Understanding changes in the timing of heavy storms: a regional case study of climate change impacts

Rigorous statistical methods are used to examine changes in the timing of heavy storms for various storm durations, to assess the degree to which climate change has influenced heavy precipitation events. The findings indicate that the timing of heavy storms (from 5-min to 24-h duration events in Ontario, Canada) is indicating that they are now predominantly occurring earlier within the calendar year. An example of the situation is that within the period from 1960 to 2017, the mean occurrence times of heavy storms have advanced by 44 days, with maximum and minimum time advances of 86 and 21 days, respectively. Trend analysis, including the Mann-Kendall test, linear regression, and Sen's slope method, all show that the times of heavy storms have advanced to earlier times within the calendar year. These earlier times of heavy storms will influence the natural and anthropogenic activities such as crop planning, drought management, and groundwater replenishment. This research provides new evidence and dimensions regarding the understanding of climate change, particularly related to the timing of heavy storms and various adaptation strategies (e.g., flood prevention and soil conservation).