Air quality modelling for air quality policy : technical support document on the use of modelling for various application domains under the Ambient Air Quality Directive : final version

This document provides technical details and support to the implementation of air quality modelling under the revised Directive (EU) 2024/2881 of the European Parliament and of the Council of 23 October 2024 on ambient air quality and cleaner air for Europe (recast) (European Commission, 2024). To this effect, this document presents an overview of current knowledge and good practices, while at the same time signposting to existing technical guidance on air quality modelling and to sources of ongoing guidance development. Over the past decades, scientific understanding of the driving principles of atmospheric pollution has improved significantly. This increased insight in combination with unprecedented computer power and novel computational and statistical techniques have resulted in air quality modelling systems capable of capturing the fundamental processes of air pollution. Air quality modelling systems represent and comprise our current understanding of atmospheric pollution processes. As a result, they are a mature and essential part of the toolbox to support air quality assessment and management practices from global to local scale. Under the previous Ambient Air Quality Directive (2008/50/EC), air quality modelling was already mentioned in several provisions and used by competent authorities to support the implementation of air quality policy. The modelling capacity in Europe has since then improved significantly and a much more harmonised and mature understanding exists today. In the revised Ambient Air Quality Directive (Directive (EU) 2024/2881), modelling is given a more prominent role in the provisions related to air quality assessment and management. Furthermore, it mandates the development of implementing acts to provide further technical details for modelling applications. This will include how results from modelling applications and indicative measurements shall be considered when assessing air quality, how potential exceedances that are identified by those assessment methods can be verified, and technical details for determining the spatial representativeness of sampling points.