spectral exitance (temp. & ) = 1.0. earth’s reflective (sun) & emissive (reradiation)...

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