Data of the Along Track Scanning Radiometer (ATSR) aboard the ERS-2 Satellite and the Advanced ATSR (AATSR) aboard the Envisat Satellite were used to obtain a data set of the percentage snow cover fraction on land with a grid resolution of 0.01°. First, grid cells containing clouds, open water and glaciers are masked out. Then two approaches (one for steep topography, one for all other areas) are combined to derive the snow cover fraction in per cent for each cloud free grid cell. For details of the approaches see the Product Guide.
The snow cover fraction can be derived with daily temporal resolution taking all satellite overpasses of a certain grid cell within one day into account. However, persistent cloud coverage can cause widespread and long-duration gaps in the data set of the daily snow cover fraction. Therefore we primarily offer the monthly aggregated snow cover fraction. For this data set all satellite overpasses of a certain grid cell within an entire calendar month are taken into account to calculate an average monthly snow cover fraction. More details can again be found in the Product Guide and on the GlobSnow web page: http:www.globsnow.info. In contrast to the first version we now offer data of the two sensors ATSR and AATSR separately; they overlap from 05/2002 to 06/2003.
This is version v2.1 of this product. Note that the update from v2.0 to v2.1 is not yet complete; AATSR based data for 2002 are still from v2.0. The update was required because a reprocessed AATSR L1b data set was released.
Last data update: December 11 2014.