Aerosol samples collected over the western Pacific during the NASA/Global Tropospheric Experiment Pacific Exploratory Mission (PEM-West A) expedition (September–October 1991) revealed mean 210Pb concentrations in the free troposphere in the 5–10 fCi m−3 STP range. Most soluble ionic aerosol-associated species were near detection limits [≪40 parts per trillion by volume (pptv)] in these same samples. The altitude distribution of O3 near Asia closely resembled that of 210Pb, while no relationship was found between the concentrations of O3 and 7Be. Free tropospheric air over the western Pacific was depleted in soluble aerosol-associated species but enriched in 210Pb and O3, indicative of deep wet convection over the Asian continent. The influence of Asian air on the composition of the free troposphere over the western Pacific was evident on most of the PEM-West A flights. However, evidence of continental influence was largely restricted to those species that are relatively insoluble (or have insoluble precursors), hence escape scavenging during vertical transport from the boundary layer into the free troposphere by wet convective activity.


Earth Sciences, Earth Systems Research Center

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Journal of Geophysical Research: Atmospheres



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Copyright 1996 by the American Geophysical Union.