Fig.1: European domain at 12UT 31 July. NOx emissions tracer on 275hPa (FL320). The cross marks the pollution exported within the WCB.
Fig.2: Section along the dashed line in Fig.1 showing accumulated NOx. The part of the WCB sampled by the BA146 on 29 July is at FL250-FL300 (the lowest portion).
Fig.3: Back trajectories in the WCB (the cross on Fig. 1). Join the dots between Pease, Faial and Creil!
Fig.4: Latitude of trajectory origins 7 days before arrival. Air from over Canada containing forest fire emissions is marked by the cross (FL280-FL320). The part sampled by the BA146 on 29 July would be at FL280.
Fig.5: Back trajectories from the cross in Fig.4 tracing back towards Northern Territories where forest fires are burning.