Author(s)

E. Canepa & F. Modesti

Abstract

The statistical indices are useful air quality model evaluation tools. Two widely used, NBIAS and NMSE and two new, WNNR and NNR, air quality model performance in- dices are discussed. The behaviour of these four indices is principally analyzed comparing four hypothetical simulated concentration sets with a set of measured concentrations. 1 Introduction Air quality model evaluation tools are useful for scientists, while they are necessary when model responses are used for regulatory purposes (Fox*). Effort to assess the reliability of model estimates have been encouraged (EPA^); as a consequence, the use of performance indices for model evalu- ation is widely accepted. Two widely used, NBIAS and NMSE, and two new, WNNR and NNR (proposed by Poli and Cirillo^, and

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