Projected changes of precipitation extremes in the U.S. Northeast based on two downscaled climate datasets LOCA and MACA

Abstract:

Global warming has caused an increase in the intensity and frequency of heavy precipitation events. The resulting increase of flood hazards is a major concern for local and state climate adaptation. In the United States, observational data indicates that the Northeast region is leading the way towards more precipitation extremes. This trend is expected to continue in the future. This study assesses future changes in extreme precipitation in the Northeast based on the downscaled climate data for eight earth system models from two databases, MACA and LOCA. Both LOCA and MACA project significant increases in precipitation intensity and temporal aggregation of heavy precipitation, including for example the number of days with more than one inch of precipitation, the simple intensity index, the 99^th percentile of daily precipitation, and the fraction of annual precipitation accounted for by heavy events. The two databases are consistent in the magnitude of absolute increases. For precipitation extremes such as the annual maximum 1-day precipitation and the 1-in-20-years extreme events, both databases project significant increases in the long-term mean, but the magnitude of the projected increases is much smaller in LOCA than in MACA. These disparities are attributable to differences in not only the downscaling algorithm but also the training data. Results from this study highlight the challenges facing statistical downscaling of precipitation extremes.