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Fang-Fang Li, Ying-Hui Jia, Guang-Qian Wang, and Jun Qiu

differences in experimental settings and research objects, it is difficult to generalize the effect of sound waves, especially the mechanism of sound waves on cloud droplets, which is crucial for developing new technologies for the exploitation of atmospheric water resources. According to atmospheric physics, the mechanisms of cloud droplet growth primarily include condensation and coagulation. Sound aggregation uses the air, which vibrates with the sound propagation, to carry particles of different sizes

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Neville H. Fletcher

1. Introduction The aim of this short paper is to set out the effect of charges on the interaction between two cloud droplets, since this has major implications for the assumed effect of ionization generators on precipitation. As background, it should be noted that the median diameter of typical cloud droplets ranges from about 15 μ m for continental cumulus clouds to 30 μ m for maritime cumulus clouds ( Fletcher 1966 , chapters 6 and 7). Since a small raindrop has a diameter of at least 1 mm

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Jefferson R. Snider, David Leon, and Zhien Wang

phenomena: 1) processes that put cloud condensation nuclei (CCN) into the atmosphere, 2) the activation process that converts CCN to cloud droplets, 3) processes that reduce cloud droplet concentrations (entrainment and precipitation), and 4) processes that alter CCN distributions, commonly known as CCN activation spectra. Both observational and modeling studies have probed how CCN activation spectra influence cloud droplet number concentrations N and thus impact stratocumulus albedo and precipitation

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Xiang-Yu Li, Axel Brandenburg, Gunilla Svensson, Nils E. L. Haugen, Bernhard Mehlig, and Igor Rogachevskii

than the theoretically predicted time scale of 8 h ( Saffman and Turner 1956 ) and 60 min in simulations of classical adiabatic parcel models ( Jonas 1996 ). Condensational and collisional growth determine the formation of warm rain. In the absence of turbulence, condensational growth is effective for cloud condensation nuclei and cloud droplets smaller than 15 μ m in radius. Since the growth rate is inversely proportional to the radius, condensational growth leads to a narrow width of the droplet

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Karoline Diehl, Günter Huber, Subir K. Mitra, and Manfred Wendisch

1. Introduction Clouds in general and their radiative properties in particular, substantially affect the earth’s radiative balance and, therefore, the global climate ( Kiehl and Trenberth 1997 ). The radiative implications of clouds are strongly determined by their microphysical properties such as the droplet effective size and liquid water content. These quantities can either be retrieved from indirect, remote sensing techniques (e.g., radar or microwave radiometers; see, e.g., Crewell et al

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Vincent E. Perrin and Harmen J. J. Jonker

1. Introduction For many decades, scientists have been interested in the microphysical processes inside a cloud. Much effort is dedicated to understand how droplets form and evolve and how rain is formed. One of the unresolved problems in cloud physics is to explain the rapid growth of cloud droplets in the size range 15–40 μ m in radius for which neither the diffusional mechanism nor the gravitational collision–coalescence mechanism is effective ( Grabowski and Wang 2013 ), known as the

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Gregory Falkovich and Alain Pumir

1. Introduction There is growing evidence that cloud turbulence increases the collision rate between water droplets, thus enhancing the creation and growth of raindrops. However, both qualitative understanding and quantitative treatment are far from satisfactory (see, e.g., Jonas 1996 ; Vaillancourt and Yau 2000 ; Shaw 2003 ; and references therein). In particular, the role of turbulence in inducing collisions of equal-size droplets is very important for the evolution of narrow droplet

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Yan Xue, Lian-Ping Wang, and Wojciech W. Grabowski

1. Introduction Cloud droplets of radii less than 10–15 μ m grow efficiently through diffusion of water vapor, and droplets larger than 30–50 μ m in radii grow efficiently through gravitational collisions ( Langmuir 1948 ; Kogan 1993 ; Beard and Ochs 1993 ; Pruppacher and Klett 1997 ). An open question is why rain forms in warm (i.e., ice free) cumulus clouds as rapidly as it has sometimes been observed. Observations of radar reflectivity in tropical regions suggest that rain could form in

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Alessandra S. Lanotte, Agnese Seminara, and Federico Toschi

1. Introduction The growth of droplets by condensation is a long-standing problem of cloud physics ( Pruppacher and Klett 1997 ), meteorology (see, e.g., Houghton et al. 2001 ), medicine ( Martonen 2000 ), and engineering ( Zhao et al. 1999 ). A fundamental understanding of key issues, such as the turbulent mixing inside clouds or the interaction of turbulence with microphysics, is important for a variety of applications (e.g., the parameterization of small scales in large-scale models, the

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Charmaine N. Franklin, Paul A. Vaillancourt, and M. K. Yau

1. Introduction There have been numerous solutions proposed to answer the classical problem in cloud physics of how to produce drizzle size raindrops on the time scale observed. These ideas include entrainment and mixing of dry air, giant cloud condensation nuclei, and turbulence [see review papers by Blyth (1993) , Beard and Ochs (1993) , and Jonas (1996) ]. The effect of turbulence on the collision and coalescence of cloud droplets has been studied for over 60 yr and yet there is still a

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