Waves, Information and Local Predictability

Joseph Tribbia
National Center for Atmospheric Research

This work will re-examine the question of local predictability which was brought to the fore by Lorenz and Emanuel in the context of the utility of adaptive observations. This study approaches the questions of local predictability and expected forecast skill using the tools of two formalisms which heretofore have not been widely incorporated into such problems: wave
propagation and information theory.

Because the questions of adaptive observations are most naturally posed in physical space and not in a modal phase space, wave propagation ideas are the most convenient context within which to ask such questions as: Where should one
observe the atmosphere today to increase our confidence in a 3 day forecast over Los Angeles? An interpretation of the adaptive observing problem using the concepts of group velocities of barotropic and baroclinic waves will be given. Additionally, it will be asserted that the
relative information metric is the most useful measure for posing and gauging the efficacy of adaptive observing strategies. Examples of the usefulness of these concepts will be given using simple atmospheric models.

Presentation (PowerPoint File)

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