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MODIS Surface Albedos and Distribution of
Global Ecosystem Types
Eric G. Moody1,2, Michael D. King1, Steven Platnick1,3, Crystal Schaff4
1NASA Goddard Space Flight Center2Emergent IT, Inc.
3University of Maryland Baltimore County4Boston University
Outline• Motivation• Issues with original albedo scheme• New Ecosystem-Albedo seasonal model• Description of ecosystem classifications• Implementation of new model• Summary and future directions
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Eric G. Moody [email protected] 2
Motivation• Retrieval of Cloud Optical Properties (MOD06OD)
– Computes optical thickness and effective radius using White-Sky surface albedos at wavelengths of 0.659, 0.865, 1.24,
1.6, 2.1, and 3.7 microns.– Inaccurate albedo value will enhance or attenuate
reflectance.– Can cause retrieval failures and unreasonable/unphysical results.
• Preparation for consistent year processing.• Pre- and post-launch White Sky Surface Albedo scheme
flagged for update.
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Original Albedo Scheme
• Scheme used IGBP ecosystem classifications as a surrogate for albedo.– eg. Table of albedos for each ecosystem.
• Albedo data obtained from CERES/SARB.• Issues with the scheme:
– Broad-banded data.• Led to key bands having same surface albedo.
– No seasonal variation in albedo.• Ecosystem with growth cycles not represented.
– Coarse resolution CERES IGBP global ecosystem map.• 1 degree resolution left signatures
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Design Parameters• Fine resolution (10km) IGBP ecosystem and albedo data.• Albedos at wavelengths of interest.• Seasonally dependent albedo data set.
• Sufficient data to generate global albedo maps.-OR-
• Sufficient data to create an ecosystem-albedo surrogate.
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MODIS-Land Products.• Drs. Alan Strahler and Crystal Schaaf
– Boson Univ. Center for BRDF/Albedo Research• MOD12 - Ecosystem Classification
– 10 km resolution, globally.– Includes updates of IGBP classifications.
• MOD43B - BRDF/Albedo Product– 10 km resolution, 16-day global composites.– Includes White-Sky Albedos at specific
wavelengths of interest.
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Sufficient Data Available?
• NO (at the time of consistent year code delivery).
• Only 2 data sets certified for quantitative use.– Spanned October, 2000.
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Preliminary Analysis.• Create seasonal ecosystem-albedo scheme if:
– Northern and Southern Hemispheres differ statistically.– Sufficient data samples for each ecosystem type.– Ecosystem-Albedo correlate.
• Analysis– Compute statistics for “latitude belts” of varying sizes
• Mean, standard deviation, and sample size• Albedos at various wavelengths, for each ecosystem type.
• Results– All three criteria met.
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Model Description.
• Tropics, no seasonal effect.• Seasonally dependant.• Transition region.
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Model Data.• Seasonally Dependent Regions.
– Northern Hemisphere values assumed to be winter albedos at the winter solstice.
– Southern Hemisphere values assumed to be summer albedos at the summer solstice.
– Sinusoidal fit of these albedos to simulate seasonality.• Tropical Region (no seasonal effects)
– Albedos at various bands computed for ecosystem types• Transition Region (some seasonal effects)
– Linear fit between tropical and north/south albedos.
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IGBP Ecosystem Classifications• Forests:
– Evergreen Needle and Broadleaf, Deciduous Needle and Broadleaf, and Mixed
• “Savannas”– Closed and Open Shrublands, Woody Savanna, Savanna,
Grasslands• Other Vegetation
– Permanent Wetlands, Urban and Buildup, Cropland and Cropland Mosaics
• Miscellaneous:– Permanent Snow/Ice, Tundra, Barren/Sparse, and Water Bodies
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Global Ecosystem Distribution
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Forest Ecosystem Distribution
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Savanna Ecosystem Distribution
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Other Vegetation Distribution
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Miscellaneous Distributions
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Ecosystem Distribution - Forest Breakdown.
Evergrn needle frt3.2%
Evergrn broad frt6.0%
Decid needle frt0.8%
Decid broad frt0.9%
Mixed forest6.6%
Perm Snow/Ice34.6%
Barren/sparse veg8.6%
Tundra2.1%
Open shrublands13.8%
Cropland5.3%
Grasslands5.5%
Savanna3.2%
Woody savannas4.0%
Perm wetland0.2%
Closed shrublands0.8%
Urban & buildups0.1%
Forests18%
Cropland mosaics4.3%
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Ecosystem Distribution - Savanna Breakdown.
Closed shrublands0.8%
Open shrublands13.8%
Woody savannas4.0%
Savanna3.2%
Grasslands5.5%
Perm Snow/Ice34.6%
Tundra2.1%
"Savannas"27%
Evergrn needle frt3.2%
Evergrn broad frt6.0%
Decid needle frt0.8%Decid broad frt
0.9%Mixed forest
6.6%Perm wetland
0.2%
Cropland5.3%
Urban & buildups0.1%
Cropland mosaics4.3%
Barren/sparse veg8.6%
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Ecosystem Distribution - Other Vegetation.
Evergrn broad frt6.0%
Open shrublands13.8%
Woody savannas4.0%
Savanna3.2%
Grasslands5.5%
Perm wetland0.2%
Cropland5.3%
Urban & buildups0.1%
Cropland mosaics4.3%
Perm Snow/Ice34.6%
Barren/sparse veg8.6%
Tundra2.1%
Vegetation9.8%
Evergrn needle frt3.2%Decid needle frt
0.8%
Decid broad frt0.9%
Mixed forest6.6%
Closed shrublands0.8%
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Ecosystem Distribution - Miscellaneous.
Open shrublands13.8%
Woody savannas4.0%
Perm Snow/Ice34.6%
Barren/sparse veg8.6%
Tundra2.1%
Cropland5.3%
Urban & buildups0.1%
Cropland mosaics4.3%
Grasslands5.5%
Perm wetland0.2%
Savanna3.2%
Decid needle frt0.8%
Closed shrublands0.8%
Mixed forest6.6%
Decid broad frt0.9%
Evergrn broad frt6.0%
Evergrn needle frt3.2%
Misc.45.3%
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Winter Albedo Means (winter solstice).
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.5 1 1.5 2 2.5 3 3.5 4Wavelength (µm)
Albedo
Evergrn needle frt
Evergrn broad frt
Decid needle frt
Decid broad frt
Mixed forest
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Summer Albedo Means (summer solstice)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Wavelength (µm)
Albedo
Evergrn needle frt
Evergrn broad frt
Decid needle frt
Decid broad frt
Mixed forest
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Forest Winter (W) and Summer (S) Albedo Means
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.5 1 1.5 2 2.5 3 3.5 4Wavelenght (in microns)
Albedo
Evergrn needle frt - WEvergrn broad frt - WDecid needle frt - WDecid broad frt - WMixed forest - WEvergrn needle frt - SEvergrn broad frt - SDecid needle frt - SDecid broad frt - SMixed forest - S
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Winter Albedo Means (winter solstice).
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.5 1 1.5 2 2.5 3 3.5 4Wavelength (µm)
Albedo
Closed shrublands
Open shrublands
Woody savannas
Savannas
Grasslands
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Southern Hemisphere Albedo Means
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Wavelength (µm)
Albedo
Closed shrublands
Open shrublands
Woody savannas
Savannas
Grasslands
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Combined winter (W) and summer (S) albedos.
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.5 1 1.5 2 2.5 3 3.5 4Wavelength (in microns)
Albedo
Closed shrublands - WOpen shrublands - WWoody savannas - WSavannas - WGrasslands - WClosed shrublands - SOpen shrublands - SWoody savannas - SSavannas - SGrasslands - S
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Winter (W) and Summer (S) Albedos.
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.5 1 1.5 2 2.5 3 3.5 4Wavelength (microns)
Albedo
Perm wetlands - WCroplands - WUrban & built-up - WCropland mosaics - WPerm wetlands - SCroplands - SUrban & built-up - SCropland mosaics - S
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Standard Deviations.
• Albedo means at various wavelengths and times of year, for all ecosystem types, are within 7%.
• Majority are within 3%• Suggests a reasonable correlation between ecosystem and
albedo.
Southern HemisphereWavelength (in microns) 0.659 0.865 1.24 1.64 2.1Average % Error 2.21% 1.61% 1.52% 1.78% 2.31%Max % Error 4.10% 4.59% 6.30% 6.60% 7.18%
Northern HemisphereWavelength (in microns) 0.659 0.865 1.24 1.64 2.1Average % Error 2.56% 2.11% 1.90% 2.14% 2.58%Max % Error 4.84% 4.20% 4.79% 4.87% 5.99%
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Cropland - Seasonal Albedo Spectra.
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 50 100 150 200 250 300 350 400Julian Day
Albedo
0.659 micron0.865 micron1.24 micron1.64 micron2.14 micron3.7 micron
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Albedo Movies•Loops through bands 0.65, 0.86, 1.24, 1.64, 2.1, and 3.7•Loops through seasonal equinox and solstice, progressing from Julian days 91, 173, 293, 356
Ecosystem Color Scheme•Pink = Crops•Green = Trees•Yellows = Barren/Deserts•Blues = Savannas
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QuickTime™ and aVideo decompressor
are needed to see this picture.
Ecosystem Color Scheme•Pink = Crops•Green = Trees•Yellows = Barren/Deserts•Blues = Savannas
Albedo Movies•Loops through bands 0.65, 0.86, 1.24, 1.64, 2.1, and 3.7•Loops through seasonal equinox and solstice, progressing from Julian days 91, 173, 293, 356
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Albedo Movies•Loops through bands 0.65, 0.86, 1.24, 1.64, 2.1, and 3.7•Loops through seasonal equinox and solstice, progressing from Julian days 91, 173, 293, 356
Ecosystem Color Scheme•Pink = Crops•Green = Trees•Yellows = Barren/Deserts•Blues = Savannas
QuickTime™ and aVideo decompressor
are needed to see this picture.
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Ecosystem Color Scheme•Pink = Crops•Green = Trees•Yellows = Barren/Deserts•Blues = Savannas
Albedo Movies•Loops through bands 0.65, 0.86, 1.24, 1.64, 2.1, and 3.7•Loops through seasonal equinox and solstice, progressing from Julian days 91, 173, 293, 356
QuickTime™ and aVideo decompressor
are needed to see this picture.
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Albedo Movies•Loops through bands 0.65, 0.86, 1.24, 1.64, 2.1, and 3.7•Loops through seasonal equinox and solstice, progressing from Julian days 91, 173, 293, 356
Ecosystem Color Scheme•Pink = Crops•Green = Trees•Yellows = Barren/Deserts•Blues = Savannas
QuickTime™ and aVideo decompressor
are needed to see this picture.
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Ecosystem Color Scheme•Pink = Crops•Green = Trees•Yellows = Barren/Deserts•Blues = Savannas
Albedo Movies•Loops through bands 0.65, 0.86, 1.24, 1.64, 2.1, and 3.7•Loops through seasonal equinox and solstice, progressing from Julian days 91, 173, 293, 356QuickTime™ and a
Video decompressorare needed to see this picture.
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Conclusions• Improved surface albedo data for use in consistent
year processing.• Provided albedo and ecosystem data sets at a finer
resolution.• Added seasonal variability.• Provided albedos at specific wavelengths of
interest.• Ecosystem can be used as a surrogate for albedo.
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Future Directions
• Use a full year’s data (from consistent year) to improve ecosystem and albedo statistics.
• Investigate global albedo maps.• Investigate ecosystem-albedo surrogate.
• ISRSE presentation, April 2002.• Publish this work with BU group.