Seasonal Variations in Extreme Precipitation Trends Across the Northeast U.S.

In recent decades, the frequency and intensity of extreme precipitation has significantly increased over the Northeast United States. This rising trend is evident within all seasons, with the most notable increases in the autumn season, based on observations. Understanding the future projection of these long-term trends in regional extreme precipitation is vital for effective mitigation and adaptation, as extreme precipitation can severely impact agriculture, infrastructure, and property, posing threats to local economies and lives.

Recent studies have utilized high-resolution climate model simulations to study projected change in fall season extreme precipitation over the Northeast US, demonstrating the value of climate models in simulating extreme precipitation and producing future projections on regional scales. The objective of this research is to further investigate changes in extreme precipitation during the winter and spring seasons under both current and future climates, using the GFDL (Geophysical Fluid Dynamics Laboratory) SPEAR (Seamless System for Prediction and EArth System Research) model which generates 25-km high-resolution simulations (ten members; SPEAR_HI) for both historical simulations from 1921 to 2014 and projections under the Shared Socioeconomic Pathway 5-8.5 (SSP585) from 2014 to 2100.

Our preliminary results indicate that SPEAR_HI can effectively simulate the frequency of extreme precipitation, defined as the top 1% of daily precipitation events between 1948-2023, over the Northeast US, comparable to the observations for both winter and spring seasons. Moreover, the frequency of extreme precipitation since the 1990s is statistically significantly higher than the earlier period in both observations and SPEAR_HI ensemble mean. Ongoing research focuses on the relative contributions of extratropical cyclones and atmospheric rivers to extreme precipitation, as well as tracking the changes in snowfall versus rainfall in both historical and SSP585 simulations.