Spatiotemporal variation of snow depth in the Northern Hemisphere from 1992 to 2016

Abstract. Snow cover is an effective indicator of climate change due to its impact on regional and global surface energy and water balance, and thus also weather and climate, hydrological processes and water resources, and the ecosystem as a whole. The overall objective of this study is to investigate changes and variations of snow depth and snow mass over the Northern Hemisphere from 1992 to 2016. We developed a long term Northern Hemisphere daily snow depth and snow water equivalent product (NHSnow) by applying the support vector regression snow depth retrieval algorithm, using passive microwave remote sensing data from the period. NHSnow product was evaluated along with the other two snow cover products (GlobSnow and ERA-Interim/Land) for its accuracy across the Northern Hemisphere. The evaluation results show that NHSnow performs comparably well with relatively high accuracy (bias: −0.59 cm, mean absolute error: 15.12 cm, and root mean square error: 20.11 cm) when benchmarked against the station snow depth measurements. Further analyses were conducted across the Northern Hemisphere using snow depth, snow mass, and snow cover days as indices. Analysis results show that annual average snow mass have a significant declining trend, with a rate of about 19.72 km³ yr.⁻¹ or a 13 % reduction in snow mass. Although spatial variation pattern of snow depth and snow cover days exhibited slight regional differences, they generally reveal the decreasing trend over the most area of the Northern Hemisphere. Our work provides evidence that rapid changes in snow depth and snow mass are occurring since the beginning of the 21st century, accompanied by dramatic climate warming.