Metrics and model validation represent two key elements upon which the success of the Center for Integrated Space Weather Modeling (CISM) hinges. The routine calculation of important operationally- and scientifically-motivated metrics permits us to objectively measure and track the ability of coupled CISM models to predict essential space weather quantities. The rationale for CISM metrics selection is developed and the list of 29 metrics, along with the baseline models, first-generation physics models, and the data sets needed to compute skill scores, are outlined. While metrics provide a means for the objective assessment of long-term model improvement, model validation—the comprehensive, systematic quantitative comparison of model output with observations—is required for identifying and documenting model strengths and weaknesses. Two representative examples of initial validation efforts are summarized. The first uses case study analysis techniques and comparison with in situ observations during real events to explore the range of validity of the Lyon–Fedder–Mobarry (LFM) MHD simulation during magnetic storms. The second uses a statistical approach to compare the climatology of plasma sheet bulk properties (density, temperature, magnetic field, flows) deduced from both spacecraft observation and modeled by the LFM code.
