Mapping Land Surface Emissivity with Multispectral Thermal infrared Data from Space

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Mapping Land Surface Emissivitywith
Multispectral Thermal infrared Datafrom Space

• Tom Schmugge,
• New Mexico State University
• Las Cruces, New Mexico
• K. Ogawa, Univ. of Tokyo Hitachi Ltd
• Tokyo, Japan
• Andy French
• USDA/ARS Arid Land Agricultural Research Center
• Maricopa, AZ

Email schmugge_at_nmsu.edu
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Emissivity Observations with ASTER MODIS

• HOW
• Multispectral Thermal Infrared from ASTER
  MODIS MODerate resolution Imaging Spectrometer
• ASTER-TES Temperature Emissivity Separation
• Day/Night pairs with MODIS
• WHERE
• New Mexico White Sands Jornada Exp. Range
• North Africa Large area demonstration

Email schmugge_at_nmsu.edu
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ASTER BandsAdvanced Spaceborne Thermal Emission
and Reflection Radiometer
15m
30m
90m
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Planck Curve
ASTER channels
300 K
Window emissivity
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Spectral Emissivity

• Soil, vegetation, water, ice, snow, and rock
  samples (320)
• ASTER Spectral library at JPL, University of
  California Santa Barbara (UCSB), Our soil samples

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ASTER MODIS Response Functions
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CIMEL Multi-Channel RadiometerMesquite Site
light and dark sands
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MODIS Emissivity

• MODIS 7 Channels Day/Night Pairs
• Extracts
• 7 emissivities, 3 in 8 12 µm
• 20 (3.660-3.840), 22 (3.929-3.989), 23
  (4.020-4.080), 29 (8.400-8.700), 31
  (10.780-11.280), 32 (11.770-12.270), and 33
  (13.185-13.485)
• 2 Surface Temperatures
• 2 Air Temperatures Water Vapor
• Short wave reflectance parameter
• Assumes NO emissivity changes
• Resolution degraded to 5 km
• 8-day monthly composites
• Daily data available
• Emissivity mapping on a global scale

Email schmugge_at_nmsu.edu
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MODIS Monthly Emissivity Composite
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MODIS Monthly Composite Bd 29 June 2000
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For Comparison Land Use BasedEmissivity
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ASTER - TESTemperature Emissivity Separation

• Problem 5 measurements 6 unknowns
• Developed for use with ASTER TIR data
• Empirical relation between ?min and ??
• ?i ?i/??i?
• MMD ?max - ?min
• ?i can also be calculated from observed
  radiances
• ?i ( Li/?Li?)(?BBi(T)?/BBi(T))
• Doesnt work well for gray bodies

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Band Emissivity
Where Srfi is the system response function for
the ith band ?(?) is the spectral emissivity BB
(?,T) is the Planck radiation
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ASTER VNIR Imagery Jornada
White Sands Natl Monument
May 12, 2001 1206 MDT 60x90 km IFOV 15 m 10
Min Grid
Rio Grande Las Cruces, NM
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ASTER VNIR White Sands May 21, 2001
63 X 63 km
22 X 22 km
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CIMEL at White Sands
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ASTER EmissivitiesJune 22, 20005 Scenes
Red gt 10.7 ?m Grn gt 9.1 ?m Blu gt 8.6 ?m
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ASTER Emissivity Image North AfricaJune 22, 2000
30.6N 9.2E
Red gt 10.7 ?m Grn gt 9.1 ?m Blu gt 8.6 ?m
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Histograms of Emissivity 6/22/00
Band WL Mean SD 11 8.6 0.720
0.011 12 9.1 0.654 0.012 13 10.7
0.960 0.003
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Comparison of ASTER MODIS Emissivities
11 µm
8.6 µm
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MODIS Nadir Adjusted Reflectivity Monthly
Composite 0.05?
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Study area Sahara Desert in North Africa

• 250 scenes of ASTER data acquired from 2000 to
  2002
• Size of area 400 x 1500 km

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ASTER emissivity image
Emissivity of ASTER channels
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Comparison of Emissivity (812?m) Maps
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MODIS Temporal variation
Bd29 8.6 µm
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Sensitivity to ndvi Soil Moisture
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Broadband Emissivity Change For Jornada 2001-
2003 26 Observations Yellow gt Decrease (0.955 -gt
0.945) Blue gt No Change
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Temporal Changes at 3 Jornada Sites
LAI Ground Obs
Broadband Emissivity ASTER- 26 Obs
NDVI ASTER- 26 Obs
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Emissivities at Day and Night Observed Equally
Well with ASTER/TES Band 11 (8.6 µm)
Day 1158AM 5/31/02
Night 1112PM 5/29/02
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Day Night Band 11 (8.6 µm) Emissivities
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Conclusions

• ASTER and TES work reasonably well
• Quantitative agreement ( 1 2) with lab and
  field measures at both Jornada and White Sands
  for emissivity
• ASTER Results are repetitive
• Day / Night agreement
• Emissivity mapping on a regional scale
• MODIS provides global maps
• Needs more validation
• Temporal variability

Email schmugge_at_nmsu.edu
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Net Longwave Radiation
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ASTER EmissivitiesJune 29, 20004 Scenes
Red gt 10.7 ?m Grn gt 9.1 ?m Blu gt 8.6 ?m
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Seasonal Variation