The basis for this data set is the Normalized Difference Vegetation Index
(NDVI) data set calculated from AVHRR data by Los et al. (1994) following the
work of Tucker et al. (1986). These data were already in the form of a 1 deg.
x 1 deg. monthly composited NDVI data set; i.e., no further single channel
data or geometric information were available at the time. Some simple
procedures were used to fill in gaps in the data set, and crude corrections
were made to account for the effects of solar angle and persistent clouds to
make the temporally and spatially continuous FASIR-NDVI product, see Sellers
et al. (1994). The FASIR-NDVI data were used to create fields of FPAR, leaf
area index, and greenness, which in turn were used to calculate monthly snow-
free albedo and surface roughness fields, see Sellers et al. (1994).