The JRC-FASST model: an updated version of the global atmospheric source-receptor model based on EMEP MSC-W chemical transport model

Abstract. Air pollution remains a major global challenge, affecting human health, agricultural productivity, and climate. Reduced-form models have been widely used to support rapid assessment of emission control strategies. This study presents an updated version of a global air quality screening tool, JRC-FASST, developed using the EMEP chemical transport model. JRC-FASST is a reduced-form Source-Receptor model, which translates changes in emissions of air pollutants from different source regions into changes in atmospheric concentrations. The new model version improves the representation of air pollution, by increasing spatial detail and refining the definition of emission source regions, leading to a more accurate estimation of pollutant concentrations and population and ecosystem exposure. A key enhancement of JRC-FASST is the expanded and refined set of source regions. JRC-FASST employs 76 source regions globally simulated at 0.5° × 0.5° resolution, including 41 individual countries in Europe simulated at 0.1° × 0.1° resolution. This allows a more detailed representation of national emissions and their transboundary impacts. It incorporates an expanded set of air quality indicators, including particulate matter, nitrogen dioxide, and multiple ozone metrics relevant for both health and crop impacts. JRC-FASST reproduces the results of the full atmospheric model with high accuracy, particularly for particulate matter and ozone, while maintaining computational efficiency suitable for policy screening. Overall, the updated model provides a more robust and flexible tool for exploring air quality policies at national, regional and global scales. Moreover, the current version establishes the methodological foundation for a continuously evolving platform.