Trend analysis of winter rainfall over southern Québec and new Brunswick (Canada)

Abstract

Winter rainfall is a non‐negligible issue for urban drainage in Canada as it can generate significant flooding, especially when it occurs at the same time as high air temperature and in the presence of an appreciable snow cover. According to climate change scenarios, it is expected that the occurrence of these events will increase in a future climate. The purpose of this paper is to perform a trend analysis on six indices related to winter rainfall (January–February) at 60 weather stations located in southern Québec and New Brunswick (Canada) in order to detect possible trends in the frequency or intensity of winter rainfall events during the twentieth century. Datasets were provided by Environment Canada and come from the Canadian Daily Rehabilitated Precipitation Database. The bootstrap‐based Mann‐Kendall test is used to detect possible non‐stationarities in the dataset, while Sen's slope estimator is used to quantify the magnitude of the slope. Results show that 19 stations out of 60 present a significant trend (18 of them being positive) at a 5% level for winter (January–February) total rainfall. In most cases where a trend was detected for winter rainfall there was also an increase in the number of days with rainfall (42% of the stations). These results suggest that globally, for the region under study, rainfall during January and February was more likely to occur, often resulting in a significant increase in the total rainfall during these months. Increasing trends in maximum daily rainfall during January and February were also observed for 9 stations (15% of the stations). The spatial distribution of stations where significant trends were detected is consistent with the hypothesis that trends in winter rainfall are more likely to be observed for stations located in the southern part of the region under study.