Revision date: December 01, 2009

Summary:

This data set contains a monthly climatology of broadband surface albedos for use in global numerical weather prediction models at the National Centers for Environmental Prediction (NCEP). Monthly means of clear-sky, surface, broadband, snow-free albedos for overhead sun illumination angle were determined using data from a five-year period from April 1985-December 1987 and January 1989-March 1991. The data set is compatible in temporal coverage and spatial resolution with a monthly climatology of green vegetation fraction (Gutman and Ignatov, 1998) delivered earlier and currently in use at NCEP.

Three zip files are provided at three spatial resolutions of quarter, half and one degree, each containing 12 data files in standard ESRI ArcGIS ArcInfo Grid format, and 12 data files in ASCII format denoting defifferences between the original data set and the ISLSCP II land/sea mask.

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. Selected data sets span even longer periods. 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_noaa_albedo_5yr-av_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:

Csiszar, I.A. 2009. ISLSCP II NOAA 5-year Average Monthly Snow-free Albedo from AVHRR. 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/959

 

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: 0.25, 0.5 and 1.0 degree in both latitude and longitude

Data Set Temporal Extent: April 1985 through March 1991

Data Set Temporal Resolution: Monthly

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. All files are gridded to a common equal-angle lat/long grid. The files at different spatial resolutions each contain the following numbers of columns and rows:
     

* noaa_albedo_5year_1deg.zip: 360 columns by 180 rows

*noaa_albedo_5year_hdeg.zip: 720 columns by 360 rows

*noaa_albedo_5year_qdeg.zip: 1440 columns by 720 rows

The data files fall into the following categories:

1. noaa_albedo_5year_XX_mZZ.asc: 12 Gridded monthly albedo map files, where XX can be either "1d", "hd", or "qd" for spatial resolutions of 1.0 degree, 0.5 degree, or 0.25 degrees, respectively in both latitude and longitude. ZZ is the month from 01 to 12. Note that this albedo data set represents the monthly average using data from a five year period from April 1985 - December 1987 and January 1989 - March 1991.
2. noaa_albedo_5year_XX_mZZ.dif: ASCII tables of "differences", points in the original file that didn't match the ISLSCP-2 Land/Water mask, and were removed from or added to the ASCII map files.
3. noaa_albedo_5year_XX_chngmp.asc: Gridded ASCII map showing the differences between the ISLSCP2 land/water mask and the original data set.

Data Values:

All values are written as floating point values, expressed as a percent albedo, and the `change maps' are given as integer values ranging from -1 to 5.

Missing values over water are assigned the value of -99.0000.

Missing values over land (such as Greenland and Antarctica) are assigned the value of -88.0000.

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

 

References:

Gutman, G. and A. Ignatov, 1998: Derivation of green vegetation fraction from NOAA/AVHRR for use in numerical weather prediction models. Int. J. Remote Sensing 19, 1533-1543.

 

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