Observed trends in precipitation extreme indices as inferred from a homogenized daily precipitation dataset for Canada

Using the changepoints identified and adjusted to produce the homogenized monthly precipitation dataset, this study developed a homogenized daily precipitation dataset for Canada, in which all data gaps are infilled for the period back to 1900 for southern stations (south of 60˚˚ N), and back to the first day of 1948 or the first day of observation before 1948 for northern stations using advanced spatial interpolation of both monthly and daily values from other stations in the region. The homogenized daily precipitation dataset was then used to assess trends in a set of precipitation extreme indices, including annual maximum one-day (RX1day) and five-day (RX5day) precipitation, as well as annual number of heavy precipitation days, R10mm (annual count of days when precipitation >=10mm). The results show that both annual maximum one-day and five-day precipitation have increased significantly at most stations across Canada over their data record periods, with most stations in the Rocky Mountains and southern Prairies showing insignificance decreases over the period of 1948-2022. Increases in the annual maximum one-day and five-day precipitation are largest and significant in central to northern Canada and in the Maritimes provinces. Annual number of heavy precipitation days has increased significantly at most stations in northern Canada.