The Great Lakes Runoff Intercomparison Project (GRIP): Phase II, Lake Ontario

Abstract:

The Great Lakes runoff intercomparison project (GRIP) was established to assess a suite of models used primarily for simulating and forecasting flows from all of the major tributaries within the Great Lakes basin. These models are somewhat unique, in part because they were developed to overcome challenges of assimilating data across an international border, and in part because they are often an integral component of regional water budget models that also include simulations of over-lake precipitation and over-lake evaporation (both of which are, on annual time scales, of the same magnitude as runoff). Here, we present the next step in the evolution of GRIP (following GRIP-M, the first phase of the project that focused on Lake Michigan) with a comparison between different hydrological models (including GR4J and the NOAA large basin runoff model) and different regional precipitation data sources across the Lake Ontario basin. Results of our analysis provide insights that underscore the importance of the spatial and temporal resolution of a model domain and its forcings, along with their connections to model skill and selected objective criteria. Perhaps more importantly, our results are expected to assist in the advancement of regional hydrological models not only for improved forecasts of the Great Lakes water cycle, but in other large international freshwater basins as well.