BRDF/Albedo@BU
MODIS BRDF/Albedo
MOD43B User's Guide
BRDF/Albedo Data
MODIS User Tools
Workshops and Tutorial
BRDF/Albedo Examples
BRDF Explained
BRDF/Albedo Publications
Team members' pages
Alan
Strahler
Crystal
Schaaf
Feng
Gao
Xiaowen
Li
Wolfgang Lucht
Jan-Peter
Muller
Michael Barnsley
Philip Lewis
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The MODIS Bidirectional Reflectance Distribution Function (BRDF) and Albedo Product (MOD43B) is an
MODIS Standard Data Product that began routine production in 2000
shortly after the launch of Terra. Global Albedo (MOD43B3), BRDF
Model Parameters (MOD43B1), and Nadir-BRDF Ajusted Reflectance
(NBAR) Products (MOD43B4) are operationally produced every 16
days at a 1km spatial resolution and archived as equal area tiles
of 1200 by 1200 pixels in a sinusoidal projection (HDF-EOS
format) at the EROS Data Center (EDC) DAAC.
In addition the global Albedo (MOD43C1), BRDF Parameters (MOD43C2)
and NBAR (MOD43C3) data are also provided as Climate Modeling Grid
(CMG) products in a global geographic projection (lat/lon) at a 0.05 degree
spatial resolution every 16 days (HDF-EOS format). CMG Data
Products
are also available in a binary
format from this Science
Team Facility. The MODIS BRDF/Albedo products can also be viewed
as Browse Imagery.
An additional Filled Land Surface Albedo Product is also being
developed from the MOD43 data by the MODIS atmosphere team.
This product is provided at a 1 minute resolution in
a geographic projection and aims to provide
temporally and spatially consistent albedo maps throughout
the year. The Filled Land Surface Albedo Product is available
at: http://modis-atmos.gsfc.nasa.gov/ALBEDO/index.htm .
Collection 4 (V004) reprocessing
encompasses data from March 2000 to present and contains a V004 designator in the data labels. MODIS BRDF/Albedo V004 data begin with
the period labeled 2000049 (although only data from 2000055 to
2000064 contributed to this first period). The entire V004 data
set is classified as
"Validated Stage-1" (see Jin et
al., 2003a;b and the
MOD43 Validation section of the
MOD43B User's Guide for a description of
the validation work underway).
Team members
Principal Investigators are Alan H.
Strahler and Crystal
Schaaf (at Boston University) with Co-Investigators
Feng Gao (Boston University),
Xiaowen Li (Boston
University), and
Wolfgang Lucht
(Potsdam-Institut für Klimafolgenforschung). The European
Principal Investigator is Jan-Peter Muller (University
College London) with associate team members Philip Lewis
(University College London) and Mike Barnsley
(University of Wales, Swansea).
The research and development team is currently made up of Crystal Schaaf, Feng Gao, Wolfgang Lucht, Xiaowen Li, Jonathan Salomon,
Xiaoyang Zhang, and Elena Tsvetsinskaya (all of Boston
University). Active validation efforts are underway
at the Beltsville Agricultural Reseach Center (BARC)
in Maryland by Shunlin Liang
(University of Maryland); at Mongu, Zambia (woodland) and Skukuza,
South Africa (savanna) which are both Southern African
Regional Science Initiative (SAFARI) sites by Jeff Privette
(NASA/GSFC); at the Barton Bendish, UK
agricultural site by Mat Disney
(University College London) and Mike Barnsley
(University of Wales, Swansea); and at the Liangchen, Shunyi and
Yucheng agricultural sites in China by Xiaowen Li. Evaluation of
the product is monitored by David Roy
(University of Maryland) at the MODIS Land Data Operational
Product Evaluation (LDOPE)
facility at GSFC.
Contributors have included
Yufang Jin,
Paul Hobson
(University of Wales, Swansea),
Mike Dunderdale
(University College London), Chris Doll
(University College London),
Bob d'Entremont (AER), Trevor Tsang,
Nick Strugnell, and
Baoxin Hu
(York University Ontario).
Data Source
The MODIS BRDF/Albedo Product is generated with data acquired by
the Moderate Resolution Imaging Spectroradiometer (MODIS)
and on NASA's Earth
Observing System (EOS)
Terra and Aqua satellite
platforms. Terra is on a polar orbit with a 10:30 AM equatorial
crossing time while Aqua is on a polar orbit
with a 1:30 PM crossing time. MODIS is an across-track wide-field-of-view
scanner. The MODIS BRDF/Albedo Product
is one of the many standard products provided by the MODIS Land
Team (MODLAND).
Product Description
The BRDF, albedo and nadir surface reflectance of each pixel of
the global land surface is modeled at a spatial resolution of 1
km by inverting multidate, multiangular, cloud-free,
atmospherically corrected, surface reflectance observations
acquired by MODIS in a 16-day period (MODIS orbital double repeat
cycle). Data from MODIS on board Terra will soon be augmented
by additional MODIS data from Aqua (the Aqua products are currently
running in parallel) and eventually with MISR data
from on board Terra. The product is derived in seven
spectral bands, as well as in the visible, the near/mid-infrared
and the total shortwave broadbands. The BRDF parameters
retrieved quantify intrinsic surface properties decoupled
from the prevailing atmospheric state and hence are suited for
applications requiring characterization of the directional
anisotropy of Earth surface reflectance. The parameters are also
applicable for the computation of both the directional
hemispherical reflectance (black-sky albedo) and the
bihemispherical reflectance (white-sky albedo). This can be
achieved through the use of a simple polynomial (Lucht et al,
2000) although white_sky and black-sky (at local solar noon)
albedo computations are provided in the product for user
convenience. Nadir BRDF-Adjusted Reflectances (NBAR) at the mean
solar zenith angle of the observation period are also provided to
the user community. A complete set of quality control flags
accompanies each product and should be accessed by the user. For
more product details, refer primarily to the
MOD43B User's
Guide , as well as Schaaf et al. (2002), Lucht et al. (2000),
and Wanner et
al., (1997).
MOD43 Product Summary
- MOD43B1 BRDF/Albedo Model-1 16-Day L3 Global 1km SIN Grid
V004 (semiempirical RTLSR)
int16 BRDF_Albedo_Parameters (7 Bands, 3 Broadbands)
uint8 BRDF_Shape_Indicators
uint32 BRDF_Albedo_Quality
uint8 BRDF_Type
- MOD43B2 BRDF/Albedo Model-2 16-Day L3 Global 1km SIN Grid V004
- MOD43B3 Albedo 16-Day Global 1km SIN Grid V004
int16 Albedo (black_sky at local solar noon
and white_sky:
7 Bands, 3 Broadbands)
uint32 Albedo_Quality
- MOD43B4 Nadir BRDF-Adjusted Reflectance 16-Day L3 Global 1km
SIN V004 (NBAR)
int16 Nadir_Reflectance (at mean szn)
uint32 Nadir_Reflectance_Quality
- MOD43C1 MODIS/Terra Albedo 16-day L3 Global 0.05Deg CMG V004
int16 Black_Sky_Albedo
int16 White_Sky_Albedo
uint32 Albedo_Quality
- MOD43C2 MODIS/Terra BRDF/Albedo Parameters 16-day L3 Global
0.05Deg CMG V004 (Model-1)
int16 BRDF_Albedo_Parameter0
int16 BRDF_Albedo_Parameter1
int16 BRDF_Albedo_Parameter2
uint32 BRDF_Albedo_Quality
- MOD43C MODIS/Terra Nadir BRDF-Adjusted Reflectance 16-day L3 Global
0.05Deg CMG V004 (NBAR)
int16 Nadir_Reflectance
uint32 Nadir_Reflectance_Quality
BRDF Model
The product is derived using a kernel-driven semiempirical
BRDF model, utilizing the
RossThick-LiSparse kernel functions for characterizing isotropic,
volume and surface scattering (Wanner et al., 1995; 1997; Lucht
et al., 2000; Schaaf et al., 2002). A reciprocal version of the LiSparse kernel
is employed. When sufficient MODIS (Terra alone or Terra plus
Aqua) observations are available,
a full inversion can be utilized --- otherwise a magnitude
inversion is performed by relying on MODIS-derived archetypal BRDFs associated with that
location and season as a first guess and adjusting these by the available observations (Strugnell
and Lucht, 2001, Strugnell et al., 2001).
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Author:Crystal Schaaf
Last Updated:April 2004
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