Enabling high-resolution forecasting of severe weather and flooding events in Rio de Janeiro

Abstract

Safe operation of many cities is affected by relative extremes in weather conditions. With precipitation events, local topography and weather influence water runoff and infiltration, which directly affect flooding. Hence, the availability of highly focused predictions has the potential to mitigate the impact of severe weather on a city. Often, such information is simply unavailable. The initial step to address this gap is the application of state-of-the-art weather models at an urban scale calibrated to address this mismatch. The generation of operational forecasts at such a scale for the Rio de Janeiro metropolitan area suggests a horizontal resolution of approximately 1 km and a vertical resolution in the lower boundary layer of tens of meters. Forecasting impacts from storm-driven flooding events requires the development of a coupled hydrological model that operates at a street scale with resolution of approximately 1 m, capturing local terrain effects and simulating surface flow and water accumulation, especially for overland flow and ponding depth. This coupled approach has enabled operational prediction of storm impacts on local infrastructure, as well as measurement of the model error associated with such forecasts.