Future Changes to Extreme Rainfall over Puerto Rico in an Ensemble of Convection-Permitting Simulations

Puerto Rico is a tropical island that frequently receives heavy rainfall from a variety of systems, including tropical cyclones like Hurricane Maria (2017), mesoscale convective systems (MCSs), and isolated convection. Its two distinct rainy seasons are dictated by moisture convergence associated with the North Atlantic Subtropical High, while sea breezes and complex topography influence precipitation on the mesoscale. Previous research has examined how tropical precipitation could change in a future climate, showing a decrease in precipitation by 2100 using global climate models (GCMs). However, relatively little research has been conducted using convection-permitting climate models over the tropical Atlantic to understand how precipitation extremes could change in a warmer climate. Here, we fill this gap by dynamically downscaling a 0.25 degree GCM 10-member ensemble to 3 km using the Model Prediction Across Scales (MPAS) model for extreme precipitation events in a current (2001-2021) and future climate (2041-2061) over Puerto Rico. We show that MPAS is largely able to reproduce extreme precipitation events in the current climate when compared to observations and captures a variety of systems. We explore how future changes in extreme rainfall events in the early rainy season, which are largely driven by MCSs and isolated convection, compare to changes in the late rainy season, which are primarily due to tropical cyclones.