Background/Objectives

Increases in extreme rainfall due to climate change have caused billions of dollars of damage around the world. As greenhouse gas emissions rise, extreme rainfall is expected to intensify further, and predicting these increases using general circulation model (GCM) data has been a significant focus of research. Currently available datasets have shown a wide range of results, with many methods difficult for individual municipalities and communities to replicate.

Approach/Activities

We present three practical and easily implementable methods using Global Climate Model (GCM) output to estimate percentage increases in extreme rainfall in the coming century. Methods are designed to bracket the expected range of extreme rainfall intensification for 1 to 24-hr events with return intervals of 1 year to 100 years. The first method involves analyzing the 20 largest rainfall events in a 20-year window, while the other two methods leverage GCM projections of temperature combined with Clausius-Clapeyron assumptions.

Results/Lessons Learned

This work provides communities planning for extreme rainfall with several projection methods that aligns with their design needs and risk tolerance. Preliminary results from a case study in the Philadelphia area reveal projected end-of-century increases in extreme rain event volumes ranging from 18% to 61%, contingent upon the duration and return interval considered. These results have been benchmarked against existing, publicly available projected rainfall intensities. The results show that easily implementable methods can provide extreme rainfall intensification projections within the range of results provided by the state of the science.