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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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Vaughan T. J. Phillips

influencing the eventual global warming realized for any given radiative forcing ( Tsushima et al. 2006 ; Sherwood et al. 2020 ). Mixed-phase clouds have a special microphysical role in the water cycle of the climate system as there are two ways for precipitation to be formed: coalescence of cloud droplets to form “warm” rain (“warm rain process”), with the possibility of supercooled rain freezing at subzero levels to form “warm” graupel or hail that may then melt during fallout through the freezing

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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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Brian C. Filipiak
,
Nick P. Bassill
,
Kristen L. Corbosiero
,
Andrea L. Lang
, and
Ross A. Lazear

1. Introduction Winter weather hazards can hinder travel, utility operations, and day-to-day activities for individuals and businesses. Forecasting and communicating the impacts of winter storms, particularly on the East Coast of the United States, can be challenging due to complex terrain, continental–marine boundaries, and high-density population centers, which make accurate forecasts for these events essential (e.g., Ralph et al. 2005 ). Areas of mixed precipitation, defined in this

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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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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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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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Linette N. Boisvert
,
Melinda A. Webster
,
Chelsea L. Parker
, and
Richard M. Forbes

freezing. d. What are the drivers of differences in precipitation frequency and timing in reanalysis datasets? The precipitation phase and amount in reanalysis products largely depends on how the model for each reanalysis treats and parameterizes the microphysical processes in stratiform and convective clouds ( Table 5 ). In these reanalyses, the partitioning of precipitation phase into rain and snow is treated differently and depends on the specific assumptions of mixed-phase cloud generation

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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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