Projections in Many Directions: Extracting Meaningful Guidance for Water Resources Planning in the Western United States from the NA-CORDEX GCM-RCM Ensemble

Water management in the western United States remains a complex challenge for scientists and stakeholders alike as the balance between “feast or famine” seasonal precipitation regimes becomes increasingly critical. Growing societal demand for water, and the importance of risk mitigation from the shortage and excess thereof, compounds pressures faced in water resources planning. Science-based guidance on future precipitation states is thus of critical importance for those agencies tasked with water planning and disaster prevention. The North American CORDEX (NA-CORDEX) experiment aims to add value to the ever-growing body of climate model projections by strategically combining multiple model resolutions and a matrix of global and regional climate models to produce projections that serve both the impact and adaptation community and also to facilitate model intercomparison studies.

Model datasets such as NA-CORDEX offer appeal to stakeholders because they can, in theory, provide an array of possible future states, while also providing gridded model data output that can be used for secondary/application models. What does this GCM-RCM matrix dataset reveal about western US precipitation with respect to means, extremes, spatial distribution, temporal and precipitation type? This presentation will provide a detailed evaluation of both past and future model precipitation projections, identify dependencies on and sensitivities to model resolution, dissect GCM vs. RCM influence, and discuss how decision-makers may be able to use such information to guide future planning activities.