A projection of changes in landfalling atmospheric river frequency and extreme precipitation over western North America from the Large Ensemble CESM simulations

TitleA projection of changes in landfalling atmospheric river frequency and extreme precipitation over western North America from the Large Ensemble CESM simulations
Publication TypeJournal Article
Year of Publication2016
JournalGeophysical Research Letters
Volumeearly online
Date Published02/2016
Abstract / Summary

Simulations from the Community Earth System Model (CESM) Large Ensemble project are analyzed to investigate the impact of global warming on atmospheric rivers (ARs) making landfall in western North America. The model has notable biases in simulating the subtropical jet position and the relationship between extreme precipitation and moisture transport. After accounting for these biases, the model projects an ensemble mean increase of 35% in the number of landfalling AR days between the last 20 years of the twentieth and 21st centuries under Representative concentration pathway 8.5 (RCP8.5). However, the associated extreme precipitation days increase only by 28% because the moisture transport required to produce extreme precipitation also increases with warming. Internal variability introduces an uncertainty of ±8% and ±7% in the changes in AR days and associated extreme precipitation days compared to only about 1% difference from accountings for model biases. The significantly larger mean changes compared to internal variability, and effects of model biases highlight the robust AR responses to global warming.

URLhttp://onlinelibrary.wiley.com/wol1/doi/10.1002/2015GL067392/abstract
DOI10.1002/2015GL067392
Journal: Geophysical Research Letters
Year of Publication: 2016
Volume: early online
Date Published: 02/2016

Simulations from the Community Earth System Model (CESM) Large Ensemble project are analyzed to investigate the impact of global warming on atmospheric rivers (ARs) making landfall in western North America. The model has notable biases in simulating the subtropical jet position and the relationship between extreme precipitation and moisture transport. After accounting for these biases, the model projects an ensemble mean increase of 35% in the number of landfalling AR days between the last 20 years of the twentieth and 21st centuries under Representative concentration pathway 8.5 (RCP8.5). However, the associated extreme precipitation days increase only by 28% because the moisture transport required to produce extreme precipitation also increases with warming. Internal variability introduces an uncertainty of ±8% and ±7% in the changes in AR days and associated extreme precipitation days compared to only about 1% difference from accountings for model biases. The significantly larger mean changes compared to internal variability, and effects of model biases highlight the robust AR responses to global warming.

DOI: 10.1002/2015GL067392
Citation:
2016.  "A projection of changes in landfalling atmospheric river frequency and extreme precipitation over western North America from the Large Ensemble CESM simulations."  Geophysical Research Letters early online.  https://doi.org/10.1002/2015GL067392.