and used in respiration) Return 25 to Main Slide
- 26. 4. Sensible Heat& Latent Heat Transfer Sensible heat – the quantity of heat held by an object that can be sensed by touching or feeling Latent heat - heat that is used and stored when a substance changes state from a solid to liquid (or directly to a gas) or liquid to gas (e.g. evaporation of water) Latent heat transfer – the transfer of heat from an evaporating surface to the atmosphere 27 Return to Main Slide
- 27. 4. Sensible Heat& Latent Heat Transfer Sensible heat transfer refers to the flow of heat between the Earth’s surface and the atmosphere by conduction or convection. Latent heat transfer refers to the flow of heat carried by changes of state of water. Return 28 to Main Slide
- 28. 5. The GlobalEnergy System SOLAR ENERGY LOSSES IN THE ATMOSPHERE ALBEDO COUNTERRADIATION AND THE GREENHOUSE EFFECT GLOBAL ENERGY BUDGETS OF THE ATMOSPHERE AND SURFACE CLIMATE AND GLOBAL CHANGE 29 Return to Main Slide
- 29. SOLAR ENERGY LOSSESIN THE ATMOSPHERE Clear Sky 80% of insolation reaches Earth’s surface 20% of insolation reflected back to space (3% by scatter, 17% by molecules and dust) Cloudy Sky 30 to 60% reflected by clouds 5 to 20% absorbed in Clouds 45 to 10% reaches Earth’s surface 5. The Global Energy System 30 Return to Main Slide
- 30. ALBEDO Albedo - percentageof solar radiation reflected Snow and Ice – 0.45-0.85 (also expressed as 45 to 85%) Black Pavement – 0.03 Water - 0.02 Fields, forests, bare ground - 0.03 to 0.25. Earth and atmosphere system - 0.29 and 0.34. Planet sends back to space slightly less than one-third 5. The Global Energy System 31 Return to Main Slide
- 31. ALBEDO Fresh snow hasa high albedo, reflecting most of the sunlight it receives. Only a small portion is absorbed 5. The Global Energy System 32 Return to Main Slide
- 32. ALBEDO Asphalt paving reflects littlelight, so it appears dark or black and has a low albedo. It absorbs nearly all of the solar radiation it receives. 5. The Global Energy System 33 Return to Main Slide
- 33. ALBEDO Water absorbs solar radiation andhas a low albedo unless the radiation strikes the water surface at a low angle. In that case, Sun glint raises the albedo. 5. The Global Energy System 34 Return to Main Slide
- 34. COUNTERRADIATION AND THE GREENHOUSEEFFECT Shortwave radiation passes through atmosphere, absorbed and warms surface. 5. The Global Energy System Surface emits longwave radiation which goes (A) directly to space, or, (B) absorbed by atmosphere 35 Return to Main Slide
- 35. COUNTERRADIATION AND THE GREENHOUSEEFFECT Atmosphere radiates longwave energy back to the surface and also to space as counterradiation (C & D) Counterradiation produces the greenhouse effect. 5. The Global Energy System 36 Return to Main Slide
- 36. COUNTERRADIATION AND THE GREENHOUSEEFFECT Water vapor and carbon dioxide act like glass allowing shortwave radiation through but absorbing and radiating longwave radiation. 5. The Global Energy System 37 Return to Main Slide
- 37. GLOBAL ENERGY BUDGETSOF THE ATMOSPHERE AND SURFACE 5. The Global Energy System 38 Return to Main Slide
- 38. 6. Net Radiation,Latitude, & Energy Balance Net radiation difference between incoming and outgoing radiation At high latitudes there is an energy deficit Poleward - heat transfer moves surplus energy from low to high latitudes 39 Return to Main Slide
- 39. Ozone Layer Ozone Layer– Shield to Life Ozone – form of oxygen with 3 oxygen atoms (O3) • Shelters Earth's surface from ultraviolet radiation • Attacked by synthetic chemical components – Chlorine, fluorine and carbons – Chlorofluorocarbons (CFC’s) • 1980’s hole in ozone discovered over Antarctica • Ozone layer thins during the spring in the Southern Hemisphere (September, October) • 1987 – 23 nations signed treaty to cut CFC’s 40 Return to Main Slide
- 40. Ozone Layer Ozone Layer– Shield to Life The Antarctic ozone hole of 2006 was the largest on record 29.5 million square miles. •Low values of ozone –purple, ranging through blue, green, and yellow. •Ozone concentration is measured in Dobson units 41 Return to Main Slide
- 41. CERES – Clouds& Earth’s Radiant Energy Systems CERES – Clouds & Earth’s Radiant Energy Systems NASA study of the Earth’s radiation budget from space for 20 years •NASA Experiment—Clouds and the Earth’s Radiant Energy (CERES) •New generation of instruments in space that scan the Earth and measure the amount of shortwave and longwave radiation leaving the Earth at the top of the atmosphere. •Continuous monitoring of the Earth’s radiant energy flows •Small, long-term human or natural changes can be detected 42 Return to Main Slide
- 42. CERES – Clouds& Earth’s Radiant Energy Systems CERES – Clouds & Earth’s Radiant Energy Systems Average Shortwave Flux - 0 to 210 W/m2, March 2000 •Equator - thick clouds reflect solar radiation back to space. •Midlatitudes - cloudiness shows up as light tones. •Tropical deserts - bright. •Snow and ice is reflective, amount of radiation at poles low – so do not appear bright. •Oceans - absorb solar radiation so low shortwave fluxes. Return to Main Slide 43
- 43. CERES – Clouds& Earth’s Radiant Energy Systems CERES – Clouds & Earth’s Radiant Energy Systems Average Longwave Flux 100 to 320 W/m2, March 2000 •Equator – low values due to blanketing of thick clouds trapping longwave radiation •Tropical oceans - clear sky emits high longwave flux •Poles - surface and atmospheric temperatures drop, longwave energy emission Low Return to Main Slide 44
- 44. Chapter Review 1. Waterin the Environment 2. Humidity 3. The Adiabatic Process 4. Clouds Acid Deposition 5. Precipitation 6. Types of Precipitation 7. Thunderstorms 8. Tornadoes 9. Air Quality Observing Clouds from GOES 45 Return to Main Slide