Layer Abstract

Hall, D.K., G.A. Riggs, and V.V. Salomonson. 2006, updated daily. MODIS/Terra snow cover daily L3 global 0.05deg CMG V005. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media. Available at http://nsidc.org/data/mod10c1.html. Background: This data set consists of 7200 columns by 3600 rows of global arrays of cloud cover in a 0.05 degree Climate Modeling Grid (CMG). MODIS snow cover data are based on a snow mapping algorithm that employs a Normalized Difference Snow Index (NDSI) and other criteria tests. The amount of snow observed in a CMG cell is based on the cloud-free observations mapped into the CMG grid cell for all land in that cell. Snow and cloud discrimination techniques are based on differences between cloud and snow/ice reflectance and emittance properties. Clouds typically have high reflectance in visible and near-infrared wavelengths, while reflectance of snow decreases in near-infrared wavelengths. Only pixels having a daylight, clear-sky view of the land surface are analyzed for snow. The NDSI can generally separate snow from most obscuring cumulus clouds, but it cannot always discriminate optically-thin cirrus clouds from snow. Instead, clouds are masked using data from the MODIS Cloud Mask data product (MOD35_L2). If the cloud mask algorithm was not applied to a MOD10_L2 pixel, the snow algorithm proceeds while assuming that the pixel is unobstructed by cloud. V005 data uses the summary cloud result field and the unobstructed field-of-view flag from MOD35_L2 to generate a single cloud mask for the snow algorithm. In some cases, MOD35_L2 identifies snow as clouds, which prevents the snow algorithm from mapping true snow extent.

Server Abstract

This map server from the National Snow and Ice Data Center (NSIDC) provides cryospheric data and information pertinent to the Northern Hemisphere. Map images and source data are provided through Open Geospatial Consortium, Inc. (OGC) protocols (WMS, WFS, and WCS). For other related OGC data sets from NSIDC, see also the Atlas of the Cryosphere at: http://nsidc.org/data/atlas/. If you have questions, comments or suggestions, please contact NSIDC User Services at +1.303.492.6199 or nsidc@nsidc.org.

Keywords

Arctic Cryosphere Earth Science Northern Hemisphere Polar earth science Atmosphere Clouds

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