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ATMOSPHERE AND SURFACE ENERGY BALANCES • ENERGY PATHWAYS AND PRINCIPLES • ENERGY BALANCE IN THE TROPOSPEHERE • ENERGY BALANCE AT EARTH’S SURFACE • SOLAR ENERGY – ENERGY OF THE FUTURE? Kuala Lumpur, capital city of Malaysia with the Petronas Twin ENERGY PATHWAYS AND PRINCIPLES (I) Insolation (II) Transmission (III) Refraction (IV) Albedo and Reflection (V) Clouds and the Atmosphere’s Albedo (VI) Scattering and Diffuse Radiation (VII) Absorption (VIII) Conduction, Convection and Advection INSOLATION • Solar radiation that reaches a horizontal plane at Earth is called INSOLATION • Insolation means “Intercepted Solar Radiation” • Insolation refers to the input of Solar Radiation into the EarthAtmosphere system • Insolation at the top of the atmosphere is expressed as the SOLAR CONSTANT (1.94 cal/m2/min-1) • Insolation is the single energy input driving the Earth-Atmosphere system • Insolation also includes all the radiation that arrives at the earth’s surface, both DIRECT RADIATION and DIFFUSE RADIATION • The distribution of insolation is UNEVEN through the different layers of the atmosphere • The distribution of insolation is UNEVEN on the Earth’s surface 100 200 260 180 180 260 240 100 Insolation at the Earth’s surface is unevenly distributed. Which are the “Source” areas and which are the “Sink” areas? What are the factors causing the uneven distribution of insolation on the earth’s surface? • Solar Output – solar maximum (sunspots) & solar minimum • Curvature of the earth’s surface & Latitude • Earth’s tilt & Seasons • Clouds • Atmospheric pollutants • Surface characteristics: (I) land or sea (II) dark or light (III) rough or smooth (IV) urban or rural (V) type of land use (VI) Orientation or Slope Angle (Aspect) (VII) Total Albedo SOLAR OUTPUT – Solar Radiation is at a maximum during sunspots or Solar maximums & at a minimum during Solar Minimums – 11 year-cycle EARTH’S CURVATURE - Curvature of the earth’s surface & Latitude result in Equatorial areas receiving more solar radiation than Polar areas Solar radiation is diffuse in Polar areas Solar radiation is concentrated in Equatorial areas Solar radiation is diffuse in Polar areas EFFECT OF SLOPE ORIENTATION ON INSOLATION North slope is always in the shade – less solar radiation South slope is always in the Sun – More solar radiation North slope is always in the Sun – More solar radiation South slope is always in the shade – Less solar radiation North Slope South Slope North Slope South Slope TRANSMISSION •Transmission refers to the the passage of LONGWAVE and SHORTWAVE energy through either the atmosphere or water • During the DAY, transmission of SHORTWAVE solar radiation takes place in the form of radiation inputs – UV-A, UV-B, UV-C, VISIBLE LIGHT and NEAR-INFRARED wavelengths • At NIGHT, transmission of LONGWAVE thermal Earth radiation (thermal infrared) takes place as radiation outputs, passing through the atmosphere into space A simplified model of the Earth-Atmosphere energy system – notice that incoming transmission of daytime solar radiation is balanced by outputs of earth radiation transmission at night. REFRACTION • When insolation enters the atmosphere, it passes from one medium (empty space) to another (atmospheric gases), or from air into water. When this happens, it subjects the insolation to a change of SPEED which also shifts its DIRECTION • This causes the insolation (light) to BEND – a bending action called REFRACTION • An example of refraction is light passing through a PRISM which refracts light, bending different wavelengths to different angles, separating the light into its component colors to display the spectrum • Another example of refraction in nature is the RAINBOW which is formed when visible light passes through myriad raindrops & is refracted and reflected to us at a precise angle • A MIRAGE (an image appearing near the horizon) is another example of refraction where light waves are refracted by layers of air of different temperatures on a hot day • A final example would be the refraction of the image of a SETTING SUN over the horizon. Light from a low sun must penetrate more air before reaching us & is refracted by different layers of air (of different densities). REFRACTION The setting Sun here is only a MIRAGE! The Sun has actually gone below the Horizon We still see it because it is Refracted over the horizon for about 4 minutes We also see the Sun earlier during sunrise, about 4 minutes earlier Hence, REFRACTION has added 8 minutes of DAYLIGHT each day! ALBEDO and REFLECTION • Albedo is related & dependent on the rate of reflection of insolation, the higher the reflectance the higher is the Albedo • Why is there reflection? This is because a portion of insolation passes through the atmosphere, reaches the earth surface & bounces back into space without performing any work, i.e. without being absorbed • Albedo is the reflective quality (or brightness) of a surface, the brighter a surface the more reflective it is • Hence, Albedo is defined as the “Percentage of Reflected Insolation” • 0 % Albedo is TOTAL ABSORPTION • 100 % Albedo is TOTAL REFLECTANCE • See some examples of albedo values in the next slide Albedo values (% reflected) 6–8% Fresh snow 80 – 95 % Earth’s albedo (average) = 31 % Water bodies 10 – 60 % (low solar angles = greater reflection) Forests 10 – 20 % Crops, grasslands 10 – 25 % Grass 25 – 30 % Asphalt 5 – 10 % Dark roof 8 – 18 % Light roof 35 – 50 % Brick, Stone Dry concrete 20 – 40 % 17 – 27 % TOTAL ALBEDOS FOR JULY AND JANUARY WHICH ARE THE HIGH ALBEDO AREAS? •NORTH & SOUTH POLES July 0% •DESERT AREAS WHICH ARE THE LOW ALBEDO AREAS? •THES SEAS AROUND THE January TROPICS •EQUATORIAL AREAS •FORESTED AREAS 36 84 CLOUDS AND THE ATMOSPHERE’S ALBEDO • The sun's rays are often siphoned out by clouds which reflect, scatter and absorb a significant portion of the electromagnetic radiation incident (falling) on them • Clouds are a major determinant of the weather and climate of equatorial regions, keeping temperatures from being too high • (i) Clouds are an important climatic resource as they: produce precipitation (and freshwater); (ii) act as reflective surfaces from the sun's rays; (iii) absorb part of the sun's radiation; (iv) protect the earth surface temperature from getting too hot; (v) produce lightning (which is a form of electricity and fire source); (vi) are a medium from which energy transfer takes place; (vii) influence atmospheric humidity; (viii) affect visibility (especially low clouds); (ix) cleanse the air of pollutants; and (x) are an indicator of weather (usually bad weather depending on the cloud type); etc. CLOUD ALBEDO FORCING • Cloud Albedo Forcing refers to an increase in albedo caused by reflection of solar radiation by clouds (A) CLOUD GREENHOUSE FORCING • Cloud Greenhouse Forcing refers to an increase in atmospheric temperatures caused by absorption of solar radiation by clouds (B) DAY A NIGHT B HIGH CLOUDS HAVE A NET GREENHOUSE FORCING & ATMOSPHERIC WARMING EFFECT (A): High clouds [ice-crystals cirrus clouds] transmit almost all of insolation but absorb & delay outgoing longwave terrestrial radiation, producing a net-warming effect LOW CLOUDS HAVE A NET ALBEDO FORCING & ATMOSPHERIC COOLING EFFECT (B): Low clouds [thick stratus/cumulonimbus clouds] reflect most of incoming shortwave & radiate longwave infrared to space, producing a net-cooling effect DAY A NIGHT B SCATTERING and DIFFUSE RADIATION •Scattering – When insolation travels from space to the earth’s surface (i.e. through the air), it encounters an increasing density of atmospheric gases (remember air pressure increases downwards or decreases upwards) • When the insolation is absorbed by air molecules and then re-emitted (i.e. passed through it) without altering its wavelengths, scattering has occurred • Scattering, however, will change the direction of the light • Scattering is responsible for 7 % of Earth’s reflectivity or Albedo • Major atmospheric components responsible for scattering: • Dust particles, pollutants, ice, cloud droplets & water vapour • The sky’s blue color is a result of scattering WHY IS THE SKY BLUE ? •SKY BLUE – is caused by scattering of visible light in the blue wavelength (0.45 micron) because: • 1881 – “Rayleigh Scattering” established the relationship between wavelength of light to the size of molecules/particles that cause the scattering: • The shorter the wavelength, the greater the scattering • The longer the wavelength, the less the scattering • Thus, the shorter wavelengths of visible light (the blues & violets) are scattered the most • And since there are more BLUE than VIOLET wavelengths in light, a blue sky prevails WHY IS THE SKY AT SUNRISE & SUNSET RED ? • SKY RED – is caused by scattering of visible light in the red wavelength (0.71 micron) because: • The angle of the sun’s rays is low on the horizon during sunrise & sunset • As a result, the rays have to pass through greater thickness of the atmosphere (hence encounter more molecules [i.e. more absorption] on its way to the observer) • Hence, more of the sunlight is absorbed at sunrise & sunset, leaving only the longer wavelengths of ORANGE & RED to reach the observer • In the lower atmosphere near the ground (i.e. near the horizon), the atmospheric particles are mostly made up of larger particles, which will absorb the blues & violets but scatter the oranges & reds DIFFUSE RADIATION • DUE TO SCATTERING, SOME INCOMING INSOLATION IS DIFFUSED BY CLOUDS AND ATMOSPHERE & TRANSMITTED TO EARTH AS DIFFUSE RADIATION • DIFFUSE RADIATION IS THE DOWNWARD COMPONENT OF THE SCATTERED LIGHT • DIFFUSE RADIATION IS LIGHT WHICH IS MULTIDIRECTIONAL • HENCE, DIFFUSE RADIATION CASTS SHADOWLESS LIGHT ON THE GROUND DIRECT RADIATION DIFFUSE RADIATION ABSORPTION • Absorption is the assimilation of radiation by molecules of matter in the atmosphere (air molecules, gases, water vapour, cloud droplets, pollutants, etc) • Absorption involves the conversion of one form of energy to another (e.g. from solar energy to sensible heat energy) • If Earth’s albedo is 31 %, then insolation (both direct & diffuse) that is not part of the 31 % reflected back into space will be absorbed (some in the atmosphere & some on earth’s surface) • Solar energy absorbed can either be converted into infrared radiation or chemical energy (by plants via photosynthesis) • During absorption, the temperature of the absorbing surface is raised – that warmer surface will then radiate more total energy at shorter wavelengths (the hotter the surface the shorter the wavelengths emitted) • On the earth’s surface, total absorption by land & oceans add up to 45 % of incoming insolation • In the atmosphere, total absorption is about 24 % (mostly by clouds, gases, dust & stratospheric ozone) In the Stratosphere (Ozonosphere), total absorption by Ozone of UVradiation is about 3 % of total solar radiation received by the EarthAtmosphere System CONDUCTION, CONVECTION & ADVECTION 24 CONDUCTION is the molecule-to-molecule transfer of heat energy as it diffuses through a substance As molecules warm (get hotter), their vibration increases, causing collisions that produce motion in neighboring molecules, thus transferring heat from warmer to cooler materials Different materials of differing densities (gases, liquids & solids) conduct sensible heat directionally from areas of higher temperature to those of lower temperature Conduction of heat (heat transfer) takes place at differing rates depending on the conductivity of the material: • Solids are better conductors of heat than liquids • Liquids are better conductors than gases • Land (Earth) is a better conductor than air (Atmosphere) • Land (Earth) is a better conductor than water (Hydrosphere) • Moist Air is a better conductor than Dry Air 25 CONVECTION is the transfer of heat energy in the form of a vertical motion, usually in the form of a loop or circle In the atmosphere or bodies of water, warmer (less dense) masses tend to rise and cooler (denser) masses tend to sink, establishing CONVECTION Convection is the dominant process in heat transfer in gases (Atmosphere) and liquids (Hydrosphere) but is also present in heat transfer from Earth’s Core to the Earth’s Crust It is the convection of heat from Core (liquid) to Crust that fuels Plate Tectonics and results in CONTINENTAL DRIFT ADVECTION is similar to convection but proceeds at a LATERAL direction rather than a vertical one. 26 EXAMPLES OF CONDUCTION, CONVECTION & ADVECTION IN THE NATURAL WORLD CONDUCTION •Surface Energy Budgets •Temperature differences between land & sea •The heating of land surfaces & overlying layers of air •Differing Soil temperatures at differing layers CONVECTION •Atmospheric Circulation (air masses, winds, fronts, etc) •Oceanic Circulation (ocean currents) •Weather Systems •Internal motions within Earth’s Core ADVECTION •Horizontal movement of winds – e.g. land & sea breeze •Fog that moves from one area to another •Local winds that blow from rural to urban areas 27 ENERGY BALANCE IN THE TROPOSPEHERE (i) Earth’s Radiation and the Greenhouse Effect (ii) Clouds and the Earth’s “Greenhouse” (iii)Earth-Atmosphere Radiation Balance DETAILS OF EARTH-ATMOSPHERE ENERGY BALANCE Total lost by EarthAtmosphere=69 Total Albedo=31 Total lost by Atmos =21 Total Absorption=69 Total lost by Stratosphere =3 Total lost by Earth= 45 ENERGY BUDGET BY LATITUDE & TRANSFER OF HEAT Clouds and the Earth’s “Greenhouse” Cirrus clouds – 50 % Albedo & stops Longwave Radiation from escaping into space Cumulonimbus/Stratus clouds – 90 % Albedo & allows Longwave Radiation to escape HIGH CLOUDS – NET GREENHOUSE FORCING & ATMOSPHERIC WARMING : [ice-crystals DAYHigh clouds NIGHT cirrus clouds] transmit almost all of insolation but absorb & delay outgoing longwave terrestrial radiation, producing a netwarming B effect SOLAR ENERGY – ENERGY OF THE FUTURE? SOLAR ENERGY – ENERGY OF THE FUTURE? Firewood is no longer the solution as forests are depleted and land degraded Kenyan women use solar panel cookers which collect direct & diffuse insolation through transparent glass or plastic & trap infrared radiation in an enclosed box or cooking bag (This is a small-scale application of the Green House Effect). Temperatures > 105 o C (220 o F) can be used for baking, purifying water & sterilizing SOLAR OVENS – CHEF OF THE FUTURE? •Solar ovens save energy, keep your kitchen more cool on hot days, cook better tasting food, and make meals more fun. In remote areas, no need to buy, collect, carry, and store fuel. •No burned food, no smoke, no air pollution. Saves trees and soil, safe around children. These durable and high quality models commonly reach 350 degrees F. •Weighs 30 pounds and has an interior oven dimension of 14" x 14" x 10". Electric back-up fits on the glass and heats oven over 400 degrees F. Even broils. Uses 500 watts at 117V AC - 1/7th the power of a conventional oven. Black pot and thermometer make cooking fast and easy. •Model A Sun Oven (AA140) $229.00 •Electric back-up (AA139) coming soon (in development) 3 qt. black pot (AA146) $15.00 Thermometer (AA147) $5.00 SOLAR ENERGY – ENERGY OF THE FUTURE? NREL Outdoor test facility in Golden, Colorado – a variety of photovoltaic cell arrays convert sunlight directly into electricity Kramer International Solar Thermal Energy installation, California The Sacramento Municipal Utility District installed a PV array that doubles as a parking lot cover Photovoltaic cells – The way to clean energy and zero pollution? SOLAR BATTERY – RECYCLEABLE, REUSABLE & ENVIRONMENTALLY FRIENDLY THE SOLAR-POWERED CAR – NO LONGER A DREAM BUT A REALITY & NECESSITY AS FOSSIL FUELS RUN OUT •CATCHING SOME RAYS: Solar vehicle team member Lance Mobly (right) takes his turn in the driver's seat of Aurora-II, during the car's unveiling Tuesday. •Aurora-II is the team's second sun-powered vehicle, built to compete against other students' solar-powered cars in a race from Indianapolis, Ind. to Golden, Colo. •Twenty University students have been constructing the car for almost two years. "We actually began designing this model in the middle of the last race," Molby said. The race begins June 20. SOLAR ROOF – GENERATES ELECTRICTY & DOUBLES UP AS PROTECTIVE ROOF (SAVES MONEY ON ROOF TILES & UTILITY/POWER) A SOLAR REMOTE HOUSE (VACATION HOME) – 100 % DEPENDENT ON SOLAR ENERGY FOR POWER (MOSTLY USED IN SUMMER WHEN SUNSHINE IS ABUNDANT) SOLAR EFFICIENT HOUSE – HOUSE OF THE FUTURE? SOLAR VILLAGE/COMMUNITY – VILLAGE OF THE FUTURE? A SOLAR SIGN BOARD – 100 % DEPENDENT ON SOLAR ENERGY FOR POWER (SHINES EVEN AT NIGHT AS IT USES VERY LITTLE POWER) A SOLAR POWERED TRAFFIC LIGHTS – USED IN REMOTE AREAS AND RURAL VILLAGES A SOLAR POWERED WATER WELL – USED IN REMOTE AREAS AND RURAL VILLAGES SOLAR PUMP A SOLAR POWERED PORTABLE ELECTRICITY GENERATOR – CAN BE USED ANYWHERE WHEN THE SUN IS SHINNING INSOLATION INDEX MAP OF THE UNITED STATES – AN INDICATION OF SOLAR ENERGY POTENTIALS SOLAR COMPANIES & MULTINATIONALS – THE LOGICAL & ETHICAL WAY FOR SURVIVAL OF OIL COMPANIES IN THE FUTURE? END THANK YOU