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What happens to solar energy ? 1.Absorption (absorptivity= ) Results in conduction, convection and long-wave emission 2.Transmission (transmissivity= ) 3.Reflection (reflectivity= ) + + = 1
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Response varies with the surface type Snow reflects 40 to 95% of solar energy and requires a phase change to increase above 0°C Forests and oceans absorb more than dry lands Then why do dry lands still “heat up” more? Oceans transmit solar energy and have a high heat capacity
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Characteristics of Radiation Energy due to rapid oscillations of electromagnetic fields, transferred by photons The energy of a photon is equal to Planck’s constant, multiplied by the speed of light, divided by the wavelength All bodies above 0 K emit radiation Black body emits maximum possible radiation per unit area. Emissivity, = 1.0 All bodies have an emissivity between 0 and 1 E = hv
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Stefan-Boltzmann Law As the temperature of an object increases, more radiation is emitted each second
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Temperature determines E, emitted Higher frequencies (shorter wavelengths) are emitted from bodies at a higher temperature Max Planck determined a characteristic emission curve whose shape is retained for radiation at 6000 K (Sun) and 300 K (Earth) Energy emitted = (T 0 ) 4 Radiant flux or flux density refers to the rate of flow of radiation per unit area (eg., W m -2 ) Irradiance=incident radiant flux density Emittance =emitted radiant flux density
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Wien’s Displacement Law As the temperature of a body increases, so does the total energy and the proportion of shorter wavelengths max = (2.88 x 10 -3 )/(T 0 ) *wavelength in metres Sun’s max = 0.48 m Ultraviolet to infrared - 99% short-wave (0.15 to 3.0 m) Earth’s max = 10 m Infrared - 99% longwave (3.0 to 100 m)
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Solar radiation Terrestrial radiation
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8-11 m window
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ALBEDO: April, 2002 White and red are high albedo, green and yellow are low albedo
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white snow0.80-0.95 old snow0.40-0.60 vegetation0.15-0.30 light colour soil0.25-0.40 dark colour soil0.10 clouds0.50-0.90 calm water 0.10 (noon) March 3, 2009
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DAYTIME: Q* = K - K + L - L Q* = K* + L* NIGHT: Q* = L* K = solar (shortwave) radiation ↓ = incoming L = longwave (terrestrial radiation)↑ = outgoing Q* = net all-wave radiation* = net Radiation Balance
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Source: NOAA L
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Conduction The transfer of heat from molecule to molecule within a substance
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Convection and Thermals
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Convection The transfer of heat by the mass movement of a substance (eg. air) Rising air expands and cools Sinking air is compressed and warms
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The Hydrological Cycle
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Heat capacity The amount of heat energy absorbed (or released) by unit volume of a substance for a corresponding temperature rise (or fall) of 1 °C Specific heat The amount of heat energy absorbed (or released) by unit mass of a substance for a corresponding temperature rise (or fall) of 1 °C
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Latent heat The heat energy required to change a substance from one state to another Sensible heat Heat energy that we can feel and sense with a thermometer
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Thermometer and radiation shield SENSIBLE HEAT Radiation Sensors (PAR and K ) Raingauge Datalogger Photo: Weather station, Tausa, Cundinamarca, Colombia (3,243 m asl)
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http://www.jgiesen.de/sunshine/index.htm Check this out:
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N
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Dec 15, 2004 Jan 19, 2005 Temperature ( C)
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Dec 15, 2004 Jan 19, 2005
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Dec 15, 2004Jan 19, 2005 Temperature ( C)
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10 – 100 m ●
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0.0001 – 0.001 m ●
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Mie scattering 0.01 to 1.0 m ●
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LONG PATH LENGTH OF LIGHT THROUGH THE EARTH’S ATMOSPHERE MOST OF THE THE VIOLET, BLUE AND GREEN LIGHT IS SCATTERED
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(from Pacific) (prairie cold)
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