File Name Convention
--------------------
The files in this data set are named using the following naming convention:

                   snowfree_albedo_1d_YYYYmm.asc

where:
snowfree_albedo    identifies the snow-free albedo data set.
1d                 identifies the spatial resolution of the data set where 1d 
                   stands for a spatial resolution of 1 degree in both latitude
                   and longitude.
YYYY               is the four-digit year from 1982 to 1998.
mm00               is the two-digit month from 01 to 12.


This data set also includes files that contain estimates of the reflectance of the 
soil/litter background in both visible and Near-Infrared wavelengths. These files 
are named "bkgrd_refl_vis_1d.asc" and "bkgrd_refl_nir_1d.asc", respectively. 
Each of these files has two additional files associated with them that show the 
differences between the original land/water mask used with the data and the 
land/water mask used in this ISLSCP Initiative II Data Collection. Files named 
"bkgrd_refl_yyy_1d.dif" are called ÔdifferencesÕ files and contain any points 
that have either been added or removed from the original data because of a 
mismatch with the ISLSCP II land/water mask. Files named 
"bkgrd_refl_yyy_1d_changemap.asc" are ASCII gridded maps that show the 
differences between the land/water boundaries of the original soil/litter 
reflectance files and the ISLSCP Initiative II land/water mask. For all of these 
files "yyy" can denote either nir or vis. Note also that the differences files and 
"change" maps are not available for the snow-free albedo data set.

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ASCII File Format
------------------
All of the files in the ISLSCP Initiative II data collection are in the ASCII, or 
text format. The file format consists of numerical fields of varying length, which 
are delimited by a single space and arranged in columns and rows. All values in 
these files are written as real numbers. Water bodies are assigned the value of 
-99 while missing data are over land are assigned the value of -88. Permanent Ice 
is assigned the value of -77 on the Snow-Free albedo fields. The files in this 
data set contain exactly 360 columns by 180 rows.

The soil/litter reflectance ASCII map files (with the extension of ".asc") have 
all had the ISLSCP II land/water mask applied to them. All points removed from the 
original files are stored in "differences" files (with the extension ".dif"). 
These ASCII files contain the Latitude and Longitude location of the cell-center 
of each removed point, and the data value at that point. At the bottom of these 
files are also a list of all points added to the file through "nearest neighbor 
averaging" interpolation (see documentation), where the land/water mask indicated 
land but there was no data in the original file. There is also a column called 
"Interpolation_Level" that contains the number of times the interpolation routine 
was run to get a value for that point. The higher the number, the less reliable 
the value is. There is one ".dif" file for each ASCII map file.

The "change map" files show the results of applying the land/water mask to the 
original soil/litter reflectance files, as a viewable ASCII map: all points added 
(positive number, containing the "Interpolation_Level", see above), all points 
unchanged ("0"), and all points removed ("-1"). There are no differences files or 
change maps for the Snow-Free albedo fields.

All files are gridded to a common equal-angle lat/long grid, where the coordinates 
of the upper left corner of the files are located at 180oW, 90oN and the lower 
right corner coordinates are located at 180oE, 90oS. Data in the files are ordered 
from North to South and from West to East beginning at 180 degrees West and 90 
degrees North.