This study first developed a homogenized daily precipitation dataset for 425 long-term stations across Canada. Then, it used the homogenized data to assess trends in annual maximum one-day and five-day precipitation, annual maximum one-day snowfall and rainfall, and annual number of heavy precipitation days, of heavy snowfall days, and of heavy rainfall days.
The results show that trends in precipitation extreme indices are dominantly positive across Canada, while trends in extreme snowfall amounts are dominantly negative in southern Canada but dominantly positive in northern Canada. Over the period of 1949–2023, the rate of increase in regional mean indices is estimated to be 2.2 % and 1.7 % per decade for Canada's North and South, respectively, for annual maximum one-day precipitation, and 1.4 % and 1.3 % per decade for annual maximum five-day precipitation. The regional mean annual number of heavy precipitation days is estimated to have increased by 4.3 % per decade in Canada's North and 0.9 % per decade in Canada's South (increased at 56 % and 54 % of the stations, respectively). The regional mean annual maximum 1-day snowfall is estimated to have decreased by 0.5 % per decade in Canada's South but increased by 1.7 % per decade in Canada's North. For regional mean heavy snowfall days, the rate of decrease is estimated to be 3.4 % per decade in Canada's South, matched with an increase of 1.1 % per decade in Canada's North. Similar trend characteristics are seen at southern stations over their longer data record periods (since 1900 or later but before 1949).
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