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Hongchun Jin and Shaima L. Nasiri

1. Introduction Cloud thermodynamic phase is a highly uncertain observable from satellite observations that indicates whether a cloud is composed of liquid water droplets, ice crystals, or a mixture of the two phases of hydrometeors (i.e., mixed phase). The determination of cloud phase is an important step in the satellite-based retrieval of several cloud properties, such as cloud particle size, optical thickness, and water path. Cloud phase can significantly impact the planetary radiation

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Yongxiang Hu, David Winker, Mark Vaughan, Bing Lin, Ali Omar, Charles Trepte, David Flittner, Ping Yang, Shaima L. Nasiri, Bryan Baum, Robert Holz, Wenbo Sun, Zhaoyan Liu, Zhien Wang, Stuart Young, Knut Stamnes, Jianping Huang, and Ralph Kuehn

1. Introduction In passive remote sensing, cloud thermodynamic phase (water or ice) information typically comes from the spectral absorption difference between visible (VIS; 0.65 μ m) and shortwave infrared (SWIR; 1.5–1.6 and 3–4 μ m) wavelengths. Neither ice clouds nor water clouds absorb much visible light. However, absorption by both ice and water increases at near-infrared wavelengths, and multiple scattering enhances the absorption. At SWIR wavelengths, ice clouds absorb significantly

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Anthony E. Morrison, Steven T. Siems, Michael J. Manton, and Alex Nazarov

region 40°–55°S, investigating diverse aspects of the marine boundary layer from cloud droplet concentrations ( Boers and Krummel 1998 ) to turbulent mixing ( Russell et al. 1998 ). Long-term ground-based CCN climatologies exist from the northwest coast of Tasmania ( Gras 1995 ), and show that concentrations are usually between 10 and 110 cm −3 with an average of around 70 cm −3 , consistent with Bennartz (2007) . In situ observations of mixed-phase clouds with particular interest in

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Alexei Korolev and Paul R. Field

1. Introduction Mixed-phase clouds are notoriously difficult to represent in numerical weather prediction and climate models (e.g., Illingworth et al. 2007 ). This shortcoming has consequences ranging from the success of operational prediction of in-cloud icing for aviation to the longevity and areal extent of supercooled-layer clouds that can have an impact on the radiative balance of the atmosphere important for climate prediction. Proper simulation of mixed-phase clouds is also essential in

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Alexei Korolev

Mixed-phase clouds play an important role in the formation of precipitation, radiative transfer for cloudy atmospheres, Earth’s radiation budget, and climate. Mixed-phase clouds are thermodynamically unstable and the process of phase transformation in them is often referred to as the “ice crystal theory,” which originated in the works of Wegener (1911) , Bergeron (1935) , and Findeisen (1938) . In 1911, Alfred Wegener proposed a theory of ice crystal growth based on the difference in

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Greg M. McFarquhar, Junshik Um, and Robert Jackson

1. Introduction Mixed-phase clouds, in which supercooled water droplets and ice crystals coexist in the same volume of air, occur throughout the troposphere. Although there is ambiguity in the volume used to define where ice and water coexist and consequently in defining exactly what constitutes a mixed-phase cloud, many remote sensing (e.g., Shupe et al. 2001 ; Intrieri et al. 2002a , b ) and in situ (e.g., Cober et al. 2001b ; Lawson et al. 2001 , Fleishauer et al. 2002 ; Korolev et al

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Shaima L. Nasiri and Brian H. Kahn

1. Introduction Clouds regulate the radiative heating of the planet ( Ramanathan et al. 1989 ) and contribute to latitudinal variability in heating and cooling ( Rossow and Lacis 1990 ) and to the global transport of water in its three phases ( Baker 1997 ; Stephens 2005 ). The global net cloud radiative effect is estimated to be a cooling on the order of 20 W m −2 ( Harrison et al. 1990 ), greater by a factor of 4–5 than the radiative heating estimated to be due to the doubling of carbon

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Gerald G. Mace and Alain Protat

is predominant over the midlatitude oceans in both hemispheres, the radiation bias in models seems to be focused on situations when these clouds exist in thermodynamic conditions that cause their tops to be supercooled and the associated supercooled tops appear to be far more prevalent over the SO than the Northern Hemisphere ( Hu et al. 2010 ). Phase partitioning between ice and liquid in the SO low- and midlevel clouds is a characteristic that has emerged as crucial to our ability to accurately

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Vincent E. Larson and Adam J. Smith

1. Introduction There are several reasons that one may wish to know the fraction of liquid water in thin, mixed-phase layer clouds. One is aircraft icing. Between 1975 and 1988, there were 803 aviation accidents in the continental United States in which icing was a cause or a factor ( Bragg et al. 1998 ). Cober et al. (2001) discuss several well-documented cases of severe icing suffered by research aircraft and also mention the crash of an ATR-72 commuter aircraft near Roselawn, Indiana, in

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Yali Luo, Steven K. Krueger, and Kuan-Man Xu

cloud ice and precipitating ice. In addition to the 29-day simulations, we developed a 1D microphysics-only model implemented with either the SCM or the CRM ice-phase microphysical scheme to evaluate the assumptions of precipitating ice and ice-phase microphysical parameterizations in the SCM. The methodology is described in section 3a . The temporal evolutions of detrainment-formed cloud ice and precipitating ice due to microphysical processes were studied using the microphysics-only model. The

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