Ashraf Samaneh, Pausata Francesco S R, Leroyer Sylvie, Stevens Robin, Munoz-Alpizar Rodrigo
Department of Chemistry, University of Montreal (UdeM) Montreal QC Canada.
Centre ESCER (Étude et la Simulation du Climat à l'Échelle Régionale) and GEOTOP (Research Centre in Earth System Dynamics), Department of Earth and Atmospheric Sciences, University of Quebec in Montreal (UQAM) Montreal QC Canada.
Geohealth. 2025 Feb 1;9(2):e2023GH000975. doi: 10.1029/2023GH000975. eCollection 2025 Feb.
Extensive lockdowns during the COVID-19 pandemic caused a remarkable decline in human activities that have influenced urban climate, especially air quality and urban heat islands. However, the impact of such changes on local climate based on long term ground-level observations has hitherto not been investigated. Using air pollution measurements for the four major Canadian metropolitan areas (Toronto, Montreal, Vancouver, and Calgary), we find that PM markedly decreased during and after lockdowns with peak reduction ranging between 42% and 53% relative to the 2000-2019 reference period. Moreover, we show a substantial decline in canopy urban heat island intensity during lockdown and in the post lockdowns periods with peak reduction ranging between 0.7°C and 1.6°C in comparison with the 20-year preceding period. The results of this study may provide insights for local policymakers to define the regulation strategies to facilitate air quality improvement in urban areas.
新冠疫情期间的大规模封锁导致人类活动显著减少，这对城市气候产生了影响，尤其是空气质量和城市热岛效应。然而，基于长期地面观测，此类变化对当地气候的影响迄今尚未得到研究。利用加拿大四个主要大都市（多伦多、蒙特利尔、温哥华和卡尔加里）的空气污染测量数据，我们发现封锁期间及之后细颗粒物显著下降，与2000-2019年参考期相比，峰值降幅在42%至53%之间。此外，我们还表明，封锁期间及之后树冠层城市热岛强度大幅下降，与前20年相比，峰值降幅在0.7°C至1.6°C之间。本研究结果可为地方政策制定者确定促进城市空气质量改善的监管策略提供参考。
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