Assessment of the standard precipitation frequency estimates in the United States

Abstract

Study region: The Conterminous United States Study focus: The NOAA Atlases have provided the standard precipitation frequency estimates (PFEs) for over two decades in the United States, but they are losing that status due to climate change. This study evaluates the Atlases compared to new PFEs developed based on the Automated Surface Observing System and Regional Frequency Analysis (ASOS-RFA) as a benchmark and examines a radar-based precipitation product as a data source eligible for developing the post-Atlas. New hydrological insights for the region: The stationarity assumption of precipitation was highlighted as a significant factor in increasing the uncertainties in the Atlases. The Atlases explicitly tended to underestimate PFEs compared to the ASOS-RFA. The difference between the Atlases and the ASOS-RFA increases as the return period increases and the duration decreases. The age of the Atlases correlated with the difference, suggesting that recent observations diverge from older estimates. The radar-based PFEs are well-matched with the ASOS-RFA at frequent return periods, but the uncertainties increased as the return period increased. This is because the conventional bias correction was limited in improving the annual maximum series of precipitation. Lastly, we need to pay careful attention to an increase in precipitation frequency estimates shorter than 12-hr durations.

Keywords

• Flood
• Extreme precipitation
• Precipitation frequency estimate
• NOAA Atlas
• NEXRAD Stage-IV
• Radar-based IDF curve