Past research has unveiled important variations in total precipitation, often related to large-scale shifts in atmospheric circulation, and consistent with projected responses to enhanced greenhouse warming. Move recently, however it has been realized that important and influential changes in rha variability of daily precipitation events have also occurred in the past, often unrelated to changes in total accumulation. This study aims to uncover variations in daily precipitation intensity over Canada and to compare the observed variations with those in total accumulation and two dominant modes of atmospheric variability namely the North Atlantic Oscillation (NAO) and the Pactfic/North America teleconnection pattern (PNA). Results are examined on both annual and seasonal bases, and with regions defined by similarities in monthly variability Seasonally increasing trends in total precipitation that result from increases in all levels of evens intensity during the 20(th) century are found in southern areas of Canada. During the after half of the century increases ale concentrated in heavy and intermediate events, with the largest changes occuring in Arctic areas. Variations in precipitation intensity can, however be unrelated to variations in the total accumulation. Consistent with these differences, the precipitation responses lo the NAO and PNA are often found to occur only at specific levels of event intensity! Precipitation responses to the NAO occur in northeastern regions in summer and winter with the intensity affected in Both seasons. The PNA strongly influences precipitation in many regions of the the country during autumn and winter. In particular, it strongly influences variations in southern British Columbia and the Prairies, affecting the intensity in only some areas. However, it only influences the frequency of heavier events in autumn and winter in Ontario and southern Quebec, where this response is actually more robust than the response in total accumulation. During these seasons a negative PNA generally leads to more extreme precipitation events.
