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Franziska Glassmeier and Ulrike Lohmann

–Bergeron–Findeisen (WBF) process ( Wegener 1911 ; Bergeron 1935 ; Findeisen 1938 ; Korolev 2007 ). Aerosol-induced increases in cloud ice lead to a rapid transfer of available cloud liquid onto crystals, that is, the glaciation of a cloud (glaciation indirect effect) ( Lohmann 2002 ; Storelvmo et al. 2008 ; Lohmann and Hoose 2009 ). Complete glaciation transforms a mixed-phase into an ice cloud. Nevertheless, evidence of aerosol-induced changes in precipitation has proven ambiguous and nonrobust ( Boucher et al

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Stanley G. Benjamin, John M. Brown, and Tatiana G. Smirnova

1. Introduction Diagnosis of precipitation type from weather forecast model predictions is important for public forecasting of winter storms, and also for air and surface transportation, energy, hydrology, and other applications. The advent of mixed-phase bulk microphysics schemes in some NOAA operational numerical prediction models [Rapid Update Cycle (RUC; Benjamin et al. 2004a , b ); Rapid Refresh (RAP; Benjamin et al. 2016 ); and High-Resolution Rapid Refresh (HRRR; Smith et al. 2008

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Lulin Xue, Amit Teller, Roy Rasmussen, Istvan Geresdi, Zaitao Pan, and Xiaodong Liu

aerosols are described. The different solubilities and size distributions of regenerated aerosol affect cloud and precipitation properties by altering the microphysical pathways. Based on their effects on warm-phase clouds, it is natural to extend the study to the potential impact of aerosol solubility and regeneration on mixed-phase orographic cloud and precipitation features. Figure 1 illustrates such a scenario: the initial background aerosols consist of different chemical components (solubilities

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Franziska Glassmeier and Ulrike Lohmann

ratio of an advective time scale and a time scale of microphysical conversion, which is influenced by the abundance of CCN. According to this scaling relationship, precipitation efficiency increases for decreasing droplet, or CCN, numbers for low and intermediate precipitation efficiencies. At high precipitation efficiencies, where the time for precipitation formation is always sufficiently long, the aerosol effect levels off. In polluted mixed-phase clouds, the slowing effect of decreased droplet

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Kyoko Ikeda, Matthias Steiner, and Gregory Thompson

1. Introduction Subtle changes in the vertical structure of cold-season precipitating weather systems determine the form of precipitation reaching the ground. Whether precipitation at the surface is liquid (rain), solid (snow, graupel, ice pellets), or mixed phase (herein, mixed phase is either a mixture of both liquid and solid precipitation particles, solely freezing drizzle, or freezing rain since it forms ice upon contact with surface objects) significantly influences the decision

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Daniel D. Tripp, Elinor R. Martin, and Heather D. Reeves

utility for the cool season, with previous studies focusing on measuring Artic and Antarctic environments and not necessarily during active precipitation ( Curry et al. 2004 ; Inoue et al. 2008 ; Cassano et al. 2016 ; de Boer et al. 2018 ). This study employs UAVs as a new observational tool to provide insight into winter-weather processes in an Oklahoma mixed-phase environment. UAV vertical profiles of active winter precipitation that were collected in February 2019 are compared to the local

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Julie M. Thériault and Ronald E. Stewart

completely melt whereas larger ones will only partially melt. The collisions between these different types of precipitation can furthermore alter their amounts and sizes or even form another category of particle, as in mixed phase precipitation ( Stewart et al. 1990a ). For instance, Hogan (1985) states that the freezing of a falling liquid drop can be initiated by a collision with an ice crystal. In this case, it will decrease the amount of supercooled rain and ice crystals and ice pellets are formed

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Mélissa Cholette, Hugh Morrison, Jason A. Milbrandt, and Julie M. Thériault

2001 ; Hanesiak and Stewart 1995 ; Lin and Stewart 1986 ). The precipitation types formed when the temperature is near 0°C involve several microphysical processes including melting, refreezing, vapor deposition, collection, and wet growth. For example, when T > ~0°C, wet snow is formed from the partial melting of snow during which the melted water tends to accumulate on the ice core to form mixed-phase particles ( Fujiyoshi 1986 ). Ice pellets are formed by refreezing in cold layers of the

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Kyoko Ikeda, Matthias Steiner, James Pinto, and Curtis Alexander

; Ressler et al. 2012 ; Grout et al. 2012 ). Accurate predictions of precipitation, especially its timing (onset and duration), spatial extent, intensity, and phase (liquid, solid, or mixed), are important for taking appropriate and timely precautionary measures to minimize potential impacts ( Branick 1997 ). Cold-season precipitation has been the focus of numerous numerical weather prediction (NWP) modeling studies in the past such as the evaluation of quantitative precipitation forecasts, rain

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E. B. Łupikasza and K. Cielecka-Nowak

regional climate change due to its slower signal compared to air temperature ( Krasting et al. 2013 ), many studies have used phase-based precipitation indices to monitor and detect responses to current climate change ( Huntington et al. 2004 ; Dai 2008 ; Ke et al. 2009 ; Deng et al. 2017 ). Long-term changes in liquid–mixed–solid precipitation structures have already been reported in various regions. Snowfall or snowfall-to-precipitation ( S / P ) ratios have decreased over some parts of North

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