become “spectrally aware” ! arm sgp site is dominated by two land cover types “grass...
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Become “spectrally aware” !
• ARM SGP site is dominated by two land cover types “grass vegetation” and “bare soil”.• U. of Wisconsin measured the IR emissivity at high spectral resolution.
Grass Vegetation
Bare Soil
12 m
9 m
4 m0.75
1.0
Em
issi
vity
Wavenumber (cm-1)500 3000
UW AERIbago
NTB
NNNe
S
totatmobs
)(
/)(
• Best fit to Tskin when spectral variance in emissivity is minimum.
Tskin = 295.4 K
Validation Case Study: Southern Great Plains SiteS-HIS Observation
Aircraft validation measurements are consistent with a linear combination of vegetation and bare soil.
Aircraft S-HISLSE
Wavenumber (cm-1)
0.85
1.0
Bare Soil
Pure Vegetation
S-HIS OBS
12 m 9 m
Infrared Radiative Transfer Equation (lambertian surface) NeTBedPTBN tot
Stot )1()())((
atmNSurfaceEmission
SurfaceReflection
Skin Temperature & Surface Emissivity
Ndn (60deg)
Emissivity Survey• ARM SGP site is dominated by two land cover types “pasture” and “wheat”.• Notice that the measured wheat field emissivity can be approximated by a linear combination of pure scene types;
bare soil and grass.
• QUARTZ Reflectivity (JPL Spectral Library from Lab Tests).
IR Land Surface Signatures: QUARTZ
R
R
SolidCoarseFine
0.0
0.5
0.0
0.5
> 75 m> 2 m & < 75 m
• QUARTZ Emissivity (JPL Spectral Library from Lab Tests).
1-R
1-R SolidCoarseFine
1.0
0.5
0.5
1.0
> 75 m> 2 m & < 75 m
IR Land Surface Signatures: QUARTZ
• QUARTZ Emissivity (JPL Spectral Library from Lab Tests).
R
R
0.5
0.0
0.0
0.5
IR Land Surface Signatures: JPL Library
GraniteSandy LoamQuartz (coarse grain)