James C. McWilliams
Institute of Geophysics and Planetary Physics &
Department of Atmospheric and Oceanic Sciences, UCLA

Irreducible Imprecision in Atmospheric and Oceanic Simulations

Atmospheric and oceanic computational simulation models often successfully depict chaotic space-time patterns, flow phenomena, dynamical balances, and equilibrium distributions that mimic nature. This is accomplished through necessary but non-unique choices for discrete algorithms, parameterizations, and coupled contributing processes that introduce structural instability into the model. Therefore, we should expect a degree of irreducible imprecision in quantitative correspondences with nature even with plausibly formulated models and careful calibration (tuning) to several empirical measures. Where precision is an issue (e,g,m in a climate forecast or a Large Eddy Simulation), only simulation ensembles made across systematically designed model families allow an estimate of the level of relevant irreducible imprecision.