Influence of vertical transport on free tropospheric aerosols over the central USA in springtime

Abstract

Measurements of the atmospheric aerosol chemical composition during the Subsonic Aircraft: Contrail and Cloud Effects Special Study (SUCCESS) indicate substantial vertical transport of boundary layer aerosol to the free troposphere over the south-central United States during springtime. Mixing ratios of water-soluble aerosol Ca2+ at 6-12 km altitude exhibited a median mixing ratio of 20 pptv, with 15% of the measurements ≥100 pptv and a maximum of 1235 pptv. In air parcels with enhanced Ca2+, the ratios K+/Ca2+, Mg2+/Ca2+, and Na+/Ca2+ in the bulk aerosols were distinctly characteristic of those in limestone and/or cement. Significantly enhanced mixing ratios of aerosol SO2-4, suggesting transport of both crustal and anthropogenic aerosols to the upper troposphere. The mass concentration of water-soluble aerosol material was in the range 0.1-6 μg m-3 STP, and estimated crustal dust levels were 7-160 μg m-3 STP.