Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 6 7 2006 10.5194/acp-6-2017-2006 http://www.atmos-chem-phys.net/6/2017/2006/ http://www.atmos-chem-phys.net/6/2017/2006/acp-6-2017-2006.html http://www.atmos-chem-phys.net/6/2017/2006/acp-6-2017-2006.pdf 2017 2038 2006-06-09 Critical assessment of the current state of scientific knowledge, terminology, and research needs concerning the role of organic aerosols in the atmosphere, climate, and global change S. Fuzzi M. O. Andreae B. J. Huebert M. Kulmala T. C. Bond M. Boy S. J. Doherty A. Guenther M. Kanakidou K. Kawamura V.-M. Kerminen U. Lohmann L. M. Russell U. Pöschl Istituto di Scienze dell’Atmosfera e del Clima, Consiglio Nazionale delle Ricerche, 40129 Bologna, Italy Biogeochemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany Department of Oceanography, University of Hawaii, Honolulu, HI 96822, USA Department of Physical Sciences, University of Helsinki, 00014 Helsinki, Finland Department of Civil and Environmental Engineering, University of Illinois, Urbana, IL 61801, USA IGAC Core Project Office, Seattle, WA 98115, USA Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, CO 80307-3000, USA Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, 71409 Heraklion, Greece Institute of Low Temperature Science, Hokkaido University, Sapporo, Hokkaido 060-0819, Japan USA Finnish Meteorological Institute, 00810 Helsinki, Finland ETH, Institute for Atmospheric and Climate Science, 8093 Zurich, Switzerland Germany Scripps Institution of Oceanography, University of California, La Jolla, CA 92093-0221, USA Institute of Hydrochemistry, Technical University of Munich, 81377 Munich, Germany In spite of impressive advances in recent years, our present understanding of organic aerosol (OA) composition, physical and chemical properties, sources and transformation characteristics is still rather limited, and their environmental effects remain highly uncertain. This paper discusses and prioritizes issues related to organic aerosols and their effects on atmospheric processes and climate, providing a basis for future activities in the field. Four main topical areas are addressed: i) sources of OA; ii) formation transformation and removal of OA; iii) physical, chemical and mixing state of OA; iv) atmospheric modelling of OA. Key questions and research priorities regarding these four areas are synthesized in this paper, and outstanding issues for future research are presented for each topical area. In addition, an effort is made to formulate a basic set of consistent and universally applicable terms and definitions for coherent description of atmospheric OA across different scales and disciplines.