a, Seven-day trajectories (grey lines) launched every 6 h and originated from wildfires during the period of 26 October to 4 November 2019 and black carbon AOD from the same period shown as the background map. The trajectory origins are depicted by black circles. The distribution of trajectories generally follows the black AOD pattern. b, Seven-day trajectories (grey lines) originated from wildfires during the period of 26 November to 5 December 2019. c, The spatial distribution of 7-day trajectory endpoints frequencies in 2° by 2° grid over the period of November 2019 to January 2020. The trajectory origins are depicted by black circles to represent the major fires’ locations. The 7-day air parcel forward trajectories were launched daily. The red contours depict regions where [Chla] more than doubled during the same period compared with their climatologies. The large [Chla] anomalies generally occurred in regions over which the trajectories passed.