PNNL

Abstract

Winter storms are responsible for billion-dollar economic losses in the western US. As storm structures are not well resolved by global climate models, event-scale storm response to warming has not been well established. Here regional storm-resolving simulations are used to investigate climate change impact on western US winter storms. In mid-century under a high emissions scenario, precipitation volume from the top 20% of winter storms is projected to increase by up to 40% across the region. Increased area coverage and storm intensity explain 69% and 60% of this increase, respectively, while a robust sharpening of future storms with larger increase in storm center precipitation than increase in storm area offsets the increase by 31%. Ignoring the changing area-intensity relationship due to storm sharpening could overestimate the watershed design storms by up to 10% or 7-75mm across the western US. Future storm structural changes have broad infrastructure, hydrological, and ecological implications.