final_program_abstracts[1]

11 IMSC Session Program
The MVL diagram: A diagnostic tool to characterize ensemble
simulations
Thursday - Poster Session 1
J. Fernández 1 , S. Herrera 2 , J.M. Gutiérrez 2 and M.A. Rodríguez 2
1 Universidad de Cantabria, Spain
2 Instituto de Física de Cantabria, Spain
This work illustrates the usefulness of some recent spatiotemporal analysis tools in the
field of weather and climate simulation. To this aim we present a recent
characterization of spatiotemporal error growth (the so called mean-variance
logarithmic (MVL) diagram, Primo et al. 2005, Gutiérrez et al. 2008). Behind a
simple calculation procedure, the MVL diagram comes from a sound theoretical basis
borrowed from the growth of rough interfaces (López et al. 2004), and has several
applications as a diagnostic tool in the characterization of ensemble prediction
systems. Namely, it is useful in characterizing (1) the initial perturbations applied in a
simulation, (2) the model dynamics, acting as a fingerprint for different models and
(3) the climatological fluctuations of the perturbations specific of each model. As
opposite to the standard temporal analysis (spatially-averaged or single-point), the
MVL spatiotemporal analysis accounts for the nontrivial localization of fluctuations,
thus allowing disentangling the effects of the different initialization procedures
(random, lagged, singular vectors) and the different model formulations.
We show an application of this diagram using a coupled ocean-atmosphere Ensemble
Prediction System (Fernández et al. 2009); in particular we consider the DEMETER
multimodel seasonal hindcast and focus on both initial conditions (three different
perturbation procedures) and model errors (seven coupled GCMs). We show that the
shared building blocks of the GCMs (atmospheric and ocean components) impose
similar dynamics among different models and, thus, contribute to poorly sampling the
model formulation uncertainty. We also illustrate how multiple scales in dynamical
systems impose non-trivial effects on the growth of perturbations.
Abstracts 270