High Spectral Resolution Land Surface Emissivity and Temperature

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High Spectral Resolution Land Surface
Temperature and Emissivity in the Thermal Infrared
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INTRODUCTION 1.

• Technique for ground-based validation of land
  surface emissivity/temperature with atmospheric
  sounding.
• Implements new class of algorithm on workable
  scale for later extension to space-borne (AIRS,
  IASI, CrIS) application.
• Emissivity measurement linked with other
  fields, eg geology and land use (ASTER, MODIS).

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INTRODUCTION 2.
Surface Temperature
TIR emission from land surface
Composition
Emissivity
Texture
View Angle
Derived from single spectral measurement N
measurements N1 unknowns
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INTRODUCTION 3.

• Temperature/emissivity separation problem in
  past solved assuming surface characteristic.
• Surface emission is spectrally smoother than
  atmospheric - extra constraint needed.
• Resolved atmospheric lines are used rather than
  discarded.

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ALGORITHM 1.
RTE for downlooking sensor
Make assumptions 1. Neglect sub-sensor
atmosphere 2. BRDF constant f ?? 3.
Kirchhoff ? 1 - ?
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ALGORITHM 2.
Final working equation
Downwelling emission characterized by
Optimum quadrature - 50 to 60 degrees from zenith
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ALGORITHM 3.
Example AERI upwelling and downwelling spectra
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ALGORITHM 4.
Optimum skin temperature at minimal atmospheric
lines shown in middle trace below.
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ALGORITHM 5.
Implemented by determining surface temperature at
minimum mean squared derivative of a spectral
window
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ASPHALT SURFACE 1.
45, 60 70 surface measurement of
quasi-diffuse asphalt parking lot with uniform
temperature. Quartz!
Christensen Frequency
Reststrahlen
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ASPHALT SURFACE 2.
Sensitivity of derived emissivity to choice of
sky view angle. 60 degree surface view used with
T 293.5K.
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DIURNAL MEASUREMENTS 1.
Measurements taken over pre-sunrise to
mid-morning period of heating. Variation in
derived skin temperature
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DIURNAL MEASUREMENTS 2.
Average emissivities 1 standard deviation
during this period of morning heating (total
measurements 14). Shows no moisture and good
repeatability to 1.
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PLAYA CHARACTERIZATION 1. - LAKE RODGERS
At least 2 surface types visible on Lake Rodgers
however
Darker
Lighter
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PLAYA CHARACTERIZATION 2. - IVANPAH PLAYA
A similar playa reveals possible source for the 2
distinct signatures - weathering.
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PLAYA CHARACTERIZATION 3. - LAKE RODGERS
Back to Lake Rodgers - AERI shows signatures of 2
differently colored surfaces also different in
TIR. Go to MAS for spatial
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PLAYA CHARACTERIZATION 4. - LAKE RODGERS
MAS Visible RGB Composite Bands 3/2/1 Shows
visible differences on the playa surface.
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PLAYA CHARACTERIZATION 5. - LAKE RODGERS
MAS TIR Bands 42 - 43 Highlights the
brown-colored surface with feature at 1040 cm-1.
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PLAYA CHARACTERIZATION 6. - DECORRELATION STRETCH
Inv. Transform
Band A
Source Gillespie et al, 1986
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PLAYA CHARACTERIZATION 7. - LAKE RODGERS
MAS TIR Decorr. Stretch Bands 42/43/46
Silicate
Brown surface previously identified
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LAND USE CHARACTERIZATION 1. - SUCCESS (OKLAHOMA)
Further combined use of AERI and MAS for
identifying land use in Oklahoma.
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LAND USE CHARACTERIZATION 2. - SUCCESS (OKLAHOMA)
MAS TIR Bands 42 - 45 Red Vegetation Green Bar
e Soil Blue Strong Silicate (Near River)
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MISCELLANEOUS SURFACES