Indirect and Semi-direct Aerosol Campaign

The Impact of Arctic Aerosols on Clouds

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  • 1 University of Illinois at Urbana–Champaign, Urbana, Illinois
  • | 2 Pacific Northwest National Laboratory, Richland, Washington
  • | 3 The Pennsylvania State University, University Park, Pennsylvania
  • | 4 Science and Technology Branch, Environment Canada, Downsview, Ontario, Canada
  • | 5 Pacific Northwest National Laboratory, Richland, Washington
  • | 6 National Research Council of Canada, Ottawa, Ontario, Canada
  • | 7 Pacific Northwest National Laboratory, Richland, Washington
  • | 8 +Los Alamos National Laboratory, Los Alamos, New Mexico
  • | 9 Pacific Northwest National Laboratory, Richland, Washington
  • | 10 Science and Technology Branch, Environment Canada, Downsview, Ontario, Canada
  • | 11 Pacific Northwest National Laboratory, Richland, Washington
  • | 12 Lawrence Berkeley National Laboratory, Berkeley, California
  • | 13 Pacific Northwest National Laboratory, Richland, Washington
  • | 14 Stratton Park Engineering Company, Boulder, Colorado
  • | 15 Science and Technology Branch, Environment Canada, Downsview, Ontario, Canada
  • | 16 Pacific Northwest National Laboratory, Richland, Washington
  • | 17 Scripps Institution of Oceanography, La Jolla, California
  • | 18 +Los Alamos National Laboratory, Los Alamos, New Mexico
  • | 19 Science and Technology Branch, Environment Canada, Downsview, Ontario, Canada
  • | 20 Lawrence Berkeley National Laboratory, Berkeley, California
  • | 21 National Center for Atmospheric Research, Boulder, Colorado
  • | 22 Pacific Northwest National Laboratory, Richland, Washington
  • | 23 Cooperative Institute for Research in Environmental Science, Climate Diagnostics Center, and NOAA/ESRL, Boulder, Colorado
  • | 24 University of Wisconsin—Madison, Madison, Wisconsin
  • | 25 Lawrence Livermore National Laboratory, Livermore, California
  • | 26 Pacific Northwest National Laboratory, Richland, Washington
  • | 27 University of Illinois at Urbana–Champaign, Urbana, Illinois
  • | 28 Texas A&M University, College Station, Texas
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Abstract

A comprehensive dataset of microphysical and radiative properties of aerosols and clouds in the boundary layer in the vicinity of Barrow, Alaska, was collected in April 2008 during the Indirect and Semi-Direct Aerosol Campaign (ISDAC). ISDAC's primary aim was to examine the effects of aerosols, including those generated by Asian wildfires, on clouds that contain both liquid and ice. ISDAC utilized the Atmospheric Radiation Measurement Pro- gram's permanent observational facilities at Barrow and specially deployed instruments measuring aerosol, ice fog, precipitation, and radiation. The National Research Council of Canada Convair-580 flew 27 sorties and collected data using an unprecedented 41 stateof- the-art cloud and aerosol instruments for more than 100 h on 12 different days. Aerosol compositions, including fresh and processed sea salt, biomassburning particles, organics, and sulfates mixed with organics, varied between flights. Observations in a dense arctic haze on 19 April and above, within, and below the single-layer stratocumulus on 8 and 26 April are enabling a process-oriented understanding of how aerosols affect arctic clouds. Inhomogeneities in reflectivity, a close coupling of upward and downward Doppler motion, and a nearly constant ice profile in the single-layer stratocumulus suggests that vertical mixing is responsible for its longevity observed during ISDAC. Data acquired in cirrus on flights between Barrow and Fairbanks, Alaska, are improving the understanding of the performance of cloud probes in ice. Ultimately, ISDAC data will improve the representation of cloud and aerosol processes in models covering a variety of spatial and temporal scales, and determine the extent to which surface measurements can provide retrievals of aerosols, clouds, precipitation, and radiative heating.

A supplement to this article is available online:

DOI: 10.1175/2010BAMS2935.2

Abstract

A comprehensive dataset of microphysical and radiative properties of aerosols and clouds in the boundary layer in the vicinity of Barrow, Alaska, was collected in April 2008 during the Indirect and Semi-Direct Aerosol Campaign (ISDAC). ISDAC's primary aim was to examine the effects of aerosols, including those generated by Asian wildfires, on clouds that contain both liquid and ice. ISDAC utilized the Atmospheric Radiation Measurement Pro- gram's permanent observational facilities at Barrow and specially deployed instruments measuring aerosol, ice fog, precipitation, and radiation. The National Research Council of Canada Convair-580 flew 27 sorties and collected data using an unprecedented 41 stateof- the-art cloud and aerosol instruments for more than 100 h on 12 different days. Aerosol compositions, including fresh and processed sea salt, biomassburning particles, organics, and sulfates mixed with organics, varied between flights. Observations in a dense arctic haze on 19 April and above, within, and below the single-layer stratocumulus on 8 and 26 April are enabling a process-oriented understanding of how aerosols affect arctic clouds. Inhomogeneities in reflectivity, a close coupling of upward and downward Doppler motion, and a nearly constant ice profile in the single-layer stratocumulus suggests that vertical mixing is responsible for its longevity observed during ISDAC. Data acquired in cirrus on flights between Barrow and Fairbanks, Alaska, are improving the understanding of the performance of cloud probes in ice. Ultimately, ISDAC data will improve the representation of cloud and aerosol processes in models covering a variety of spatial and temporal scales, and determine the extent to which surface measurements can provide retrievals of aerosols, clouds, precipitation, and radiative heating.

A supplement to this article is available online:

DOI: 10.1175/2010BAMS2935.2

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