Quantifying The Trend of Winter Cold Wave Changes in Toronto from 2011 To 2025

Yiren Wang

doi:10.54097/sveh1772

Authors

Yiren Wang

DOI:

https://doi.org/10.54097/sveh1772

Keywords:

Cold waves; Winter temperature; Linear regression.

Abstract

Winter extreme low-temperature events threaten urban operations and public health, but quantitative descriptive studies on changes in cold waves in Toronto are still relatively limited. Existing work mostly focuses on the perspectives of alerts and public health, or on winter temperature and case-specific circulation. Therefore, this article obtains the frequency and intensity of cold days/cold waves in Toronto from winters 2011 to 2025 and builds a linear regression between cold-day frequency and the seasonal mean temperature of non-cold days by using the baseline from 1981 to 2010 and calendar-day P10 to define a cold wave, then uses CMd/CWMId to characterize cold-wave event intensity. The results show that cold waves are unevenly distributed over the 15 years: 2014–2015 is the strongest and has the longest duration, while 2021–2024 almost have no cold waves, and found that the coldest single day does not necessarily occur within the strongest cold wave. With the linear regression, this article found that cold-day frequency decreases by about 3% per +1 °C of background warming (R² ≈ 0.46). Overall, cold waves in Toronto show a weakening trend during 2011-2025, which is consistent with background warming. But because cold waves are also modulated by interannual circulation, the simple and consistent statistical framework used in this paper may serve as a basis for subsequently incorporating factors such as circulation mechanisms.

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