What is the difference between the Spatially Complete Albedo Product and the official MODIS albedo product (MOD43B3)?
The main difference is that a temporal interpolation technique has been applied to fill MOD43B3 pixels with geophysically realistic values. MOD43B3 pixels are filled due to that pixel not having an observation, being lower quality, or being snow-covered. Additional differences include the format (1'CMG equal angle storage versus Sinusoidal projection of the MOD43B3 data), and that the filled product is snow-free whereas the MOD43B3 product is snow full. The spatially complete albedo product maintains MOD43B3 data of high quality and provides QA to discern which pixels are filled.
What is the difference between white-sky and black-sky albedo?
White-sky is the bihemispherical reflectance under conditions of isotropic illumination, so it has the angular dependency removed. Black-sky is the directional hemispherical reflectance computed at local solar noon.
Can the black-sky albedo be computed for different solar zenith angles?
Yes. The official Boston University's MOD43 website (see FAQ #9), explains how to compute black-sky albedo at other solar zenith angles from the BRDF parameters.
What wavelengths are available?
Just like the MOD43B3 data, the albedo is provided for the first 7 MODIS narrow bands (0.47, 0.555, 0.67, 0.858, 1.24, 1.64, 2.13µm) and three broadbands (0.3-0.7, 0.3-5.0, 0.7-5.0µm). Data is provided for both white- and black-sky albedo.
What Quality Assurance (QA) is available?
The original MOD43B3 General and Band Specific QA are stored in separate hdf files (for convenience and to reduce data volume). In addition, QA describing the application of the fill technique are available for each band. Both the white-sky and the black-sky use the same QA.
What data is available?
The spatially complete data consists of the product maps (stored in 1' CMG), QA (MOD43B3 and Processing), statistics of the albedo product (various resolutions by all pixels in a grid cell and by all pixels of each IGBP ecosystem class), the IGBP ecosystem map (stored in 1' CMG), and images of the IGBP ecomap, the MOD43B3 data and the Filled Products.
What years have been processed?
Collection 4 years 2000-2004 have been processed and are available for download. In addition, a five-year aggregate climatology has been generated.
What is the five-year aggregate climatology?
Five years of MOD43B3 data was screened to remove pixels of lower quality and snow-covered. The screened data was then aggregated (5-year mean) for each pixel of each wavelength of each 16-day period to create a year of aggregated MOD43B3 data. The temporal interpolation technique was then applied to the aggregate MOD43B3 data to generate a spatially complete five-year aggregate albedo climatology.
Where can the data be downloaded?
The data is available via ftp pull download from the anonymous ftp site modis-atmos.gsfc.nasa.gov. The data (images, statistics, product maps, and QA) are available for download in the L3LandSurfaceProducts directory.
Where can I find information about the official MOD43B3 product?
Boston University has created a website that documents the MOD43 suite of albedo/BRDF products from the Terra and Aqua MODIS instrument. The website address is http://geography.bu.edu/brdf/userguide/albedo.html
Have the algorithms been documented?
Yes. Two papers have been written. The first paper (Moody, E. G., M. D. King, S. Platnick, C. B. Schaaf, and F. Gao, 2005: Spatially complete global spectral surface albedos: Value-added datasets derived from Terra MODIS land products. IEEE Transactions on Geoscience and Remote Sensing, Vol. 43, 144-158)
describes the temporal interpolation technique, data available, and provides error analysis.
The second paper, in preparation, describes refinements in the algorithm and compares temporal and spatial trends of MOD43B3 pixels and filled pixels in the spatially complete product.
The five-year climatology is also described in this second paper.
Are there programs to read and use the spatially complete albedo products?
Yes. There is a page in this section called Analysis Tools.
There are two tools listed on this page for download. The first allows users to spatially subset the albedo and ecosystem data (FilledMapSubsetter),
while the second set of routines allows users to read in any file of the spatially complete suite of products (SpatialCompProd_IOUtils).
These tools are written in FORTAN 90 with the HDF Toolkit.