Abstract
The increasing complexity of coupled hydrodynamic-ecosystem models
may require skill assessment methods that both quantify various aspects
of model performance and visually summarize these aspects within
compact diagrams. Hence summary diagrams, such as the Taylor diagram
Taylor, 2001, Journal of Geophysical Research, 106, D7, 7183â7192,
may meet this requirement by exploiting mathematical relationships
between widely known statistical quantities in order to succinctly
display a suite of model skill metrics in a single plot. In this
paper, sensitivity results from a coupled model are compared with
Sea-viewing Wide Field-ofviewSensor (SeaWiFS) satellite ocean color
data in order to assess the utility of the Taylor diagram and to
develop a set of alternatives. Summary diagrams are only effective
as skill assessment tools insofar as the statistical quantities they
communicate adequately capture differentiable aspects of model performance.
Here we demonstrate how the linear correlation coefficients and variance
comparisons (pattern statistics) that constitute a Taylor diagram
may fail to identify other potentially important aspects of coupledmodel
performance, even if these quantities appear close to their ideal
values. An additional skill assessment tool, the target diagram,
is developed in order to provide summary information about howthe
pattern statistics and the bias (difference of mean values) each
contribute to the magnitude of the total Root-Mean-Square Difference
(RMSD). In addition, a potential inconsistency in the use of RMSD
statistics as skill metrics for overall model and observation agreement
is identified: underestimates of the observed field?s variance are
rewardedwhen the linear correlation scores are less than unity. An
alternative skill score and skill score-based summary diagram is
presented.
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