Impact
Estimating Extreme Precipitation Rates For Use in Planning U.S. Roads, Bridges, and Additional Infrastructure
Objective
To develop a state-of-the-science approach for estimating future precipitation rates in the continental United States and its territories impacted by climate change.
Approach
Collaborate with the Office of Water Prediction (of the NOAA National Weather Service) to analyze historical precipitation data and employ advanced methodologies for more reliable estimation of extreme precipitation events over the coming decades.
Impact
The NOAA Atlas 15 precipitation-frequency values will streamline the estimation process and assist designers of roads, bridges, and other infrastructure in meeting federal, state, and local guidelines and regulations.
Knowing how much rain and snow for a specific location and return period over the next 100 years is critical in designing the nation’s infrastructure. RTI International is working with the National Oceanic and Atmospheric Association (NOAA) to develop a system that will have a significant impact on predicting the frequency of extreme precipitation events over the coming decades.
Enhancing Precipitation Rate Data for a Shifting Climate
Following the success of the NOAA Atlas 14 project, NOAA Atlas 15 will use a novel approach that adopts newer statistical techniques, streamlines the estimation process, and develops future precipitation estimates while accounting for climate change. The team will spend the next several years studying historical precipitation data, combined with new methodologies and global future climate model data, to estimate precipitation frequency for the continental United States, Alaska, Hawaii, and other affiliated territories.
Research activities for the NOAA Atlas 15 project are supported in part by a partnership with the University of Alabama’s Cooperative Institute for Research to Operations in Hydrology (CIROH), which supports goals of the NOAA Office of Water Prediction (OWP), the U.S. Army Corps of Engineers, and the U.S. Geological Survey. CIROH is a national consortium of academic institutions, private companies, and nonprofit organizations working together to improve water resources management through improved science, data, forecast information guidance, and equitable decision support services.
Incorporating Climate Change Information in Precipitation Estimates
Estimating the frequency of extreme precipitation has become more complicated over the past several years due to climate change. Relying on historical data alone will not produce reliable results. Research from OWP and other collaborators is being used in conjunction with downscaled climate projections as part of the new methodologies.
Precipitation-frequency estimates are the amounts of rain or snowfall projected for a specified storm duration and an average annual exceedance probability (for example, 24-hour precipitation with a 1% probability of exceedance in a given year). Precipitation frequency data enable engineers to determine the expected impacts of extreme weather events on design. This is instrumental in designing future roads, bridges, and additional infrastructure that meet federal, state, and local guidelines and regulations.
Applying an Innovative Methodology to Precipitation Analysis
The team is analyzing historical data and identifying trends in extreme precipitation occurrences over time, employing a “maximum likelihood approach” to establish precipitation-frequency estimates over a cohesive grid for the United States and its territories.
Downscaled global climate model data will be used to understand how climate change affects extreme precipitation and to create future precipitation-frequency estimates. This will be accomplished by evaluating the latest climate model datasets, downscaling methodologies, and proposed methods for incorporating future climate scenarios into precipitation-frequency estimates.
The updated estimates will be derived using two models. One model will provide estimates based on historical precipitation gauge data observations, and the other will provide future estimates derived from climate model projections across various potential future climate scenarios. Both will provide tailored estimates for engineering design applications.
Timeline for NOAA Atlas 15
The NOAA Atlas 15 work is expected to last 4 years. In the fall of 2024, we are piloting NOAA Atlas 15 development in the state of Montana to collect feedback on preliminary precipitation estimation and the data delivery interface. In 2025, the program will extend to the remaining 47 continental United States, with estimates, documentation, and supplementary information for these states publicly released in 2026.
In 2026, we also will initiate peer reviews for states and territories outside the continental United States (Alaska, Hawaii, Puerto Rico, U.S. Virgin Islands, and selected Pacific territorial islands). In 2027, we will deliver estimates, documentation, and supplementary information for these states and territories.
Shaping a Climate Resilient Future
The NOAA Atlas 15 project represents a critical step forward in enhancing our ability to estimate extreme precipitation events accurately amid a changing climate. Through innovative methodologies and collaborative efforts, we aim to provide tailored estimates that will inform crucial decision-making in infrastructure design and resilience.
With the support of our partners and stakeholders, we are committed to advancing extreme precipitation estimation and preparing communities for the challenges posed by climate variability. Together, we strive to build a more resilient future for generations to come.
Learn more about RTI’s Center for Water Resources.
