Large discrepancy between measured and remotely sensed snow water equivalent in the northern Europe and western Siberia during boreal winter

Accurate information on snowpack conditions is crucial for understanding changes in the hydrological cycle and its impacts on the climate system, especially at the middle and high latitudes. Two satellite-derived products that cover Eurasia from 1979 to 2006, i.e., the snow water equivalent (SWE) data provided by the National Snow and Ice Data Center (NSIDC; SWENSIDC) and the GlobSnow dataset provided by the Finnish Meteorological Institute (FMI) (SWEGS) are selected for examination in the present study. The performances of these datasets in representing snowpack conditions are evaluated by comparing the datasets with the observations of snow depth (SD) recorded in the Historical Soviet Daily Snow Depth (HSDSD; SDHSDSD) dataset. The results indicate that the SWEGS dataset is more consistent with the SDHSDSD dataset over northern Eurasia than the SWENSIDC dataset. In particular, the SWENSIDC dataset exhibits large discrepancies in northern Europe and western Siberia (NE-WS), indicating problems or even errors in the SWENSIDC dataset. Based on snow formation criteria (e.g., temperature and precipitation), we further explore and confirm the existence of problems in the SWENSIDC dataset. These problems may be associated with the retrieval method used to generate this dataset; this method is based on a static algorithm. Our findings suggest that satellite-derived SWE datasets (e.g., SWENSIDC) should be used with caution when investigating the impacts of snow in different research fields (e.g., climatology, hydrology, and ecology).