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Snow and climate interactions
The snow cover is a key component of the climate system. Over large areas of the Northern Hemisphere and in mountains areas, it plays a major role in many physical, chemical and biological processes affecting the water cycle and many ecosystems. Due to its unique radiative and thermal properties, the snow cover is a clear source of positive feedbacks in the climate system. Consequently, it acts at once as a very sensitive indicator and a driver of climate change. The snow cover exhibits a high interannual variability. Any analysis of its climatological characteristics and trends requires reliable historical gridded data. Satellite observations provide reliable series of the snow cover extent over the Northern Hemisphere but they do not cover more than the past 5 decades and they still cannot provide accurate estimations of the snow water equivalent without using ground-based observations and making assumptions on snow density.
New approaches have been recently developed for reanalysing historical meteorological conditions over the past 150 years, using mainly the historical observations of sea level pressure. Using these historical meteorological reanalyses for forcing snow models makes it possible to reconstruct many characteristics of the snow conditions which prevailed before the satellite era at the global scale. Recent literature provides various examples of the potential and performance of such approaches.