Understanding snow conditions in Japanese Mountains through a quarter century of insights

Japan features a wide variety of snow environments, with significant differences in snow distribution based on region and elevation. The effects of ongoing climate change are expected to alter snow conditions significantly, highlighting the need for a comprehensive understanding of these changes and their implications.

Meteorological observation sites managed by the Japan Meteorological Agency are predominantly concentrated in low-altitude areas, with only a limited number in high-altitude regions. Consequently, the lack of long-term and spatially extensive observational data has hindered the quantitative understanding of snow conditions in Japan's mountainous regions. To address this gap, the Snow and Ice Research Center (SIRC) of the National Research Institute for Earth Science and Disaster Resilience has operated a Snow and Weather Observation Network for over 25 years. This network spans a wide area, from northern to western Japan, monitoring meteorological and snow conditions fluctuations at high elevations. This study utilizes the long-term data collected through the network to analyze trends in snow conditions across Japan's mountainous regions. Particular emphasis is placed on examining the variation characteristics of maximum snow depth and maximum snow water equivalent, including their differences, elevation dependencies, and contrasts between mountainous and flat areas.

Our results indicate that although the trends in maximum snow depth and maximum snow water equivalent are generally consistent, the variability in maximum snow water equivalent is greater than that of maximum snow depth. Additionally, the variation in maximum snow depth shows a distinct dependence on elevation, with different trends observed in mountainous and flat regions. These findings enhance our understanding of the effects of climate change on Japan's snow environments and provide essential insights for improving future projections of snow conditions, as well as for developing strategies to mitigate snow-related disasters.