Development and Evaluation of the High-Resolution MUSICA UK Domain: A Case Study of Global and Regional Biomass Burning Impacts

Zhiyi Song, James A. King, Wenfu Tang, Jun Zhang, Haofan Wang, Louisa Emmons, James D. Allan, David O. Topping, Maria Val Martin, Zhonghua Zheng

Regional air quality models provide insights into local pollution and exposure, but limitations in representing large-scale atmospheric processes and long-range transport can introduce inconsistencies across spatial scales, which can be addressed using multi-scale chemical transport models. We develop the first UK-specific regionally refined grid (UKne30×16; ∼7 km), alongside a global uniform grid (ne60; ∼56 km), within the Multi-Scale Infrastructure for Chemistry and Aerosols version 0 (MUSICAv0), and evaluated against in situ observations and reanalysis data. MUSICAv0 reproduces the spatial patterns of annual mean surface O3 (R = 0.87; NMB = 12.80%) and PM2.5 (R = 0.64; NMB =-15.70%) across the UK. Compared with ne60, the UK refined configuration better represents transboundary pollution transport, resolves fine-scale horizontal dispersion and vertical mixing, and more accurately captures the spatial variability during pollution episodes. Using biomass burning (BB) as case studies, we show that long-range BB transport elevates springtime PM2.5 by 15–25% and O3 by 5–8%, while summer enhancements of ∼10–14% are associated with local BB emissions, highlighting the importance of non domestic emissions for UK air quality. Further analysis of the 2018 Saddleworth Moor wildfire shows MUSICAv0’s ability to resolve plume transport and vertical structure, with wildfire smoke extending to ∼5.5 km altitude and significantly degrading air quality.