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Timothy H. Raupach, Merhala Thurai, V. N. Bringi, and Alexis Berne

DVD provided good resolution (about 0.17 mm) for larger drops. The instruments’ overlap region (0.7–1.2 mm) was found to be in good agreement. The combined spectra exhibited a large number of small drops in a “drizzle mode” (for diameters less than about 0.5–0.7 mm), and a precipitation mode for larger drops, often separated by a shoulder (or plateau) region. These modes were previously identified in aircraft imaging probe data collected in oceanic warm-rain clouds by Abel and Boutle (2012) , and

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Claudia Acquistapace, Ulrich Löhnert, Maximilian Maahn, and Pavlos Kollias

distributed horizontally and vertically in space. However, drizzle formation can modify cloud water content distributions by removing water content from the cloud; it can also alter in this way the cloud lifetime and the cloud cover, with direct effects on the radiation and also on the thermodynamical structure of the planetary boundary layer (PBL). Drizzle plays a central role in the description of PBL liquid clouds in general circulation models (GCMs). However, drizzle is generally overestimated in GCMs

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Andrew S. Ackerman, Margreet C. vanZanten, Bjorn Stevens, Verica Savic-Jovcic, Christopher S. Bretherton, Andreas Chlond, Jean-Christophe Golaz, Hongli Jiang, Marat Khairoutdinov, Steven K. Krueger, David C. Lewellen, Adrian Lock, Chin-Hoh Moeng, Kozo Nakamura, Markus D. Petters, Jefferson R. Snider, Sonja Weinbrecht, and Mike Zulauf

stratocumulus-topped marine boundary layer, with average cloud droplet concentrations of ∼140 cm −3 ( vanZanten et al. 2005 ) and no measurable precipitation below cloud base ( Stevens et al. 2005b ). Models that reduced subgrid-scale mixing at cloud top were found best able to maintain sufficient radiative cooling while concurrently limiting entrainment at cloud top, resulting in a well-mixed boundary layer topped by an optically thick cloud layer, as observed. Cloud water sedimentation and drizzle were

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Shashank S. Joshil, Cuong M. Nguyen, V. Chandrasekar, J. Christine Chiu, and Yann Blanchard

1. Introduction Boundary layer clouds are fundamental to Earth’s radiation budget due to their vast cloud cover and high albedo ( Hartmann et al. 1992 ; Hahn and Warren 2007 ). They drizzle frequently ( Petty 1995 ; Rémillard et al. 2012 ; Wu et al. 2017 ); the drizzle process not only influences cloud organization and life cycle, but also modulates boundary layer structure and the energy budget ( Wood 2012 ; Ahlgrimm and Forbes 2014 ; Yamaguchi et al. 2017 ; Zhou et al. 2017 ). These

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Efthymios Serpetzoglou, Bruce A. Albrecht, Pavlos Kollias, and Christopher W. Fairall

of the various boundary layer and cloud properties observed on the three cruises and highlight the differences between the three observational periods. Mean profiles of the MABL thermodynamic structure for each cruise for the period for which the research vessels remained stationed at the ORS location are also constructed and compared in section 3 . Section 4 discusses the physical properties of clouds and drizzle in an attempt to illuminate the various processes that modulate cloud life cycle

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Peng Wu, Xiquan Dong, and Baike Xi

Dufresne 2005 ; Wood et al. 2009 ). Despite their importance, climate models often underestimate low cloud cover but overestimate their optical thickness ( Nam et al. 2012 ; Bony and Dufresne 2005 ) and simulate different signs and magnitudes of the low cloud feedback ( Zelinka et al. 2020 ; Vial et al. 2013 ; Bony and Dufresne 2005 ). MBL clouds frequently produce precipitation, most often in the form of drizzle ( Wood 2012 ; Rémillard et al. 2012 ; Dong et al. 2014a ; Wu et al. 2015 , 2017

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Edward P. Luke and Pavlos Kollias

1. Introduction Advancing our understanding of the cloud-scale physical processes that affect cloud lifetime requires high-resolution measurements in clouds ( Brenguier and Wood 2009 ). One area of great interest is the separation of cloud and drizzle microphysics and turbulence in warm clouds to shed light on precipitation initiation, including the role of aerosols and dynamics. Aircraft penetrations can provide detailed in situ measurements of these quantities; however, they are expensive

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Xiaoli Zhou, Andrew S. Ackerman, Ann M. Fridlind, and Pavlos Kollias

frequently observed embedded in unbroken cloud fields and share similar meteorological conditions of adjacent closed-cellular clouds ( Stevens et al. 2003 ; Wood and Hartmann 2006 ). Such embedded open-cell features, commonly referred to as the pockets of open cells (POCs), are associated with patchy drizzle ( Stevens et al. 2005 ; Rosenfeld et al. 2006 ; Sharon et al. 2006 ; Comstock et al. 2005 , 2007 ; Wood et al. 2011 ). Plentiful aircraft and radar measurements (e.g., Frisch et al. 1995

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M. Pinsky, L. Magaritz, A. Khain, O. Krasnov, and A. Sterkin

1. Introduction The precipitating, radiative, and reflectivity properties of warm stratiform clouds strongly depend on the shape of droplet size distributions (DSDs), which can vary substantially at the scales of several tens of meters ( Korolev and Mazin 1993 ; Korolev 1994 , 1995 ). Especially strong changes of DSDs are related to drizzle formation (e.g., Stevens et al. 1998 ; vanZanten et al. 2005 ; Petters et al. 2006 ). The investigations of DSD formation mechanisms, as well as those

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Yefim L. Kogan, Zena N. Kogan, and David B. Mechem

any convective clouds where the warm rain process applies through a deep vertical layer. Lognormal fits to forward scattering spectrometer probe (FSSP) spectra observed during the Atlantic stratocumulus transition experiment (ASTEX) yielded reasonable values of effective radius, with greater uncertainty associated with enhanced concentrations of drizzle droplets ( r > 20 μ m) ( Gerber 1996 ). Cerro et al. (1997) found that the gamma distribution was generally able to represent rain drop

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