Atlas of probabilistic extreme precipitation based on the early 21st century records in the United States

Abstract

Study regionThe Conterminous United States Study focusExtreme precipitation property defined by the National Oceanic and Atmospheric Administration’s Precipitation-Frequency Atlas of the United States (NOAA Atlas 14) is losing its representativeness as the standard measure due to the impacts of climate change. This study aims to spatially and quantitatively assess the changes in extreme precipitation properties by comparing the NOAA Atlas 14 with a new atlas of precipitation frequency estimates (PFE) developed in this study from early 21st-century records New hydrological insights for the regionThe NOAA Atlas 14 has quantitatively diverged from the recent 20-year records due to precipitation non-stationarity across the United States. The NOAA Atlas 14 is characterized by more spatially smoothed PFEs compared to the new PFEs, suggesting that employing the NOAA Atlas 14 could lead to an underestimation of physical flood risk at a local scale. As the “new normal” in the 21st century, the majority of the United States faces three times more occurrences of extreme storms corresponding to a 1-in-100-year return period of the 20th century. The recent 20-year extreme events should be treated as the new normal. Until the NOAA Atlas 14 is updated to account for climate-driven non-stationarity and can be shown to resolve local effects better, it is recommended to employ new values between the upper and middle bounds of PFE that capture the non-stationarity of precipitation for the regions where the underestimation of PFEs is highlighted in this study