Sharpening of cold-season storms over the western United States

How the spatial structures of large storms will change is not well resolved in most climate models. Here the authors use high-resolution models to show that winter storms become sharper under warming because precipitation in the storm centre increases more strongly than the storm area. Winter storms are responsible for billion-dollar economic losses in the western United States. Because storm structures are not well resolved by global climate models, it is not well established how single events and their structures change with warming. Here we use regional storm-resolving simulations to investigate climate change impact on western US winter storms. 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 by mid-century. The average increase in precipitation volume (31%) is contributed by 22% from increasing area coverage and 19% from increasing storm intensity, while a robust storm sharpening with larger increase in storm centre precipitation compared with increase in storm area reduces precipitation volume by 10%. Ignoring storm sharpening could result in overestimation of the changes in design storms currently used in infrastructure planning in the region.

Automated summary

The spatial structures of large storms are not well understood in most climate models. Using high-resolution models, the authors demonstrate that winter storms become sharper under warming, with precipitation in the storm center increasing more than the storm area. Winter storms lead to significant economic losses in the western US. Ignoring storm sharpening could overestimate changes in design storms used in infrastructure planning.