MODIS BRDF/Albedo Product (MOD43) Validation
Reprocessed (V004) MODIS BRDF/Albedo products have been assigned a "Validated (Level 1)
Status".
This section describes some of the initial evaluations that
led to this upgrade in status.
Users are urged to use the band specific quality flags to
isolate the highest quality full inversion results for their own
science applications. MOD43B and MOD43C products continue to be
evaluated and validated by the MODIS
Science Team and MODIS Validation Scientists.
Validation Efforts Currently Underway
MODIS albedo pixel values created using combined observations (V004) from
MODIS instruments aboard the Terra (EOS AM-1) and Aqua (EOS PM-1)
platforms showed good agreementin direct comparisons to tower data from
the six
SURFRAD
sites and two
ARM/SGP
sites in the United States for the years 2003 and 2004. In addition, pixel
values from combined observations matched well with pixel values created
from Terra observations alone. For specifics, see:
- 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.,
to be published, 2006.
Figure 1a. Comparisons between MODIS pixel albedos and SURFRAD
tower albedos in 2003 and 2004 at Fort Peck, MT,
Penn State, PA, and Bondville, IL. Large changes in MODIS albedo
during snow periods (changes in surface albedo greater than 0.5)
are due to reversals of the QA snow flag (see referenced text).
Figure 1b. Comparisons between MODIS pixel albedos and SURFRAD
tower albedos in 2003 and 2004 at Table Mountain, CO,
Desert Rock, NV, and Goodwin Creek, MS. Large changes in MODIS
albedo during snow periods (changes in surface albedo greater
than 0.5) are due to reversals of the QA snow flag (see
referenced text).
High quality reprocessed MODIS albedo pixel values from 2001 (V003) showed good
agreement during the growing season in direct comparisons to tower data from the six
SURFRAD
sites in the United States. For specifics, see:
- Jin, Y., C. B. Schaaf, C. E. Woodcock, F. Gao, X. Li, A. H. Strahler,
W. Lucht, S. Liang, Consistency of MODIS surface BRDF/Albedo retrievals:
1. Algorithm performance, J. Geophys. Res., 108(D5), 4158,
doi:10.1029/2002JD002803, 2003.
- Jin, Y., C. B. Schaaf, C. E. Woodcock, F. Gao, X. Li, A. H. Strahler,
W. Lucht, S. Liang, Consistency of MODIS surface BRDF/Albedo retrievals:
2. Validation, J. Geophys. Res., 108(D5),
4159, doi:10.1029/2002JD002804, 2003.
Figure 2a. Comparisons between MODIS pixel albedos, SURFRAD
tower albedos, and CERES TOA albedos in 2001 at Fort Peck, MT,
Penn State, PA, and Bondville, IL.
Figure 2b. Comparisons between MODIS pixel albedos, SURFRAD
tower albedos, and CERES TOA albedos in 2001 at Table Mountain, CO,
Desert Rock, NV, and Goodwin Creek, MS.
Good agreement was achieved in a limited number of comparisons in
November and December 2000 between field data associated with an
instrumented tower at the Beltsville Agricultural Research Center
(BARC) and MODIS pixel
values. For
specifics see:
- Liang, S., H. Fang, M. Chen, C. J. Shuey, C. Walthall, C. Daughtry,
J. Morisette, C. Schaaf and A. Strahler, Validating MODIS Land
Surface Reflectance and Albedo Products: Methods and Preliminary
Results, Remote Sens. Environ., 83, 149-162, 2002.
A paper comparing MODIS albedos with field data from BSRN core
sites was completed and published by Andreas Roesh in JGR.
For specifics see:
- A. Roesch, 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, D12105, doi:10.1029/2004JD004552, 2004.
A paper comparing MODIS albedos with field data at the Barton
Bendish core site was completed by our British colleagues and
published in IJRS. For specifics see:
A paper comparing MODIS albedos with field data in Tibet was
completed by our Chinese colleagues and published in JGR. For
specifics see:
- Kaicun Wang, Jingmiao Liu, Xiuji Zhou, Michael Sparrow, Min Ma,
Zhian Sun, and Wenhua Jiang, alidation of the MODIS global land
surface albedo product using ground measurements in a semidesert
region on the Tibetan Plateau, J. Geophys. Res., 109, D05107,
doi:10.1029/2003JD004229, 2004.
A paper comparing snow albedos from the MODIS data product with field
sites in Greenland was completed by Stroeve, et al. and published in
RSE. For specifics see:
- J. Stroeve, J. E. Box, F. Gao, S. Liang, A. Nolin, and C. Schaaf,
Accuracy assessment of the MODIS 16-day albedo product for snow:
comparisons with Greenland in situ measurements, Remote Sensing
of Environment, 94, 46-60, 2005
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