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A validation case study conducted at the Southern Great Plains site using high spectral resolution measurements to determine the IR emissivity of grass vegetation and bare soil. Aircraft validation measurements show a linear combination of vegetation and bare soil, with best fit obtained when spectral variance in emissivity is minimized.
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12 m 9 m 4 m UW AERIbago Become “spectrally aware” ! 1.0 Grass Vegetation Emissivity Bare Soil • 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. 0.75 500 3000 Wavenumber (cm-1)
Tskin = 295.4 K Validation Case Study: Southern Great Plains Site S-HIS Observation • Best fit to Tskin when spectral variance in emissivity is minimum.
12 m 9 m Aircraft validation measurements are consistent with a linear combination of vegetation and bare soil. Pure Vegetation 1.0 Aircraft S-HIS LSE S-HIS OBS Bare Soil 0.85 Wavenumber (cm-1)
Infrared Radiative Transfer Equation (lambertian surface) SurfaceEmission Surface Reflection Ndn (60deg) Skin Temperature & Surface Emissivity
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.
IR Land Surface Signatures: QUARTZ 0.5 Solid > 75 m Coarse R > 2 m & < 75 m Fine 0.0 0.5 R 0.0 • QUARTZ Reflectivity (JPL Spectral Library from Lab Tests).
IR Land Surface Signatures: QUARTZ 1.0 1-R Solid Coarse > 75 m > 2 m & < 75 m Fine 0.5 1.0 1-R 0.5 • QUARTZ Emissivity (JPL Spectral Library from Lab Tests).
IR Land Surface Signatures: JPL Library 0.5 Granite Sandy Loam R Quartz (coarse grain) 0.0 0.5 R 0.0 • QUARTZ Emissivity (JPL Spectral Library from Lab Tests).
IR Land Surface Signatures: JPL Library 1.0 1-R 0.5 1.0 1-R Granite Sandy Loam Quartz (coarse grain) 0.5 • QUARTZ Emissivity (JPL Spectral Library from Lab Tests).