1. MODIS BRDF/Albedo Products from Terra and Aqua
Crystal Schaaf
Alan Strahler, Xiaowen Li, Jonathan Salomon, Jicheng Liu, Feng Gao et al.
Department of Geography
Boston University

2. MODIS BRDF/Albedo Algorithm
BRDF model—linear combination of a constant (fiso) and two weighted (fvol, fgeo) trigonometric functions (kvol, kgeo) derived from physical models of volumetric and geometric-optical surface scattering.
Full model inversions are used when sufficient high quality atmospherically-corrected cloud-free observations are available over a 16-day period to adequately sample the BRDF.
Otherwise, lower quality magnitude inversions are performed which couple a priori knowledge of the surface anisotropy with any high quality MODIS observations that are available for a location.

3. MODIS BRDF/Albedo Standard Products
Collection 4 (V004) reprocessed MODIS Land Products (March 2000 to present).
BRDF Model Parameters
MODIS bands 1-7 plus three broadbands
Albedos
white-sky and black-sky (at local solar noon)
Nadir BRDF-Adjusted Reflectances (NBAR)
MODIS bands 1-7
Extensive Quality Assurance Flags
Quality of the product, processing method used, and whether a snow or snow-free albedo was retrieved.
Blue-sky albedos
Can be computed as an interpolation between black-sky and white-sky albedos as a function of diffuse skylight.
Validated Stage-1
Product accuracy has been estimated using a small number of independent measurements obtained from selected locations and time periods and ground-truth/field program effort.

4. MODIS BRDF/Albedo Standard Products
V005 Level2G/Level3 Standard Land Products (MCD43B)
HDF-EOS
Sinusoidal equal-area projection
Tiles x1200 pixels for the 1-km products
Tiles – 2400x2400 pixels for the 500-m products
Revised format and QA (snow and mandatory separate bytes)
V005 Climate Modeling Grid Products (CMG) (MCD43C)
Geographic (lat/lon) projection
Coarse resolution degree (3 arc min or ~5km)
Include snow free version
Revised format and QA

5. NBAR January 1-16, 2001 (2001001) April 7-22, 2001 (2001097)
July 12-27, 2001 ( ) October 16-31, 2001 ( )

6. Albedo of Sahara
1 km albedo – RGB composite

7. CMG Broadband White-Sky Albedo (0.3-5.0mm) January 2001
No Data

8. CMG Broadband White-Sky Albedo (0.3-5.0mm) June 2001
No Data

9. Spatially Complete Snow-Free MODIS Albedo Product
MODIS Atmosphere Group- Eric Moody
Fill values, poorest quality results, and seasonally snow covered results are replaced with temporal estimations and spatial interpolation.
1 arc minute geographic lat/lon
Moody, E. G., M. D. King, S. Platnik, C. B. Schaaf, F. Gao, Spatially Complete Surface Albedo Datasets: Value-Added Products Derived from Terra MODIS Land Products, IEEE, Trans Geosci. Remote Sens., 2005.

10. Spatially Complete White-Sky Albedo January 1-16, 2002
Snow-free
0.8
0.6
Snow-covered
Surface Albedo (0.86 µm)
0.4
0.2
0.0

11. Combined Aqua + Terra Processing
BRDF specification requires multiple observations to capture anisotropy across viewing/illumination geometry
Combining observations from Aqua and Terra
Increase high-quality inversions
Best fit BRDF model retrieved directly from observations
Fewer lower-quality retrievals using the back-up algorithm
Back-up method relies on a priori designation of BRDF
Combined Aqua+Terra V004 reprocessing completed Jan 05
V005 – MCD43 product only (Terra alone prior to May 2002)

12. CMG Broadband Black-sky Albedo (0. 3-5
CMG Broadband Black-sky Albedo ( mm) Terra (April 2004) Terra + Aqua

13. CMG Broadband Black-sky Albedo (0. 3-5
CMG Broadband Black-sky Albedo ( mm) Terra (April 2004) Terra + Aqua
Green: high quality Red: poorer quality

14.
V m White-Sky Albedo
500m km

15. Validation Sites Baseline Surface Radiation Network (BSRN)
SURFRAD Network (US BSRN sites)
EOS core validation sites (200x200 pixels subsets)
MODIS 7x7 pixel subsets in ascii at ORNL
276 sites (BSRN stations archiving albedo, EOS core sites, and Flux network sites
Greenland Climate Network (GC-Net) Automatic Weather Stations (AWS) -
Stroeve, J., J. E. 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 , doi: /j.rse , Remote Sens. Environ., 2004.
Validated Stage-1
Product accuracy has been estimated using a small number of independent measurements obtained from selected locations and time periods and ground-truth/field program effort.

16. Fort Peck, Montana
V004, 2003

17. ARM SGP Central Site
V004, 2003

18. Boulder, CO
V004, 2003

19. Desert Rock, NV
V004, 2003

20. Validation with Greenland in situ Measurements
Description of the Greenland GC-Net AWS Albedo Measurements
Upward and downward shortwave radiation fluxes are measured at several AWS distributed widely in latitude and elevation using pairs LI-COR 200SZ photoelectric diode pyranometers (0.4 m – 1.1 m).
A correction to the LI-COR albedo are made to convert them from a narrowband albedo (e.g. 0.4 m – 1.1 m) to a broadband (0.285 m – 2.8 m) albedo.
Comparisons with precision pyranometers suggest a residual uncertainty with an RMSE of (absolute albedo).

21. MODIS Albedo Vs Greenland In Situ Albedo
Comparison between MOD43 16-day albedo and 16-day in situ albedo for both black sky (triangles) and white sky (squares) albedo for 15 Greenland AWS stations. MODIS albedo from both the “main” (closed symbols) and “backup” (open symbols) algorithm results are shown.
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, 2005.

22. Albedo/BRDF References
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: /2004JD
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 Trans. Geosci. Remote Sens., 43, , 2005.
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: /j.rse , 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: /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: /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: /2002JD003326, 2003.
Gao et al., Detecting vegetation structure using a kernel-based BRDF model. Remote Sens. Environ., 86(2), , 2003.
Oleson et al., Assessment of global climate model land surface albedo using MODIS data, Geophys. Res. Letters, 30(8), 1443, doi: /2002GL016749, 2003.
Jin et al., Consistency of MODIS surface BRDF/Albedo retrievals: 1. Algorithm performance, J. Geophys. Res., 108(D5), 4158, doi: /2002JD002803, 2003.
Jin et al., Consistency of MODIS surface BRDF/Albedo retrievals: 2.Validation, J.Geophys. Res., 108, 4159, doi: /2002JD002804, 2003.
Schaaf et al., First Operational BRDF, Albedo and Nadir Reflectance Products from MODIS, Remote Sens. Environ., 83, , 2002.
Liang et al., Validating MODIS Land Surface Reflectance and Albedo Products: Methods and Preliminary Results, Remote Sens. Environ., 83, , 2002.
Jin et al., Improving MODIS Surface BRDF/Albedo Retrieval with MISR Multi-angle Observations, IEEE Trans. Geosci. Remote Sens., 40, , 2002.
Jin et al., How does snow impact the albedo of vegetated land surfaces as analyzed with MODIS data?, Geophys. Res. Let., 29, /2001GL014132, 2002.
Tsvetsinskaya et al., Relating MODIS derived surface albedo to soils andlandforms over Northern Africa and the Arabian Peninsula, Geophys. Res. Let., 29, /2001GL014096, 2002.
Gao et al., Bidirectional NDVI and Atmospherically Resistant BRDF Inversion for Vegetation Canopy, IEEE Trans. Geosci. Remote Sens., 40, , 2002.
MODIS BRDF/Albedo User Guide (