Comparison of the temporal variability of summer temperature and rainfall as it relates to climate indices in southern Quebec (Canada)

The temporal variability of daily mean maximum and minimum temperatures and seasonal rainfall totals in summer (June to September) measured at 25 stations from 1950 to 2010 was analyzed in light of five climate indices. Long-term trend analysis using the Mann-Kendall method revealed a significant increase in maximum temperatures at 44% of stations and in minimum temperatures at 68% of stations. In contrast, a significant decrease in rainfall totals is observed for 16% of stations. The Lombard test revealed that shifts in mean values of maximum and minimum temperatures occurred after the 1970s decade whereas shifts in mean values of rainfall occurred before that decade. Daily mean maximum and minimum temperatures primarily show a positive correlation with summer (June to September) Atlantic Multidecadal Oscillation (AMO) and Arctic Oscillation (AO) indices, whereas rainfall totals are negatively correlated with the Southern Oscillation Index (SOI). The study shows that, contrary to the generally accepted view, summer warming is more widespread than winter warming in southern Quebec. Climate models used to predict future temperatures must take this into account.