CEN/TC 264/WG 43 - Model quality objectives

This document defines and describes the methodology to calculate Modelling Quality Indicators (MQI) and determine fulfilment of the Modelling Quality Objectives (MQO). MQO are provided to help ensure that modelling-based assessments of air quality in the context of the ambient air quality directive [1] are objective and comparable, and of sufficient quality to obtain reliable information about concentrations of air pollutants in ambient air. The method uses measurement uncertainty and a level of stringency as a benchmark for the acceptable level of difference between modelled and measured values.
This document concerns the performance of an entire modelling system therefore the term “modelling quality objectives” is used rather than “model quality objectives”. This document concerns the use of modelling results for assessment as specified in [2]. Such modelling systems aim to capture both the spatial and temporal variability of the environmental indicator under assessment in the modelling domain. This document establishes a method to determine if the results of a modelling system fulfil the MQO and therefore reach an adequate data quality level within the modelling domain defined for assessment.
The procedures described in this document are limited in scope as they concern only statistical performance indicators. A full evaluation of a modelling system considers additional elements of quality assurance, but such procedures are outside the scope of this document.
This document only addresses modelling applications where measurements of pollutant concentrations are available that meet the data requirements for the validation defined in this document. This document specifies MQO that are applicable to all concentration ranges that may occur in ambient air. In the context of this document, MQI and MQO are specified for:
-   daily and annual averaged concentrations of particulate matter with aerodynamic diameter less or equal to 2,5 µm (PM2.5);
-   daily and annual averaged concentrations of particulate matter with aerodynamic diameter less or equal to 10 µm (PM10);
-   hourly, daily and annual averaged concentrations of nitrogen dioxide (NO2);
-   maximum daily 8-hour mean and seasonal averaged concentrations of ozone (O3);
-   hourly, daily and annual averaged concentrations of sulphur dioxide (SO2);
-   maximum daily 8-hour mean and daily averaged concentrations for carbon monoxide (CO);
-   annual averaged concentrations for benzene (C6H6);
-   annual averaged concentrations for lead (Pb);
-   annual averaged concentrations for arsenic (As);
-   annual averaged concentrations for cadmium (Cd);
-   annual averaged concentrations for nickel (Ni);
-   annual averaged concentrations for benzo[a]pyrene (BaP).
This document addresses competent authorities, research institutions, consultants, or other bodies responsible for the performance of air quality modelling when applied for assessment purposes.
NOTE   Fulfilment of MQO is either normative or informative, depending on the quality of information used to determine the uncertainty parameters and stringency factors set out in this document.