Projected Changes in Future Extreme Precipitation over the Northeast United States 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%/°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%/°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.

Roles of External Forcing and Internal Variability in Precipitation Changes of a Sub‐Region of the U.S. Mid‐Atlantic During 1979–2019

“…Extreme precipitation has more important societal and economic impacts through its impacts on flash flooding, landslides, strong winds, agriculture and food production (Biasutti et al., 2016). Significant uncertainty has been revealed in the future projection of extreme precipitation over the northeastern U.S. that partly overlaps with this region (Nazarian et al., 2022). Clarifying the contributions of extreme precipitation in the seasonality change and their large‐scale drivers is a logical question to be explored.…”

“…Hurrell et al (2003) and Huang et al (2021) addressed the role of the Atlantic multidecadal variability and the North Atlantic Oscillation (NAO) in regulating precipitation variations over the region. Due to the complex factors associated with external forcing and internal variability affecting precipitation and models have varying skill in capturing different mechanisms, large uncertainties are notable in model simulated precipitation change in the northeastern U.S. (Nazarian et al, 2022;Sheffield et al, 2013;Sillmann et al, 2013).…”

Contributions of Tropical Cyclones and Atmospheric Rivers to Extreme Precipitation Trends Over the Northeast US

“…Further, SPEAR_HI can reasonably simulate the relative contributions of ARs and TC-related events to the NEUS extreme precipitation. As extreme precipitation over the NEUS is expected to become more frequent due to anthropogenic warming (e.g., DeGaetano & Castellano, 2017;Hayhoe et al, 2007;Jong et al, 2023;Nazarian et al, 2022;Ning et al, 2015;Picard et al, 2023), we next use SPEAR_HI to evaluate how the contributions of ARs and TC-related events to the NEUS extreme precipitation will change in response to anthropogenic warming.…”

“…The Northeast US (NEUS; all acronyms used in this paper are listed in Table S1 in Supporting Information S1), the most populated region in North America including the Boston to DC metro corridor area, has experienced the most rapid increase in the frequency of extreme precipitation in the US, especially since the mid-1990s (e.g., Brown et al, 2010;Crossett et al, 2023;DeGaetano, 2009;DeGaetano et al, 2020;Frei et al, 2015;Guilbert et al, 2015;Hoerling et al, 2016;Howarth et al, 2019;Huang, Patricola, Winter, et al, 2021;Huang et al, 2017Huang et al, , 2018Jong et al, 2023;Olafdottir et al, 2021). Extreme precipitation frequency over the NEUS, moreover, is projected to increase in the future warming climate (e.g., DeGaetano & Castellano, 2017;Hayhoe et al, 2007;Jong et al, 2023;Nazarian et al, 2022;Ning et al, 2015;Picard et al, 2023). In the face of warming climate and mounting threats from highimpact weather events such as extreme precipitation, long-term infrastructure development and planning depend on climate model future projections of these extreme events and their contributing meteorological processes.…”

“…Multiple climate models have projected that extreme precipitation over the NEUS will increase in the future with global warming (e.g., DeGaetano & Castellano, 2017;Hayhoe et al, 2007;Jong et al, 2023;Nazarian et al, 2022;Ning et al, 2015;Picard et al, 2023). In recent work, Jong et al (2023) used a high-resolution model (25 km horizontal grid) to show the frequency of extreme precipitation events in the fall season (defined as the top 1% of daily precipitation based upon the historical climatology for the 1951-2020 period) would double by the end of the 21st century.…”