1Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado, USA
2Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA
3Norsk Institutt for Luftforskning, Kjeller, Norway
4Langley Research Center, National Aeronautics and Space Administration, Hampton, Virginia, USA
5Ames Research Center, National Aeronautics and Space Administration, Moffett Field, California, USA
6Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
7Earth and Atmospheric Science, Georgia Institute of Technology, Atlanta, Georgia, USA
8National Environmental Satellite, Data, and Information Service, National Oceanic and Atmospheric Administration, Madison, Wisconsin, USA
9Atmospheric and Oceanic Sciences, University of Colorado, Boulder, Colorado, USA
10Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration, Seattle, Washington, USA
11Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado, USA
*now at: Laboratoire de Glaciologie et Géophysique de l'Environnement, Grenoble, France
**now at: Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
***now at: Droplet Measurement Technologies Inc., Boulder, Colorado, USA
****now at: Biogeochemistry, Max Planck Institute for Chemistry, Mainz, Germany
Received: 08 Oct 2010 – Published in Atmos. Chem. Phys. Discuss.: 11 Nov 2010
Abstract. We present an overview of the background, scientific goals, and execution of the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) project of April 2008. We then summarize airborne measurements, made in the troposphere of the Alaskan Arctic, of aerosol particle size distributions, composition, and optical properties and discuss the sources and transport of the aerosols. The aerosol data were grouped into four categories based on gas-phase composition. First, the background troposphere contained a relatively diffuse, sulfate-rich aerosol extending from the top of the sea-ice inversion layer to 7.4 km altitude. Second, a region of depleted (relative to the background) aerosol was present within the surface inversion layer over sea-ice. Third, layers of dense, organic-rich smoke from open biomass fires in southern Russia and southeastern Siberia were frequently encountered at all altitudes from the top of the inversion layer to 7.1 km. Finally, some aerosol layers were dominated by components originating from fossil fuel combustion.
Revised: 28 Jan 2011 – Accepted: 04 Mar 2011 – Published: 16 Mar 2011
Of these four categories measured during ARCPAC, the diffuse background aerosol was most similar to the average springtime aerosol properties observed at a long-term monitoring site at Barrow, Alaska. The biomass burning (BB) and fossil fuel layers were present above the sea-ice inversion layer and did not reach the sea-ice surface during the course of the ARCPAC measurements. The BB aerosol layers were highly scattering and were moderately hygroscopic. On average, the layers produced a noontime net heating of ~0.1 K day−1 between 3 and 7 km and a slight cooling at the surface. The ratios of particle mass to carbon monoxide (CO) in the BB plumes, which had been transported over distances >5000 km, were comparable to the high end of literature values derived from previous measurements in wildfire smoke. These ratios suggest minimal precipitation scavenging and removal of the BB particles between the time they were emitted and the time they were observed in dense layers above the sea-ice inversion layer.
Citation: Brock, C. A., Cozic, J., Bahreini, R., Froyd, K. D., Middlebrook, A. M., McComiskey, A., Brioude, J., Cooper, O. R., Stohl, A., Aikin, K. C., de Gouw, J. A., Fahey, D. W., Ferrare, R. A., Gao, R.-S., Gore, W., Holloway, J. S., Hübler, G., Jefferson, A., Lack, D. A., Lance, S., Moore, R. H., Murphy, D. M., Nenes, A., Novelli, P. C., Nowak, J. B., Ogren, J. A., Peischl, J., Pierce, R. B., Pilewskie, P., Quinn, P. K., Ryerson, T. B., Schmidt, K. S., Schwarz, J. P., Sodemann, H., Spackman, J. R., Stark, H., Thomson, D. S., Thornberry, T., Veres, P., Watts, L. A., Warneke, C., and Wollny, A. G.: Characteristics, sources, and transport of aerosols measured in spring 2008 during the aerosol, radiation, and cloud processes affecting Arctic Climate (ARCPAC) Project, Atmos. Chem. Phys., 11, 2423-2453, doi:10.5194/acp-11-2423-2011, 2011.