Projected Changes in Future Extreme Precipitation over the Northeast US
in the NA-CORDEX Ensemble
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.