Assessment of future changes in intensity-duration-frequency curves for Southern Ontario using North American (NA)-CORDEX models with nonstationary methods

Study region Southern Ontario, Canada. Study focus The evaluation of possible climate change consequence on extreme rainfall has significant implications for the design of engineering structures and socioeconomic resources development. To date, there has been no comprehensive comparison or evaluation of intensity-duration-frequency (IDF) statistics at a regional scale, considering both stationary versus nonstationary models for the future climate projection. To understand how extreme precipitation may affect future IDFs, we used an ensemble of three regional climate models (RCMs) participating in the NA-CORDEX domain over eight selected rainfall stations across Southern Ontario, one of the most densely populated and major economic regions in Canada. We modeled precipitation extremes, at different durations using extreme value distributions considering parameters that are either stationary or nonstationary, as a linear function of time. New hydrological insights for the region Extreme precipitation intensity driven by future climate forcing shows a significant increase in intensity for 10-year events in the 2050s (2030–2070) relative to 1990s (1970–2010) baseline period across most of the locations. For longer return period (i.e., 25-year), we note detectable changes in design storm considering a nonstationary model than that of the stationary ones. Finally, the results of this study are not only limited to develop nonstationary IDFs for the future emission scenario but the proposed framework can serve as a basis to improve weather generator accounting nonstationary nature of extreme precipitation.