In this talk we review basic and general aspects of the
parameterization problem and attempt to identify important conceptual
issues which remain outstanding. Basic types of parameterization
strategies are identified, as well as motivations for choosing
different strategies. A current trend in parameterization, at least
for atmospheric flows, is on the introduction of proxy variables which
act as agents of the parameterized process and are timestepped with
the standard state variables of the flow. We also discuss recent
trends in parameterization, both super-parameterization and the ad hoc
introduction of noise. The growing sophistication of parameterization
often belies an underlying simplicity, a recognition of which could
prompt new strategies for parameterization development and testing, as
well as more rigorous means for addressing issues such as poor
sampling of parameterized processes, and noise.
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