7.3 Consideration of Uncertainties Beyond Parametric/Data Uncertainty

In addition to the uncertainties associated with model inputs, there are often uncertainties associated with model formulation and structure. Model uncertainty arises mainly when competing models, ranging from simplified to more detailed models, exist. When a model application involves both model and data uncertainties, it is important to identify the relative magnitudes of the uncertainties associated with data and model formulation. Such a comparison is useful in focusing resources where it is most appropriate (e.g., filling data gaps versus refining a model).

The case study involving the development of a three dimensional version of the Reactive Plume Model (RPM-3D, Chapter 6) examines the issues associated with the characterization of uncertainties associated with model formulation. Lack of sufficient model resolution could in fact result in model predictions that may either significantly over-estimate or under-estimate the quantities that are important for decision making. The case study stresses the need for comprehensive hierarchical models, for the systematic evaluation of the simplified models.