How Strongly Are Mean and Extreme Precipitation Coupled?

• Published in: Geophysical research letters 2021-05, Vol.48 (10), p.n/a
• Main Authors: Nishant, Nidhi, Sherwood, Steven C.
• Format: Article
• Language: English
• Subjects: extreme precipitation; future projections; mean precipitation; regional climate modeling
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL092075

Changes in mean and extreme precipitation are among the most important consequences of climate change. Here, we examine the relationship between the mean and three different measures of extreme precipitation over Australia, from a regional climate model (RCM) ensemble. We show that model uncertainty in mean and extreme precipitation are tightly coupled for both the present‐day climate and future changes. On the continental scale, strong correlations (0.79–0.99) are observed across models between the changes in mean and extreme precipitation. We also find that except in eastern coastal regions, precipitation statistics projected by RCM are highly predictable (up to 60%–70% of variance explained) from the mean precipitation of the global climate model (GCM) providing the boundary conditions. In coastal locations where RCMs are more accurate than GCMs for the present climate, they are less predictable, hence provide information—but this impact disappears for climate change, suggesting that improved present‐day accuracy may not carry over to climate change. Plain Language Summary In this study, we report a surprisingly strong relationship between the mean and extremes in predicted precipitation at the regional scale in Australia, which applies to both the present‐day climate and future changes from global warming. That is, if one knew the change in mean precipitation (which is currently not well known), this would substantially narrow the uncertainty in the extremes. We also show that forecasts using detailed regional climate models end up depending mainly on what happens to the mean precipitation in the driving global climate models, which is determined by global drivers and responses. This result affects how climate change data are interpreted, and how we should focus climate research in the future. Key Points Model spread in precipitation extremes over Australia is strongly related to spread in mean precipitation on the continental scale Precipitation statistics projected by a regional modeling system are highly predictable from the mean precipitation of the global model Improved projections of regional extreme precipitation require better simulations of changes in the atmospheric general circulation