Future changes in intensity and seasonal pattern of occurrence of daily and multi-day annual maximum precipitation over Canada

Daily and multi-day extreme precipitation events can cause important flooding. Assessment of the future evolution of heavy precipitation is therefore crucial in a context of climate change. Simulation results for Canada from the Canadian Global Climate Model (CGCM3) have been analyzed for 1 to 5-day annual maximum (AM) precipitation events over the 1850-2100 period using simulation series from five ensemble members. Trend analysis showed that daily and multi-day intense precipitation series were stationary over the 1850-1980 period while trends emerged during the period 1980-2005. Probabilities of occurrence of AM precipitation for the various months were also estimated. For the historical climate (1850-1980), a comparison with observed data suggested that the model adequately reproduced the observed regional patterns of seasonal occurrence of AM events. Future projections suggest that, for many Canadian regions, a shift will take place from summer to spring and/or autumn in the seasonal occurrence of AM precipitation events. Moreover, statistical frequency analysis of models series suggests that daily and multi-day events will be more intense and frequent in a future climate for all regions except the Prairies. In some regions (e.g. west coast of British Columbia), the return period associated with a given precipitation intensity in historical climate will decrease by a factor of five over the 2080-2100 period. No significant differences have been observed between daily and multi-day projections for intensity/frequency occurrence of AM events. (C) 2010 Elsevier B.V. All rights reserved.