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Baolin Jiang, Bo Huang, Wenshi Lin, and Suishan Xu

1. Introduction The annual discharge of anthropogenic aerosols into the atmosphere is considerable, but the effects of those aerosols on weather and climate remain very uncertain ( IPCC 2007 ). Aerosols can absorb and reflect solar radiation, thereby reducing the surface temperature and planetary boundary layer height, but they also act as cloud condensation nuclei (CCN) or ice nuclei, affecting cloud microphysics and subsequent precipitation rates, and increasing cloud coverage, albedo, and

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Yvonne Boose, Zamin A. Kanji, Monika Kohn, Berko Sierau, Assaf Zipori, Ian Crawford, Gary Lloyd, Nicolas Bukowiecki, Erik Herrmann, Piotr Kupiszewski, Martin Steinbacher, and Ulrike Lohmann

1. Introduction The ice phase in clouds remains one of the largest challenges in predicting Earth’s radiative budget accurately ( Boucher et al. 2013 ). In the atmosphere, pure water freezes homogeneously at temperatures below 235 K ( Lamb and Verlinde 2011 ). In mixed-phase clouds, temperatures are warmer, and supercooled water and ice coexist. Here, ice formation is initiated heterogeneously by ice nucleating particles (INPs), which represent only a small fraction of ambient aerosol particles

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Yan Yang, Jiwen Fan, L. Ruby Leung, Chun Zhao, Zhanqing Li, and Daniel Rosenfeld

constitute the largest uncertainty in climate forcing and projection ( IPCC 2013 ). Through ARI, aerosol particles reduce the energy reaching the surface by scattering and absorbing solar radiation. Absorbing aerosols such as black carbon (BC) can also heat the lower-level atmosphere by absorbing sunlight, which may increase atmospheric stability locally and influence the large-scale circulation, convection, and precipitation (e.g., Fan et al. 2008 , 2015 ; Lau and Kim 2006 ; Zhang et al. 2009a

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Yun Lin, Yuan Wang, Bowen Pan, Jiaxi Hu, Yangang Liu, and Renyi Zhang

. The YSU scheme ( Hong et al. 2006 ) and the thermal diffusion scheme are adopted for the planetary boundary layer parameterization and for the land surface, and no cumulus parameterization is considered. ARE is separately considered by modifying the Goddard radiation scheme to calculate aerosol optical properties ( Fan et al. 2008 ). An internal aerosol mixture with a mass combination of 95% ammonium sulfate and 5% black carbon is assumed when calculating the aerosol radiative properties

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Daniel Rothenberg and Chien Wang

1. Introduction Interactions between aerosol and clouds yield one of the largest sources of uncertainty in understanding climate and future climate change on regional and global scales ( Boucher et al. 2013 ). Within Earth’s atmosphere, homogeneous liquid water droplet formation is not thermodynamically favorable ( Pruppacher and Klett 1997 ); instead, the pathway to nucleating cloud droplets is aided by the presence of ambient aerosol, a subset of which possess physical and chemical

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Wojciech W. Grabowski and Hugh Morrison

approach because differences between ensemble members are large in the second half of the simulations. For illustration, Fig. 2 shows snapshots of the top of the atmosphere (TOA) albedo for randomly selected D-PRI (left column) and D-POL (right column) simulations for hours 2, 6, and 10. In agreement with the cloud fraction profiles in Fig. 1 (and maps of the liquid plus ice water path in Fig. 2 of G15 ), only shallow and optically thin cumuli are present at hour 2. Because the two simulations

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Stacey Kawecki, Geoffrey M. Henebry, and Allison L. Steiner

% elemental carbon fraction of PM 2.5 is a lower limit for semidirect radiative effects to be important ( Meier et al. 2012 ), suggesting that absorption and heating by black carbon (i.e., the semidirect effect) would be minimal. Simulated organic carbon aerosol concentrations are also relatively low. Organic aerosol is derived from primary emissions and secondary formation in the atmosphere from anthropogenic species, but the SORGAM SOA module is known to underpredict SOA formation ( Ahmadov et al. 2012

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