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Martin K. Hill, Barbara J. Brooks, Sarah J. Norris, Michael H. Smith, Ian M. Brooks, and Gerrit de Leeuw

1. Introduction Sources and sinks of atmospheric aerosol are a key component of the climate system, affecting the global radiation budget both directly, via scattering of incoming solar radiation, and indirectly via their effect on cloud properties. Primary aerosol derived from natural sources include biogenic materials from natural forest fires, pollens, spores, sea salt, and volcanic ash; secondary sources include aerosol arising from the conversion of dimethyl sulfide to sulfates and from

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Yangyang Song, Guoxing Chen, and Wei-Chyung Wang

1. Introduction Aerosol climate effects consist of the initial forcing that perturbs atmospheric radiation through both the direct radiative effect and the modulation of radiatively important cloud microphysics, and the subsequent changes in atmospheric states (e.g., instability and circulation) that could further affect cloud macro- and microphysics ( Tao et al. 2012 ; Fan et al. 2016 ). These processes are not only sensitive to aerosol properties (e.g., concentration, refractive index, size

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Tyler J. Thorsen, David M. Winker, and Richard A. Ferrare

1. Introduction Aerosols continue to be responsible for the largest uncertainty in determining the anthropogenic radiative forcing of the climate. Aerosols influence anthropogenic forcing indirectly via modifications to cloud properties as well as directly through the scattering and absorption of solar radiation—the aerosol direct radiative forcing (DRF). Placing constraints on the DRF solely using observations is difficult since current satellite observations can only crudely identify

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Tyler J. Thorsen, Richard A. Ferrare, Seiji Kato, and David M. Winker

1. Introduction The most elementary understanding of how aerosols influence forcing of Earth’s climate begins with the aerosol direct radiative effect (DRE)—the effect of aerosol scattering and absorption on the shortwave radiation at the top of the atmosphere (TOA). Passive satellite remote sensing estimates of the aerosol DRE ( Yu et al. 2006 , and references therein) can be highly uncertain outside of cloud-free ocean scenes ( Li et al. 2009 ; Kokhanovsky et al. 2010 ). Advances have been

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Chen Pan, Bin Zhu, Chenwei Fang, Hanqing Kang, Zhiming Kang, Hao Chen, Duanyang Liu, and Xuewei Hou

1. Introduction As an absorbing aerosol, black carbon (BC) is regarded as the second most important contributor to current global warming, only after carbon dioxide ( Ramanathan and Carmichael 2008 ; Bond et al. 2013 ). BC absorbs solar radiation to heat the atmosphere and reduces sunlight to reach Earth’s surface, thereby enhancing atmospheric stability and eventually affecting the general circulation and precipitation ( Menon et al. 2002 ; Chung and Zhang 2004 ; Ramanathan et al. 2005

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Adam Varble

aloft through increased fusion. This has the potential to increase cloud-top height and decrease CTT through warmer, stronger updrafts that reach higher altitudes. This process is termed “aerosol convective invigoration” and has many theoretical (e.g., Rosenfeld et al. 2008 ; Stevens and Feingold 2009 ), modeling (e.g., Khain et al. 2005 ; van den Heever et al. 2006 ; Tao et al. 2007 ; Lebo and Seinfeld 2011 ; Storer and van den Heever 2013 ), and observational (e.g., Andreae et al. 2004

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Cheng Liu, Evgeni Fedorovich, Jianping Huang, Xiao-Ming Hu, Yongwei Wang, and Xuhui Lee

and dynamic properties of the CBL entrainment can be modified by the presence of atmospheric aerosols due to their shortwave radiative absorption effect ( Yu et al. 2002 ; Barbaro et al. 2013 ). In particular, uncertainties of entrainment quantification under conditions of strong aerosol pollution tend to be larger as compared to the entrainment predictions for the CBL without aerosols or with a low load of aerosols. Parameterizations of entrainment are vital to regional or global numerical

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Yuan Wang, Jonathan H. Jiang, Hui Su, Yong-Sang Choi, Lei Huang, Jianping Guo, and Yuk L. Yung

climate system are subject to the influence from external forcings such as man-made greenhouse gases (GHG) ( Notz and Stroeve 2016 ) and aerosols ( Najafi et al. 2015 ), as well as natural variability ( Ding et al. 2017 ) such as the Pacific decadal oscillation (PDO) ( Screen and Francis 2016 ), Arctic Oscillation ( Rigor et al. 2002 ), and even Earth orbital variations ( Lee et al. 2017 ). In addition to energy perturbations from lower latitudes ( Alexeev et al. 2005 ), radiative forcing of aerosols

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Yiquan Jiang, Xiu-Qun Yang, Xiaohong Liu, Yun Qian, Kai Zhang, Minghuai Wang, Fang Li, Yong Wang, and Zheng Lu

-emitted aerosols on climate have received more attention recently. The fire aerosols’ radiative effect (RE) and radiative forcing (RF) are estimated to quantify its impacts. RE represents the instantaneous radiative impact of atmospheric particles on Earth’s energy balance ( Heald et al. 2014 ), and RF is calculated as the change of RE between two different periods (e.g., preindustrial and present-day). The fire aerosols’ radiative effects/forcings could be due to aerosol–radiation interaction (ARI), aerosol

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Angela Benedetti and Frédéric Vitart

1. Introduction The impact of aerosol particles is widely recognized as an important factor for accurate climate and weather predictions. The role of aerosols in Earth’s radiation balance has been addressed by the climate modeling community since the early 90s ( Crutzen and Andreae 1990 ; Charlson et al. 1992 ; Hansen et al. 1992 , to mention a few). Both natural and anthropogenic aerosols are deemed crucial for a correct representation of present-day and future climate/weather scenarios

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