This data set provides a global distribution of nine subgrid snow-depth-variability categories and a coefficient of variation applicable to each category, as the result of the Subgrid SNOW Distribution (SSNOWD) submodel that defines subgrid snow-depth and snow-cover variability. This data set provides the distribution of those nine categories and their coefficient-of-variation values on a global, 2.5 arc-min latitude-longitude (approximately 5-km) grid. The time period covered is 1 January 1994 through 1 January 2004.
The SSNOWD submodel was formulated to improve the depiction of autumn through spring land-atmosphere interactions and feedbacks within global weather, climate, and hydrologic models. From both atmospheric and hydrologic perspectives, the subgrid snow-depth distribution is an important quantity to account for within large-scale models. In the natural system, these subgrid snow-depth distributions are largely responsible for the mosaic of snow-covered and snow-free areas that develop as the snow melts, and the impacts of these fractional areas must be quantified in order to realistically simulate grid-averaged surface fluxes. SSNOWD's formulation incorporates observational studies showing that snow distributions can be described by a lognormal distribution and the snow-depth coefficient-of-variation (CV). Using an understanding of the physical processes that lead to these observed snow-depth variations, a global distribution of nine subgrid snow-depth-variability categories was developed, and coefficient-of-variation values were assigned to each category based on published measurements.
Data are in binary format, and are available via NCAR.
Liston, Glen E. 2005. Global Snow-Water Equivalent Depth Coefficient-of-Variation Classification. Boulder, CO: National Center for Atmospheric Research, ARCSS Data Archive.
| Category | Description |
|---|---|
| Data format | 2-byte binary integers |
| Spatial coverage and resolution | Global; 2.5 arc-min latitude-longitude (approximately 5 km). |
| Temporal coverage and resolution | Winter, from 01 January 1994 through 01 January 2004 |
| File size | Files range in size from 1 KB to 214 KB. |
| Parameter(s) | Snow cover, snow melt, snow-water equivalent |
| Procedures for obtaining data | Data are available for ordering through NCAR. |
1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information
Glen E. Liston
Department of Atmospheric Sciences
Colorado State University
Fort Collins, CO 50523-1371 USA
The National Science Foundation (NSF) Geography and Regional Sciences and Arctic System Science (ARCSS) programs funded the data project. The following grants apply:
National Science Foundation Grant OPP 9415386: The Role of Snow Cover and its Distribution in Governing Heat and Mass Exchange in the Arctic.
National Science Foundation Grant OPP 0229973: Winter Precipitation, Sublimation, and Snow-Depth in the Pan-Arctic: Critical Processes and a Half Century of Change.
National Science Foundation Grant OPP 9732077: Snow, Shrubs and Weather: Winter Pathways of Change in the Arctic..
This data set provides a global distribution of nine subgrid snow-depth-variability categories, as the result of the Subgrid SNOW Distribution (SSNOWD) submodel that defines subgrid snow-depth and snow-cover variability. These categories apply to land areas; water and sea ice areas are excluded from the category system.
The data consist of two-byte binary integers. This data set is a single, global, two-dimensional array on a latitude-longitude grid, with a 2.5 arc-minute (approximately 5-km) grid increment.
The data indicate the nine snow-depth-variability categories. These categories have values of 1 through 9 over all land. All water grid cells have been given an undefined value of -9999.
The snow cover categories, the integer value assigned to each category, and the coefficient of variation (CV) assigned to each category are as follows:
Category |
General description |
CV value |
|---|---|---|
1 |
Ephemeral snow |
0.06 |
2 |
Mid-latitude, non-mountainous forest |
0.09 |
3 |
High-latitude, non-mountainous forest |
0.12 |
4 |
High-latitude, mountainous forest |
0.17 |
5 |
Arctic tundra |
0.40 |
6 |
Mid-latitude, prairie |
0.50 |
7 |
Mid-latitude, mountainous forest |
0.60 |
8 |
High-latitude, mountains |
0.70 |
9 |
Mid-latitude, treeless mountains |
0.85 |
The data set consists of four files. The files include a FORTRAN routine ("ssnowd_cv_classes.f") that when compiled, will extract the data. When compiled, a text file is output that includes a text header with additional descriptive information about the data structure.
File sizes range from 1 KB to 214 MB.
The spatial coverage of the classification system is global, but applies to only land. All water grid cells have been given an undefined value of -9999.
Southernmost Latitude: 90.00 S
Northernmost Latitude: 90.00 N
Westernmost Longitude: 180.00 W
Easternmost Longitude: 180.00 E
Data are on a 2.5 arc-min latitude-longitude grid (0.041666667 degree; approximately 5-km).
The grid defines 8640 grid points in the W-E (x) direction, with the first grid point starting at -179.97916666666667 degree and incrementing by 0.041666667 degree. There are 4320 grid points in the S-N (y) direction, with the first grid point starting at -89.97916666666667 degree and incrementing by 0.041666667 degree. In other words, the center of the lower left grid cell is located at -179.97916666666667 degrees longitude, and -89.97916666666667 degrees latitude, and the grid increment is 2.5 arc-minute (0.041666667 degree; approximately 5-km).
Data reflect conditions during winter, from 01 January 1994 through 01 January 2004.
Snow cover, snow melt, snow-water equivalent
Data are available for ordering through NCAR.
The data set includes a FORTRAN routine ("ssnowd_cv_classes.f") for extracting the data.
The classification categories and the corresponding coefficient-of-variation values are based on the Subgrid SNOW Distribution (SSNOWD) submodel that defines subgrid snow-depth and snow-cover variability. Snow depths vary greatly at subgrid scales; the SSNOWD model was formulated to account for subgrid snow distributions by defining nine snow-distribution categories. The nine categories are based on factors that influence snow-depth variability: air temperature, topographic variability, and wind speed. The coefficient of variation (CV, equal to the ratio of the standard deviation to the mean of the snow variation) defines the variability of snow distribution for each category. The theory of measurements and CV values are described in detail in the following published article about this data set:
Liston, G. E. 2004. Representing subgrid snow cover heterogeneities in regional and global models. Journal of Climate 17(6): 1381-97.
Categories were mapped to the grid using global distributions of air temperature, topographic variability, and wind speed from several data sets. Specific coefficient-of-variation values were assigned to each of the SSNOWD categories based on published snow-distribution measurements; see Liston (2004) for a discussion of the CV values.
Liston, G. E. 2004. Representing subgrid snow cover heterogeneities in regional and global models. Journal of Climate 17(6): 1381-97.
See also Global Seasonal Snow Classification System
20 January 2005
http://data.eol.ucar.edu/codiac/dss/id=106.ARCSS138