Revision date: November 20, 2009

Summary:

This data set contains monthly average snow-free surface shortwave albedo calculated for the period 1982-1998 and estimates of background soil/litter reflectances in the visible (0.4-0.7 μm) and near-infrared (NIR) (0.7-1.0 μm) wavelengths. Biophysical Parameters derived from the FASIR-NDVI (Fourier Adjusted, Solar zenith angle correction, Interpolation, and Reconstruction of Normalized Difference Vegetation Index) data set (Sietse, 2010) developed for the ISLSCP Initiative II data collection for the months of January 1982 through December 1998 were used to calculate monthly mean surface albedos at 1 X 1 degree spatial resolution for vegetated land surfaces (Sellers et al, 1996b) for the wavelength interval from 0.4 to 3.0 µm. The instantaneous albedo is a function of the properties of the land surface and the solar zenith angle. The monthly mean albedo is an average weighted over time weighted by the incident radiation. NDVI data are used to generate the biophysical parameters leaf area index (LAI) and green fraction of vegetation (Greenness) used by the canopy radiative transfer model of the Simple Biosphere (SiB2) model (Sellers et al, 1996a), which computes the instantaneous albedo. This is coupled to the Colorado State University (CSU) General Circulation Model (GCM) (Randall et al, 1989) which integrates the SiB2 radiative transfer through time. The incident radiation for weighting the time-averaged albedo was provided by a previous run of the GCM using the atmospheric radiation parameterization of Harshvardhan et al (1987). The Harshvardhan parameterization estimates radiative transfer through the atmosphere in both the longwave and shortwave bands, including the effects of cloudiness and water vapor, carbon dioxide and ozone. The shortwave radiation distinguishes between the direct and diffuse components of the solar beam.

This data sets contains two *.zip files, the first file when extrapolated contains 204 *.asc files in standard ESRI ArcInfo ASCII GRID format, 12 monthly average snow-free surface shortwave calculated albedo files for the years 1982 through 1998. The second zip file when extrapolated, contains 6 files, four *.asc files and two *.dif files of estimates of the reflectance of the soil/litter background in both visible and Near-Infrared wavelengths, a change map for each, and differences after the ISLSCP II land/water mask was applied.

Additional Documentation

This data set is one of the products of the International Satellite Land-Surface Climatology Project, Initiative II (ISLSCP II) data collection which contains 50 global time series data sets for the ten-year period 1986 to 1995. A complete description of the data, their derivation, acknowledgements, and references provided by the ISLSCP II Data Management Staff is included with this data set as a companion file named 1_snowfree_albedo_doc.pdf.

ISLSCP II is a consistent collection of data sets that were compiled from existing data sources and algorithms, and were designed to satisfy the needs of modelers and investigators of the global carbon, water and energy cycle. The data were acquired from a number of U.S. and international agencies, universities, and institutions. The data and documentation have undergone two peer reviews.

ISLSCP is one of several projects of Global Energy and Water Cycle Experiment (GEWEX) [http://www.gewex.org/] and has the lead role in addressing land-atmosphere interactions -- process modeling, data retrieval algorithms, field experiment design and execution, and the development of global data sets.

 

Data Citation:

Cite this data set as follows:

Dazlich, D.A. and S.O. Los. 2009. ISLSCP II Monthly Snow-Free Albedo, 1982-1998, and Background Soil Reflectance. In Hall, Forrest G., G. Collatz, B. Meeson, S. Los, E. Brown de Colstoun, and D. Landis (eds.). ISLSCP Initiative II Collection. Data set. Available on-line [http://daac.ornl.gov/] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. doi:10.3334/ORNLDAAC/956

 

Data Description:

The archived data sets for ISLSCP II have been organized by categories. This data set is in the vegetation category--a collection of vegetation and albedo data sets.

Data Set Spatial Extent: Global gridded

Western most Longitude: -180 W

Easternmost Longitude: 180 E

Northernmost Latitude: 90N

Southernmost Latitude: -90S

Projection: Geographic

Data Set Spatial Resolution: 1 degree in both latitude and longitude

Data Set Temporal Extent: January 1982 through December 1998

Data Set Temporal Resolution:Synoptic months

 

Data File Format

All of the data files in each data set within the ISLSCP Initiative II data collection are in ESRI ASCII GRID format for ArcInfo. The snow-free albedo files consist of numerical fields of varying length, which are delimited by a single space and arranged in columns and rows. The files in this data set are on a 1 degree by 1 degree grid and contain 360 columns by 180 rows. All files are gridded to a common equal-angle lat/long grid.

This data set also includes files that contain estimates of the reflectance of the soil/litter background in both visible and Near-Infrared wavelengths:

bkgrd_refl_vis_1d.asc, bkgrd_refl_vis_1d_changemap.asc

bkgrd_refl_nir_1d.asc, bkgrd_refl_vis_1d_changemap.asc

The data files have been combined for background and snow-free albedo measurements:

* background_refl_1deg.zip

*snowfree_albedo_1deg.zip

 

Data Values:

All values are written as floating point values.

Missing values are assigned the value of -99.0000 on all data layers.

Missing values over land are assigned the value of -88.0000

Permanent ice in the Snow-Free albedo fields is -77.0000

Data file naming conventions are described in the 0_snowfree_albedo_readme.txt

 

Data Access:

These data are available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC)  [http://daac.ornl.gov].

Data Archive Contact Information:

E-mail: uso@daac.ornl.gov
Telephone: +1 (865) 241-3952

 

References:

Sietse, O.L. 2010. ISLSCP II FASIR-adjusted NDVI Biophysical Parameter Fields, 1982-1998. In Hall, Forrest G., G. Collatz, B. Meeson, S. Los, E. Brown de Colstoun, and D. Landis (eds.). ISLSCP Initiative II Collection. Data set. Available on-line [http://daac.ornl.gov/] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A.

Sellers, P.J., D.A. Randall, C.J. Collatz, J.A. Berry, C.B. Field, D.A. Dazlich, C. Zhang, and C.D. Collelo, 1996a. A revised land surface parameterization (SiB2) for atmospheric GCMs. Part 1: Model formulation. Journal of Climate, 9, 676-705. doi:10.1175/1520-0442(1996)009<0676:ARLSPF>2.0.CO;2

Sellers, P.J., S.O. Los, C.J. Tucker, C.O. Justice, D.A. Dazlich, G.J. Collatz, and D.A. Randall, 1996b. A revised land surface parameterization (SiB2) for atmospheric GCMs. Part 2: The generation of global fields of terrestrial biophysical parameters from satellite data. Journal of Climate, 9, 706-737. doi:10.1175/1520-0442(1996)009<0706:ARLSPF>2.0.CO;2

Randall, D.A., Harshvardhan, D.A. Dazlich, and T.G. Corsetti, 1989. Interactions among radiation, convection, and large-scale dynamics in a general circulation model. J. Atmos. Sci., 46:1943-1970. doi:10.1175/1520-0469(1989)046<1943:IARCAL>2.0.CO;2

Harshvardhan, R. Davies, D.A. Randall, and T.G. Corsetti, 1987. A fast radiation parameterization for general circulation models. J. Geophys. Res., 92:1009-1016. doi:10.1029/JD092iD01p01009