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

cloud optical properties [the first indirect effect ( Twomey 1977 )]. Through decreasing cloud drop size, the number of CCN can also change precipitation patterns and cloud lifetimes, which can increase the lifetime of the cloud [the second indirect effect ( Albrecht 1989 )]. On weather time scales, the amount of aerosol present in a given meteorological system affects the efficiency of cloud microphysics and precipitation development, thereby altering the macrostructure and lifetime of the cloud

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Wojciech W. Grabowski

regime change; this does not apply to the case considered here.) The forcings refer to a prescribed initial meteorological situation (e.g., the sounding), surface sensible and latent heat fluxes, radiative cooling of the atmosphere, and the large-scale advection of temperature and moisture. The latter can be included through realistic lateral boundary conditions [as in typical limited-area numerical weather prediction (NWP) simulations] or through prescribed tendencies imposed over a finite

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Tianmeng Chen, Jianping Guo, Zhanqing Li, Chuanfeng Zhao, Huan Liu, Maureen Cribb, Fu Wang, and Jing He

distribution of mean atmospheric visibility observed at 0800 Beijing time (BJT) across China during the warm months for the selected period. These visibility measurements are made four times a day at ground-based weather stations in China. The region of interest (ROI), namely the red box (20°–40°N, 110°–125°E), is selected for its very low visibility on average as a test bed to examine how aerosol pollution impacts clouds associated with the monsoon weather regime. Of the 2129 weather stations collecting

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

, which in turn modifies the atmospheric temperature structure and cloud lifetime ( Hansen et al. 1997 ; Ackerman et al. 2000 ; Wang et al. 2013b ), referred to as the aerosol semidirect effect. The aerosol direct and semidirect effects commonly are considered together as the aerosol radiative effects (ARE). Currently, the understanding of the aerosol effects on weather and climate remain uncertain, since representation of the aerosol and cloud processes, particularly the subgrid cloud dynamics and

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Jianjun Liu, Zhanqing Li, and Maureen Cribb

-Range Weather Forecasts (ECMWF) model runs for ARM analysis provided by the ECMWF ( ECMWF 1994 ). Output from model runs are generated hourly for a 0.56° × 0.56° box centered on the site and include zonal and meridional wind components, temperature, relative humidity, and vertical velocity at 91 pressure levels from the surface to 10 hPa. In this study, clouds with LWP < 20 g m −2 (when retrieval errors are large) or LWP > 700 g m −2 (when precipitation contamination likely occurs) ( Dong et al. 2008

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Jie Peng, Zhanqing Li, Hua Zhang, Jianjun Liu, and Maureen Cribb

1. Introduction By acting as cloud condensation nuclei (CCN) and/or ice nuclei, aerosols affect Earth’s energy budget through the modification of cloud properties, which is often referred to as the aerosol indirect effect (AIE) ( Twomey 1977 ; Albrecht 1989 ; Ramaswamy et al. 2001 ; Lohmann and Feichter 2005 ; Tao et al. 2012 ). A greater number of smaller cloud droplets formed in a dirty environment suppresses collision and coalescence processes and thus delays or inhibits rainfall. This

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Jiwen Fan, Yuan Wang, Daniel Rosenfeld, and Xiaohong Liu

–cloud interaction mechanisms for different cloud types (i.e., shallow maritime clouds, deep convective clouds, mixed-phase stratiform clouds, and cirrus clouds) and then discuss the significance of aerosol impacts (i.e., radiative forcing, precipitation, extreme weather, and large-scale circulations), the current challenges in modeling and observations, and research directions needed toward reducing the uncertainties of climate prediction. Those topics have been the subject of the recent Aerosol

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