Rain, Rain, Go Away: Historic Rainfall Analysis in the Baltimore Region

Abstract

In July of 2016 a devastating 3-hour rainstorm with a predicted return interval of 1000 years struck Ellicott City, Maryland. In May of 2018, a 3-hour rainstorm with the same predicted 1000 year return interval struck Ellicott City again. These anomalous events bring into question whether methods assuming stationary climate are accurate and if precipitation or storm intensity is increasing as a result of climate change. The Ellicott City storms are assessed using basin-averaged precipitation over the entire Baltimore Region and evaluated by creating a high resolution 20-year dataset. These analyses allow for high spatial and temporal resolution to be focused on a small region. Single Polarimetric Radar and Dual Polarimetric Radar data are also used to create a 20-year high resolution rainfall dataset. I conclude that there is not strong evidence for increasing frequency in precipitation for the mid-Atlantic region encompassing Ellicott City. Assessing fluctuating frequency of extreme precipitation is notoriously difficult but using this 20-year novel data set provides insight into how potential hazards can be addressed in the warming climate. Precipitation changes are additionally put into context with the 2020 pandemic and its ramifications for economic sector change and energy policy. Methodologies created here can be applied to other high resolution rainfall datasets to assess non-stationarity within other regions, providing further insight into small urban watersheds.