The EuroClim products include sea ice concentration, land snow cover, and snow temperature at the surface.

The sea ice concentration (SIC) parameter is the fraction of sea surface covered by sea ice. Different sensors and methods can be used to map this fraction, but due to the Arctic climate (dark in winter, cloudy most of the year) microwave sensors are used in preference to optical sensors. In the latest version of EuroClim, SSM/I passive microwave data are used. Data are taken from NSIDC in the form of daily brightness temperature values for the current SSM/I satellite
(DMSP F13).

The snow cover area (SCA) parameter refers to the fraction of land cover by snow. Different sensors and methods can be used to map this fraction also. In the current version of EuroClim, AVHRR data are used together with ground observations from meteorological observing stations.

The optical AVHRR sensor is used to distinguish between clouds, snow and snow free land. The method therefore relies on cloud free conditions. The classification algorithm determines if each pixel over land is cloudy, snow covered or snow free. The fraction of snow is therefore 0 or 1.

The ground observations give the snow cover at about 500 stations scattered all over Norway. These are interpolated to each AVHRR pixel using a Digital Elevation Model (DEM), so that each pixel over Norway is given a snow fraction of 0 or 1. The AVHRR and interpolated observation fields are then compared and merged into the final product.

The snow temperature surface (STS) parameter refers to the surface temperature of the snow cover. It can be observed by means of remote sensing in the thermal domain. The polar atmospheres are not very well known, but a few algorithms exist for retrieval of snow surface temperature. These EuroClim products use Key’s algorithm (Key et al. 1997), which is calibrated for AVHRR and MODIS data.