Keseimbangan energi di bumi

Copyright © 2011 by John Wiley & Sons, Inc.

Alan Strahler

Introducing

Physical

Geography

Return to Main

Slide

Chapter 2 The Earth’s Global Energy Balance

The Earth’s Global Energy

Balance

Chapter 2 Return

to Main Slide 2

Return

Chapter Outline 1. Electromagnetic Radiation Ozone Layer

2. Insolation over the Globe 3. Composition of the Atmosphere 4. Sensible Heat & Latent Heat Transfer

5. The Global Energy System

Energy Balance Click Section

to go to Main

contentSlide 3

CERES – Clouds & Earth’s Radiant Energy Systems

6. Net Radiation, Latitude, &

to Main Slide

1. Electromagnetic Radiation RADIATION AND TEMPERATURE SOLAR RADIATION CHARACTERISTICS OF SOLAR ENERGY LONGWAVE RADIATION FROM THE EARTH THE GLOBAL RADIATION BALANCE Return

4

Return to Main

Slide 5

1. Electromagnetic Radiation All surfaces 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

Return to Main

Slide 6

1. Electromagnetic Radiation Gamma rays 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.

1. Electromagnetic Radiation Return

to Main Slide 7

to Main Slide 1. Electromagnetic Radiation 8

RADIATION AND TEMPERATURE Hot objects radiate 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. Return

SOLAR RADIATION Sun - ball of constantly churning gases heated by continuous nuclear reactions (hydrogen to helium at high temperatures


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.

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 Return


CHARACTERISTICS OF SOLAR ENERGY Sun emits 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. Return


LONGWAVE RADIATION FROM THE EARTH 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 Return

THE GLOBAL RADIATION BALANCE Shortwave radiation from the Sun transmitted through space, intercepted by the Earth. Absorbed radiation is then emitted as Longwave radiation to

outer space. 1. Return


THE GLOBAL RADIATION BALANCE Incoming solar radiation is either: • reflected (scattered) back to space, or • absorbed by the atmosphere or surface Return


to Main Slide 1. Electromagnetic Radiation

THE GLOBAL RADIATION BALANCE Absorption of shortwave radiation by the Earth and atmosphere provides energy that the Earth – atmosphere system radiates away in all directions. Return

to Main Slide

2. Insolation over the Globe DAILY INSOLATION THROUGH THE YEAR ANNUAL INSOLATION BY LATITUDE WORLD LATITUDE ZONES Return

15

to Main Slide 16

2. Insolation over the 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. Return

2. Insolation over the Globe

Return to Main

Slide

• 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

to Main Slide 2. Insolation over the Globe 18

DAILY INSOLATION THROUGH THE YEAR 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 Return

DAILY INSOLATION THROUGH THE YEAR Return


DAILY INSOLATION THROUGH THE YEAR 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. Return



DAILY INSOLATION THROUGH THE YEAR North Pole Sun moves in a circle in the sky at an elevation that changes with the seasons. Return

DAILY INSOLATION THROUGH THE YEAR Tropic of Capricorn - the Sun is in the sky longest and reaches its highest elevations at the December solstice. Return


ANNUAL INSOLATION BY LATITUDE


Tilted Axis • 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.

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. Return


WORLD LATITUDE ZONES Globe divided into broad latitude zones based on the seasonal patterns of daily insolation observed globally Return

to Main Slide 25

3. Composition of the 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

to Main Slide 27

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 Return

to Main Slide 28

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

to Main Slide

5. The Global Energy 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 Return

29

to Main Slide 5. The Global Energy System 30

SOLAR ENERGY LOSSES IN 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 Return


ALBEDO Albedo - percentage of 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 Return

ALBEDO Fresh snow has a high albedo, reflecting most of the sunlight it receives. Only a small portion is absorbed Return



ALBEDO Asphalt paving reflects little light, so it appears dark or black and has a low albedo. It absorbs nearly all of the solar radiation it receives. Return


ALBEDO Water absorbs solar radiation and has a low albedo unless the radiation strikes the water surface at a low angle. In that case, Sun glint raises the albedo. Return

COUNTERRADIATION AND THE GREENHOUSE EFFECT

Shortwave radiation passes through atmosphere, absorbed and warms surface.


Surface emits longwave radiation which goes (A) directly to space, or, (B) absorbed by atmosphere Return


COUNTERRADIATION AND THE GREENHOUSE EFFECT Atmosphere radiates longwave energy back to the surface and also to space as counterradiation (C & D) Counterradiation produces the greenhouse effect. Return


COUNTERRADIATION AND THE GREENHOUSE EFFECT Water vapor and carbon dioxide act like glass allowing shortwave radiation through but absorbing and radiating longwave radiation. Return

GLOBAL ENERGY BUDGETS OF THE ATMOSPHERE AND SURFACE Return


to Main Slide 39

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 Return

Ozone Layer – Shield to Life Ozone Layer

to Main Slide 40

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 Return

Ozone Layer – Shield to Life Ozone Layer

to Main Slide 41

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 Return

Return to Main

Slide


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

43


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

44


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

Chapter Review 1. Water in the Environment 2. Humidity

Return to Main Slide

3. The Adiabatic Process 4. Clouds 5. Precipitation 6. Types of Precipitation 7. Thunderstorms 8. Tornadoes 9. Air Quality

Acid Deposition Observing Clouds from GOES

45

Keseimbangan energi di bumi

Education

Transcript of Keseimbangan energi di bumi