Canadian record-breaking wildfires in 2023 and their impact on US air quality

In recent years, extreme climate has increasingly triggered record boreal wildfires. The year 2023 saw a significant surge in wildfire occurrences in Canada, far surpassing the historical record. In this study, multi-source data were utilized for a comprehensive analysis of the development of the Canadian wildfires in 2023, the pathways of wildfire smoke, and its impact on the air quality in the US. The results indicate that the 2023 Canadian wildfires mainly occurred in western Canada (accounting for 60% of the burned area) and Quebec (eastern Canada, 29% of the burned area). Weather systems played a key role throughout wildfires and smoke plume transport processes. Specifically, high temperatures and dry weather caused by the blocking high-pressure systems was conducive to the enhancement of wildfire activities. Additionally, the southward airflow ahead of the ridge facilitated the transport of wildfires plume towards the south. This transport pattern frequently manifests under the Weather Regimes (WR) associated with the Alaskan Ridge (AkR) and Arctic High (ArH). In May and July, the smoke originating from the wildfires in western Canada, guided by the North American trough, affected the midwestern US. In June, smoke from eastern Canada led to severe air pollution in the northeastern US. Throughout the wildfire season, particulate matter dominated pollution in the US. The daily average PM2.5 concentration peaked at 258.9 mu g/m3, exceeding the World Health Organization standard guidelines (15 mu g/m3) by 17.3 times. This study highlights that wildfire has become one of the major environmental challenges facing the world under the influence of extreme climate.