[ACG52-P01] Increase in Rain-on-Snow events in Japan as projected by large ensemble of regional climate simulations
キーワード：雪上降水、気候変動、領域気候モデル、自己組織化マップ、気象パターン、洪水
The phenomenon of rainfall on snow is called a rain-on-snow (ROS) event that can cause severe snowmelt hazards such as river flooding, snow avalanches, full-scale avalanches, slope failure, landslides that have significant impacts on various sectors (ecosystem, water resources, risk management and flood forecast). This study investigated the influence of climate change on the frequency of ROS events during the winter season in Japan. Climate projections obtained from the database for Policy Decision-making for Future climate change (d4PDF) is used to investigate the climate change impacts. The projected future climate in the regional model simulations showed increase in the ROS events over Japan Alps (mountainous regions in central Japan) and Hokkaido (northern part of Japan) where the region will record still large snow amount in the future.
Self-organizing maps (SOMs) was applied using the surface atmospheric circulation to determine the dominant snowmelt related weather patterns (WPs). The SOMs showed that some WPs had a significant effect on the cause of ROS events. Additionally, the difference in the impacts of climate change between WPs was evaluated to understand the future changes in runoff and snowmelt associated with ROS events. The SOM analysis results suggest that the increase of ROS events in the future climate is attributed to the changes in dominant ROS-related WP (from cyclonic-type to cold-surge-type) corresponding with the variations in the freezing point line (region of the atmospheric layer at temperatures near 0 °C i.e., rain-snow transition layer). These findings can help inform water hazard/resource-management requirements to withstand regional climate change.
Self-organizing maps (SOMs) was applied using the surface atmospheric circulation to determine the dominant snowmelt related weather patterns (WPs). The SOMs showed that some WPs had a significant effect on the cause of ROS events. Additionally, the difference in the impacts of climate change between WPs was evaluated to understand the future changes in runoff and snowmelt associated with ROS events. The SOM analysis results suggest that the increase of ROS events in the future climate is attributed to the changes in dominant ROS-related WP (from cyclonic-type to cold-surge-type) corresponding with the variations in the freezing point line (region of the atmospheric layer at temperatures near 0 °C i.e., rain-snow transition layer). These findings can help inform water hazard/resource-management requirements to withstand regional climate change.