Origin and quantification of isotopic signal heterogeneity in urban precipitation

Cécile Carton

Previous studies have shown that urban precipitation dynamics undergo significant changes due to Urban Heat Islands (UHI), building density and height, and anthropogenic emissions of water vapor and aerosols. These changes are of major interest for water resources management, but they remain poorly understood because the spatial and temporal heterogeneity of urban environments makes it difficult to acquire sufficiently representative measurements of these different processes.

Nevertheless, the current acceleration of urbanization requires an improved understanding of how urbanization affects the frequency, amount, and distribution of precipitation so that we can adapt effectively. In response to this problem, stable isotopes of the water molecule, commonly used in hydrology as flow tracers, provide information on the conditions and trajectories of weather events that can be used to study controls on urban precipitation at various spatial and temporal scales.

The results of the meteorological reanalysis highlighted the impact that the city of Montreal has on local temperatures, and on the frequency and quantity of precipitation. The next steps of the project include the implementation of Collect’O, the local participatory rain and snow sample collection network, whose analyses will allow us to determine if the use of stable isotopes of the water molecule as a tracer of urban precipitation is a valid approach. This method could provide a valuable tool for understanding the different processes that can modify urban precipitation, which is necessary for the future regulation and adaptation of cities to urbanization.