1. MODIS BRDF/Albedo Products from Terra and Aqua Jonathan Salomon Crystal Schaaf, Alan Strahler, Jicheng Liu, Ziti Jiao, Yanmin Shuai, John Hodges, Xiaowen Li, Feng Gao Department of Geography Boston University (schaaf@bu.edu)

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. Retrieved BRDF models are used to derive intrinsic measures of albedo (fully diffuse or white-sky albedo and direct beam or black-sky albedo).

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.

4. NBAR January 1-16, 2001 (2001001)April 7-22, 2001 (2001097) July 12-27, 2001 (2001193)October 16-31, 2001 (2001289)

5. Spectral Albedo of Sahara 1 km albedo – RGB true color composite

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

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

8. Combined Aqua + Terra Processing BRDF specification requires multiple observations to capture anisotropy across viewing/illumination geometry Combining observations from Aqua and Terra –Increased 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 V004 Aqua+Terra MCD43 Products available (May 2002 to present)

9. CMG Broadband Black-sky Albedo (0.3-5.0mm) Terra (April 2004) Terra + Aqua

10. Green: high quality Red: poorer quality

11. Aqua + Terra (April 2004)

12. MODIS BRDF/Albedo Standard Products V005 Level2G/Level3 Standard Land Products (MCD43B) –Single combined Aqua+Terra product (Terra alone prior to May 2002) –Sinusoidal equal-area projection - HDF-EOS –Tiles - 1200x1200 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) projectionm –HDF-EOS –Global - coarse resolution - 0.05degree (3 arc min or ~5km) –Include snow free version –Revised format and QA

13. V005 500m White-Sky Albedo 500m 1km 2001193

14. Validation Sites 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. Baseline Surface Radiation Network (BSRN) http://bsrn.ethz.ch/ SURFRAD Network (US BSRN sites) http://www.srrb.noaa.gov/surfrad/index.html EOS core validation sites (200x200 pixels subsets) http://modis-land.gsfc.nasa.gov/val/coresite_gen.asp 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:10.1016/j.rse.2004.09.001, Remote Sens. Environ., 2004. MODIS 7x7 pixel subsets in ascii at ORNL 276 sites (BSRN stations, EOS core sites, Flux sites and LTER sites) http://www.modis.ornl.gov/modis/index.cfm

15. MODIS Subsets

16. Boulder, CO V004, 2003

17. ARM SGP Central Site V004, 2003

18. Fort Peck, Montana V004, 2003

19. Desert Rock, NV V004, 2003

20. 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.

21. 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:10.1029/2004JD005190. 2005. 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, 144-158, 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: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. Gao et al., Bidirectional NDVI and Atmospherically Resistant BRDF Inversion for Vegetation Canopy, IEEE Trans. Geosci. Remote Sens., 40, 1269-1278, 2002. MODIS BRDF/Albedo User Guide (http://geography.bu.edu/brdf/userguide/index.html)

22. 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 0.035 (absolute albedo).