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T. J. Wallington, J. H. Seinfeld, and J. R. Barker

1. Introduction Any historical account of a field as broad and deep as atmospheric chemistry must, by necessity, be selective. In a short account, such as this one, many important individuals, concepts, and discoveries must be omitted from discussion, despite their importance. Moreover, a selective account, such as this one gives the impression that progress was made by following a singular path. This impression could not be further from the truth! Progress in atmospheric chemistry proceeds by

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R. G. Hanea, G. J. M. Velders, A. J. Segers, M. Verlaan, and A. W. Heemink

ensemble-type and square root–type algorithms and it can be interpreted as a variance reducer for the EnKF. In this paper the COFFEE algorithm was coupled with the EUROS model. Contrary to Heemink et al. (2001) , in this study, a real-life, large-scale atmospheric chemistry model with a complex ozone chemistry scheme was used, with the grid covering the whole of Europe ( Hanea et al. 2004 ). The complexity of the model and the large-scale properties make this application very interesting from the

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Irene Cheng, Leiming Zhang, Huiting Mao, Zhuyun Ye, and Robert Keenan

-phase species. The modeled vertical profiles will also have some uncertainties given that the atmospheric Hg chemistry in the free troposphere is also uncertain. Aerosol liquid water content (LWC) is one of the parameters controlling gas-particle partitioning of oxidized Hg in the model, which is modeled as the uptake of GOM species to the aerosol aqueous phase by mass transfer ( Ye et al. 2016 ). Sensitivity simulations showed that varying the LWC has a strong effect on modeled GOM (supplemental section S

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Philip A. Feiner, William H. Brune, David O. Miller, Li Zhang, Ronald C. Cohen, Paul S. Romer, Allen H. Goldstein, Frank N. Keutsch, Kate M. Skog, Paul O. Wennberg, Tran B. Nguyen, Alex P. Teng, Joost DeGouw, Abigail Koss, Robert J. Wild, Steven S. Brown, Alex Guenther, Eric Edgerton, Karsten Baumann, and Juliane L. Fry

1. Introduction Copious emissions of biogenic volatile organic compounds (BVOCs) dictate the atmospheric chemical composition and chemistry in forests. During the day, these BVOCs are oxidized primarily through reactions with the hydroxyl radical (OH) and ozone (O 3 ), which leads to the production of many oxygen-containing volatile, semivolatile, and low-volatility compounds and secondary organic aerosol. Because forests blanket almost a third of the global land, understanding forest oxidation

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Feng Li, John Austin, and John Wilson

responsible for the changes. 2. Model and simulations Details of the new GFDL coupled chemistry–climate model, the Atmospheric Model with Transport and Chemistry (AMTRAC), are described in Austin et al. (2007) and Austin and Wilson (2006) . The model is an extension of the GFDL Atmospheric Model version 2 (AM2; GFDL Global Atmospheric Model Development Team 2004 ). AMTRAC has 48 levels with the top at 0.002 hPa. The horizontal resolution is 2° latitude by 2.5° longitude. All of the physical and

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Golam Sarwar and Prakash V. Bhave

1. Introduction Tropospheric ozone (O 3 ) is produced by complex reactions involving volatile organic compounds (VOC), nitrogen oxides (NO x ), and atmospheric oxidants in the presence of sunlight. Historically, chlorine emissions have not been included in photochemical models for air quality and, thus, the effects of such emissions on O 3 have been neglected. The effect of chlorine chemistry on O 3 has been studied as early as 1985 ( Hov 1985 ). The author used a photochemical model that

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A. Gannet Hallar, Steven S. Brown, Erik Crosman, Kelley C. Barsanti, Christopher D. Cappa, Ian Faloona, Jerome Fast, Heather A. Holmes, John Horel, John Lin, Ann Middlebrook, Logan Mitchell, Jennifer Murphy, Caroline C. Womack, Viney Aneja, Munkhbayar Baasandorj, Roya Bahreini, Robert Banta, Casey Bray, Alan Brewer, Dana Caulton, Joost de Gouw, Stephan F.J. De Wekker, Delphine K. Farmer, Cassandra J. Gaston, Sebastian Hoch, Francesca Hopkins, Nakul N. Karle, James T. Kelly, Kerry Kelly, Neil Lareau, Keding Lu, Roy L. Mauldin III, Derek V. Mallia, Randal Martin, Daniel L. Mendoza, Holly J. Oldroyd, Yelena Pichugina, Kerri A. Pratt, Pablo E. Saide, Philip J. Silva, William Simpson, Britton B. Stephens, Jochen Stutz, and Amy Sullivan

) Atmospheric Chemistry Program and the National Oceanic and Atmospheric Administration (NOAA) Atmospheric Chemistry, Climate and Carbon Cycle Program, the workshop brought together ∼120 air quality experts and meteorologists from across the globe, representing 50 institutions and five countries. As summarized in this article, the workshop outlined the rationale and design for a comprehensive study that couples atmospheric chemistry and meteorology for wintertime poor air quality episodes in mountain basins

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Catherine Wilka, Susan Solomon, Timothy W. Cronin, Doug Kinnison, and Rolando Garcia

chemical constituents and processes will also be affected. For example, all reactants with a steep equator-to-pole concentration gradient are expected to be affected by the Matsuno–Gill wind pattern described here. Reactions with a sufficiently strong temperature sensitivity will also be influenced. For both chlorine-dependent and other reactions, continuing to investigate the impacts of zonally asymmetric circulation patterns on atmospheric chemistry is an area that is ripe for further research

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Marcos Andrade-Flores, Nestor Rojas, Megan L. Melamed, Olga L. Mayol-Bracero, Michel Grutter, Laura Dawidowski, Juan Carlos Antuña-Marrero, Carlos Rudamas, Laura Gallardo, Ruben Mamani-Paco, Maria de Fatima Andrade, and Nicolas Huneeus

socioeconomic issues. However, to understand atmospheric chemistry in the region and its impacts on human health, ecosystems, and climate, it is of the utmost importance to address the heterogeneity of the LAC region’s physical and human geography ( Fig. 1 , left). For example, the climate of northern Mexico is hot and dry, while the climates of many Central America and Caribbean countries consist of a prolonged wet summer season that includes many tropical storms and hurricanes. Within South America the

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Annmarie G. Carlton, Joost de Gouw, Jose L. Jimenez, Jesse L. Ambrose, Alexis R. Attwood, Steven Brown, Kirk R. Baker, Charles Brock, Ronald C. Cohen, Sylvia Edgerton, Caroline M. Farkas, Delphine Farmer, Allen H. Goldstein, Lynne Gratz, Alex Guenther, Sherri Hunt, Lyatt Jaeglé, Daniel A. Jaffe, John Mak, Crystal McClure, Athanasios Nenes, Thien Khoi Nguyen, Jeffrey R. Pierce, Suzane de Sa, Noelle E. Selin, Viral Shah, Stephanie Shaw, Paul B. Shepson, Shaojie Song, Jochen Stutz, Jason D. Surratt, Barbara J. Turpin, Carsten Warneke, Rebecca A. Washenfelder, Paul O. Wennberg, and Xianling Zhou

is mired with uncertainty, in part due to an inability to accurately predict the complex atmospheric processes that are responsible for and respond to pollution. The Southeast Atmosphere Studies (SAS) science topics were chosen to contribute to elucidation of these processes and feedbacks: 1) atmosphere–biosphere interactions, 2) nitrogen chemistry during the day and night, 3) anthropogenic emissions and the related trends in ambient concentrations, 4) atmospheric mercury, 5) gas-phase and

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