Spatial patterns of extreme precipitation and their changes under ~ 2 °C global warming: a large-ensemble study of the western USA

• Published in: Climate dynamics 2022-10, Vol.59 (7-8), p.2363-2379
• Main Authors: Rupp, David E., Hawkins, Linnia R., Li, Sihan, Koszuta, Matthew, Siler, Nicholas
• Format: Article
• Language: English
• Subjects: Annual precipitation; Climate change; Climate models; Climatology; Daily precipitation; Distribution; Earth and Environmental Science; Earth Sciences; Extreme values; Extreme weather; Geophysics/Geodesy; Global climate; Global climate models; Global warming; Influence; Mountains; Oceanography; Plateaus; Precipitation; Precipitation distribution; Precipitation variability; Shape; Slopes; Spatial variability; Spatial variations; Tails; Valleys; Variability
• ISSN: 0930-7575; 1432-0894
• DOI: 10.1007/s00382-022-06214-3

Extreme precipitation events are expected to increase in magnitude in response to global warming, but the magnitude of the forced response may vary considerably across distances of ~ 100 km or less. To examine the spatial variability of extreme precipitation and its sensitivity to global warming with high statistical certainty, we use a large (16,980 years), initial-condition ensemble of dynamically downscaled global climate model simulations. Under approximately 2 °C of global warming above a recent baseline period, we find large variability in the change (0 to > 60%) of the magnitude of very rare events (from 10 to 1000-year return period values of annual maxima of daily precipitation) across the western United States. Western (and predominantly windward) slopes of coastal ranges, the Cascades, and the Sierra Nevada typically show smaller increases in extreme precipitation than eastern slopes and bordering valleys and plateaus, but this pattern is less evident in the continental interior. Using the generalized extreme value shape parameter to characterize the tail of the precipitation distribution (light to heavy tail), we find that heavy tails dominate across the study region, but light tails are common on the western slopes of mountain ranges. The majority of the region shows a tendency toward heavier tails under warming, though some regions, such as plateaus of eastern Oregon and Washington, and the crest of the Sierra Nevada, show a lightening of tails. Spatially, changes in long return-period precipitation amounts appear to partially result from changes in the shape of the tail of the distribution.