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  • Author or Editor: G. M. McFarquhar x
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A. Korolev
,
G. McFarquhar
,
P. R. Field
,
C. Franklin
,
P. Lawson
,
Z. Wang
,
E. Williams
,
S. J. Abel
,
D. Axisa
,
S. Borrmann
,
J. Crosier
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J. Fugal
,
M. Krämer
,
U. Lohmann
,
O. Schlenczek
,
M. Schnaiter
, and
M. Wendisch

Abstract

Mixed-phase clouds represent a three-phase colloidal system consisting of water vapor, ice particles, and coexisting supercooled liquid droplets. Mixed-phase clouds are ubiquitous in the troposphere, occurring at all latitudes from the polar regions to the tropics. Because of their widespread nature, mixed-phase processes play critical roles in the life cycle of clouds, precipitation formation, cloud electrification, and the radiative energy balance on both regional and global scales. Yet, in spite of many decades of observations and theoretical studies, our knowledge and understanding of mixed-phase cloud processes remains incomplete. Mixed-phase clouds are notoriously difficult to represent in numerical weather prediction and climate models, and their description in theoretical cloud physics still presents complicated challenges. In this chapter, the current status of our knowledge on mixed-phase clouds, obtained from theoretical studies and observations, is reviewed. Recent progress, along with a discussion of problems and gaps in understanding the mixed-phase environment is summarized. Specific steps to improve our knowledge of mixed-phase clouds and their role in the climate and weather system are proposed.

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D. Baumgardner
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L. Avallone
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A. Bansemer
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S. Borrmann
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P. Brown
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U. Bundke
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P. Y. Chuang
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D. Cziczo
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P. Field
,
M. Gallagher
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J.-F. Gayet
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A. Heymsfield
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A. Korolev
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M. Krämer
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G. McFarquhar
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S. Mertes
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O. Möhler
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S. Lance
,
P. Lawson
,
M. D. Petters
,
K. Pratt
,
G. Roberts
,
D. Rogers
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O. Stetzer
,
J. Stith
,
W. Strapp
,
C. Twohy
, and
M. Wendisch

No abstract available.

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J. Verlinde
,
J. Y. Harrington
,
G. M. McFarquhar
,
V. T. Yannuzzi
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A. Avramov
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S. Greenberg
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N. Johnson
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G. Zhang
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M. R. Poellot
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J. H. Mather
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D. D. Turner
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E. W. Eloranta
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B. D. Zak
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A. J. Prenni
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J. S. Daniel
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G. L. Kok
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D. C. Tobin
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R. Holz
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K. Sassen
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D. Spangenberg
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P. Minnis
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T. P. Tooman
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M. D. Ivey
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S. J. Richardson
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C. P. Bahrmann
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M. Shupe
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P. J. DeMott
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A. J. Heymsfield
, and
R. Schofield

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.

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Greg M. McFarquhar
,
Christopher S. Bretherton
,
Roger Marchand
,
Alain Protat
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Paul J. DeMott
,
Simon P. Alexander
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Greg C. Roberts
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Cynthia H. Twohy
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Darin Toohey
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Steve Siems
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Yi Huang
,
Robert Wood
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Robert M. Rauber
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Sonia Lasher-Trapp
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Jorgen Jensen
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Jeffrey L. Stith
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Jay Mace
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Junshik Um
,
Emma Järvinen
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Martin Schnaiter
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Andrew Gettelman
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Kevin J. Sanchez
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Christina S. McCluskey
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Lynn M. Russell
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Isabel L. McCoy
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Rachel L. Atlas
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Charles G. Bardeen
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Kathryn A. Moore
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Thomas C. J. Hill
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Ruhi S. Humphries
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Melita D. Keywood
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Zoran Ristovski
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Luke Cravigan
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Robyn Schofield
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Chris Fairall
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Marc D. Mallet
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Sonia M. Kreidenweis
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Bryan Rainwater
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John D’Alessandro
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Yang Wang
,
Wei Wu
,
Georges Saliba
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Ezra J. T. Levin
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Saisai Ding
,
Francisco Lang
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Son C. H. Truong
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Cory Wolff
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Julie Haggerty
,
Mike J. Harvey
,
Andrew R. Klekociuk
, and
Adrian McDonald

Abstract

Weather and climate models are challenged by uncertainties and biases in simulating Southern Ocean (SO) radiative fluxes that trace to a poor understanding of cloud, aerosol, precipitation, and radiative processes, and their interactions. Projects between 2016 and 2018 used in situ probes, radar, lidar, and other instruments to make comprehensive measurements of thermodynamics, surface radiation, cloud, precipitation, aerosol, cloud condensation nuclei (CCN), and ice nucleating particles over the SO cold waters, and in ubiquitous liquid and mixed-phase clouds common to this pristine environment. Data including soundings were collected from the NSF–NCAR G-V aircraft flying north–south gradients south of Tasmania, at Macquarie Island, and on the R/V Investigator and RSV Aurora Australis. Synergistically these data characterize boundary layer and free troposphere environmental properties, and represent the most comprehensive data of this type available south of the oceanic polar front, in the cold sector of SO cyclones, and across seasons. Results show largely pristine environments with numerous small and few large aerosols above cloud, suggesting new particle formation and limited long-range transport from continents, high variability in CCN and cloud droplet concentrations, and ubiquitous supercooled water in thin, multilayered clouds, often with small-scale generating cells near cloud top. These observations demonstrate how cloud properties depend on aerosols while highlighting the importance of dynamics and turbulence that likely drive heterogeneity of cloud phase. Satellite retrievals confirmed low clouds were responsible for radiation biases. The combination of models and observations is examining how aerosols and meteorology couple to control SO water and energy budgets.

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