The Mixed-Phase Arctic Cloud Experiment (M-PACE) was conducted from 27 September through 22 October 2004 over the Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) on the North Slope of Alaska. The primary objectives were to collect a dataset suitable to study interactions between microphysics, dynamics, and radiative transfer in mixed-phase Arctic clouds, and to develop/evaluate cloud property retrievals from surface-and satellite-based remote sensing instruments. Observations taken during the 1977/98 Surface Heat and Energy Budget of the Arctic (SHEBA) experiment revealed that Arctic clouds frequently consist of one (or more) liquid layers precipitating ice. M-PACE sought to investigate the physical processes of these clouds by utilizing two aircraft (an in situ aircraft to characterize the microphysical properties of the clouds and a remote sensing aircraft to constraint the upwelling radiation) over the ACRF site on the North Slope of Alaska. The measurements successfully documented the microphysical structure of Arctic mixed-phase clouds, with multiple in situ profiles collected in both single- and multilayer clouds over two ground-based remote sensing sites. Liquid was found in clouds with cloud-top temperatures as cold as −30°C, with the coldest cloud-top temperature warmer than −40°C sampled by the aircraft. Remote sensing instruments suggest that ice was present in low concentrations, mostly concentrated in precipitation shafts, although there are indications of light ice precipitation present below the optically thick single-layer clouds. The prevalence of liquid down to these low temperatures potentially could be explained by the relatively low measured ice nuclei concentrations.
The Pennsylvania State University, University Park, Pennsylvania
University of Illinois at Urbana—Champaign, Urbana, Illinois
University of North Dakota, Grand Forks, North Dakota
Pacific Northwest National Laboratory, Richland, Washington
University of Wisconsin—Madison, Madison, Wisconsin
Sandia National Laboratories, New Mexico, Albuquerque, New Mexico
Colorado State University, Fort Collins, Colorado
NOAA Earth System Research Laboratory, Boulder, Colorado
Droplet Measurement Technologies, Inc., Boulder, Colorado
University of Alaska, Fairbanks, Fairbanks, Alaska
Analytical Services & Materials, Inc., Hampton, Virginia
NASA Langley Research Center, Hampton, Virginia
Sandia National Laboratories, California, Livermore, California
National Center for Atmospheric Research, Boulder, Colorado
The Cooperative Institute of Research in Environmental Sciences, University of Colorado, Boulder, Colorado
NOAA Earth System Research Laboratory, Boulder, and The Cooperative Institute of Research in Environmental Sciences, University of Colorado, Boulder, Colorado
