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. 2019 Dec 4;116(51):25728–25733. doi: 10.1073/pnas.1907414116

Fig. 3.

Fig. 3.

Map of the back trajectories of air masses sampled at MLO. Each line shows a representative trajectory of the air masses grouped by the last continental landmass it was over in the 15 d before its arrival at MLO. Air masses having been over North America (55% of samples) are represented by the trajectory arriving at MLO on August 17, 2000, in green. Air masses having been over Asia (41% of samples) are represented by the trajectory arriving at MLO on December 1, 2000, in orange. Air masses that were not over a landmass in the past 60 d, or since formation (2% of samples), are represented by the trajectory arriving at MLO on September 29, 2011, in blue. Samples having last been over South America, Oceania, or Kauai (collectively 2% of samples) are not represented.