English: Figure 1. Population count (km−2) (2015) in the model domain with the Automated Urban and Rural Network (AURN) sites used in the model evaluation over plotted (table S1). Sites where elevated PM2.5 was observed are indicated by red stars and those where concentrations remained below 50 µg m−3 by black circles. The locations of Saddleworth Moor and Winter Hill are indicated by black triangles. Fire emissions, from FINNv1.5 (time-varying scaling), between June 23rd and June 30th are indicated by red circles—each circle represents a fire hotpot from MODIS, while the size of the circles is relative to the mass of PM2.5 emitted in kg day−1 (scale on left). The area over which scaling was applied to the FINN fire emissions is also shown by the blue box. More details on AURN sites can be found in table S1.