spectral exitance (temp. & ) = 1.0. earth’s reflective (sun) & emissive (reradiation)...
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Spectral Exitance (Temp. & Spectral Exitance (Temp. & ))
= 1.0= 1.0
= 1.0= 1.0
= 1.0= 1.0
Earth’s reflective (sun) & Earth’s reflective (sun) & emissive (reradiation) regionsemissive (reradiation) regions
Inverse distance & intensity
5880 K: 6.8 x107 W/m2
2815 W/m2
1459 W/m2
632 W/m2
C->P: 7x10C->P: 7x108 8 m m C->V: 1.0x10C->V: 1.0x101111m m C->E: 1.5x10C->E: 1.5x101111m m C->M: 2.3x10C->M: 2.3x101111
Total: 4.1x1026 W
Inverse distance & intensity
Visible-thermal-microwave
Spectral Spectral ReflectanceReflectanceAsphalt & Asphalt & Concrete Concrete RR=1-A=1-A
Green Veg Green Veg & &
Astroturf Astroturf RR=1-A=1-A
In situ Spectra of Fall Leaves
Wavelength (µm)
Refl
ecta
nce (
%)
0.90
0.60
0.50
0.40
0.30
0.000.35 0.60 0.85 1.10 1.35 1.60 1.85 2.352.10
0.20
0.10
Fall Leaves0.80
0.70
2.60
Green leaves from a broadleaf tree beginning to change color as nutrients withdraw into the tree core
Deciduous broadleaf tree with its colors changed and some leaves fallen on the ground
Broadleaf Trees Changing Color
Green Veg & Fall Colors
RR=1-A=1-A
Plant PigmentsPlant PigmentsSo, what absorbs in functioning leaves?So, what absorbs in functioning leaves?
(Reflectance = 1.0 - Absorption
Snow, Clouds, Water, Soil, & Green VegSnow, Clouds, Water, Soil, & Green Veg
RR=1-A=1-A
Snow, Clouds, Snow, Clouds, Water, Soil, & Water, Soil, &
Green Veg Green Veg RR=1-A=1-A
Basic Interactions between Electromagnetic Energy and the Earth’s Surface
RR=1-A=1-A
Specular versus Diffuse Reflectance
RR=1-A=1-A
Bidirectional Reflectance ofBlack Spruce & Jack Pine
in shadow
no shadows
RR=1-A=1-A
Bidirectional Reflectance ofBlack Spruce & Jack Pine
in shadow
no shadows
RR=1-A=1-A
Bidirectional Reflectance ofBlack Spruce & Jack Pine
in shadow
no shadows
RR=1-A=1-A
~1370 watts/m2
Total Energy Flux: M = M = TT4 4 (w/m2
= 5.67x10-8 w/m2*K4
92%
Incoming/Outgoing
max = 2898/5880 = 0.49 m
max = 9.7 m
Solar Irradiance at Earth’s Surface
Exoatmospheric Solar Irradiance
atmospheric limb
Blackbody RadiationBlackbody Radiation
The wavelength where the radiance is the greatest is given by
max=,
known asWien’ s displacement law,wheremax = wavelength of maximum radianceT = ( )temperature K
, From blackbody radiation the emitted radiation followsPlanck’ s law
I =
E =∆ Iλ(T)dλ = σT4
wherec = speed of light (2.998 x 1010 cm s-1)h = Planck’s constant (6.626 x 10-27 erg s)k = Boltzmann’s constant (1.381 x 10-16 erg K-1)σ = Stefan-Boltzmann constant (5.6697 x 10-8 W m-2 K-4)
2898 µm KT
2hc2
λ5 [exp(hc/λkT) – 1]
0
∞
Stefan-Boltzmann LawStefan-Boltzman constant
RadiationSpeed of light = * frequency
Total Energy Flux: M = T4
= 5.67x10-8 w/m2*K4
Wavenumber = 1/
(# per unit distance)
Energy per photon:
Ep = h * frequency
Ep = h*c/Ep*J sec *3*108m sec-1
Ergo: X-rays and -rays are energetic!
Rayleigh Scattering:why the sky is blue
1
Kirchoff’s Radiation LawKirchoff’s Radiation Law
For any object that intercepts EM radiant energy
r + + = 1
at thermal IR wavelengths,
= 0 and =
Therefore
1 = r +
Apparent Radiant Temperature - Trad
- radiant flux – the amount of radiant energy per unit time pass through or from an object
• Trad is simply the radiant flux being
emitted by an object because of its temperature, the radiant temperature
Kinetic vs. radiant Kinetic vs. radiant temperaturetemperature
Trad4 = Tkin
4 ; Trad = 1/4Tkin
ObjectEmissivity
Kinetic Temperature
KRadiant TemperatureK
Blackbody . .Vegetation .98 298.5
Wet Soil .95 29.2Dry Soil .92 29.8
FLIR Images
Thermal history of helicopters