Greg McFarquhar                                                               University of Illinois

ISDAC
The National Research Council of Canada Convair-580 parked outside of the hangar at Fairbanks, Alaska, getting ready for a mission to be flown over Barrow, Alaska. A "golden day" of single-layer stratocumulus deck covering the area over Barrow, Alaska. On this day (April 20 2008), the Convair-580 executed legs above, below and at varying altitudes within the cloud to get data to be used to better understand cloud-aerosol interactions. The ISDAC crew poses in fron of the Convair-580
Matt Freer works on calibrating probes during ISDAC in Fairbanks, Alaska. No trip to Alaska is complete without a visit to Denali National Park. Prof. McFarquhar poses in front of the mountains. ISDAC boasted the most complete set of cloud microphysical probes ever installed on a research aircraft. Some of the probes used during ISDAC are depicted here.
ISDAC: The Indirect and Semi-Direct Aerosol Campaign, based out of Fairbanks Alaska in April 2008, was motivated by an attempt to understand the potential roles of clouds and aerosols in the rapid sea ice loss that is occurring in the Arctic. An additional goal was to enhance the understanding of cloud-aerosol interactions in ice- or mixed-phase clouds, where interactions should be more complex than in the warm clouds where such interactions have been previously studied. ISDAC was held in the arctic in the spring when mixed-phase clouds are almost ubiquitous and when variations in the composition and concentrations of aerosols were expected.The specific science questions addressed by ISDAC were as follows: 1) how do the properties of arctic aerosol measured during April differ from those measured in October during M-PACE?; 2) To what extent do the varying properties of arctic aerosol produce differences in the microphysical and macrophysical properties of clouds and the surface energy balance?; 3) To what extent can cloud models and the cloud parameterizations used in climate models simulate the sensitivity of arctic clouds and the surface energy budget to variations in aerosol properties?; and 4) how well can long-term surface-based measurements at the the Department of Energy's North Slope of Alaska site provide retrievals of aerosol, cloud, precipitation, and radiative heating in the Arctic?
Uof Illinois Role and Interests: Together with Dr. Steve Ghan of the Pacific Northwest National Laboratory, Prof. McFarquhar was the lead PI of ISDAC and played a central role in setting the flight sampling strategy for the National Research Council (NRC) of Canada Convair-580. Matt Freer played a big role in processing and archiving the data from some of the cloud microphysical probes installed on the NRC-Convair and stayed in Fairbanks for the entire project. Graduate student Kenny  Bae spent one week in Fairbanks during ISDAC and is using the data collected in cirrus for his M.S. thesis characterizing the microphysical properties of arctic cirrus.

Publications arising from ISDAC:

To follow.

Thesis arising from ISDAC:

Bae, Kenny, 2009: A comparison of the microphysical properties of arctic cirrus against those of mid-latitude and tropical cirrus. M.S. thesis, In progress.

 

Jackson, Robert, 2011: The dependence of the microphysical properties of arctic boundary layer stratus on temperature and surface and aerosol properties. M.S. thesis, In progress.