Regional Frequency Studies of Annual Extreme Precipitation in the United States based on Regional L-moments Analysis

The paper discusses an L-moments based regional rainfall frequency approach and its application in large areas with many regions and across a broad range of durations. Advantages of the technique in terms of robustness to outliers and stability of quantile estimates are demonstrated through real examples. This paper provides an overview of NOAA Atlas 14, the updates of the rainfall frequency atlases and technical papers published by the National Oceanic and Atmospheric Administration’s National Weather Service for the Semiarid Southwest United States and the Ohio River Basin and surrounding states, focusing on technical/statistical aspects and developments and findings during the studies, such as 1) the criteria for identifying and verifying homogenous regions in a large area, 2) the goodness-of-fit for comparison and identification of distributions to best model the data in a region, 3) the concept of the real-data check and its use in regional frequency analysis, 4) consistency adjustments over a broad range of durations from 1-hour to 60-days, 5) identification of intersite dependence of the annual extreme precipitation and its impact on quantile estimates, 6) confidence limits as an uncertainty measure of the quantile estimates and, 7) the ratios of Partial Duration Series quantiles to Annual Maxima Series quantiles.