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Projected Changes in Future Extreme Precipitation over the Northeast US in the NA-CORDEX Ensemble
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  • Robert Nazarian,
  • James Vizzard,
  • Carissa Agostino,
  • Nicholas Lutsko
Robert Nazarian
Fairfield University, Fairfield University, Fairfield University

Corresponding Author:rnazarian@fairfield.edu

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James Vizzard
Fairfield University, Fairfield University, Fairfield University
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Carissa Agostino
Fairfield University, Fairfield University, Fairfield University
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Nicholas Lutsko
Scripps Institution of Oceanography, Scripps Institution of Oceanography, Scripps Institution of Oceanography
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Abstract

The northeast United States is a densely-populated region with a number of major cities along the climatological storm track. Despite its economic and social importance, as well as the area’s vulnerability to flooding, there is significant uncertainty regarding future trends in extreme precipitation over the region. Here, we undertake a regional study of the projected changes in extreme precipitation over the NEUS through the end of the 21st century using an ensemble of high-resolution, dynamically-downscaled simulations from the NA-CORDEX project. We find that extreme precipitation increases throughout the region, with the largest changes in coastal regions and smaller changes inland. These increases are seen throughout the year, though the smallest changes in extreme precipitation are seen in the summer, in contrast to earlier studies. The frequency of heavy precipitation also increases, such that there are relatively fewer days with moderate precipitation and relatively more days with either no or strong precipitation. Averaged over the region, extreme precipitation increases by +3-5\%/$^{\circ}$C of local warming, with the largest fractional increases in southern and inland regions, and occurring during the winter and spring seasons. This is lower than the +7\%/$^{\circ}$C rate expected from thermodynamic considerations alone, and suggests that dynamical changes damp the increases in extreme precipitation. These changes are qualitatively robust across ensemble members, though there is notable intermodel spread associated with models’ climate sensitivity and with changes in mean precipitation. Together, the NA-CORDEX simulations suggest that this densely populated region may require significant adaptation strategies to cope with the increase in extreme precipitation expected at the end of the next century.