Total and Extreme Precipitation Changes over the Northeastern United States

Precipitation in the northeastern United States has experienced a large increase over recent decades. Here we evaluate the sensitivity of calculated precipitation changes to choices of time period, domain, and data set. Specifically, we assess annual and seasonal changes in total and extreme precipitation in the Northeast over multiple time periods spanning 1901-2014, and compare results from station, gridded, and reanalysis data. Our results show that both observed total and extreme precipitation (i.e. the heaviest 1% of all daily precipitation events) in the Northeast have increased significantly since 1901, with an accelerated increase in more recent decades and especially since 1996. Generally, coastal areas experience more total and extreme precipitation, and have seen larger increases in total and extreme precipitation, than inland areas. Averaged regionally, extreme precipitation has experienced a larger increase (30.3% per decade during 1979-2011) than total precipitation (5.2% per decade during 1979-2011). Since 1901, total precipitation has increased significantly in fall, while since 1979 total precipitation has increased significantly in summer. The increase in extreme precipitation 1996-2014 is driven by significant increases in spring and fall. Gridded observations generally reproduce averages of annual total, seasonal total, and extreme precipitation from station observations at both regional and station scales, whereas North American Regional Reanalysis generally underestimates annual and seasonal total and extreme precipitation relative to station observations. To reduce uncertainties in detecting long-term precipitation changes, we suggest alternatives to the traditional linear trend to better quantify the change.