East shift of Canada severe hail activities in a changing climate

Abstract

Severe hail activities have significant impacts on our society because they damage property and are dangerous to people and animals. However, we have little knowledge on recent changes in geographic locations of severe hail activity center over Canada. Prior to exploring this, we have carried out Canada hail data consistency and reliability checks using solid trend analyses of three independent methods for time series of hail counts and days, and robust verifications of reported hail data by a recently developed approach of sample generation by replacement. Here, we discover for the first time a statistically significant east shift of Canada severe hail activity and total hail activity using discriminant analysis. The spatial shift is from the western portion of continental Canada during 2005–2013 to the eastern Canada with a maritime environment during 2014–2022. With increase of hail severity, the hail activities increase from the colder period 2005–2013 to the warmer period 2014–2022. Our composite analyses show that over the continental Canada, the hail activities are enriched through thermodynamically driven convective instability and precipitable water associated with the warming climate, as well as dynamically driven processes such as vertical wind shear and vertically integrated water vapor flux convergence. Over the maritime Canada with the colder condition, the hail activities are enhanced by dynamically driven moisture advection and convergence as well as vertical wind shear, thermodynamically driven process of precipitable water, and partially due to convective instability. This research promotes our understanding of climate change impact on hail activities, shedding lights on long-term hail projection, adaptation, and mitigation strategies.