MODIS Reflectance Anisotropy and Albedo MODIS Reflectance Anisotropy and Albedo (Collection V005)(Collection V005)

Crystal Schaaf, Alan Strahler, Jicheng LiuDepartment of Geography and Environment,

Center for Remote Sensing, Boston University

MODIS: System CharacteristicsMODIS: System Characteristics

EOS-Terra Platform• Sun-synchronous, near-polar, 705.3

km, 98.21° inclination• 10:30 AM local solar equatorial

crossing time (descending node• Launched December 18, 1999

EOS-Aqua Platform• Sun-synchronous, near-polar,

705.3km, 98.21° inclination• 1:30 PM local solar equatorial

crossing time (ascending node)• Launched May 4, 2002

MODIS Surface Reflectance (MOD09)MODIS Surface Reflectance (MOD09)

The MODIS surface reflectance product is an estimate of the surface spectral reflectance for each band as it would have been measured at ground level if there were no atmospheric scattering and absorption.

Bands (in nm):1 620-670 2 841-8763 459-4794 545-5655 1230-1250 Daily Browse 6 6 1628-1652 Mostly Cloudy!7 2105-2155

Home page: http://modis-sr.ltdri.org/html/surfref.htm 3

MODIS Anisotropy and AlbedoMODIS Anisotropy and Albedo

• Output• High quality full inversions provide well-sampled, best-fit anisotropy models of global land surfaces

• Ross Thick Li Sparse Reciprocal semi-empirical model captures volumetric and geometric-optical scattering

• Lower quality back-up algorithm performs magnitude inversions by coupling available reflectances with an a priori BRDF database

• Inputs

• Cloud-free, atmospherically-corrected, spectral surface reflectances from Aqua and Terra (MOD09/MYD09 BRFs) to sample the surface anisotropy over a 16 day period

MODIS Anisotropy and AlbedoMODIS Anisotropy and Albedo

30 60 90

0

60

180

270

30

120

150210

240

300

330

H17V07(850,400)

Black=Aqua ObsPink=Terra ObsBlue=True Aqua SunYellow=True Terra Sun

Semi-Empirical BRDF ModelSemi-Empirical BRDF Model

Isotropic GeometricVolumetric

Rλ (θ

i, Φ

i; θ

r, Φ

r) = f

iso + f

volk

vol + f

geok

geo

kvol, kgeo are kernels of view and illumination geometry

fiso, fvol, fgeo are spectrally dependent weights

(Roujean et al., 1992)

Kernel ModelsKernel Models

Kernel model derivation To derive a kernel model, we simplify and

manipulate a complete physical model until it reaches the form

where k is a function only of view and illumination geometry (and fixed physical parameters)

c1 and c2 are constants containing variable physical parameters

MODIS Anisotropy and Albedo ProductsMODIS Anisotropy and Albedo Products

• BRDF Model parameters• RossThickLiSparseR model parameters

– Use parameters directly in simple polynomial to estimate albedo or reflectance quantities

– BRDF shape factors capture some measure of structure

• Nadir BRDF-Adjusted Reflectance (NBAR)• View angle corrected surface reflectances

– Operational MODIS land cover classification and phenology

• Albedo quantities• Bihemispherical reflectance under isotropic illumination

(BHRiso)– White-sky albedo (wholly diffuse)

• Directional-hemispherical reflectance (DHR) at local solar noon– Black-sky albedo (direct)

• Intrinsic albedos can be combined as a function of diffuse skylight (optical depth) to obtain instantaneous actual albedos

MODIS Anisotropy and Albedo Product MODIS Anisotropy and Albedo Product

• Product Output

• Spectral (Collections 004 and 005)– 7 shortwave bands and three broad bands

• Spatial– Sinusoidal 10deg2 tiles

• 500m (005)• 1km (004, 005)

– Climate Modeling Grid (CMG)• 0.05deg in global lat/lon (004, 005)• 30arcsec in global lat/lon (005)

• Temporal – Every 16 days (004)– Every 8 days based on the last 16 days (005)

Multi-angle Indications of Vegetation Multi-angle Indications of Vegetation StructureStructure

MODIS BRDF Shape Factors

MISR RPV Classification

M. Hill, Univ. North Dakota

NBARNBAR

Differences between MODIS surface reflectances from adjoining swaths and MODIS NBAR (Great Lakes/NY, 6 Sep 2000).

NIR (0.10-0.45) Red (0.0-0.1) Green (0.0-0.15)

NBARNBAR

January 1-16, 2001 (2001001) April 7-22, 2001 (2001097)

July 12-27, 2001 (2001193) October 16-31, 2001 (2001289)

Temporal SignalTemporal Signal

Evergreen Needleleaf Forest (Latitude: 30-40N)

0

0.05

0.1

0.15

0.2

0.25

2000

305

2000

321

2000

337

2000

353

2001

001

2001

017

2001

033

2001

049

2001

065

2001

081

2001

097

2001

113

2001

129

2001

145

2001

193

2001

209

2001

225

2001

241

2001

257

2001

273

2001

289

Julian Day

Alb

edo

Deciduous Broadleaf Forest (Latitude: 30-40N)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

2000

305

2000

321

2000

337

2000

353

2001

001

2001

017

2001

033

2001

049

2001

065

2001

081

2001

097

2001

113

2001

129

2001

145

2001

193

2001

209

2001

225

2001

241

2001

257

2001

273

2001

289

Julian Day

Alb

edo

Grassland (Latitude: 30-40N)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

2000

305

2000

321

2000

337

2000

353

2001

001

2001

017

2001

033

2001

049

2001

065

2001

081

2001

097

2001

113

2001

129

2001

145

2001

193

2001

209

2001

225

2001

241

2001

257

2001

273

2001

289

Julian Day

Alb

edo

WSA-VIS WSA-NIR WSA-SWBSA-VIS BSA-NIR BSA-SW

MODIS Land Cover Product —IGBPMODIS Land Cover Product —IGBP

MODIS data Nov 00–Oct 01

Friedl, M. A., D. K. McIver, J. C. F. Hodges, X. Zhang, D. Muchoney, A. H. Strahler, C. E. Woodcock, S. Gopal, A. Schnieder, A. Cooper, A. Baccini, F. Gao, and C. Schaaf, Global land cover from MODIS: Algorithms and early results, Remote Sens. Environ., 83, 287-302, 2002.

~2300 sites globally

Initial Efforts to Distinguish Crop TypesInitial Efforts to Distinguish Crop Types

Credit W. Boykin-Morris

MODIS Vegetation Phenology:MODIS Vegetation Phenology:

(Zhang et al. 2003, RSE; Zhang et al. 2004 GCB; (Zhang et al. 2003, RSE; Zhang et al. 2004 GCB; Zhang et al. 2004, GRL; Zhang et al., 2006, JGR)Zhang et al. 2004, GRL; Zhang et al., 2006, JGR)

• Quantifies Intra-annual Variation (phenology)– Greenup, maturity, senescence, dormancy

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 50 100 150 200 250 300 350 400

Julian day

Maturity stabilitySenescence onset

Dormancy onset

Dormancy stability

Duration of greenness

Duration of maturity

Maximum Greenness

Greenup onset

Greenup stability

Maturity onset

Senescence stability

Use logistic functions fit to time trajectories of NBAR-EVI and use extreme points of the change rate of curvature to calculate phenology transition dates

Global Results -2001(e.g., Northern Hemisphere Green Wave)

2001-2004 V004 MCD12Q2 availableCredit: X. Zhang, M. Friedl, Bin Tan

MODIS PhenologyMODIS Phenology

Harvard Forest

V005 500m White-Sky Albedo V005 500m White-Sky Albedo

500m 1km

2001193

Albedo of SaharaAlbedo of Sahara

1 km albedo – RGB compositeTsvetsinskaya et al., Relating MODIS derived surface albedo to soils andlandforms over Northern

Africa and the Arabian Peninsula, Geophys. Res. Let., 29, 10.1029/2001GL014096, 2002.

CMG Broadband White-Sky Albedo (CMG Broadband White-Sky Albedo (0.3-5.0mm0.3-5.0mm))January 2001January 2001

No Data

CMG Broadband White-Sky Albedo (CMG Broadband White-Sky Albedo (0.3-5.0mm0.3-5.0mm))June 2001June 2001

No Data

Collection V005 Emphasis on Collection V005 Emphasis on Validation/IntercomparisonValidation/Intercomparison

• BSRN/Surfrad calibrated albedometers – http://www.gewex.org/bsrn.html– http://bsrn.ethz.ch/

• CERES/ARM Validation Experiment (CAVE)– http://www-cave.larc.nasa.gov/cave/cave2.0/SfcObs.html

• EOS core sites (200x 200km)– http://landval.gsfc.nasa.gov/

• ORNL subsets (7x7 km to 200X200 km) – http://www.modis.ornl.gov/modis/index.cfm

• Field Campaigns: SAFARI, ARM CLASIC – CLASIC - Cloud and LAnd Surface Interaction Campaign

• Southern Great Plains, 10-30 June 2007• Additional towers (radiation and flux), MAS, CAR• http://www.ars.usda.gov/Research/docs.htm?

docid=15299

Oak Ridge National Lab SubsetsOak Ridge National Lab Subsets

http://www.modis.ornl.gov/modis/index.cfm

Boulder, CO

MODIS Anisotropy and Albedo ValidationMODIS Anisotropy and Albedo Validation

ARM SGP EF-15 2003

ARM CLASIC – Cloud and LAnd Surface Interaction Campaign 10-30 June 2007

MODIS Anisotropy and Albedo ValidationMODIS Anisotropy and Albedo Validation

2003

Liu et al., GRL in review

CEOS/WGCV/LPV (Land Product Validation) CEOS/WGCV/LPV (Land Product Validation) Surface Radiation SubgroupSurface Radiation Subgroup

• Workshops

– October 2002 Boston– April 2005 Vienna

•Product Intercomparison/Validation– Roujean et al.,

(POLDER/SEVIRI/MODIS)– Pinty et al.,

(MISR/MODIS/Meteosat)– Rutan et al., (MODIS/CERES)

– Spring 2008 (Gabriela Schaepman-Strub has offered to host – venue TBD)

• Website (supported by NASA)

– http://lpvs.gsfc.nasa.gov

MODIS/CERES IntercomparisonMODIS/CERES Intercomparison

♦ Continental

♦ Deserts

Dave Rutan et al., 2007 ARM Meeting

MODIS Albedo for Modeling ApplicationsMODIS Albedo for Modeling Applications

• Produce CMG products and gap-filled (snow-free) products for model evaluations and parameterizations– NCAR CLM (Dickinson, Zeng, Oleson,

Lawrence)– ECMWF (Morcrette)– ETH ECHAM (Roesch)– NCEP Noah (Mitchell)– GMAO LSM (Koster, Bounoua/Moody/King)

– GISS (Y.-C. Zhang)

• Establish long term data sets by linking MODIS with historical meterological satellites (AVHRR) – LTDR effort (Eric Vermote)– http://ltdr.nascom.nasa.gov/ltdr/ltdr.html

CMG Broadband Black-sky CMG Broadband Black-sky Albedo Albedo (0.3-5.0mm)(0.3-5.0mm)

30 60 90

0

60

180

270

30

120

150210

240

300

330

H17V07(850,400)

Black=Aqua ObsPink=Terra ObsBlue=True Aqua SunYellow=True Terra Sun

Use multiple MODIS sensors to increase the directional sampling of the surface and thus increase high quality anisotropy and albedo

retrievals Te rra Terra + Aqua

Green: high quality Red: poorer quality

Spatially Complete White-Sky Albedo (LSN) January Spatially Complete White-Sky Albedo (LSN) January 1-16, 20021-16, 2002

0.60.6

0.80.8

0.00.0

0.20.2

Su

rface

Alb

edo (

0.8

6 µ

m)

Su

rface

Alb

edo (

0.8

6 µ

m)

0.40.4

Snow-Snow-freefree

Snow-Snow-coveredcovered

Moody, E. G., M. D. King, S. Platnick, C. B. Schaaf, and F. Gao, Spatially complete global spectral surface albedos: Value-added datasets derived from Terra MODIS land products, IEEE Transactions on Geoscience and Remote Sensing, Vol. 43, 144-158, 2005.

Annual data sets and 5 year mean

2000-2004

http://modis-atmos.gsfc.nasa.gov/ALBEDO/index.html

Gap-Filled Anisotropy ProductsGap-Filled Anisotropy Products

True color WSA based on gap-filled BRDF Model Parameters September 2001-2005

http://www-modis.bu.edu/brdf_albedo/gapfill5years.html Q. Zhang et al., in preparation

MODIS Land Products: MODIS Land Products: Data and ImageryData and Imagery

• Collection 4 (V004) reprocessed MODIS Land Products (March 2000 to 2006).

• Collection 5 (V005) reprocessing started (2000-mid 2002 complete – 2007 on).

– LAADS (Collection V005 only)

• http://ladsweb.nascom.nasa.gov:8300/index.html

– EDC DAAC EDG (entire data set is available) and Data Pool (limited extent)

• http://edcimswww.cr.usgs.gov/pub/imswelcome/

• http://lpdaac.usgs.gov/datapool/datapool.asp

– ORNL DAAC MODIS subsets over vegetation field sites

• http://www.modis.ornl.gov/modis/index.cfm

• Gap-filled (V004) Terra Albedo (snow-free)

• http://modis-atmos.gsfc.nasa.gov/ALBEDO/index.html

• Gap-filled (V004) Terra Aqua BRDF model parameters

• http://www-modis.bu.edu/brdf_albedo/gapfill5years.html

• Global Browse Imagery

• http://landweb.nascom.nasa.gov/cgi-bin/browse/browse.cgi

MODIS Land Products: DescriptionsMODIS Land Products: Descriptions

• MODIS BRDF/Albedo Product

– Product description and userguide

• http://www-modis.bu.edu/brdf/

• http://www-modis.bu.edu/brdf/userguide/index.html

• MODLAND

• http://modis-land.gsfc.nasa.gov/

• MODLAND QA

– Single most useful site with links to QA Known Issues, Product Definitions (Users Guides and Specs), Global Browse, etc.

• http://landweb.nascom.nasa.gov/cgi-bin/QA_WWW/newPage.cgi

• MODLAND Validation

• http://landval.gsfc.nasa.gov/

Albedo/BRDF References Albedo/BRDF References Salomon, J., C. B. Schaaf, A. H. Strahler, F. Gao, Y. Jin, Validation of the MODIS Bidirectional Reflectance Distribution Function and Albedo

Retrievals Using Combined Observations from the Aqua and Terra Platforms, IEEE Trans. Geosci. Remote Sens. Vol. 44, 2006. Gao, F., C. Schaaf, A. Strahler, A. Roesch, W. Lucht, and R. Dickinson, The MODIS BRDF/Albedo Climate Modeling Grid Products and the

Variability of Albedo for Major Global Vegetation Types, J. Geophys. Res., 110, D01104, doi:10.1029/2004JD005190. 2005.Moody, E. G., M. D. King, S., Platnick, C. B. Schaaf, and F. Gao, 2005: Spatially complete global spectral surface albedos: Value-added datasets

derived from Terra MODIS land products. IEEE Trans. Geosci. Remote Sens., 43, 144-158.Stroeve, J., J. Box, F. Gao, S. Liang, A. Nolin, C. Schaaf, Accuracy Assessment of the MODIS 16-day Albedo Product for Snow: Comparisons

with Greenland in situ Measurements., Remote Sens. Environ., 94, 46-60, doi:10.1016/j.rse.2004.09.001, 2005. Roesch, A., C. Schaaf and F. Gao, Use of Moderate-Resolution Imaging Spectroradiometer bidirectional reflectance distribution function products

to enhance simulated surface albedos, J. Geophys. Res., 109, D12, doi: 10.1029/2004JD004552, 2004. Tian, Y., R. E. Dickinson, L. Zhou, R. B. Myneni, M. Friedl, C. B. Schaaf, M. Carroll, and F. Gao, Land boundary conditions from MODIS data

and consequences for the albedo of a climate model, Geophys. Res. Let., 31, doi:10.1029/2003GL019104, 2004.Wang, Z., X. Zeng, M. Barlage, R. E. Dickinson, F. Gao, and C. Schaaf, Using MODIS BRDF and Albedo Data to Evaluate Global Model Land

Surface Albedo, J. Hydrometeor., 5, 3-14, 2004. Zhou, L.et al., Comparison of seasonal and spatial variations of albedos from Moderate-Resolution Imaging Spectroradiometer (MODIS) and

Common Land Model. J. Geophys. Res., 108, D15, 4488, doi:10.1029/2002JD003326, 2003.Gao et al., Detecting vegetation structure using a kernel-based BRDF model. Remote Sens. Environ., 86(2), 198-205, 2003.Oleson et al., Assessment of global climate model land surface albedo using MODIS data, Geophys. Res. Letters, 30(8), 1443,

doi:10.1029/2002GL016749, 2003. Jin et al., Consistency of MODIS surface BRDF/Albedo retrievals: 1. Algorithm performance, J. Geophys. Res., 108(D5), 4158,

doi:10.1029/2002JD002803, 2003.Jin et al., Consistency of MODIS surface BRDF/Albedo retrievals: 2.Validation, J.Geophys. Res., 108, 4159, doi:10.1029/2002JD002804, 2003.Schaaf et al., First Operational BRDF, Albedo and Nadir Reflectance Products from MODIS, Remote Sens. Environ., 83, 135-148, 2002.Liang et al., Validating MODIS Land Surface Reflectance and Albedo Products: Methods and Preliminary Results, Remote Sens. Environ., 83,

149-162, 2002.Jin et al., Improving MODIS Surface BRDF/Albedo Retrieval with MISR Multi-angle Observations, IEEE Trans. Geosci. Remote Sens., 40,

1593-1604, 2002.Jin et al., How does snow impact the albedo of vegetated land surfaces as analyzed with MODIS data?, Geophys. Res. Let., 29,

10.1029/2001GL014132, 2002.Tsvetsinskaya et al., Relating MODIS derived surface albedo to soils andlandforms over Northern Africa and the Arabian Peninsula, Geophys.

Res. Let., 29, 10.1029/2001GL014096, 2002.

MODIS BRDF/Albedo User Guide (http://www-modis.bu.edu/brdf/userguide/index.html)