Twenty-first century increases in total and extreme precipitation across the Northeastern United States

The northeastern United States has experienced a dramatic increase in total and extreme precipitation over the past twenty-five years. Whether this enhanced precipitation will continue and how precipitation will evolve across the Northeast by the end of the 21st century remain open questions. To examine the future of precipitation in the Northeast, we used a regional climate model (Weather Research and Forecasting model), driven by a global climate model (Community Earth System Model), to simulate precipitation for historical (1976-2005) and future (2070-2099, Representative Concentration Pathway 8.5) time periods. We compared precipitation from historical regional climate model simulations and gridded observations (Daymet), finding a 5% dry bias and 8% wet bias for total and extreme precipitation, respectively. Regional climate model projections indicate that averaged across the Northeast, total precipitation will increase 10% and extreme precipitation will increase 52% by the end of the twenty-first century. Winter is projected to have the largest increase in total precipitation (16%) and extreme precipitation (110%), and all seasons except fall have significant increases in total and extreme precipitation. To determine the drivers of precipitation change, we analyzed several atmospheric variables and found that projected extreme precipitation increases are strongly related to enhanced precipitable water over the eastern United States and Atlantic Ocean. Finally, we tested the sensitivity of our results to greenhouse gas emissions scenario (Representative Concentration Pathway 4.5) and large-scale forcing (Max Planck Institute Earth System Model). Understanding potential increases of total and extreme precipitation is critical for stakeholders in the Northeast to prepare for the widespread impacts of an intensified hydrologic cycle.