On the dependence between extreme rainfall and preceding temperature conditions across major Canadian cities

Abstract:

Climate change intensifies hydorologic cycle. As far as rainfall generation is concerned, more available incoming radiative forcing can intensify latent heat flux from land and water surfaces. On the other hand, warmer air parcels can hold more moisture and therefore when they cool down, they pour heavier rainfall intensities. This can have enormous implications on socio-economic activities, engineering design and infrastructure operation and maintenance.Current projections of Global Climate Models’ (GCMs) confirm this hypothesis and it is expected that extreme rainfall increases across majority of global land surface at least across some durations and return periods, depending on the region considered. Having said that if this hypothesis is fully true, past empirical data should also show some modes of dependencies between extreme rainfall intensities and preceding temperature conditions. In this presentation, we look at five modes of dependence between extreme rainfall and preceding temperature conditions using in-situ rainfall and temperature data from the 30 largest Canadian cities, spread in southern part of the country, coast to coast. We show that in some important cities, such dependencies are indeed present and significant. Closer look at the data shows that dependencies between extreme rainfall intensities and preceding temperature conditions are subject to change; and both magnitudes and signs of dependence are subject to temporal variations. We investigate how such dependencies and their temporal variations are preserved by gridded climate forcing data as well as downscaled GCM projections that are commonly used for impact assessment. Accordingly, we highlight current challenges and opportunities for future development.