Global Snow Extent and Snow Depth

This file describes snow data available to our work group for use with macroscale model applications. Currently we have two datasets, Weekly Snow Cover and Sea Ice Extent and Global Monthly Snow Cover and Snow Depth.

Nimbus-7 SMMR Global Monthly Snow Cover and Snow Depth

This data set consists of monthly global snow cover and snow depths derived from Nimbus-7 SMMR data for October, 1978 through August, 1987. The SMMR data are interpolated for spatial and temporal gaps. Maps are based on six-day average brightness temperature data from the middle week of each month

Separate tar files for each year can be downloaded below. Each file contains maps of snow depth for each month.

• plds_snow78 (size 65063)
• plds_snow79 (size 237308)
• plds_snow80 (size 232222)
• plds_snow81 (size 235722)
• plds_snow82 (size 240089)
• plds_snow83 (size 238636)
• plds_snow84 (size 241882)
• plds_snow85 (size 239389)
• plds_snow86 (size 233990)
• plds_snow87 (size 161420)

Data Description:

Maps are at 1/2 degree latitude by 1/2 degree longitude resolution in polar stereographic projection. The maps have the following specifications:

• Latitude: 85S - 85N
• Longitude: 180W - 180E
• Columns: 720
• Rows: 341 (340 data, plus one 720-byte header)
• Data type: unsigned 8-bit integers

Grid elements may have the following values:

• 255: water
• 254: permanent ice
• 253: no data available, or data failed quality filters
• 252,251: unused
• 3-250: snow depth in centimeters
• 0: no snow, or snow less than 2.5 cm

README for an explanation of the high number of no data values coincident with snowmelt in mid-latitude regions.

Available Utilities:

The program get_nimbus.c can be used to extract monthly time series for two degree grid cells centered on the specified lat/lon. Disclaimer: This programs were written for my own personal use, as such there may be bugs!

Northern Hemisphere EASE-Grid Weekly Snow Cover

This data set provides snow cover extent for January, 1971 through August 1995. Snow cover extent is based on the digital NOAA-NESDIS Weekly Northern Hemisphere Snow Charts, originally derived from manual interpretation of AVHRR, GOES and other visible-band satellite data. The data are available on two cd-roms held in Wilcox 70B.

Data Description:

Data are provided at 25 km resolution in a Lambert equal-area azimuthal projection (NSIDC EASE - Grid). The north pole is aligned with the center of the pixel at column 361, row 361. The maps have the following specifications:

• Spatial coverage: northern hemisphere
• Columns: 721
• Rows: 721
• Radius of the earth: 6371.228 km
• Map scale: 25.0675 km
• Pixel area: 628.3795 sq. km.
• Data type: unsigned 8-bit integers

Grid elements may have the following values:

• 255: open ocean
• 254: "corner" pixels (outside Northern Hemisphere)
• 253: unclassifiable water due to mask mismatches
• 6-252: not used
• 5: QC snow, pixel set to snow via QC during regridding
• 4: QC ocean, pixel set to ocean via QC during regridding
• 3: QC sea ice, pixel set to sea ice via QC during regridding
• 2: sea ice
• 1: snow covered land
• 0: snow free land