Regional Analysis of Snow Presence Trends in the Northern Hemisphere

Abstract This study presents a statistical analysis of snow-cover trends in the Northern Hemisphere using the Rutgers Northern Hemisphere 24 km Weekly Snow Cover Extent, September 1980 Onward, Version 1, data which observe either snow presence or absence at each cell in binary format. A quality control procedure is applied prior to trend assessment to identify problematic cells, which are excluded from further analysis. Of the cells studied over the Northern Hemisphere that meet the quality control requirements, 9.4% indicate a statistically significant positive trend, while 23.8% report a statistically significant negative trend, indicating a roughly 2.5:1 ratio of area with snow-cover declines relative to snow-cover increases. On a seasonal scale, there is a general positive trend in snow-covered area across the Northern Hemisphere beginning in August and peaking in early November, followed by negative trends beginning in March, reflecting a general shift toward earlier snowpack generation and melt. Regional analyses show this seasonal pattern is most prevalent across Europe and central Asia, which are also characterized by general negative trends in annual snow presence. Increasing trends are noted through central Canada and the northern Great Plains in the United States, although snow trends in all regions exhibit a clear local-scale influence from topographical patterns. Additionally, the southern border of the seasonal snow-cover extent shows significant decreasing trends in snow presence in most locations across the Northern Hemisphere. Significance Statement Snow presence is a key element of Earth’s radiation budget due to its high albedo and insulating effects, thereby playing a crucial role in large-scale atmospheric processes. Snow cover enhances Arctic climatic stability, and reduced snow-cover presence could facilitate large-scale releases of carbon and methane gas due to subsequent increases in temperature and exposure of permafrost. Quantification of trends in snow presence is, therefore, a crucial aspect of understanding global climatic change. This paper presents an analysis of snow-cover trends in the Northern Hemisphere by applying a statistical analysis capable of assessing trends in binary snow presence data to a recently released high-resolution data product. Weekly snow-cover presence over the 43-yr study period is analyzed.