Analysis of long‐range transport events at Alert, Northwest Territories, during the Polar Sunrise Experiment

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Abstract
In situ measurements of carbon dioxide, methane, black carbon, peroxyacetylnitrate, condensation nuclei, and radon were made from the Canadian Baseline Atmospheric Monitoring Observatory at Alert, Northwest Territories, Canada (82°28′N, 62°30′W′) during the “Polar Sunrise Experiment” (January 16 to April 20, 1992). The time series of methane, carbon dioxide, peroxyacetylnitrate, and black carbon were frequently highly correlated during January and February during well‐defined episodes lasting from 2 to 5 days. This is consistent with data from earlier years. Shortly after polar sunrise, the temporal variability in both trace gases and aerosols diminished. Using a definition of black carbon concentrations exceeding 100 ng m−3, 11 long‐range transport episodes were defined. Lagrangian 5‐day back trajectories along with the concentration data were classified into six geographical sectors to characterize the major episodes. The winter variability is related to synoptic meteorology, weak vertical mixing, and rapid air mass transport originating from Siberian and/or European source regions. Measurements of the radon daughter (222Rn) activity in the atmosphere were used to further explore the transport of continental material across the Arctic basin.