Climatic drivers of the Canadian wildfire episode in 2023

Extreme wildfires broke out in Canada from May 2023 and persisted four months. Tremendous fire emissions posed significant impacts on the air quality in both local and downwind regions. Here, the authors explored the meteorological factors driving this wildfire episode and the associated large-scale circulation. Relative to the mean value of 2001–2022, the 2023 Canadian fires released 0.37 Gt more CO₂ (527.1%) during May–August. Such enhancement was strongly associated with the anomalous surface warming, especially in May–June, when the daily maximum temperature on average increased by 8.11°C, with regional hotspots up to 10°C in central and eastern Canada. Consistent with the surface warming, positive anomalies of geopotential height were observed at high levels in central and western Canada. The dispersion of Rossby waves led to the long-lasting dominance of high-pressure systems and the consequent warming through anomalous subsidence. The phase-locked wave pattern induced by favorable topography and the strong warming tendency in the pan-Arctic regions are expected to jointly escalate the probability of extreme wildfires over central and western Canada in the future.

摘要

2023年5月加拿大发生极端野火事件并持续4个月时间. 野火污染物排放对当地和下风向的空气质量造成了严重影响. 本文对驱动此次野火事件的气象因子和相关大尺度环流进行了探究. 研究表明, 此次极端野火排放的二氧化碳相较往年同期增长了0.37Gt (527.1%) . 受罗斯贝波频散影响, 同期加拿大中西部区域出现持续的位势高度正异常, 促进气流下沉并引发局地高温, 中西部区域5–6月最高温平均上升8.11°C, 部分区域甚至超过10°C, 导致野火排放的显著增长. 受有利地形和泛北极地区快速增暖的影响, 预期未来加拿大中西部发生极端野火的概率可能会显著上升.