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: Linking diverse nutrient patterns to different water masses within anticyclonic eddies in the upwelling system off Peru Yonss Saranga José, Heiner Dietze, and Andreas Oschlies Biogeosciences, 14, 1349-1364, doi:10.5194/bg-14-1349-2017, 2017 This study aims to investigate the diverse subsurface nutrient patterns observed within anticyclonic eddies in the upwelling system off Peru. Two simulated anticyclonic eddies with opposing subsurface nitrate concentrations were analysed. The results show that diverse nutrient patterns within anticyclonic eddies are related to the presence of water mass from different origins at different depths, responding to variations in depth of the circulation strength at the edge of the eddy.

Description: Gas chromatography vs. quantum cascade laser-based N 2 O flux measurements using a novel chamber design Christian Brümmer, Bjarne Lyshede, Dirk Lempio, Jean-Pierre Delorme, Jeremy J. Rüffer, Roland Fuß, Antje M. Moffat, Miriam Hurkuck, Andreas Ibrom, Per Ambus, Heinz Flessa, and Werner L. Kutsch Biogeosciences, 14, 1365-1381, doi:10.5194/bg-14-1365-2017, 2017 We present a novel chamber design for measuring soil–atmosphere N 2 O fluxes and compare the performance of a commonly applied gas chromatography (GC) setup with laser-based (QCL) concentration detection. While GC was still a useful method for longer-term investigations, we found that closure times of 10 min and sampling every 5 s is sufficient when using a QCL system. Further, extremely low standard errors (

Description: Drivers of multi-century trends in the atmospheric CO 2 mean annual cycle in a prognostic ESM Jessica Liptak, Gretchen Keppel-Aleks, and Keith Lindsay Biogeosciences, 14, 1383-1401, doi:10.5194/bg-14-1383-2017, 2017 We analyzed the evolution of the atmospheric CO 2 mean annual cycle simulated during 1950–2300 under three scenarios designed to separate the effects of climate change, CO 2 fertilization, and land use change. CO 2 fertilization in boreal and temperate ecosystems drove mean annual cycle amplification over the NH midlatitudes during 1950–2300. Boreal and Arctic climate change drove high-latitude amplification before 2200, after which CO 2 fertilization contributed nearly equally to amplification.

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: Viable cold-tolerant iron-reducing microorganisms in geographically diverse subglacial environments Sophie L. Nixon, Jon P. Telling, Jemma L. Wadham, and Charles S. Cockell Biogeosciences, 14, 1445-1455, doi:10.5194/bg-14-1445-2017, 2017 Despite their permanently cold and dark characteristics, subglacial environments (glacier ice–sediment interface) are known to harbour active microbial communities. However, the role of microbial iron cycling in these environments is poorly understood. Here we show that subglacial sediments harbour active iron-reducing microorganisms, and they appear to be cold-adapted. These results may have important implications for global biogeochemical iron cycling and export to marine ecosystems.

Description: Can land degradation drive differences in the C exchange of two similar semiarid ecosystems? Ana López-Ballesteros, Cecilio Oyonarte, Andrew S. Kowalski, Penélope Serrano-Ortiz, Enrique P. Sánchez-Cañete, M. Rosario Moya, and Francisco Domingo Biogeosciences Discuss., doi:10.5194/bg-2017-77,2017 Manuscript under review for BG (discussion: open, 0 comments) The concept of land degradation stems from the loss of an ecosystem's biological productivity, which in turn relies on several degradation processes, such as long-term loss of natural vegetation, depletion of soil nutrients, soil compaction or water and wind erosion, to which drylands are especially vulnerable. Currently, drylands occupy more than one third of the global terrestrial surface and will probably expand under future climate change scenarios. Drylands' key role in the global C balance has been recently demonstrated, but the effects of land degradation on C sequestration by these ecosystems needs further research. In the present study, we compare net carbon exchange, together with satellite data and meteorological, ambient and vadose zone (CO 2 , water content and temperature) variables, between two nearby (~23 km) experimental sites representing natural (i.e. site of reference) and degraded grazed semiarid grasslands located in SE Spain, via eddy covariance measurements over 6 years, with highly variable precipitation magnitude and distribution. Results show a striking difference in the annual C balances with an average release of 196 ± 40 and −23 ± 20 g C m −2 yr −1 for the degraded and natural sites, respectively. At the seasonal scale, differing patterns in net CO 2 fluxes were detected over both growing and dry seasons. As expected, during the growing seasons, greater net C uptake over longer periods was observed in the natural site, however, much greater net C release was measured in the degraded site during drought periods. We tested differences in all monitored meteorological and soil variables and found it most relevant that CO 2 at 1.50 m belowground was around 1000 ppm higher in the degraded site. Thus, we believe that subterranean ventilation of this vadose zone CO 2 , previously observed at both sites, largely drives the differences in C dynamics between them, especially during the dry season maybe due to enhanced subsoil-atmosphere interconnectivity in the degraded site. Overall, the 12 site-years of data allow direct exploration of the roles of climate and land degradation in the biological and non-biological processes that ultimately control the C sequestration capacity of semiarid ecosystems.

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: Quantifying nutrient fluxes with a new hyporheic passive flux meter (HPFM) Julia Vanessa Kunz, Michael D. Annable, Jaehyun Cho, Wolf von Tümpling, Kirk Hatfield, Suresh Rao, Dietrich Borchardt, and Michael Rode Biogeosciences, 14, 631-649, doi:10.5194/bg-14-631-2017, 2017 The hyporheic zone, the subsurface region of streams, is a key compartment for in-stream nutrient retention. Knowledge on actual hyporheic processing rates is still limited due to methodological restrictions which are mainly related to the high local and temporal variability of subsurface flow patterns and nutrient transformation processes. We present a new device which allows quantitative assessment of hyporheic nutrient fluxes and demonstrate its advantages in an exemplary field testing.

Description: Simulating precipitation decline under a Mediterranean deciduous Oak forest: effects on isoprene seasonal emissions and predictions under climatic scenarios Anne-Cyrielle Genard-Zielinski, Christophe Boissard, Elena Ormeño, Juliette Lathière, Ilja M. Reiter, Henri Wortham, Jean-Philippe Orts, Brice Temine-Roussel, Bertrand Guenet, Svenja Bartsch, Thierry Gauquelin, and Catherine Fernandez Biogeosciences Discuss., doi:10.5194/bg-2017-17,2017 Manuscript under review for BG (discussion: open, 0 comments) From seasonal in situ observations on how a Mediterranean ecosystem responds to drought, a specific isoprene emission (ER) algorithm was developed, upon which 2100 projections (IPCC RCP2.6 and RCP8.5 scenarios) were made. ER were found to be mainly sensitive to soil water content, and poorly represented by current empirical emission model. Drought was found to aggravate thermal stress on ER, increase ER intensity and their frequency response to environmental conditions (present and future).

Description: Evaluating environmental drivers of spatial variability in free-living nematode assemblages along the Portuguese margin Lidia Lins, Frederik Leliaert, Torben Riehl, Sofia Pinto Ramalho, Eliana Alfaro Cordova, André Morgado Esteves, and Ann Vanreusel Biogeosciences, 14, 651-669, doi:10.5194/bg-14-651-2017, 2017 Anthropogenic impacts in the deep sea are regarded as high disturbers of the deep-sea bottom. This study focus in trying to understand the impact of disturbance in the ecosystem and how important functions, such as hydrodynamics and surface primary productivity, affect benthic organisms. Our results showed that high sediment variability due to hydrodynamics, and consequently disturbance, combined with high resource availability are probably the main factors promoting deep-sea species coexistence

Description: Small-scale variability in geomorphological settings influences mangrove-derived organic matter export in a tropical bay Geraldina Signa, Antonio Mazzola, James Kairo, and Salvatrice Vizzini Biogeosciences, 14, 617-629, doi:10.5194/bg-14-617-2017, 2017 Using a combined analytical approach (fatty acid and isotopic markers), we found that the different settings of the creeks flowing into Gazi Bay influenced the mangrove export to the adjacent seagrasses and coral reef. Given the major influence that organic matter exchange between habitats has on organic matter availability and consumption by fauna, the small-scale variability in mangrove export may have far-reaching consequences for local food webs and for the functioning of the whole ecosystem.

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: Amplification of global warming through pH-dependence of DMS-production simulated with a fully coupled Earth system model Jörg Schwinger, Jerry Tjiputra, Nadine Goris, Katharina Six, Alf Kirkevåg, Øyvind Seland, Christoph Heinze, and Tatiana Ilyina Biogeosciences Discuss., doi:10.5194/bg-2017-33,2017 Manuscript under review for BG (discussion: open, 0 comments) Transient global warming under the high emission scenario RCP8.5 is amplified by up to 6 % if a pH-dependency of marine DMS-production is assumed. Importantly, this additional warming is not spatially homogeneous but shows a pronounced north-south gradient. Over the Antarctic continent, the additional warming is almost twice the global average. In the Southern Ocean we find a small DMS-climate feedback that counteracts the original reduction of DMS-production due to ocean acidification.

Description: Isoprene emission and photosynthesis during heat waves and drought in black locust Ines Bamberger, Nadine K. Ruehr, Michael Schmitt, Andreas Gast, Georg Wohlfahrt, and Almut Arneth Biogeosciences Discuss., doi:10.5194/bg-2017-32,2017 Manuscript under review for BG (discussion: open, 0 comments) We studied the effects of two weeks long summer heat waves and drought on photosynthesis and isoprene emissions in black locust trees. While photosynthesis decreased, isoprene emission increased sharply in response to heat and heat-drought stress. Comparing isoprene emissions at the same temperature, however, demonstrated that stressed trees emitted less isoprene than expected. This reveals that in order to predict isoprene emissions during heat waves, model parameters need to be re-evaluated.

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: An assessment of geographical distribution of different plant functional types over North America simulated using the CLASS-CTEM modelling framework Rudra K. Shrestha, Vivek K. Arora, Joe R. Melton, and Laxmi Sushama Biogeosciences Discuss., doi:10.5194/bg-2017-35,2017 Manuscript under review for BG (discussion: open, 0 comments) Computer models of vegetation provide a tool to assess how future changes in climate may affect geographical distribution of vegetation. However, such models must first be assessed for their ability to reproduce present day geographical distribution of vegetation. Here, we assess the ability of one such dynamic vegetation model. We find that while the model is broadly successful in reproducing the geographical distribution of trees and grasses in North America some limitations remain.

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: Implications of sea-ice biogeochemistry for oceanic production and emissions of dimethyl sulfide in the Arctic Hakase Hayashida, Nadja Steiner, Adam Monahan, Virginie Galindo, Martine Lizotte, and Maurice Levasseur Biogeosciences, 14, 3129-3155, https://doi.org/10.5194/bg-14-3129-2017, 2017 In remote regions, cloud conditions may be strongly influenced by oceanic source of dimethylsulfide (DMS) produced by plankton and bacteria. In the Arctic, sea ice provides an additional source of these aerosols. The results of this study highlight the importance of taking into account both the sea-ice sulfur cycle and ecosystem in the flux estimates of oceanic DMS near the ice margins and identify key uncertainties in processes and rates that would be better constrained by new observations.

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: Leveraging 35 years of forest research in the southeastern U.S. to constrain carbon cycle predictions: regional data assimilation using ecosystem experiment R. Quinn Thomas, Evan Brooks, Annika Jersild, Eric Ward, Randolph Wynne, Timothy J. Albaugh, Heather Dinon Aldridge, Harold E. Burkhart, Jean-Christophe Domec, Thomas R. Fox, Carlos A. Gonzalez-Benecke, Timothy A. Martin, Asko Noormets, David A. Sampson, and Robert O. Teskey Biogeosciences Discuss., doi:10.5194/bg-2017-46,2017 Manuscript under review for BG (discussion: open, 0 comments) Quantitative predictions of forest productivity in a changing world were improved when ecosystem manipulation experiments, including experiments that altered water and nutrient availability, were used to calibrate a mathematical forest model. When ecosystem experiments were not included in calibration, the predictions were overly sensitive to nutrient fertilization but not sensitive enough to drought in the Southeastern U.S., a region that supplies a large fraction of wood products to the world.

Description: Modelling past, present and future peatland carbon accumulation across the pan-Arctic Nitin Chaudhary, Paul A. Miller, and Benjamin Smith Biogeosciences Discuss., doi:10.5194/bg-2017-34,2017 Manuscript under review for BG (discussion: open, 0 comments) We employed an individual- and patch-based dynamic global ecosystem model to quantify long-term C accumulation rates and to assess the effects of historical and projected climate change on peatland C balances across the pan-Arctic. We found peatlands in Scandinavia, Europe, Russia and C. & E. Canada will become C source while Siberia, Far East Russia, Alaska and W. & N. Canada increase their sink capacity by the end of 21st century.

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: Response of export production and dissolved oxygen concentrations in oxygen minimum zones to p CO 2 and temperature stabilization scenarios in the biogeochemical model HAMOCC 2.0 Teresa Beaty, Christoph Heinze, Taylor Hughlett, and Arne M. E. Winguth Biogeosciences, 14, 781-797, doi:10.5194/bg-14-781-2017, 2017 In this study HAMOCC2.0 is used to address how mechanisms of oxygen minimum zone (OMZ) expansion respond to changes in CO 2 radiative forcing within the model. Atmospheric p CO 2 is increased at a rate of 1 % annually until stabilized. Our study suggests that expansion in the Pacific Ocean within the model is controlled largely by changes in particulate organic carbon export (POC). The vertical expansion of the OMZs in the Atlantic and Indian oceans is linked to reduced oxygen solubility.

Description: Bayesian calibration of terrestrial ecosystem models: A study of advanced Markov chain Monte Carlo methods Dan Lu, Daniel Ricciuto, Anthony Walker, Cosmin Safta, and William Munger Biogeosciences Discuss., doi:10.5194/bg-2017-41,2017 Manuscript under review for BG (discussion: open, 0 comments) Calibration of terrestrial ecosystem models is important but challenging. Bayesian inference implemented by Markov chain Monte Carlo (MCMC) sampling provides a comprehensive framework to estimate model parameters and associated uncertainties using their posterior distributions. The effectiveness and efficiency of the method strongly depend on the MCMC algorithm used. In this study, a Differential Evolution Adaptive Metropolis (DREAM) algorithm was used to estimate posterior distributions of 21 parameters for the data assimilation linked ecosystem carbon (DALEC) model using 14 years of daily net ecosystem exchange data collected at the Harvard Forest Environmental Measurement Site eddy-flux tower. The DREAM is a multi-chain method and uses differential evolution technique for chain movement, allowing it to be efficiently applied to high-dimensional problems, and can reliably estimate heavy-tailed and multimodal distributions that are difficult for single-chain schemes using a Gaussian proposal distribution. The results were evaluated against the popular Adaptive Metropolis (AM) scheme. DREAM indicated that two parameters controlling autumn phenology have multiple modes in their posterior distributions while AM only identified one mode. The calibration of DREAM resulted in a better model fit and predictive performance compared to the AM. DREAM provides means for a good exploration of the posterior distributions of model parameters. It reduces the risk of false convergence to a local optimum and potentially improves the predictive performance of the calibrated model.

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: Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems Maximilian Weigand and Andreas Kemna Biogeosciences, 14, 921-939, doi:10.5194/bg-14-921-2017, 2017 Root systems are essential in nutrient uptake and translocation, but are difficult to characterize non-invasively with existing methods. We propose electrical impedance tomography (EIT) as a new tool for the imaging and monitoring of crop root systems. In a laboratory experiment we demonstrate the capability of the method to capture physiological responses of root systems with high spatial and temporal resolution. We conclude that EIT is a promising functional imaging technique for crop roots.

Description: The Oligotrophy to the UlTra-oligotrophy PACific Experiment (OUTPACE cruise, Feb. 18 to Apr. 3, 2015) Thierry Moutin, Andrea Doglioli, Alain De Verneil, and Sophie Bonnet Biogeosciences Discuss., doi:10.5194/bg-2017-50,2017 Manuscript under review for BG (discussion: open, 0 comments) The overall goal of OUTPACE was to obtain a successful representation of the interactions between planktonic organisms and the cycle of biogenic elements in the western tropical South Pacific Ocean across trophic and N 2 fixation gradients. The international OUTPACE cruise took place between 18 February and 3 April 2015 aboard the RV L'Atalante and involved 60 scientists. The transect covered ~ 4 000 km from the western part of the Melanesian Archipelago to the western boundary of the gyre.

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: Daily variation in net primary production and net calcification in coral reef communities exposed to elevated pCO 2 Steeve Comeau, Peter J. Edmunds, Coulson A. Lantz, and Robert C. Carpenter Biogeosciences Discuss., doi:10.5194/bg-2017-58,2017 Manuscript under review for BG (discussion: open, 0 comments) Here we investigate how CO 2 enrichment affects in coral reef communities the relationships light–production and light–calcification. For the three communities tested, CO 2 did not affect the light–production, while calcification was lower at elevated CO 2 for all light levels. Our result indicates that CO 2 can modify the balance between net calcification and net photosynthesis of reef communities by depressing community calcification, but without affecting community photosynthesis.

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.