Title: MODIS BRDF/Albedo Products from Terra and Aqua
1MODIS 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
- (schaaf_at_bu.edu)
2MODIS BRDF/Albedo Algorithm
- BRDF modellinear 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.
3MODIS 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.
4MODIS BRDF/Albedo Standard Products
- V005 Level2G/Level3 Standard Land Products
(MCD43B) - HDF-EOS
- Sinusoidal equal-area projection
- 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) - HDF-EOS
- Geographic (lat/lon) projection
- Coarse resolution - 0.05degree (3 arc min or
5km) - Include snow free version
- Revised format and QA
5NBAR
January 1-16, 2001 (2001001) April 7-22, 2001
(2001097)
July 12-27, 2001 (2001193) October 16-31, 2001
(2001289)
6Albedo of Sahara
1 km albedo RGB composite
7 CMG Broadband White-Sky Albedo (0.3-5.0mm)January
2001
No Data
8CMG Broadband White-Sky Albedo (0.3-5.0mm)June
2001
No Data
9Spatially 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
- http//modis-atmos.gsfc.nasa.gov/ALBEDO/index.html
0.0 0.8
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.
10Spatially Complete White-Sky AlbedoJanuary 1-16,
2002
Snow-free
0.8
0.6
Surface Albedo (0.86 µm)
Snow-covered
0.4
0.2
0.0
11Combined 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 AquaTerra V004 reprocessing completed
Jan 05 - V005 MCD43 product only (Terra alone prior to
May 2002)
12CMG Broadband Black-sky Albedo (0.3-5.0mm) Terra
(April 2004) Terra Aqua
13CMG Broadband Black-sky Albedo (0.3-5.0mm) Terra
(April 2004) Terra Aqua
Green high quality Red poorer quality
14V005 500m White-Sky Albedo
2001193
500m 1km
15Validation Sites
- 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.a
sp - MODIS 7x7 pixel subsets in ascii at ORNL
- 276 sites (BSRN stations archiving albedo, EOS
core sites, and Flux network sites - http//www.modis.ornl.gov/modis/index.cfm
- 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 ,
doi10.1016/j.rse.2004.09.001, 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.
16Fort Peck, Montana V004, 2003
17ARM SGP Central Site V004, 2003
18Boulder, CO V004, 2003
19Desert Rock, NV V004, 2003
20Validation 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).
21MODIS 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.
22Albedo/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,
doi10.1029/2004JD005190. 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, doi10.1016/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, doi10.1029/2003GL019104,
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, doi10.1029/2002JD003326, 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, doi10.1029/2002GL01674
9, 2003. - Jin et al., Consistency of MODIS surface
BRDF/Albedo retrievals 1. Algorithm performance,
J. Geophys. Res., 108(D5), 4158,
doi10.1029/2002JD002803, 2003. - Jin et al., Consistency of MODIS surface
BRDF/Albedo retrievals 2.Validation, J.Geophys.
Res., 108, 4159, doi10.1029/2002JD002804, 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, 10.1029/2001GL01413
2, 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)