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ISLSCP Initiative II Home General Data Overview Vegetation Data Overview |
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ISLSCP Initiative II |
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Vegetation Data
The AVHRR (Advanced Very High Resolution Radiometer) Albedo/BRDF (Bidirectional Reflectance Distribution Function) Products provide measures of clear sky surface albedo and BRDF model parameters for two months in 1995 (representing the northern hemisphere winter and summer). BRDF parameters, white-sky albedo (bihemispherical reflectance) and black-sky albedo (directional hemispherical reflectance) at local solar noon are generated for three broad bands. Since black-sky albedo represents the direct beam contribution while white-sky represents the completely diffuse contribution, these measures can be linearly combined as a function of the fraction of diffuse skylight (itself a function of optical depth) to provide an actual or instantaneous albedo at local solar noon.
Data Provider: Alan H. Strahler, Crystal L.B. Schaaf, Elena Tsvetsinskaya
 Data Files (ISLSCP II Disc #1) |
 Data Set Documentation |
 Image Viewing Tutorial |
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. The files at different spatial resolutions each contain the following numbers of column and rows:
One degree: 360 columns by 180 rows
1/2 degree: 720 columns by 360 rows
1/4 degree: 1440 columns by 720 rows
All values are written as floating point values. Missing values are assigned the value of -99 on all data layers. 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 180°W, 90°N and the lower right corner coordinates are located at 180°E, 90°S. Data in the files are ordered from North to South and from West to East beginning at 180 degrees West and 90 degrees North. The data files are PKZip compressed.
The data files fall into the following categories:
| Black Sky Albedo (BSA) | Black-sky albedo derived from AVHRR data from 1995. Albedo is the fraction of incident solar radiation that a surface reflects -- in this case under entirely direct solar illumination conditions. |
| White Sky Albedo (WSA) | Albedo White-sky albedo derived from AVHRR data from 1995. Albedo is the fraction of incident solar radiation that a surface reflects -- in this case under entirely diffuse solar illumination conditions. |
| BRDF parameters (BRDF) | Three BRDF Model Parameters (isotropic, volumetric and geometric) derived from AVHRR data from 1995. |
Related Pages:
ISLSCP Initiative II Home
General Data Overview
Vegetation Data Overview
AVHRR Albedo and BRDF from 1995
Revision Date: October 8, 2004