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Shichao Zhu, Xueliang Guo, Guangxian Lu, and Lijun Guo

1. Introduction Stratiform clouds with embedded convection constitute an important precipitation system that typically has a long lifetime and that may bring either continuous or intermittent precipitation to a large region ( Hobbs and Locatelli 1978 ; Matejka et al. 1980 ; Hobbs et al. 1980 ; Herzegh and Hobbs 1981 ; Evans et al. 2005 ). Because of the presence of high ice crystal concentrations and supercooled water content in embedded convection regions ( Evans et al. 2005 ; Hobbs and

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Andrew L. Molthan and Walter A. Petersen

over 80% of profiles measured over the global oceans ( Battaglia et al. 2007 ), but multiple scattering effects on the order of 1 dB or more can occur when reflectivity exceeds 10–15 dB Z ( Matrosov and Battaglia 2009 ). When applied to cold season precipitation, the use of bulk, soft sphere-shaped representations are inadequate for representing scattering effects of ice crystals and their aggregates at a variety of frequencies ranging from 3 to 35.6 GHz ( Botta et al. 2010 ). Liu (2004

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Paul J. Connolly, Michael J. Flynn, Z. Ulanowski, T. W. Choularton, M. W. Gallagher, and K. N. Bower

correct the oversizing. Furthermore, the theory also provides useful background for developing a correction for nonspherical particles, as we shall see when we develop the correction for ice crystals. In section 4 , it will be shown that the F–K approximation for circular opaque discs cannot be applied directly to the CPI for droplets, but some modifications are needed because of the optical system. c. Justification for the Fresnel–Kirchhoff approximation The F–K approximation can be applied

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Christopher David Westbrook, Robin J. Hogan, and Anthony J. Illingworth

are not available, and in numerical models (e.g., Wilson and Ballard 1999 ) a capacitance based on one of the shapes in Table 1 is usually applied in its place. It is far from clear whether this approximation is a reasonable one, or what the capacitance of realistic ice particles actually is, particularly for large particles, which may be complex aggregates. Chiruta and Wang (2003) suggested a refinement to this situation by approximating bullet rosette crystals by a set of smooth lobes and

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B. Kärcher, A. Dörnbrack, and I. Sölch

1. Introduction Tropospheric ice clouds exist in different temperature regimes: the cold cloud regime, below about 235 K, where liquid water in supercooled cloud or aerosol droplets freezes spontaneously, and the mixed-phase cloud regime at higher temperatures extending up to the melting point, where water droplets and ice crystals might coexist. As pure ice clouds, cirrus reside in the upper troposphere. Mixed-phase clouds are thermodynamically instable and turn, at lower altitudes, into pure

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C. G. Schmitt and A. J. Heymsfield

1. Introduction At any give time, 30% of the midlatitudes are covered with high-altitude cirrus clouds ( Wylie and Menzel 1999 ). Cirrus clouds have been identified as one of the most uncertain components regulating the earth’s climate system ( Lynch et al. 2002 ; Liou 1986 ). Midlatitude cirrus clouds are often composed of bullet rosette– and column-shaped ice crystals ( Heymsfield et al. 2002 ). Lawson et al. (2006) showed that bullet rosette– and column-shaped ice crystals are responsible

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Ping Yang, Lei Bi, Bryan A. Baum, Kuo-Nan Liou, George W. Kattawar, Michael I. Mishchenko, and Benjamin Cole

1. Introduction Numerous studies have elaborated on the important role that natural ice clouds and contrails play in the atmospheric radiation budget essential to weather and climate systems [see Liou (1986) ; Lynch et al. (2002) ; Baran (2009) ; Yang et al. (2010) ; and references therein]. The single-scattering properties of ice crystals are fundamental to the development of a variety of applications involving these clouds. For example, the properties are indispensable in both the

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Mariko Oue, Matthew R. Kumjian, Yinghui Lu, Johannes Verlinde, Kultegin Aydin, and Eugene E. Clothiaux

). Recently developed numerical models that are capable of describing particle growth with diverse sizes, aspect ratios, and densities in such mixed-phase clouds (e.g., Harrington et al. 2013 ; Sulia et al. 2013 , 2014 ) require validation with observations. Polarimetric radar observables offer the capability of identification of hydrometeor species ( Hall et al. 1984 ; Straka and Zrnić 1993 ; Vivekanandan et al. 1999 ; and many others), including ice hydrometeors such as pristine crystal habits (e

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Xiping Zeng, Wei-Kuo Tao, Toshihisa Matsui, Shaocheng Xie, Stephen Lang, Minghua Zhang, David O’C Starr, and Xiaowen Li

1. Introduction Ice nuclei (IN), a class of aerosol particles, can significantly affect cloud ensembles via ice crystal concentration ( Phillips et al. 2005 , 2007 ; Ekman et al. 2007 ; Zeng et al. 2008 ), which in turn impacts radiation (e.g., Zeng et al. 2009b ) and even global warming (e.g., Zeng et al. 2009a ; DeMott et al. 2010 ). To quantify the effect of IN variability on global warming, it is imperative to know other dominant factors of ice crystal concentration besides IN. The

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Matthew Bailey and John Hallett

1. Introduction A comprehensive habit diagram has recently resulted from laboratory studies of ice crystal growth in comparison with extensive observations of atmospheric ice crystals with the Cloud Particle Imager (CPI; Bailey and Hallett 2009 , hereafter BH09 ). The CPI ( Lawson et al. 1998 ; Korolev et al. 1999 , 2000 ; Baker and Lawson 2006 ; Lawson et al. 2006a , b ) has dramatically advanced our knowledge of ice crystal shapes in clouds, while laboratory results ( Bailey and Hallett

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