In a recent paper, Gutiérrez et al (2008) introduced a new characterization of spatiotemporal error growth –the so called Mean-Variance Logarithmic (MVL) diagram- and applied it to study Ensemble Prediction Systems (EPS); in particular they analyzed the different techniques used in practise to perturb the initial conditions. In the present work, the MVL diagram is applied to multi-model ensembles analyzing the effect of both the initialization procedures and the model formulation differences. To this aim, the MVL diagram is systematically applied to the multi-model ensemble produced in the EU-funded DEMETER project. It is shown that the shared building blocks (atmospheric and ocean components) impose similar dynamics among different models and, thus, contribute to poorly sampling the model formulation uncertainty. This dynamical similarity should be taken into account, at least as a pre-screening process, before applying any objective weighting method.
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