ALBERT

Description: Interannual variation, decadal trend, and future change in ozone outflow from East Asia Jia Zhu, Hong Liao, Yuhao Mao, Yang Yang, and Hui Jiang Atmos. Chem. Phys., 17, 3729-3747, doi:10.5194/acp-17-3729-2017, 2017 Asian O 3 outflow exhibited a small and statistically insignificant decadal trend with large interannual variations from 1986–2006. The latter were mainly caused by variations in the meteorological conditions. Future climate change will aggravate the effects of the increases in anthropogenic emissions on future changes in the Asian O 3 outflow. These findings help us to understand the variations in tropospheric O 3 in the regions downwind of East Asia on different timescales.

Description: Tracing changes in atmospheric moisture supply to the drying Southwest China Chi Zhang, Qiuhong Tang, Deliang Chen, Laifang Li, Xingcai Liu, and Huijuan Cui Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-147,2017 Manuscript under review for ACP (discussion: open, 0 comments) Precipitation over Southwest China (SWC) decreased significantly in recent years. By attributing precipitation to its sources, we found that the reduced precipitation is resulted from the reduced moisture supply from regions influenced by the South Asian Summer Monsoon and the westerlies. Further study revealed the dynamic variations in circulation dominate the interannual variations in precipitation over SWC. Changes in circulation systems may be related to the recent changes in SSTs.

Description: Potential impact of carbonaceous aerosols on the Upper Troposphere and Lower Stratosphere (UTLS) during Asian summer monsoon in a global model simulation Suvarna Fadnavis, Gayatry Kalita, K. Ravi Kumar, Blaz Gasparini, and Jui-Lin Frank Li Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-197,2017 Manuscript under review for ACP (discussion: open, 0 comments) In this study, the model simulations show that monsoon convection over the Bay of Bengal, the South China Sea and Southern flanks of the Himalayas transport Asian carbonaceous aerosol into the UTLS. Carbonaceous aerosol induces enhancement in heating rate, vertical velocity and water vapor transport in the UTLS.Doubling of BC + OC aerosols creates an anomalous warming over the TP. It elicits monsoon Hadley circulation and thus increases precipitation over India and northeast China.

Description: Sensitivity of transatlantic dust transport to chemical aging and related atmospheric processes Mohamed Abdelkader, Swen Metzger, Benedikt Steil, Klaus Klingmüller, Holger Tost, Andrea Pozzer, Georgiy Stenchikov, Leonard Barrie, and Jos Lelieveld Atmos. Chem. Phys., 17, 3799-3821, doi:10.5194/acp-17-3799-2017, 2017 We present a modeling study on the impacts of the key processes (dust emission flux, convection and dust aging parameterizations) that control the transatlantic dust transport using an advanced version of the EMAC atmospheric chemistry general circulation model. We define the direct effect of dust aging as an increase in the AOD as a result of hygroscopic growth. We define the indirect effect as a reduction in the dust AOD due to the higher removal of the aged dust particles.

Description: Global distribution of CO 2 in the upper troposphere and stratosphere Mohamadou Diallo, Bernard Legras, Eric Ray, Andreas Engel, and Juan A. Añel Atmos. Chem. Phys., 17, 3861-3878, doi:10.5194/acp-17-3861-2017, 2017 We construct a new monthly zonal mean CO 2 distribution from the upper troposphere to the stratosphere over the 2000–2010 period. The main features of the CO 2 distribution are consistent with expected variability due to the transport of long-lived trace gases by the Brewer–Dobson circulation. The method used to construct this CO 2 product is unique and should be useful for model and satellite validation in the upper troposphere and stratosphere.

Description: On biases in atmospheric CO inversions assimilating MOPITT satellite retrievals Yi Yin, Frederic Chevallier, Philippe Ciais, Gregoire Broquet, Anne Cozic, Sophie Szopa, and Yilong Wang Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-166,2017 Manuscript under review for ACP (discussion: open, 0 comments) CO inverse modelling studies have so far reported significant discrepancies between model concentrations optimised with the Measurement of Pollution in the Troposphere (MOPITT) satellite retrievals and surface in-situ measurements. Here, we assess how well a global CTM fits a large variety of independent CO observations before and after assimilating MOPITTv6 retrievals to optimise CO sources/sink and discuss potential sources of errors and their implications for global CO modelling studies.

Description: The Variability of Relationship between Black Carbon and Carbon Monoxide over the Eastern Coast of China: BC Aging during Transport Qingfeng Guo, Min Hu, Song Guo, Zhijun Wu, Jianfei Peng, and Yusheng Wu Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-56,2017 Manuscript under review for ACP (discussion: open, 0 comments) To characterize primary emissions over the eastern coast of China, a cascade of field campaign was conducted. The high loadings of both BC and CO imply the severe anthropogenic pollution over the areas. The slopes between BC and CO at different areas reveal the vehicular emission as the common source and the distinct fuel structures between North and South China. The comparisons of slopes and correlation coefficient among these areas indicate the more aging of BC in East China Sea.

Description: Temporal characteristics of atmospheric ammonia and nitrogen dioxide over China based on emission data, satellite observations and atmospheric transport modeling since 1980 Lei Liu, Xiuying Zhang, Wen Xu, Xuejun Liu, Yi Li, Xuehe Lu, Yuehan Zhang, and Wuting Zhang Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-106,2017 Manuscript under review for ACP (discussion: open, 0 comments) We conducted the temporal trend analysis of atmospheric NH 3 and NO 2 in China since 1980 based on emission data (during 1980–2010), satellite observations (for NH 3 since 2008 and for NO 2 since 2005) and atmospheric chemistry transport modeling (during 2008–2015). Our findings provided an overall insight on the temporal trends of both NO 2 and NH 3 since 1980 and the multivariate data used in this study have implications for estimating long-term Nr deposition datasets.

Description: Sulfate geoengineering: a review of the factors controlling the needed injection of sulfur dioxide Daniele Visioni, Giovanni Pitari, and Valentina Aquila Atmos. Chem. Phys., 17, 3879-3889, doi:10.5194/acp-17-3879-2017, 2017 This review paper summarizes the state-of-the-art knowledge of the direct and indirect side effects of sulfate geoengineering, that is, the injection of sulfur dioxide into the stratosphere in order to offset the warming caused by the anthropic increase in greenhouse gasses. An overview of the various effects and their uncertainties, using results from published scientific articles, may help fine-tune the best amount of sulfate to be injected in an eventual realization of the experiment.

Description: Top-down and Bottom-up aerosol-cloud-closure: towards understanding sources of uncertainty in deriving cloud radiative flux Kevin J. Sanchez, Greg C. Roberts, Radiance Calmer, Keri Nicoll, Eyal Hashimshoni, Daniel Rosenfeld, Jurgita Ovadnevaite, Jana Preissler, Darius Ceburnis, Colin O'Dowd, and Lynn M. Russell Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-201,2017 Manuscript under review for ACP (discussion: open, 0 comments) Top-down and bottom-up aerosol-cloud-radiative flux closures were conducted at the Mace Head atmospheric research station in Galway, Ireland in August 2015. This study is part of the BACCHUS (Impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) European collaborative project, with the goal of understanding key processes affecting aerosol-cloud-radiative flux closures to improve future climate predictions and develop sustainable policies for Europe. Instrument platforms include ground-based, unmanned aerial vehicles (UAV), and satellite measurements of aerosols, clouds and meteorological variables. The ground-based and airborne measurements of aerosol size distributions and cloud condensation nuclei (CCN) concentration were used to initiate a 1D microphysical aerosol-cloud parcel model (ACPM). UAVs were equipped for a specific science mission, with an optical particle counter for aerosol distribution profiles, a cloud sensor to measure cloud extinction, or a 5-hole probe for 3D wind vectors. UAV cloud measurements are rare and have only become possible in recent years through the miniaturization of instrumentation. These are the first UAV measurements at Mace Head. ACPM simulations are compared to in-situ cloud extinction measurements from UAVs to quantify closure in terms of cloud radiative flux. Two out of seven cases exhibit sub-adiabatic vertical temperature profiles within the cloud, which suggests that entrainment processes affect cloud microphysical properties and lead to an overestimate of simulated cloud radiative flux. Including an entrainment parameterization and explicitly calculating the entrainment fraction in the ACPM simulations both improved cloud-top radiative closure. Entrainment reduced the difference between simulated and observation-derived cloud-top radiative flux (δRF) by between 30 W m −2 and 40 W m −2 . After accounting for entrainment, satellite-derived cloud droplet number concentrations (CDNC) were within 30 % of simulated CDNC. In cases with a well-mixed boundary layer, δRF is less than 25 W m −2 after accounting for cloud-top entrainment, compared to less than 50 W m −2 when entrainment is not taken into account. In cases with a decoupled boundary layer, cloud microphysical properties are inconsistent with ground-based aerosol measurements, as expected, and δRF is as high as 88 W m −2 , even after accounting for cloud-top entrainment. This work demonstrates the need to take in-situ measurements of aerosol properties for cases where the boundary layer is decoupled as well as consider cloud-top entrainment to accurately model stratocumulus cloud radiative flux.

Description: Upper tropospheric cloud systems derived from IR sounders: properties of cirrus anvils in the tropics Sofia E. Protopapadaki, Claudia J. Stubenrauch, and Artem G. Feofilov Atmos. Chem. Phys., 17, 3845-3859, doi:10.5194/acp-17-3845-2017, 2017 Upper tropospheric clouds cover about 30 % of the Earth and play a key role in the climate system by modulating the Earth's energy budget and heat transport. In this article, we study upper tropospheric cloud systems using cloud properties deduced from infrared sounders. Our analyses show that the size of the systems as well as the fraction of thin cirrus over the total anvil area increases with increasing convective depth.

Description: Lower tropospheric distributions of O 3 and aerosol over Raoyang, a rural site in the North China Plain Rui Wang, Xiaobin Xu, Shihui Jia, Ruisheng Ma, Liang Ran, Zhaoze Deng, Weili Lin, Ying Wang, and Zhiqiang Ma Atmos. Chem. Phys., 17, 3891-3903, doi:10.5194/acp-17-3891-2017, 2017 Knowledge about the vertical distributions of air pollutants is limited. We present first unmanned aerial vehicle (UAV) observations of vertical profiles of O 3 and size-resolved aerosol number concentrations over a rural site in the North China Plain. We show the determination of mixed and residual layer depth and characterization of diurnal O 3 and aerosol number concentrations in the mixed and residual layer. We confirm a rapid increase of O 3 in the lower troposphere during the recent decade.

Description: Estimation of bubbled-mediated air/sea gas exchange from concurrent DMS and CO 2 transfer velocities at intermediate-high wind speeds Thomas G. Bell, Sebastian Landwehr, Scott D. Miller, Warren J. de Bruyn, Adrian Callaghan, Brian Scanlon, Brian Ward, Mingxi Yang, and Eric S. Saltzman Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-85,2017 Manuscript under review for ACP (discussion: open, 0 comments) The mechanisms that determine the air/sea exchange of gases such as carbon dioxide are not well understood. During a research cruise in the North Atlantic, we simultaneously measured the air/sea transfer of two gases with contrasting solubility over a range in wind and wave conditions. We compare the transfer of these gases to improve understanding of how bubbles from breaking waves may mediate air/sea gas fluxes.

Description: Nitrate radicals and biogenic volatile organic compounds: oxidation, mechanisms, and organic aerosol Nga Lee Ng, Steven S. Brown, Alexander T. Archibald, Elliot Atlas, Ronald C. Cohen, John N. Crowley, Douglas A. Day, Neil M. Donahue, Juliane L. Fry, Hendrik Fuchs, Robert J. Griffin, Marcelo I. Guzman, Hartmut Herrmann, Alma Hodzic, Yoshiteru Iinuma, José L. Jimenez, Astrid Kiendler-Scharr, Ben H. Lee, Deborah J. Luecken, Jingqiu Mao, Robert McLaren, Anke Mutzel, Hans D. Osthoff, Bin Ouyang, Benedicte Picquet-Varrault, Ulrich Platt, Havala O. T. Pye, Yinon Rudich, Rebecca H. Schwantes, Manabu Shiraiwa, Jochen Stutz, Joel A. Thornton, Andreas Tilgner, Brent J. Williams, and Rahul A. Zaveri Atmos. Chem. Phys., 17, 2103-2162, doi:10.5194/acp-17-2103-2017, 2017 Oxidation of biogenic volatile organic compounds by NO 3 is an important interaction between anthropogenic and natural emissions. This review results from a June 2015 workshop and includes the recent literature on kinetics, mechanisms, organic aerosol yields, and heterogeneous chemistry; advances in analytical instrumentation; the current state NO 3 -BVOC chemistry in atmospheric models; and critical needs for future research in modeling, field observations, and laboratory studies.

Description: Measurements of sub-3 nm particles using a particle size magnifier in different environments: from clean mountain top to polluted megacities Jenni Kontkanen, Katrianne Lehtipalo, Lauri Ahonen, Juha Kangasluoma, Hanna E. Manninen, Jani Hakala, Clémence Rose, Karine Sellegri, Shan Xiao, Lin Wang, Ximeng Qi, Wei Nie, Aijun Ding, Huan Yu, Shanhu Lee, Veli-Matti Kerminen, Tuukka Petäjä, and Markku Kulmala Atmos. Chem. Phys., 17, 2163-2187, doi:10.5194/acp-17-2163-2017, 2017 The concentrations of ~1–3 nm particles were investigated at nine sites around the world. Sub-3 nm particle concentrations were highest at the sites with strong anthropogenic influence. Electrically neutral particles dominated sub-3 nm particle concentrations in polluted environments and in boreal forest during spring and summer. Sub-3 nm particle concentrations were observed to be determined by the availability of precursor vapors rather than the sink caused by preexisting aerosol particles.

Description: Formation of secondary organic aerosols from the ozonolysis of dihydrofurans Yolanda Diaz-de-Mera, Alfonso Aranda, Larisa Bracco, Diana Rodriguez, and Ana Rodriguez Atmos. Chem. Phys., 17, 2347-2357, doi:10.5194/acp-17-2347-2017, 2017 Criegee intermediates are involved in the formation of secondary organic aerosols. How? Recent works show that they contribute to the oxidation of SO 2 to SO 3 . We have found that the studied ozonolysis reactions only led to nucleation in the presence of SO 2 , which behaved as a catalyst. So the role of SO 2 to form SOA depends on the structure of the alkene. For these reactions, the formation of low-volatility organic acid is expected to be responsible for nucleation, since SO 3 was not released.

Description: Origin and variability of volatile organic compounds observed at an Eastern Mediterranean background site (Cyprus) Cécile Debevec, Stéphane Sauvage, Valérie Gros, Jean Sciare, Michael Pikridas, Iasonas Stavroulas, Thérèse Salameh, Thierry Leonardis, Vincent Gaudion, Laurence Depelchin, Isabelle Fronval, Roland Sarda-Esteve, Dominique Baisnée, Bernard Bonsang, Chrysanthos Savvides, Mihalis Vrekoussis, and Nadine Locoge Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1178,2017 Manuscript under review for ACP (discussion: open, 0 comments) An intensive field campaign was conducted in March 2015 in the Eastern Mediterranean region, at a background site of Cyprus. we performed a detailed analysis of the chemical composition of air masses in gas and aerosol phase and we applied a source apportionment analysis in order to identify the various origins of VOCs. The results suggest that VOCs are mainly of biogenic and regional background origins.

Description: Atmospheric CO 2 observations and models suggest strong carbon uptake by forests in New Zealand Kay Steinkamp, Sara E. Mikaloff Fletcher, Gordon Brailsford, Dan Smale, Stuart Moore, Elizabeth D. Keller, W. Troy Baisden, Hitoshi Mukai, and Britton B. Stephens Atmos. Chem. Phys., 17, 47-76, doi:10.5194/acp-17-47-2017, 2017 The exchange of carbon dioxide between the land biosphere in New Zealand and the atmosphere is estimated by combining measurements of the concentration of the gas in the air with model simulations of atmospheric circulation. The results indicate that over the study period of 2011–2013, New Zealand is a larger net sink for CO 2 than estimated in the National Inventory Report. Regions in the western South Island, especially those covered predominantly by forests, contribute the most to this signal.

Description: Air quality improvement in a megacity: implications from 2015 Beijing Parade Blue pollution control actions Wen Xu, Wei Song, Yangyang Zhang, Xuejun Liu, Lin Zhang, Yuanhong Zhao, Duanyang Liu, Aohan Tang, Daowei Yang, Dandan Wang, Zhang Wen, Yuepeng Pan, David Fowler, Jeffrey L. Collett Jr., Jan Willem Erisman, Keith Goulding, Yi Li, and Fusuo Zhang Atmos. Chem. Phys., 17, 31-46, doi:10.5194/acp-17-31-2017, 2017 This paper evaluates the effectiveness of emission control measures implemented in Beijing during the Parade Blue period by integrating our own results, official-released data and modeling data. We demonstrate that emission control measures make a major contribution to air quality improvement in Beijing and surrounding regions. We conclude a joint local and regional control of secondary aerosol precursors to be key to curbing air pollution in Beijing.

Description: Simultaneous measurements of new particle formation in 1-second time resolution at a street site and a rooftop site Yujiao Zhu, Caiqing Yan, Renyi Zhang, Zifa Wang, Mei Zheng, Huiwang Gao, Yang Gao, and Xiaohong Yao Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1143,2017 Manuscript under review for ACP (discussion: open, 0 comments) In this paper we use two identical FMPS for simultaneously measuring particle number size distributions at a street site and a rooftop site. The street canyon likely exerts distinct seasonal effects on new particle formation (NPF) because of on-road vehicle emissions: reduced NPF in spring but enhanced NPF in winter. The oxidization of biogenic organics plays a role in growing new particles. This study contributes to the understanding of enhanced NPF and new particles growth in the atmosphere.

Description: Improved provincial emission inventory and speciation profiles of anthropogenic non-methane volatile organic compounds: a case study for Jiangsu, China Yu Zhao, Pan Mao, Yaduan Zhou, Yang Yang, Jie Zhang, Shekou Wang, Yanping Dong, Fangjian Xie, Yiyong Yu, and Wenqing Li Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1121,2017 Manuscript under review for ACP (discussion: open, 0 comments) We improve and evaluate NMVOC emission inventory for Jiangsu. Field measurements were conducted to obtain NMVOC source profiles of typical chemical engineering processes. The emission inventory of NMVOC with chemistry profiles was developed for 2005–2014, and the uncertainties were quantified. The discrepancies between various inventories in source profiles and spatial patterns were evaluated. Chemistry transport model was applied to test the improvement of the provincial NMVOC inventory.

Description: Wintertime aerosol chemistry and haze evolution in an extremely polluted city of North China Plain: significant contribution from coal and biomass combustions Haiyan Li, Qi Zhang, Qiang Zhang, Chunrong Chen, Litao Wang, Zhe Wei, Shan Zhou, Caroline Parworth, Bo Zheng, Francesco Canonaco, André S. H. Prévôt, Ping Chen, Hongliang Zhang, and Kebin He Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1058,2017 Manuscript under review for ACP (discussion: open, 0 comments) The sources and aerosol evolution processes of the severe pollution episodes were investigated in Handan during wintertime using real-time measurements. An in-depth analysis of the data uncovered that primary emissions from coal combustion and biomass burning together with secondary formation of sulfate (mainly from SO 2 emitted by coal combustion) are important driving factors for haze evolution. Our findings provide useful insights into air pollution control in the heavily polluted regions.

Description: Global deposition of total reactive nitrogen oxides from 1996 to 2014 constrained with satellite observations of NO 2 columns Jeffrey A. Geddes and Randall V. Martin Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1100,2017 Manuscript under review for ACP (discussion: open, 0 comments) Here we apply NO 2 observations from multiple satellite records with the help of a chemical transport model to constrain the global deposition of reactive nitrogen oxides (NO y ) over the last two decades. NO y deposition decreased by up to 60 % in eastern North America, doubled in regions of East Asia, and declined by 20 % in parts of Western Europe. We also find changes in the export of NO y via atmospheric transport, with direct impacts on countries downwind of source regions.

Description: Overview of the European framework for online integrated air quality and meteorology modelling (EuMetChem) Alexander Baklanov Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1174,2017 Manuscript under review for ACP (discussion: open, 0 comments) The article provides an introduction to the COST Action ES1004 – European framework for online integrated air quality and meteorology modelling (EuMetChem) – goals and outcomes for this Special Issue "Coupled chemistry–meteorology modelling: status and relevance for numerical weather prediction, air quality and climate communities" which collects key scientific papers of EuMetChem and its collaborators from different continents.

Description: Air Stagnations for China (1985–2014): Climatological Mean Features and Trends Qianqian Huang, Xuhui Cai, Yu Song, and Tong Zhu Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1072,2017 Manuscript under review for ACP (discussion: open, 0 comments) Air stagnation is an important meteorological measurement for unfavorable air pollution conditions. Previous studies found that stagnation events are usually related to air pollution episodes. Now China is experiencing heavy air pollutions, but to our knowledge, little is known about air stagnations of this country. In this manuscript, we conducted a comprehensive investigation of air stagnation climatology in China, based on sounding and surface observations across the country.

Description: A missing source of aerosols in Antarctica – beyond long-range transport, phytoplankton, and photochemistry Michael R. Giordano, Lars E. Kalnajs, Anita Avery, J. Douglas Goetz, Sean M. Davis, and Peter F. DeCarlo Atmos. Chem. Phys., 17, 1-20, doi:10.5194/acp-17-1-2017, 2017 This paper summarizes two field measurements of particles and gases made in coastal Antarctica and represents the first real-time composition measurements of particles in this understudied area of the world. Using the combined data from both field measurements, we find that there is a constant background of particles in coastal Antarctica and that they are mostly sulfate. Seasonal transitions from winter to spring add additional particles, and that from spring to summer adds additional sulfate.

Description: Secondary organic aerosol formation from in situ OH, O 3 , and NO 3 oxidation of ambient forest air in an oxidation flow reactor Brett B. Palm, Pedro Campuzano-Jost, Douglas A. Day, Amber M. Ortega, Juliane L. Fry, Steven S. Brown, Kyle J. Zarzana, William Dube, Nicholas L. Wagner, Danielle C. Draper, Lisa Kaser, Werner Jud, Thomas Karl, Armin Hansel, Cándido Gutiérrez-Montes, and Jose L. Jimenez Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1080,2017 Manuscript under review for ACP (discussion: open, 0 comments) Ambient forest air was oxidized by OH, O 3 , or NO 3 inside an oxidation flow reactor, leading to formation of particulate matter from any gaseous precursors found in the air. Closure was achieved between the amount of particulate mass formed from O 3 and NO 3 oxidation and the amount predicted from speciated gaseous precursors, which was in contrast to previous results for OH oxidation (Palm et al. ACP 2016). Elemental analysis of the particulate mass formed in the reactor is presented.

Description: Why do general circulation models overestimate the aerosol cloud lifetime effect? A case study comparing CAM5 and a CRM Cheng Zhou and Joyce E. Penner Atmos. Chem. Phys., 17, 21-29, doi:10.5194/acp-17-21-2017, 2017 Observation-based studies have shown that the aerosol cloud lifetime effect or the increase of cloud liquid water with increased aerosol loading may have been overestimated in climate models. Here, by simulating the same shallow, warm clouds using a global climate model (CAM5) and a cloud resolving model (CRM) which has more complete and detailed cloud physics, we show how a climate model can overestimate the aerosol cloud lifetime effect due to its simplified representation of cloud processes.

Description: Four years of atmospheric mercury records in Northwestern Patagonia (Argentina): potential sources, concentration patterns and influence of environmental variables observed at the GMOS EMMA station Maria C. Diéguez, Patricia E. Garcia, Mariantonia Bencardino, Francesco D'Amore, Jessica Castagna, Sergio Ribeiro Guevara, and Francesca Sprovieri Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1076,2017 Manuscript under review for ACP (discussion: open, 0 comments) First continuous records of gaseous elemental Hg (GEM) concentrations monitored at the GMOS EMMA monitoring station in Nahuel Huapi National Park (Northwestern Patagonia, Argentina) showed seasonal and daily variation with mean values higher during spring and winter (ca. 0.92 ng m −3 ) and higher day-time levels across all seasons. GEM levels were determined by the westerly winds and backward trajectory analysis highlighted the influence of clean oceanic air masses and volcanoes in the Andes.

Description: Regional effects of atmospheric aerosols on temperature: an evaluation of an ensemble of on-line coupled models Rocío Baró, Laura Palacios-Peña, Alexander Baklanov, Alessandra Balzarini, Dominik Brunner, Renate Forkel, Marcus Hirtl, Luka Honzak, Juan Luis Pérez, Guido Pirovano, Roberto San José, Wolfram Schröder, Johannes Werhahn, Ralf Wolke, Rahela Zabkar, and Pedro Jiménez-Guerrero Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1157,2017 Manuscript under review for ACP (discussion: open, 0 comments) The objective of this work is to assess whether the inclusion of atmospheric aerosol-radiation-cloud interactions in an ensemble of on-line regional chemistry/climate models improves the simulation results for maximum, mean and minimum temperature over Europe. The results indicate that including these feedbacks clearly improves the spatio-temporal variability of the temperature signal simulated by current models, having broad implications for reducing the uncertainty in climate projections.

Description: Photochemical aging of organic and inorganic ambient aerosol from the Potential Aerosol Mass (PAM) reactor experiment in East Asia Eunha Kang, Meehye Lee, William H. Brune, Taehyung Lee, and Joonyoung Ahn Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1133,2017 Manuscript under review for ACP (discussion: open, 0 comments) The Potential Aerosol Mass (PAM) reactor expedites slow atmospheric oxidation reactions and enables to observe chemical aging processes and determine the aerosol-forming power of an air mass. A PAM reactor was first deployed at Baengnyeong Island in the Yellow Sea and experiment results confirm the key role of SO 2 in generating secondary aerosols in northeast Asia and the contribution of organics to secondary aerosols is more variable during transport in the atmosphere.

Description: Seasonal and Spatial Changes in Trace Gases over Megacities from AURA TES Observations Karen E. Cady-Pereira, Vivienne H. Payne, Jessica L. Neu, Kevin W. Bowman, Kazuyuki Miyazaki, Eloise A. Marais, Susan Kulawik, Zitely A. Tzompa-Sosa, and Jennifer D. Hegarty Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-110,2017 Manuscript under review for ACP (discussion: open, 0 comments) Air quality is a major issue for megacities. Our paper looks at satellite measurements over Mexico City and Lagos of several trace gases gases related to air quality to determine the temporal and spatial variability of these gases, and relates this variability to local conditions, such as topography, winds and biomass burning events. We find that while Mexico City is known for severe pollution events, the levels of of pollution in Lagos are much higher and more persistent.

Description: A decadal time series of water vapor and D / H isotope ratios above Zugspitze: transport patterns to central Europe Petra Hausmann, Ralf Sussmann, Thomas Trickl, and Matthias Schneider Atmos. Chem. Phys., 17, 7635-7651, https://doi.org/10.5194/acp-17-7635-2017, 2017 We present FTIR soundings (2005–15) of water vapor (H 2 O) and its isotope ratio (δD) at Zugspitze. Significant {H 2 O, δD} signatures are found for intercontinental transport events and stratospheric air intrusions to central Europe using backward trajectories and validation by lidar and in situ data. Our results show that {H 2 O, δD} observations at Zugspitze can serve as indicators for moisture pathways and long-range-transport events, potentially impacting central European climate and air quality.

Description: Nonlinear response of tropical lower stratospheric temperature and water vapor to ENSO Chaim I. Garfinkel, Amit Gordon, Luke D. Oman, Feng Li, Sean Davis, and Steven Pawson Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-520,2017 Manuscript under review for ACP (discussion: open, 0 comments) The impact of El Niño-Southern Oscillation in the lower stratosphere. While moderate El Niño events lead to cooling in this region, strong El Niño events appear to lead to warming, and hence the water vapor response is nonlinear too. The net effect is that strong El Nino events, such as in 1997/1998 and 2015/2016, lead to qualitatively different water vapor impacts.

Description: Aerosol optical properties and instantaneous radiative forcing based on high temporospatial resolution CARSNET ground-based measurements over eastern China Huizheng Che, Bing Qi, Hujia Zhao, Xiangao Xia, Philippe Goloub, Oleg Dubovik, Victor Estelles, Emilio Cuevas-Agulló, Luc Blarel, Yunfei Wu, Jun Zhu, Rongguang Du, Yaqiang Wang, Hong Wang, Ke Gui, Jie Yu, Yu Zheng, Tianze Sun, Quanliang Chen, Guangyu Shi, and Xiaoye Zhang Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-530,2017 Manuscript under review for ACP (discussion: open, 0 comments) Variations in the optical properties of aerosols and their effects on radiative forcing were investigated based on long-term synchronous observations from 2011 to 2015 over seven CARSNET adjacent urban, suburban and rural sites in the Yangtze River Delta, Eastern China. This is the first time to do the detailed, long-term, ground-based aerosol optical properties observations in metropolis scale (~10–40 km) in China to improve the aerosol retrieval and simulation performance in future.

Description: Influence of biomass burning from Southeast Asia at a high-altitude mountain receptor site in China Jing Zheng, Min Hu, Zhuofei Du, Dongjie Shang, Zhaoheng Gong, Yanhong Qin, Jingyao Fang, Fangting Gu, Mengren Li, Jianfei Peng, Jie Li, Yuqia Zhang, Xiaofeng Huang, Lingyan He, Yusheng Wu, and Song Guo Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1117,2017 Manuscript under review for ACP (discussion: open, 0 comments) By monitoring the aerosol properties as a function of high-resolution chemical composition, this study sheds light on the evolution processes of particles in the Tibetan Plateau background environment during pre-monsoon season. Positive matrix factorization analysis integrated with a mesoscale meteorological model clearly shows that the southeastern edge of the Tibetan Plateau was affected by air pollutants transported from active biomass burning areas in Southeast Asia.

Description: Impacts of the July 2012 Siberian fire plume on air quality in the Pacific Northwest Andrew D. Teakles, Rita So, Bruce Ainslie, Robert Nissen, Corinne Schiller, Roxanne Vingarzan, Ian McKendry, Anne Marie Macdonald, Daniel A. Jaffe, Allan K. Bertram, Kevin B. Strawbridge, W. Richard Leaitch, Sarah Hanna, Desiree Toom, Jonathan Baik, and Lin Huang Atmos. Chem. Phys., 17, 2593-2611, doi:10.5194/acp-17-2593-2017, 2017 We present a case study of an intense wildfire smoke plume from Siberia that affected the air quality across the Pacific Northwest on 6–10 July 2012. The transport, entrainment, and chemical composition of the plume are examined to characterize the event. Ambient O 3 and PM 2.5 from surface monitoring is contrast to modelled baseline air quality estimates to show the overall contribution of the plume to exceedances in O 3 and PM 2.5 air quality standards and objectives that occurred.

Description: Chemical characterization of atmospheric ions at the high altitude research station Jungfraujoch (Switzerland) Carla Frege, Federico Bianchi, Ugo Molteni, Jasmin Tröstl, Heikki Junninen, Stephan Henne, Mikko Sipilä, Erik Herrmann, Michel J. Rossi, Markku Kulmala, Christopher R. Hoyle, Urs Baltensperger, and Josef Dommen Atmos. Chem. Phys., 17, 2613-2629, doi:10.5194/acp-17-2613-2017, 2017 We present measurements of the chemical composition of atmospheric ions at high altitude (3450 m a.s.l.) during a 9-month campaign. We detected remarkably high correlation between methanesulfonic acid (MSA) and SO 5 − . Halogenated species were also detected frequently at this continental location. New-particle formation events occurred via the condensation of highly oxygenated molecules (HOMs) at very low sulfuric acid concentration or, less frequently, due to ammonia–sulfuric acid clusters.

Description: Estimating regional scale methane flux and budgets using CARVE aircraft measurements over Alaska Sean Hartery, Róisín Commane, Jakob Lindaas, Colm Sweeney, John Henderson, Marikate Mountain, Nicholas Steiner, Kyle McDonald, Steven J. Dinardo, Charles E. Miller, Steven C. Wofsy, and Rachel Y.-W. Chang Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-72,2017 Manuscript under review for ACP (discussion: open, 0 comments) Methane is the 2nd most important greenhouse gas but its emissions from northern regions is still poorly constrained. This study uses aircraft measurements of methane from Alaska to estimate surface emissions. We found that methane emission rates depend on the soil temperature at depths where its production was taking place, and that total emissions were similar between tundra and boreal regions. These results provide a simple way to predict methane emissions in this region.

Description: Typical meteorological conditions associated with extreme nitrogen dioxide (NO 2 ) pollution events over Scandinavia Manu Anna Thomas and Abhay Devasthale Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1091,2017 Manuscript under review for ACP (discussion: open, 0 comments) Episodes of extreme pollution events of nitrogen dioxide (NO2) can seriously hamper air quality. But under which meteorological conditions such extreme pollution events occur over Scandinavia? Using purely observational and reanalysis data it is shown that the southwesterly winds that sustain at least few days dominate during extreme events, cause increase in humidity and clouds. The southeasterly winds have the second largest contribution and the pollution transport is rapid when they prevail.

Description: Stratospheric Aerosol Climatology over Ethiopia and Retrieval of its Size Distribution Milkessa Gebeyehu Homa, Gizaw Mengistu Tsidu, and Derese Tekestebrihan Nega Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-133,2017 Manuscript under review for ACP (discussion: open, 0 comments) This article provides aerosol climatology of Ethiopia for 21 years. The result showed that aerosol loading over the region is steadily increasing in different sizes. The dominant radius of the particulate matters are between 0.452–0.525 μm, & dominated by reflective type aerosol. This influence the solar radiation budget of the earth, which in turn influences the Earth's climate in different ways. Hence, it is the right time to give the right attention to air quality & climate change impacts.

Description: Global carbonyl sulfide (OCS) measured by MIPAS/Envisat during 2002–2012 Norbert Glatthor, Michael Höpfner, Adrian Leyser, Gabriele P. Stiller, Thomas von Clarmann, Udo Grabowski, Sylvia Kellmann, Andrea Linden, Björn-Martin Sinnhuber, Gisèle Krysztofiak, and Kaley A. Walker Atmos. Chem. Phys., 17, 2631-2652, doi:10.5194/acp-17-2631-2017, 2017 To date, information on the global distribution of atmospheric carbonyl sulfide (OCS) is still rather sparse. However, detailed knowledge of the OCS distribution is of scientific interest, because this trace gas is on one of the major sources of atmospheric sulfur, which is a prerequisite of the stratospheric aerosol layer. Under this aspect we present a comprehensive space-borne data set of global OCS concentrations covering the period from June 2002 to April 2012.

Description: Soluble iron nutrients in Saharan dust over the central Amazon rainforest Joana A. Rizzolo, Cybelli G. G. Barbosa, Guilherme C. Borillo, Ana F. L. Godoi, Rodrigo A. F. Souza, Rita V. Andreoli, Antônio O. Manzi, Marta O. Sá, Eliane G. Alves, Christopher Pöhlker, Isabella H. Angelis, Florian Ditas, Jorge Saturno, Daniel Moran-Zuloaga, Luciana V. Rizzo, Nilton E. Rosário, Theotonio Pauliquevis, Rosa M. N. Santos, Carlos I. Yamamoto, Meinrat O. Andreae, Paulo Artaxo, Philip E. Taylor, and Ricardo H. M. Godoi Atmos. Chem. Phys., 17, 2673-2687, doi:10.5194/acp-17-2673-2017, 2017 Particles collected from the air above the Amazon Basin during the wet season were identified as Saharan dust. Soluble minerals were analysed to assess the bioavailability of iron. Dust deposited onto the canopy and topsoil can likely benefit organisms such as fungi and lichens. The ongoing deposition of Saharan dust across the Amazon rainforest provides an iron-rich source of essential macronutrients and micronutrients to plant roots, and also directly to plant leaves during the wet season.

Description: Multi-model simulations of aerosol and ozone radiative forcing due to anthropogenic emission changes during the period 1990–2015 Gunnar Myhre, Wenche Aas, Ribu Cherian, William Collins, Greg Faluvegi, Mark Flanner, Piers Forster, Øivind Hodnebrog, Zbigniew Klimont, Marianne T. Lund, Johannes Mülmenstädt, Cathrine Lund Myhre, Dirk Olivié, Michael Prather, Johannes Quaas, Bjørn H. Samset, Jordan L. Schnell, Michael Schulz, Drew Shindell, Ragnhild B. Skeie, Toshihiko Takemura, and Svetlana Tsyro Atmos. Chem. Phys., 17, 2709-2720, doi:10.5194/acp-17-2709-2017, 2017 Over the past decades, the geographical distribution of emissions of substances that alter the atmospheric energy balance has changed due to economic growth and pollution regulations. Here, we show the resulting changes to aerosol and ozone abundances and their radiative forcing using recently updated emission data for the period 1990–2015, as simulated by seven global atmospheric composition models. The global mean radiative forcing is more strongly positive than reported in IPCC AR5.

Description: Summer ozone in the Northern Front Range Metropolitan Area: Weekend-weekday effects, temperature dependences and the impact of drought Andrew A. Abeleira and Delphine K. Farmer Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-160,2017 Manuscript under review for ACP (discussion: open, 0 comments) Contrary to most regions in the U.S., ozone in the Northern Front Range Metropolitan Area (NFRMA) of Colorado was either stagnant or increasing between 2000 and 2015, despite substantial reductions in NO x emissions. We used available long-term ozone and NO x data in the NFRMA to investigate these trends. Ozone increased from weekdays to weekends for a number of sites in the NFRMA with weekend reductions in NO 2 at two sites in downtown Denver, indicating that the region was in a NO x -saturated ozone production regime. The stagnation and increases in ozone in the NFRMA are likely the result of (1) decreasing NO x emissions in a NO x -saturated environment, and (2) increased anthropogenic VOC emissions in the NFRMA. Further investigation of the weekday-weekend effect showed that the region outside of the most heavily trafficked Denver area was transitioning to peak ozone production towards NO x -limited chemistry. This transition implies that continued NO x decreases will result in ozone being less sensitive to changes in either anthropogenic or biogenic VOC reactivity in the NFRMA. Biogenic VOCs are unlikely to have increased in the NFRMA between 2000 and 2015, but are temperature dependent and likely vary by drought year. Ozone in the NFRMA has a temperature dependence, consistent with biogenic VOC contributions to ozone production in the region. We show that while ozone increased with temperature in the NFRMA, which is consistent with a NOx-saturated regime, this relationship is suppressed in drought years. We attribute this drought year suppression to decreased biogenic isoprene emissions due to long-term drought stress.

Description: A comprehensive biomass burning emission inventory with high spatial and temporal resolution in China Ying Zhou, Xiaofan Xing, Jianlei Lang, Dongsheng Chen, Shuiyuan Cheng, Lin Wei, Xiao Wei, and Chao Liu Atmos. Chem. Phys., 17, 2839-2864, doi:10.5194/acp-17-2839-2017, 2017 A 1 km gridded and comprehensive biomass burning emission inventory including domestic and in-field straw burning, firewood burning, livestock excrement burning, and forest and grassland fires is developed for mainland China in 2012 based on county-level activity data, satellite data, and updated source-specific emission factors. The detailed emission inventory could provide useful information for air-quality modelling and supports the development of appropriate pollution-control strategies.

Description: Microphysical properties of frozen particles inferred from Global Precipitation Measurement (GPM) Microwave Imager (GMI) polarimetric measurements Jie Gong and Dong L. Wu Atmos. Chem. Phys., 17, 2741-2757, doi:10.5194/acp-17-2741-2017, 2017 Under certain temperature or aerodynamic conditions, ice crystals prefer to orient along certain directions. The preferred orientation direction of non-spherical ice particles would result in a difference in the satellite remote sensing using different polarized channels. This paper studies this polarization difference using the Global Precipitation Measurement Microwave Imager, where we can infer the dominant ice particle orientation and shape factors from passive remote sensing measures.

Description: A decadal satellite record of gravity wave activity in the lower stratosphere to study polar stratospheric cloud formation Lars Hoffmann, Reinhold Spang, Andrew Orr, M. Joan Alexander, Laura A. Holt, and Olaf Stein Atmos. Chem. Phys., 17, 2901-2920, doi:10.5194/acp-17-2901-2017, 2017 We introduce a 10-year record (2003–2012) of AIRS/Aqua observations of gravity waves in the polar lower stratosphere. The data set was optimized to study the impact of gravity waves on the formation of polar stratospheric clouds (PSCs). We discuss the temporal and spatial patterns of gravity wave activity, validate explicitly resolved small-scale temperature fluctuations in the ECMWF data, and present a survey of gravity-wave-induced PSC formation events using joint AIRS and MIPAS observations.

Description: A comparison of two chemistry and aerosol schemes on the regional scale and resulting impact on radiative properties and warm and cold aerosol-cloud interactions Franziska Glassmeier, Anna Possner, Bernhard Vogel, Heike Vogel, and Ulrike Lohmann Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1092,2017 Manuscript under review for ACP (discussion: open, 0 comments) The description of atmospheric aerosol in numerical models requires selection and simplification. We compare two chemistry and aerosol schemes, one designed for air-quality, the other for climate applications. For distribution, composition and radiative properties, the choice of aerosol types and processes turns out to be more important than their implementation. For aerosol-cloud interactions, we find cloud processes, in particular ice formation, to be the bottleneck to our understanding.

Description: Speciation of organic aerosols in the Saharan Air Layer and in the free troposphere westerlies M. Isabel García, Barend L. van Drooge, Sergio Rodríguez, and Andrés Alastuey Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-108,2017 Manuscript under review for ACP (discussion: open, 0 comments) Organic aerosols in the Saharan Air Layer and in the free troposphere westerlies.

Description: Organic molecular tracers in the atmospheric aerosols from Lumbini, Nepal, in the northern Indo-Gangetic Plain: Influence of biomass burning Xin Wan, Shichang Kang, Quanlian Li, Dipesh Rupakheti, Qianggong Zhang, Junming Guo, Pengfei Chen, Lekhendra Tripathee, Maheswar Rupakheti, Arnico K. Panday, Wu Wang, Kimitaka Kawamura, Shaopeng Gao, Guangming Wu, and Zhiyuan Cong Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1176,2017 Manuscript under review for ACP (discussion: open, 0 comments) Biomass burning (BB) tracers in the aerosols in Lumbini, northern IGP were studied for the first time. The levoglucosan was the predominant tracer and BB significantly contributed to the air quality in Lumbini. Mixed crop residues and hardwood were main burning materials. BB emissions constituted large fraction of OC, especially during the post-monsoon season. The sources of BB aerosols in Lumbini varies seasonally due to the influence of local emissions and long-range transport.

Description: Two global data sets of daily fire emission injection heights since 2003 Samuel Rémy, Andreas Veira, Ronan Paugam, Mikhail Sofiev, Johannes W. Kaiser, Franco Marenco, Sharon P. Burton, Angela Benedetti, Richard J. Engelen, Richard Ferrare, and Jonathan W. Hair Atmos. Chem. Phys., 17, 2921-2942, doi:10.5194/acp-17-2921-2017, 2017 Biomass burning emission injection heights are an important source of uncertainty in global climate and atmospheric composition modelling. This work provides a global daily data set of injection heights computed by two very different algorithms, which coherently complete a global biomass burning emissions database. The two data sets were compared and validated against observations, and their use was found to improve forecasts of carbonaceous aerosols in two case studies.

Description: Impact of aerosols and clouds on decadal trends in all-sky solar radiation over the Netherlands (1966–2015) Reinout Boers, Theo Brandsma, and A. Pier Siebesma Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-88,2017 Manuscript under review for ACP (discussion: open, 0 comments) In the Netherlands 9 W m −2 more solar radiation falls on the surface today than 50 year ago. Often this increase which has also been detected in surrounding western Europe has been attributed to decreasing air pollution due to improved regulatory practices. However, over the Netherlands clouds play an important but ambiguous role. Cloud cover has increased but have become optically thinner as well. Here, the impact of clouds on radiation is in fact more important than that of air pollution.

Description: Sources of Springtime Surface Black Carbon in the Arctic: An Adjoint Analysis Ling Qi, Qinbin Li, Daven K. Henze, Hsien-Liang Tseng, and Cenlin He Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1112,2017 Manuscript under review for ACP (discussion: open, 0 comments) We find that Asian anthropogenic sources are the largest contributors (~ 40 %) to surface BC in spring in the Arctic, inconsistent with previous studies which repeatedly identified sources of surface BC as anthropogenic emissions from Europe and Russia. It takes 12–17 days for Asian anthropogenic emissions to be transported to the Arctic surface. Additionally, a large fraction (40–65 %) of Asian contribution is in the form of 'chronic pollution' on 1–2 month timescales.

Description: Effects of ozone–vegetation coupling on surface ozone air quality via biogeochemical and meteorological feedbacks Mehliyar Sadiq, Amos P. K. Tai, Danica Lombardozzi, and Maria Val Martin Atmos. Chem. Phys., 17, 3055-3066, doi:10.5194/acp-17-3055-2017, 2017 Surface ozone harms vegetation, which can influence not only climate but also ozone air quality itself. We implement a scheme for ozone damage on vegetation into an Earth system model, so that for the first time simulated vegetation and ozone can coevolve in a fully coupled simulation. With ozone–vegetation coupling, simulated ozone is found to be significantly higher by up to 6 ppbv. Reduced dry deposition and enhanced isoprene emission contribute to most of these increases.

Description: Evaluation and error apportionment of an ensemble of atmospheric chemistry transport modeling systems: multivariable temporal and spatial breakdown Efisio Solazzo, Roberto Bianconi, Christian Hogrefe, Gabriele Curci, Paolo Tuccella, Ummugulsum Alyuz, Alessandra Balzarini, Rocío Baró, Roberto Bellasio, Johannes Bieser, Jørgen Brandt, Jesper H. Christensen, Augistin Colette, Xavier Francis, Andrea Fraser, Marta Garcia Vivanco, Pedro Jiménez-Guerrero, Ulas Im, Astrid Manders, Uarporn Nopmongcol, Nutthida Kitwiroon, Guido Pirovano, Luca Pozzoli, Marje Prank, Ranjeet S. Sokhi, Alper Unal, Greg Yarwood, and Stefano Galmarini Atmos. Chem. Phys., 17, 3001-3054, doi:10.5194/acp-17-3001-2017, 2017 As part of the third phase of AQMEII, this study uses timescale analysis to apportion error to the responsible processes, detect causes of model error, and identify the processes and scales that require dedicated investigations. The analysis tackles model performance gauging through measurement-to-model comparison, error decomposition, and time series analysis of model biases for ozone, CO, SO 2 , NO, NO 2 , PM 10 , PM 2.5 , wind speed, and temperature over Europe and North America.

Description: Enhanced trans-Himalaya pollution transport to the Tibetan Plateau by cut-off low systems Ruixiong Zhang, Yuhang Wang, Qiusheng He, Laiguo Chen, Yuzhong Zhang, Hang Qu, Charles Smeltzer, Jianfeng Li, Leonardo M. A. Alvarado, Mihalis Vrekoussis, Andreas Richter, Folkard Wittrock, and John P. Burrows Atmos. Chem. Phys., 17, 3083-3095, doi:10.5194/acp-17-3083-2017, 2017 We use short-lived reactive aromatics as proxies to diagnose transport of pollutants to Tibet. In situ observations of short-lived reactive aromatics across the Tibetan Plateau are analyzed using a regional chemistry and transport model. Our results suggest that the cut-off low system is a major pathway for long-range transport of pollutants such as black carbon. The modeling analysis reveals that even the state-of-the-science reanalysis cannot simulate this cut-off system accurately.

Description: Classification of summertime synoptic patterns in Beijing and their associations with boundary layer structure affecting aerosol pollution Yucong Miao, Jianping Guo, Shuhua Liu, Huan Liu, Zhanqing Li, Wanchun Zhang, and Panmao Zhai Atmos. Chem. Phys., 17, 3097-3110, doi:10.5194/acp-17-3097-2017, 2017 Three synoptic patterns associated with heavy aerosol pollution in Beijing were identified using an objective classification approach. Relationships between synoptic patterns, aerosol pollution, and boundary layer height in Beijing during summer were revealed as well. Further, factors/mechanisms leading to the low BLHs in Beijing were unraveled. The key findings have implications for understanding the crucial roles that meteorological factors play in forecasting aerosol pollution in Beijing.

Description: Regional responses of surface ozone in Europe to the location of high-latitude blocks and subtropical ridges Carlos Ordóñez, David Barriopedro, Ricardo García-Herrera, Pedro M. Sousa, and Jordan L. Schnell Atmos. Chem. Phys., 17, 3111-3131, doi:10.5194/acp-17-3111-2017, 2017 Blocks and ridges are synoptic patterns associated with an anticyclonic circulation. They also divert the atmospheric flow. This work proves that near-surface ozone in Europe is sensitive to these patterns. This quantitative assessment has been performed on a seasonal basis for a 15-year period. The results can be exploited in the future to evaluate modelled ozone responses to atmospheric circulation changes and to understand the contribution of dynamic effects to air quality projections.

Description: Fast retrievals of tropospheric carbonyl sulfide with IASI R. Anthony Vincent and Anu Dudhia Atmos. Chem. Phys., 17, 2981-3000, doi:10.5194/acp-17-2981-2017, 2017 A fast method to estimate trace gases using the IASI sensor is presented and applied to tropospheric carbonyl sulphide (OCS). This rapid approach neglects non-linear effects, which introduces an 11 % error on average when estimating OCS but is significantly faster than iterative methods. All of the IASI data from 2014 were analysed to show seasonal and spatial trends in OCS. These results were compared to ground samples taken from seven different NOAA sites across the globe.

Description: Estimates of the aerosol indirect effect over the Baltic Sea region derived from 12 years of MODIS observations Giulia Saponaro, Pekka Kolmonen, Larisa Sogacheva, Edith Rodriguez, Timo Virtanen, and Gerrit de Leeuw Atmos. Chem. Phys., 17, 3133-3143, doi:10.5194/acp-17-3133-2017, 2017 The effect of aerosol upon cloud properties is studied over the Baltic Sea region, which presents a distinct contrast of aerosol loading between the clean Fennoscandia and the polluted area of central–eastern Europe. Statistically significant positive values are found over the Baltic Sea and Fennoscandia, while negative values are found over central–eastern Europe, contradicting the theory of aerosol indirect effect on clouds.

Description: Direct radiative effects of dust aerosols emitted from the Tibetan Plateau on the East Asian summer monsoon – a regional climate model simulation Hui Sun, Xiaodong Liu, and Zaitao Pan Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-55,2017 Manuscript under review for ACP (discussion: open, 0 comments) Two 20-year simulations with and without the dust emission from the Tibetan Plateau (TP) showed that the dust emitted from the TP weakens the East Asian summer monsoon by the reduction in the TP heating and in thermal contrast in the middle troposphere between the land and sea. Although contribution to the total Asian dust source from within TP is relatively small, its impacts on Asian monsoon and climate seems disproportionately large, likely owning to its higher elevation within TP itself.

Description: 30-year lidar observations of the stratospheric aerosol layer state over Tomsk (Western Siberia, Russia) Vladimir V. Zuev, Vladimir D. Burlakov, Aleksei V. Nevzorov, Vladimir L. Pravdin, Ekaterina S. Savelieva, and Vladislav V. Gerasimov Atmos. Chem. Phys., 17, 3067-3081, doi:10.5194/acp-17-3067-2017, 2017 There are only four lidar stations in the world which have almost continuously performed observations of the stratospheric aerosol layer (SAL) state over the last 30 years. The longest time series of the SAL lidar measurements have been accumulated at the Mauna Loa Observatory (Hawaii) since 1973, the NASA Langley Research Center (Hampton, Virginia) since 1974, and Garmisch-Partenkirchen (Germany) since 1976. The fourth lidar station we present started to perform routine observations of the SAL parameters in Tomsk (56.48° N, 85.05° E, Western Siberia, Russia) in 1986. In this paper, we mainly focus on and discuss the stratospheric background period from 2000 to 2005 and the causes of the SAL perturbations over Tomsk in the 2006–2015 period. During the last decade, volcanic aerosol plumes from tropical Mt. Manam, Soufrière Hills, Rabaul, Merapi, Nabro, and Kelut and extratropical (northern) Mt. Okmok, Kasatochi, Redoubt, Sarychev Peak, Eyjafjallajökull, and Grímsvötn were detected in the stratosphere over Tomsk. When it was possible, we used the NOAA HYSPLIT trajectory model to assign aerosol layers observed over Tomsk to the corresponding volcanic eruptions. The trajectory analysis highlighted some surprising results. For example, in the cases of the Okmok, Kasatochi, and Eyjafjallajökull eruptions, the HYSPLIT air mass backward trajectories, started from altitudes of aerosol layers detected over Tomsk with a lidar, passed over these volcanoes on their eruption days at altitudes higher than the maximum plume altitudes given by the Smithsonian Institution Global Volcanism Program. An explanation of these facts is suggested. The role of both tropical and northern volcanic eruptions in volcanogenic aerosol loading of the midlatitude stratosphere is also discussed. In addition to volcanoes, we considered other possible causes of the SAL perturbations over Tomsk, i.e., the polar stratospheric cloud (PSC) events and smoke plumes from strong forest fires. At least two PSC events were detected in 1995 and 2007. We also make an assumption that the Kelut volcanic eruption (Indonesia, February 2014) could be the cause of the SAL perturbations over Tomsk during the first quarter of 2015.

Description: The concentration, source apportionment and deposition flux of atmospheric particulate inorganic nitrogen during dust events Jianhua Qi, Ruifeng Zhang, Xiaojing Chen, Xuehui Lin, Huiwang Gao, and Ruhai Liu Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1183,2017 Manuscript under review for ACP (discussion: open, 0 comments) Does dust event always increase the atmospheric input of nitrogen to the ocean? We found that a dust event did not simply increase nutrient concentrations. The atmospheric input of nitrogen to the ocean depends on the "dilution effect" of a dust event. Dust deposition was an uncertain source of nitrogen to the ocean. The contribution of dust events to marine nitrogen input will be overestimated if the flux simply considers dust concentrations and a constant ratio of nutrients to particles.

Description: Long-term chemical analysis and organic aerosol source apportionment at 9 sites in Central Europe: Source identification and uncertainty assessment Kaspar R. Daellenbach, Giulia Stefenelli, Carlo Bozzetti, Athanasia Vlachou, Paola Fermo, Raquel Gonzalez, Andrea Piazzalunga, Cristina Colombi, Francesco Canonaco, Christoph Hueglin, Anne Kasper-Giebl, Jean-Luc Jaffrezo, Federico Bianchi, Jay G. Slowik, Urs Baltensperger, Imad El Haddad, and André S. H. Prévôt Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-124,2017 Manuscript under review for ACP (discussion: open, 0 comments) We present offline-AMS analyses for the organic aerosol (OA) in PM10 at 9 sites in central Europe for the year 2013. Primary OA is separated in a traffic, a cooking, and a wood burning component. Also a factor explaining sulfur-containing ions, with an event-driven time series, is separated. We observe enhanced production of secondary OA (SOA) in summer, following biogenic emissions with temperature. In winter a SOA component is dominant which correlates with anthropogenic inorganic species.

Description: Possibility for an infrared sounder as IASI to document the HCOOH chemistry in biomass burning plumes Matthieu Pommier, Cathy Clerbaux, and Pierre-Francois Coheur Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-126,2017 Manuscript under review for ACP (discussion: open, 0 comments) A new estimation of enhancement ratio to CO for HCOOH over seven biomass burning regions is proposed. Fire-affected HCOOH and CO total columns are defined by combining total columns from IASI, geographic location of the fires from MODerate resolution Imaging Spectroradiometer (MODIS) and the surface wind speed field from the European Centre for Medium-Range Weather Forecasts (ECMWF). Australian and Siberian fires may be underestimated in terms of direct emission or secondary production of HCOOH.

Description: The contribution of wood burning and other pollution sources to wintertime organic aerosol levels in two Greek cities Kalliopi Florou, Dimitrios K. Papanastasiou, Michael Pikridas, Christos Kaltsonoudis, Evangelos Louvaris, Georgios I. Gkatzelis, David Patoulias, Nikolaos Mihalopoulos, and Spyros N. Pandis Atmos. Chem. Phys., 17, 3145-3163, doi:10.5194/acp-17-3145-2017, 2017 The composition of fine particulate matter (PM) in two major Greek cities (Athens and Patras) was measured during two wintertime campaigns in 2012 and 2013. Residential wood burning has dramatically increased due to the Greek financial crisis, contributing around 50 % of the fine PM on average and more than 80 % during nighttime. Cooking is also an important source during both midday and evening, while transportation dominates only during the morning rush hour.

Description: Resolving anthropogenic aerosol pollution types – deconvolution and exploratory classification of pollution events Mikko Äijälä, Liine Heikkinen, Roman Fröhlich, Francesco Canonaco, André S. H. Prévôt, Heikki Junninen, Tuukka Petäjä, Markku Kulmala, Douglas Worsnop, and Mikael Ehn Atmos. Chem. Phys., 17, 3165-3197, doi:10.5194/acp-17-3165-2017, 2017 Mass spectrometric measurements commonly yield data on hundreds of variables over thousands of points in time. Refining and synthesising this “raw” data into chemical information necessitates the use of advanced, statistics-based data analysis techniques. Here we present an example of combining data dimensionality reduction (factorisation) with exploratory classification (clustering) and show that the results complement and broaden our current perspectives on aerosol chemical classification.

Description: US surface ozone trends and extremes from 1980 to 2014: quantifying the roles of rising Asian emissions, domestic controls, wildfires, and climate Meiyun Lin, Larry W. Horowitz, Richard Payton, Arlene M. Fiore, and Gail Tonnesen Atmos. Chem. Phys., 17, 2943-2970, doi:10.5194/acp-17-2943-2017, 2017 US ozone pollution responds to varying global-to-regional precursor emissions and climate, with implications for designing effective air quality control policies. Asian anthropogenic emissions of ozone precursors tripled since 1990, contributing 65 % to western US ozone increases in spring, outpacing ozone decreases attained via 50 % US emission controls. In the eastern US, if emissions had not declined, more frequent hot extremes since 1990 would have worsened the highest ozone events in summer.

Description: Comparison of tropospheric NO 2 columns from MAX-DOAS retrievals and regional air quality model simulations Anne-Marlene Blechschmidt, Joaquim Arteta, Adriana Coman, Lyana Curier, Henk Eskes, Gilles Foret, Clio Gielen, Francois Hendrick, Virginie Marécal, Frédérik Meleux, Jonathan Parmentier, Enno Peters, Gaia Pinardi, Ankie J. M. Piters, Matthieu Plu, Andreas Richter, Mikhail Sofiev, Álvaro M. Valdebenito, Michel Van Roozendael, Julius Vira, Tim Vlemmix, and John P. Burrows Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1003,2017 Manuscript under review for ACP (discussion: open, 0 comments) MAX-DOAS tropospheric NO 2 column retrievals from four European measurement stations are compared to a regional model ensemble. Unlike other observational data usually applied for regional model validation, MAX-DOAS is closer to the model data in terms of horizontal and vertical resolution and several measurements are available during daylight. There generally is a good agreement between models and measurements, but large differences are found for individual pollution plumes and diurnal cycles.

Description: Impacts of emission reduction and meteorological conditions on air quality improvement during the 2014 Youth Olympic Games in Nanjing, China Qian Huang, Tijian Wang, Pulong Chen, Xiaoxian Huang, Jialei Zhu, and Bingliang Zhuang Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-114,2017 Manuscript under review for ACP (discussion: open, 0 comments) This paper investigate the decisive factor contributing to the improvement of the air quality of Nanjing, China, during the 2th Youth Olympic Games, held in August, 2014. The interesting finding is that meteorological factors are not beneficial for better air quality during YOG. However, emission reduction play a more important role, which suggest that emission reduction is an effective way to cut down air pollution for social events.

Description: Multi-species inversion and IAGOS airborne data for a better constraint of continental scale fluxes Fabio Boschetti, Valerie Thouret, Greet Janssens Maenhout, Kai Uwe Totsche, Julia Marshall, and Christoph Gerbig Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-69,2017 Manuscript under review for ACP (discussion: open, 0 comments) Airborne measurements of CO 2 , CO, and CH 4 proposed in the context of IAGOS (In-service Aircraft for a Global Observing System) will provide profiles from take-off and landing of airliners in the vicinity of major metropolitan areas useful for constraining sources and sinks. A proposed improvement of the top-down method to constrain sources and sinks is the use of a multispecies inversion. Different species such as CO 2 and CO have partially overlapping emission patterns for given fuel-combustion related sectors, and thus share part of the uncertainties, both related to the a priori knowledge of emissions, and to model-data mismatch error. We use a regional modeling framework consisting of the Lagrangian particle dispersion model STILT (Stochastic Time-Inverted Lagrangian Transport), combined with high resolution (10 km × 10 km) EDGARv4.3 (Emission Database for Global Atmospheric Research) emission inventory, differentiated by emission sector and fuel type for CO 2 , CO, and CH 4 , and combined with the VPRM (Vegetation Photosynthesis and Respiration Model) for biospheric fluxes of CO 2 . Applying the modeling framework to synthetic IAGOS profile observations, we evaluate the benefits of using correlations between different species’ uncertainties on the performance of the atmospheric inversion. The available IAGOS CO observations are used to validate the modeling framework. Prior uncertainty values are conservatively assumed to be 20 %, for CO 2 and 50 % for CO and CH 4 , while those for, GEE (Gross Ecosystem Exchange) and respiration are derived from existing literature. Uncertainty reduction for different species is evaluated on a domain encircling 50 % of the profile observations’ surface influence over Europe. We found that our modeling framework reproduces the CO observations with an average correlation of 0.56, but simulates lower mixing ratios by a factor 2.8, reflecting a low bias in the emission inventory. Mean uncertainty reduction achieved for CO 2 fossil fuel emissions is roughly 37 %; for photosynthesis and respiration flux it is 41 % and 45 %, respectively. For CO and CH 4 the uncertainty reduction is roughly 63 % and 67 %, respectively. Considering correlation between different species, posterior uncertainty can be reduced by up to 23 %; such reduction depends on the assumed error structure of the prior and on the considered timeframe. The study suggests a significant uncertainty constraint on regional emissions using multi-species inversions of IAGOS in situ observations.

Description: The impact of aged wildfire smoke on atmospheric composition and ozone in the Colorado Front Range in summer 2015 Jakob Lindaas, Delphine K. Farmer, Ilana B. Pollack, Andrew Abeleira, Frank Flocke, Rob Roscioli, Scott Herndon, and Emily V. Fischer Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-171,2017 Manuscript under review for ACP (discussion: open, 0 comments) Wildfire smoke is becoming increasingly important for air quality in the U.S. We used measurements taken during the summer 2015 near Denver, CO, to provide a case study of how wildfire smoke can impact air quality, specifically ozone, which is harmful to humans. Wildfire smoke during this time period was associated with about 15 % more ozone than we would expect under normal conditions. This smoke came from fires in the Pacific Northwest and likely impacted much of the central and western U.S.

Description: Sensitivities of Amazonian clouds to aerosols and updraft speed Micael A. Cecchini, Luiz A. T. Machado, Meinrat O. Andreae, Scot T. Martin, Rachel I. Albrecht, Paulo Artaxo, Henrique M. J. Barbosa, Stephan Borrmann, Daniel Fütterer, Tina Jurkat, Christoph Mahnke, Andreas Minikin, Sergej Molleker, Mira L. Pöhlker, Ulrich Pöschl, Daniel Rosenfeld, Christiane Voigt, Bernadett Wenzierl, and Manfred Wendisch Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-89,2017 Manuscript under review for ACP (discussion: open, 0 comments) We study the effects of aerosol particles and updraft speed on the warm-phase of Amazonian clouds. We expand the sensitivity analysis usually found in the literature by concomitantly considering cloud evolution and the effects on droplet size distribution (DSD) shape. The quantitative results show that particle concentration is the primary driver for the vertical profiles of effective diameter and droplet concentration in the warm phase of Amazonian convective clouds.

Description: Measurement of scattering and absorption properties of dust aerosol in a Gobi farmland region of northwest China — a potential anthropogenic influence Jianrong Bi, Jianping Huang, Jinsen Shi, Zhiyuan Hu, Tian Zhou, Guolong Zhang, Zhongwei Huang, Xin Wang, and Hongchun Jin Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-165,2017 Manuscript under review for ACP (discussion: open, 0 comments) We conducted a field campaign on exploring dust aerosol in Dunhuang farmland nearby Gobi deserts. The anthropogenic dust produced by agricultural cultivations exerted a significant superimposed effect on elevated dust loadings. Strong south wind in daytime scavenged the pollution and weak northeast wind at night favorably accumulated air pollutants near the surface. The local emissions remarkably modified the absorptive and optical characteristics of mineral dust in desert source region.

Description: Observations of Particles at their Formation Sizes in Beijing, China Rohan Jayaratne, Buddhi Pushpawela, Congrong He, Jian Gao, Li Hui, and Lidia Morawska Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-156,2017 Manuscript under review for ACP (discussion: open, 0 comments) Observations over a continuous three-month period in Beijing showed 26 new particle formation (NPF) events, generally coincided with periods with relatively clean air when the wind direction was from the less-industrialized north. Large particles in the atmosphere suppress the gaseous supersaturation that is required for NPF. No events were observed when the daily mean PM 2.5 concentration exceeded 43 µg m -3 . These results provide useful insight into the formation of haze events in mega cities.

Description: Horizontal and vertical structure of reactive bromine events probed by bromine monoxide MAX-DOAS spectroscopy William R. Simpson, Peter K. Peterson, Udo Frieß, Holger Sihler, Johannes Lampel, Ulrich Platt, Chris Moore, Kerri Pratt, Paul Shepson, John Halfacre, and Son V. Nghiem Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-187,2017 Manuscript under review for ACP (discussion: open, 0 comments) We investigated Arctic atmospheric bromine chemistry during March/April 2012 to improve understanding of the role of sea ice and cracks in sea ice (leads) on this phenomenon. We find that leads vertically redistribute reactive bromine, but that open/re-freezing leads are not major direct reactive halogen sources. Surface ozone depletion affects the vertical distribution and amount of reactive halogens, and aerosol particles are necessary but not sufficient to maintain reactive bromine aloft.

Description: Insights into aerosol chemistry during the 2015 China Victory Day parade: results from simultaneous measurements at ground level and 260 m in Beijing Jian Zhao, Wei Du, Yingjie Zhang, Qingqing Wang, Chen Chen, Weiqi Xu, Tingting Han, Yuying Wang, Pingqing Fu, Zifa Wang, Zhanqing Li, and Yele Sun Atmos. Chem. Phys., 17, 3215-3232, doi:10.5194/acp-17-3215-2017, 2017 We conducted aerosol particle composition measurements at ground level and 260 m with two aerosol mass spectrometers in Beijing during the 2015 China Victory Day parade. Our results showed a stronger impact of emission controls on inorganic aerosol than OA. A larger decrease in more oxidized SOA than the less oxidized one during the control period was also observed. Our results indicate that emission controls and the changes in meteorological conditions have affected SOA formation mechanisms.

Description: The representation of solar cycle signals in stratospheric ozone. Part II: Analysis of global models Amanda C. Maycock, Katja Matthes, Susann Tegtmeier, Hauke Schmidt, Rémi Thiéblemont, Lon Hood, Slimane Bekki, Makoto Deushi, Patrick Jöckel, Oliver Kirner, Markus Kunze, Marion Marchand, Daniel R. Marsh, Martine Michou, Laura E. Revell, Eugene Rozanov, Andrea Stenke, Yousuke Yamashita, and Kohei Yoshida Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-477,2017 Manuscript under review for ACP (discussion: open, 1 comment) The 11 year solar cycle is an important driver of climate variability. Changes in incoming solar ultraviolet radiation affect atmospheric ozone, which in turn influences atmospheric temperatures. Constraining the impact of the solar cycle on ozone in therefore important for understanding climate variability. This study examines the representation of the solar influence on ozone in numerical models used to simulate past and future climate. We highlight important differences among model datasets.

Description: Insight into naturally-charged Highly Oxidized Molecules (HOMs) in the boreal forest Federico Bianchi, Olga Garmash, Xucheng He, Chao Yan, Siddharth Iyer, Ida Rosendahl, Zhengning Xu, Matti P. Rissanen, Matthieu Riva, Risto Taipale, Nina Sarnela, Tuukka Petäjä, Douglas R. Worsnop, Markku Kulmala, Mikael Ehn, and Heikki Junninen Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-481,2017 Manuscript under review for ACP (discussion: open, 0 comments) Naturally charged highly oxidised molecules (HOMs) were characterized using advanced mass spectrometers. Two different classes of compounds, clustered with the most abundant inorganic acids, were identified: HOMs containing only carbon, hydrogen and oxygen and nitrogen-containing HOMs or organonitrates (ONs). They exhibit strong diurnal variations where HOMs peak during night and ONs during day. Finally, large clusters containing up to 40 carbon atoms (4 oxidized α-pinene units) were observed.

Description: Surface ozone in the Southern Hemisphere: 20 years of data from a site with a unique setting in El Tololo, Chile Julien G. Anet, Martin Steinbacher, Laura Gallardo, Patricio A. Velásquez Álvarez, Lukas Emmenegger, and Brigitte Buchmann Atmos. Chem. Phys., 17, 6477-6492, doi:10.5194/acp-17-6477-2017, 2017 There are less long-term surface ozone measurements on the Southern than on the Northern Hemisphere, which makes it difficult to thoroughly understand global ozone chemistry. We have analyzed a new, 20-year-long ozone dataset measured at 2200 m asl at El Tololo, Chile, and show that the annual cycle of ozone is mainly driven by ozone transport from the stratosphere to the troposphere. As well, we illustrate that the timing of the annual maximum is regressing to earlier in the year.

Description: Efficient bulk mass accommodation and dissociation of N 2 O 5 in neutral aqueous aerosol Goran Gržinić, Thorsten Bartels-Rausch, Andreas Türler, and Markus Ammann Atmos. Chem. Phys., 17, 6493-6502, https://doi.org/10.5194/acp-17-6493-2017, 2017 Nitrogen oxides (NO x ) largely control the ozone budget in the troposphere globally. Dinitrogen pentoxide (N 2 O 5 ) is an important species as a nighttime reservoir for nitrogen oxides. Loss of N 2 O 5 to aerosol particles is therefore important for the budget of NO x and the oxidation capacity. Here we provide direct evidence for its efficient accommodation into aqueous aerosol particles and its fast dissociation, which has not been elucidated as directly in previous studies.

Description: Near-road sampling of PM 2. 5 , BC, and fine-particle chemical components in Kathmandu Valley, Nepal Kabindra M. Shakya, Maheswar Rupakheti, Anima Shahi, Rejina Maskey, Bidya Pradhan, Arnico Panday, Siva P. Puppala, Mark Lawrence, and Richard E. Peltier Atmos. Chem. Phys., 17, 6503-6516, https://doi.org/10.5194/acp-17-6503-2017, 2017 Particulate matter levels were monitored at six major roadway intersections in the Kathmandu Valley during two seasons in 2014. The study documented distinct seasonal (dry season versus wet season) and diel variations in particulate matter levels. This study suggests traffic-related emissions, and soil–dust–construction materials were found to be a major source of particulate matter at these locations.

Description: Multi-decadal Records of Stratospheric Composition and their Relationship to Stratospheric Circulation Change Anne R. Douglass, Susan E. Strahan, Luke D. Oman, and Richard S. Stolarski Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-401,2017 Manuscript under review for ACP (discussion: open, 0 comments) Data records from instruments on satellites and on the ground are compared with a simulation for 1980 - 2016 that is made using winds and temperatures that are derived from measurements. The simulation tracks the observations faithfully after about 2000, but there are systematic errors for earlier years. Scientists must take this into account when trying to detect and quantify changes in the stratospheric circulation that are caused by climate change.

Description: Insight into naturally-charged Highly Oxidized Molecules (HOMs) in the boreal forest Federico Bianchi, Olga Garmash, Xucheng He, Chao Yan, Siddharth Iyer, Ida Rosendahl, Zhengning Xu, Matti P. Rissanen, Matthieu Riva, Risto Taipale, Nina Sarnela, Tuukka Petäjä, Douglas R. Worsnop, Markku Kulmala, Mikael Ehn, and Heikki Junninen Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-481,2017 Manuscript under review for ACP (discussion: open, 0 comments) Naturally charged highly oxidised molecules (HOMs) were characterized using advanced mass spectrometers. Two different classes of compounds, clustered with the most abundant inorganic acids, were identified: HOMs containing only carbon, hydrogen and oxygen and nitrogen-containing HOMs or organonitrates (ONs). They exhibit strong diurnal variations where HOMs peak during night and ONs during day. Finally, large clusters containing up to 40 carbon atoms (4 oxidized α-pinene units) were observed.

Description: Particulate emissions from large North American wildfires estimated using a new top-down method Tadas Nikonovas, Peter R. J. North, and Stefan H. Doerr Atmos. Chem. Phys., 17, 6423-6438, https://doi.org/10.5194/acp-17-6423-2017, 2017 The study presents a new method for estimating particulate matter emissions from large wildfires. The method relies solely on satellite observations of fire activity and particles suspended in the atmosphere. The results indicate that temperate and boreal forest fires in North America emit similar amounts of particles per unit of fire radiative power. The findings differ from estimates by modelling studies which suggest much larger emissions for boreal events compared to temperate fires.

Description: Comparison of emissions inventories of anthropogenic air pollutants and greenhouse gases in China Eri Saikawa, Hankyul Kim, Min Zhong, Alexander Avramov, Yu Zhao, Greet Janssens-Maenhout, Jun-ichi Kurokawa, Zbigniew Klimont, Fabian Wagner, Vaishali Naik, Larry W. Horowitz, and Qiang Zhang Atmos. Chem. Phys., 17, 6393-6421, https://doi.org/10.5194/acp-17-6393-2017, 2017 We analyze differences in existing air pollutant emission estimates to better understand the magnitude of emissions as well as the source regions and sectors of air pollution in China. We find large disagreements among the inventories, and we show that these differences have a significant impact on regional air quality simulations. Better understanding of air pollutant emissions at more disaggregated levels is essential for air pollution mitigation in China.

Description: Heterogeneous reactions of mineral dust aerosol: implications for tropospheric oxidation capacity Mingjin Tang, Xin Huang, Keding Lu, Maofa Ge, Yongjie Li, Peng Cheng, Tong Zhu, Aijun Ding, Yuanhang Zhang, Sasho Gligorovski, Wei Song, Xiang Ding, Xinhui Bi, and Xinming Wang Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-458,2017 Manuscript under review for ACP (discussion: open, 0 comments) We provide a comprehensive and critical review of laboratory studies of heterogeneous uptake of OH, NO 3 , O 3 , and their directly related species by mineral dust particles. Atmospheric importance of heterogeneous uptake as sinks for these species are also assessed. In addition, we have outlined major open questions and challenges in this field and discussed research strategies to address them.

Description: Surface ozone in the Southern Hemisphere: 20 years of data from a site with a unique setting in El Tololo, Chile Julien G. Anet, Martin Steinbacher, Laura Gallardo, Patricio A. Velásquez Álvarez, Lukas Emmenegger, and Brigitte Buchmann Atmos. Chem. Phys., 17, 6477-6492, https://doi.org/10.5194/acp-17-6477-2017, 2017 There are less long-term surface ozone measurements on the Southern than on the Northern Hemisphere, which makes it difficult to thoroughly understand global ozone chemistry. We have analyzed a new, 20-year-long ozone dataset measured at 2200 m asl at El Tololo, Chile, and show that the annual cycle of ozone is mainly driven by ozone transport from the stratosphere to the troposphere. As well, we illustrate that the timing of the annual maximum is regressing to earlier in the year.

Description: A modeling study of the nonlinear response of fine particles to air pollutant emissions in the Beijing-Tianjin-Hebei region Bin Zhao, Wenjing Wu, Shuxiao Wang, Jia Xing, Xing Chang, Kuo-Nan Liou, Jonathan H. Jiang, Yu Gu, Carey Jang, Joshua S. Fu, Yun Zhu, Jiandong Wang, and Jiming Hao Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-428,2017 Manuscript under review for ACP (discussion: open, 0 comments) Using over 1000 chemical transport model simulations in the Beijing-Tianjin-Hebei region, we find that primary inorganic PM 2.5 is the individual pollutant which makes the largest contribution to PM 2.5 concentrations, and thus should be prioritized in PM 2.5 control strategies. Among the precursors, PM 2.5 concentrations are primarily sensitive to the emissions of NH 3 , NMVOC + IVOC, and POA, and the sensitivities increase substantially for NH 3 and NO x with the increase in emission reduction ratio.

Description: Temporal variation of VOC fluxes measured with PTR-TOF above a boreal forest Simon Schallhart, Pekka Rantala, Maija K. Kajos, Juho Aalto, Ivan Mammarella, Taina M. Ruuskanen, and Markku Kulmala Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-394,2017 Manuscript under review for ACP (discussion: open, 0 comments) Emissions of volatile organic compounds (VOCs) have impact to air quality, human health and climate. We investigated the development of VOC exchange in a boreal forest between April and June 2013. VOC exchange and diversity increased towards summer, however, 80 % of the exchange was driven by four compounds only, methanol, monoterpenes, acetone and butene. The boreal forest emitted just 0.2 % carbon in form of VOCs in relation to the carbon uptake.

Description: Thermodynamic and dynamic responses of the hydrological cycle to solar dimming Jane E. Smyth, Rick D. Russotto, and Trude Storelvmo Atmos. Chem. Phys., 17, 6439-6453, https://doi.org/10.5194/acp-17-6439-2017, 2017 Geoengineering is a controversial proposal to counteract global warming by reducing the incoming solar radiation. Solar dimming could restore preindustrial temperatures, but global rainfall patterns would be altered. We analyze the global rainfall changes in 11 climate model simulations of solar dimming to better understand the underlying processes. We conclude that tropical precipitation would be substantially altered, in part due to changes in the large-scale atmospheric circulation.

Description: A new diagnostic for tropospheric ozone production Peter M. Edwards and Mathew J. Evans Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-378,2017 Manuscript under review for ACP (discussion: open, 0 comments) Tropospheric ozone is important for the Earth’s climate and air quality. It is produced during the oxidation of organics in the presence of nitrogen oxides. Due to the range of organic species emitted and the chain like nature of their oxidation, this chemistry is complex and understanding the role of different processes (emission, deposition, chemistry) is difficult. We demonstrate a new methodology for diagnosing ozone production based on the processing of bonds contained within emitted molecules, the fate of which is determined by the conservation of spin of the bonding electrons. Using this methodology to diagnose ozone production in the GEOS-Chem chemical transport model, we demonstrate its advantages over the standard diagnostic. We show that the number of bonds emitted, their chemistry and lifetime, and feedbacks on OH are all important in determining the ozone production within the model and its sensitivity to changes. This insight may allow future model-model comparisons to better identify the root causes of model differences.

Description: Quasi-12 h inertia–gravity waves in the lower mesosphere observed by the PANSY radar at Syowa Station (39.6° E, 69.0° S) Ryosuke Shibuya, Kaoru Sato, Masaki Tsutsumi, Toru Sato, Yoshihiro Tomikawa, Koji Nishimura, and Masashi Kohma Atmos. Chem. Phys., 17, 6455-6476, https://doi.org/10.5194/acp-17-6455-2017, 2017 The first observations made by a complete PANSY radar system (Program of the Antarctic Syowa MST/IS radar) installed at Syowa Station were successfully performed from 16 to 24 March 2015. Over this period, quasi-12 h period disturbances in the mesosphere at heights of 70 to 80 km were observed. Combining the observational data and numerical simulation outputs, we found that quasi-12 h disturbances are due to large-scale inertia–gravity waves, not to semi-diurnal migrating tides.

Description: Atmospheric Carbonyl Sulphide (OCS) measured remotely by FTIR solar absorption spectrometry Geoffrey C. Toon, Jean-Francois L. Blavier, and Keeyoon Sung Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-404,2017 Manuscript under review for ACP (discussion: open, 0 comments) OCS is the main form at atmospheric sulphur. It is produced near the earth's surface and destroyed primarily in the stratosphere, where it is converted to Stratospheric Sulphate Aerosol (SSA). SSA plays an important role in atmospheric chemistry and transport and so it is important to better understand the factors that regulate OCS and hence SSA. Ground-based and balloon borne infrared spectra observed over the past 30 years are analyzed to provide an improved OCS dataset.

Description: Modelling organic aerosol concentrations and properties during ChArMEx summer campaigns of 2012 and 2013 in the western Mediterranean region Mounir Chrit, Karine Sartelet, Jean Sciare, Jorge Pey, Nicolas Marchand, Florian Couvidat, Karine Sellegri, and Matthias Beekmann Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-312,2017 Manuscript under review for ACP (discussion: open, 0 comments) In the framework of the Chemistry-Aerosol Mediterranean Experiment, a measurement site was set up at a remote site (Ersa) on Corsica Island in the northwestern Mediterranean Sea. Measurement campaigns performed during the summers of 2012 and 2013 showed high organic aerosol concentrations, mostly from biogenic origin. This work aims at representing the organic aerosol concentrations and properties (oxidation state and hydrophilic) using the air-quality model Polyphemus with a surrogate approach for secondary organic aerosol (SOA) formation. Biogenic precursors are isoprene, monoterpenes (with α-pinene and limonene as surrogate species) and sesquiterpenes. In this work, the following model oxidation products of monoterpenes are added: (i) a carboxylic acid (MBTCA) to represent multi-generation oxidation products in the low-NO x regime, (ii) organic nitrate chemistry, (iii) extremely low volatility organic compounds (ELVOCs) formed by ozonolysis. The model shows good agreement to measurements of organic concentrations for both 2012 and 2013 summer campaigns. The modeled oxidation state and hydrophilic properties of the organic aerosols also agree reasonably well with the measurements. The influence of the different chemical processes added to the model on the oxidation level of organics is studied. Measured and simulated water-soluble organic concentrations (WSOC) show that even at a remote site next to the sea, about 64 % of the organic carbon is soluble. The concentrations of WSOC vary with the origins of the air masses and the composition of organic aerosols. The marine organic emissions only contribute to a few percents of the organic mass in PM 1 , with maxima above the sea.

Description: Primary marine aerosol physical and chemical emissions during a nutriment enrichment experiment in mesocosms in the Mediterranean Sea Allison N. Schwier, Karine Sellegri, Sébastien Mas, Bruno Charrière, Jorge Pey, Clémence Rose, Brice Terminé-Roussel, Jean-Luc Jaffrezo, David Parin, David Picard, Mickael Ribeiro, Greg Roberts, Richard Sempéré, Nicolas Marchand, and Barbara D'Anna Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-320,2017 Manuscript under review for ACP (discussion: open, 0 comments) In the present paper, we quantify sea-to-air emission fluxes of aerosol to the atmosphere and characterize their physical and chemical properties as a function of the seawater biochemical and physical properties. Fluxes are evaluated with an original approach: a lab in the field experiment that preserves the seawater and atmospheric complexity, while isolating air-to-sea exchanges from their surroundings. We show different features of the aerosol emission fluxes compared to previous findings.

Description: Connecting smoke plumes to sources using Hazard Mapping System (HMS) smoke and fire location data over North America Steven J. Brey, Mark Ruminski, Samuel A. Atwood, and Emily V. Fischer Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-245,2017 Manuscript under review for ACP (discussion: open, 0 comments) This paper presents the first regional summertime smoke transport climatology for North America using observed smoke plume and fire location data. We show that these data are well correlated with existing biomass burning emission inventories. We present the abundance of smoke over different regions of North America and estimate, where the smoke comes from, the age of smoke, and how often the smoke influences ground level air quality.

Description: Inconsistent decadal variations between surface and free tropospheric nitrogen oxides over United States Zhe Jiang, Helen Worden, John R. Worden, Daven K. Henze, Dylan B. A. Jones, Avelino F. Arellano, Emily V. Fischer, Liye Zhu, Kazuyuki Miyazaki, K. Folkert Boersma, and Vivienne H. Payne Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-382,2017 Manuscript under review for ACP (discussion: open, 0 comments) We investigated the variation of US tropospheric NO 2 in the past decade. We demonstrated significant divergence between the time variation in tropospheric NO 2 columns from OMI retrievals and surface measurements. Our analysis suggests limited contributions from local effects such as fossil fuel emissions, lightning, or instrument artifacts, and indicates possible important contributions from long-range transport of Asian emissions that are modulated by ENSO.

Description: Effects of model resolution and parameterizations on the simulations of clouds, precipitation, and their interactions with aerosols Seoung Soo Lee, Zhanqing Li, Yuwei Zhang, and Hyelim Yoo Atmos. Chem. Phys. Discuss., https//doi.org/10.5194/acp-2017-501,2017 Manuscript under review for ACP (discussion: open, 0 comments) This paper compares the contribution of resolutions to errors in the simulations of clouds, precipitation and their interactions with aerosol by the numerical weather prediction (NWP) models with that of parameterizations. This comparison shows that resolutions contribute to errors to a much greater degree than microphysics parameterizations. This finding provides a useful guideline of how to develop the NWP models and has not been discussed in the previous studies.