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List of Abstracts 136downwind of the fire.P-Transformation.26 ID:4377 10:30Global distribution of the effective aerosol hygroscopicity parameter for CCN activationKirsty Pringle 1 , Holger Tost 2 , Andrea Pozzer 3 , Jos Lelieveld 2 , Uli Poeschl 21 University of Leeds2 Max Planck Institute3 Cyprus InstituteContact: kirsty@env.leeds.ac.ukThe effective hygroscopicity parameter (Κ) offers a simple way of describing the influence of chemicalcomposition on the CCN activity of aerosol particles, this facilitates calculation of the climate effects ofaerosols. Andreae and Rosenfeld (2008) reviewed observed values of Κ and suggested that continental andmarine aerosols on average tend to cluster into relatively narrow ranges of effective hygroscopicity(continental Κ = 0.3 ± 0.1; marine Κ = 0.7 ± 0.2). However, currently, the availability of observational datais not sufficient to obtain a clear picture of the global distribution and characteristic regional differences of Κ. In this study we use a general circulation model to calculate the global distribution of Κ and analyse thevariation in Κ both between and within regions.We find that the simulated global mean value of Κ at the surface is 0.27 ± 0.21 for continental and 0.72 ±0.24 for marine regions. Over the continents Κ appears to be quite uniform, but Africa and South Americahave a lower mean Κ (0.15 – 0.17) than other continental regions (0.21 -0.36). At the top of the planetaryboundary layer, Κ values can deviate significantly form surface values (by up to 30 percent). Marine valuesof Κ are seen to be influenced by continental outflow, with reduced values in marine regions where therenatural and anthropogenic aerosol pass from the continents over the ocean (e.g. the Gulf of Mexico and theSaharan outflow region) .P-Transformation.27 ID:4191 10:30Aerosol formation and growth in anthropogenic sulfur plumesRobin Stevens 1 , Charles Brock 2 , Molly Reed 3 , James Crawford 4 , John Holloway 2 , Thomas Ryerson 2 ,Greg Huey 5 , Jeffrey Pierce 11 Dalhousie University2 NOAA Earth System Research Laboratory3 Tennessee Technological University4 NASA Langley Research Center5 Georgia Institute of TechnologyContact: rgsteven@dal.caWithin the past ten years, global and regional chemical-transport models with online aerosol microphysicshave become powerful tools for understanding how humans may be changing aerosols, clouds and climate.However, large uncertainties in processes such as new-particle formation and emissions limit the predictiveability of these models. Related to both of these uncertainties is the question of how to represent sub-gridaerosol processes in large-scale models with grid-box lengths of 10s of km or larger. Sub-grid SO2 oxidationin power-plant plumes with condensation of H2SO4 onto newly-formed and existing particles is animportant example of these difficult sub-grid aerosol processes. We have developed a modeling frameworkwith aerosol microphysics in the System for Atmospheric Modelling (SAM) 1 , a Large-EddySimulation/Cloud-Resolving Model (LES/CRM), to explore these plumes in detail and developparameterizations of plume microphysics for global and regional models. We evaluate the model withiCACGP-IGAC 2010 14 July, 2010