Balloon-Borne Measurements of Vertical Profiles of Aerosols, Condensation Nuclei, and CloudCondensation Nuclei

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This project focuses on continuing and extending vertical aerosol profile measurements at Laramie, Wyoming (41░N, 105░W). The stratospheric measurements are important to assess the level at which stratospheric aerosol concentrations are maintained during volcanically quiescent, or background, periods, and thus to understand if the stratospheric aerosol level has been perturbed by anthropogenic (or natural) influences over the past 30 years. In particular, the impact of increasing air traffic is a concern. Direct effects of air traffic on aerosol concentration will be studied by looking for intersections of the balloon-borne measurements with the wakes of air traffic in the region. Characterizing the direct effects of tropospheric aerosol and the indirect effects of cloud condensation nuclei (CCN) in global climate models is a large source of uncertainty in our understanding of the global heat balance, which can be reduced through more refined measurements of tropospheric aerosol and CCN.The continuing measurements will consist of condensation nuclei (CN) and optically detectable aerosol (with a radius between 0.15 and 2.0 um), from the surface to 30 km, and CCN from the surface to about 13 km. The balloon flight frequency will be about once per month as it has been in the past. In addition to measurements in Laramie, yearly measurements from Lauder, New Zealand (45░S) will be continued. Two CCN counters and a new multi-angle aerosol instrument will be deployed, providing vertical profiles of CCN spectra for the first time. The second CCN counter will be built under this project. The two CCN instruments will allow CCN measurements at two supersaturations, thus providing CCN spectra. The multi-angle aerosol instrument, which is being developed under other support, will be used in studies of the index of refraction of tropospheric aerosol particles. To supplement these measurements, collaborations with two other investigators are planned. Dr. Darin Toohey, University of California at Irvine, will make approximately seasonal profile measurements of ClO/BrO from Laramie in conjunction with these aerosol measurements, in order to study mid latitude heterogeneous processing of ClO/BrO. An Italian colleague plans to participate with a balloon-borne laser scatterometer to investigate the index of refraction of tropospheric particles.