Analysis of Climatic Shifts in Freezing Rain Events and Patterns over Eastern North America

Freezing rain events, responsible for billions of dollars in damages over recent decades, remain among the least understood types of precipitation. These events impact both urban and rural areas, including cities and forests. However, their brief and scattered nature introduces significant limitations in reporting validity, further constraining analysis.

This study began with the utilization of ERA5 reanalysis data as a proxy for ground truth freezing rain data, allowing for an hourly temporal resolution from 1979-2020. Individual freezing rain events were identified and filtered for size and separation, and then studied through a multivariate Self-Organizing Maps (SOM) analysis. This analysis, based on four variables (500 mb height, surface and 850 mb temperature, sea level pressure), enabled the classification of these events into regimes across Eastern North America and regimes within distinct subregions. While this provided a short-term analysis of regime changes over the period, the events were further examined under a perturbed global warming framework using the Weather Research and Forecasting (WRF) model. This study, encompassing both current and future climates, provided insights into how a changing climate is expected to impact not only individual freezing rain events but also the underlying regimes. Events were analyzed in terms of duration, size, shift, and total effects to determine the potential modifications in future events due to climate change.