A Weather Regime‐Based Analysis of Freezing Rain Trends in a Warmer Climate for Eastern North America

ABSTRACT Freezing rain is a common winter weather hazard across eastern North America, resulting in damage and disruption to energy utilities, transportation, and the economy. Due to its short lasting and self‐limiting nature, observational gaps, and the need for high temporal and spatial resolution model output, this phase type is less studied in the context of climate change. Through the application of freezing rain regimes identified from prior analysis combined with additional data spanning from 2000 to 2013, a comparative analysis of historical and perturbed global warming simulations of freezing rain events is conducted. Regime‐based evolutions of precipitation type, rates, event duration, and thermal features are explored. Additionally, a novel storm‐relative compositing technique that identifies the degree of geospatial shifts in phase types and other metrics is used. Notable changes to the median values were identified, including a 258 km shift north for the primary freezing rain axis. A general increase in total precipitation (17.9%) was noted, driven by increases in rain (39%) and decreases in snow (−19.8%) and freezing rain precipitation (−14.5%). However, in two of the four full‐area regimes, freezing rain minimally declined (regime 1) or slightly increased (regime 4). These regimes were generally associated with cooler onset conditions, which in a warmer climate permitted more mixed‐phase precipitation due to increasing warm‐layer depth and magnitude, and warming the sub‐freezing surface layer to favour supercooling. This regime‐based framework thus permits us to better identify how the evolution of a winter weather event will influence how it responds to a late 21st century atmosphere.