A Framework for Error Analysis of a Long-Range Transport Model with Emphasis on Parameter Uncertainty

Alcamo, J. & Bartnicki, J. (1987). A Framework for Error Analysis of a Long-Range Transport Model with Emphasis on Parameter Uncertainty. IIASA Research Report (Reprint). IIASA, Laxenburg, Austria: RR-87-023. Reprinted from Atmospheric Environment, 21 [1987]

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Abstract

A comprehensive framework for model error analysis is applied to the EMEP-W model of long-range transport of sulfur in Europe. This framework includes a proposed taxonomy of model uncertainties. Parameter uncertainties were investigated by Monte Carlo simulation of two source receptor combinations. A 20% input parameter uncertainty (expressed as a coefficient of variation = standard deviation/mean) yielded a 15-22% output error of total sulfur deposition. The relationship between output error and input uncertainty was approximately proportional. Covariance between parameters can have an important effect on computed model error, and can either exaggerate or reduce errors compared to the uncorrelated case. Of the model state variations sulfur-dioxide air concentration and wet deposition had the highest error, and total sulfur deposition the lowest. It was also found that it is more important to specify the dispersion of the input parameter frequency distributions than their shape. The results of the model error analysis were applied to routine calculations of deposition in Europe. An error (coefficient of variation) of 20% for transfer coefficients throughout Europe yielded spatial variations in the order of a few tens to a few hundreds of km in computed deposition isolines of 2 and 5g sulfur m^{-2}a^{-1}.

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