ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-10-5191-2010 The Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission: design, execution, and first results Jacob D. J. 1 Crawford J. H. 2 Maring H. 3 Clarke A. D. 4 Dibb J. E. 5 Emmons L. K. 6 Ferrare R. A. 2 Hostetler C. A. 2 Russell P. B. 7 Singh H. B. 7 Thompson A. M. 8 Shaw G. E. 9 McCauley E. 10 Pederson J. R. 10 Fisher J. A. 1 Harvard University, Cambridge, Massachusetts, USA NASA Langley Research Center, Hampton, Virginia, USA NASA Headquarters, Washington DC, USA University of Hawaii, Honolulu, Hawaii, USA University of New Hampshire, Durham, New Hampshire, USA National Center for Atmospheric Research, Boulder, Colorado, USA NASA Ames Research Center, Moffett Field, California, USA Pennsylvania State University, State College, Pennsylvania, USA University of Alaska, Fairbanks, Alaska, USA California Air Resources Board, Sacramento, California, USA 14 06 2010 10 11 5191 5212 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/10/5191/2010/acp-10-5191-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/5191/2010/acp-10-5191-2010.pdf

The NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission was conducted in two 3-week deployments based in Alaska (April 2008) and western Canada (June–July 2008). Its goal was to better understand the factors driving current changes in Arctic atmospheric composition and climate, including (1) influx of mid-latitude pollution, (2) boreal forest fires, (3) aerosol radiative forcing, and (4) chemical processes. The June–July deployment was preceded by one week of flights over California (ARCTAS-CARB) focused on (1) improving state emission inventories for greenhouse gases and aerosols, (2) providing observations to test and improve models of ozone and aerosol pollution. ARCTAS involved three aircraft: a DC-8 with a detailed chemical payload, a P-3 with an extensive aerosol and radiometric payload, and a B-200 with aerosol remote sensing instrumentation. The aircraft data augmented satellite observations of Arctic atmospheric composition, in particular from the NASA A-Train. The spring phase (ARCTAS-A) revealed pervasive Asian pollution throughout the Arctic as well as significant European pollution below 2 km. Unusually large Siberian fires in April 2008 caused high concentrations of carbonaceous aerosols and also affected ozone. Satellite observations of BrO column hotspots were found not to be related to Arctic boundary layer events but instead to tropopause depressions, suggesting the presence of elevated inorganic bromine (5–10 pptv) in the lower stratosphere. Fresh fire plumes from Canada and California sampled during the summer phase (ARCTAS-B) indicated low NO<sub>x</sub> emission factors from the fires, rapid conversion of NO<sub>x</sub> to PAN, no significant secondary aerosol production, and no significant ozone enhancements except when mixed with urban pollution.

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