ALBERT

Description: Why did the storm ex-Gaston (2010) fail to redevelop during the PREDICT experiment? Thomas M. Freismuth, Blake Rutherford, Mark A. Boothe, and Michael T. Montgomery Atmos. Chem. Phys., 16, 8511-8519, doi:10.5194/acp-16-8511-2016, 2016 Numerical model analyses are used to investigate the role of dry, environmental air in the failed redevelopment of a tropical cyclone (ex-Gaston, 2010). As early as 12:00 UTC 2 September 2010, a dry layer at and above 600 hPa results in a decrease in the vertical mass flux and vertical, relative vorticity. The intrusion of dry air led to a reduction in vorticity and a compromised pouch at these middle levels. This study supports work looking at the role of dry air in moist convection.

Description: A comparative analysis of UV nadir-backscatter and infrared limb-emission ozone data assimilation Rossana Dragani Atmos. Chem. Phys., 16, 8539-8557, doi:10.5194/acp-16-8539-2016, 2016 We present an assessment of ultraviolet nadir-backscatter and infrared limb-emission ozone data assimilation. Understanding the differences in the impact produced by the assimilation of limb and nadir ozone data is relevant to many applications, including climate reanalysis and air quality. The results show the potential and limitations of each dataset and support the need for a more balanced long-term availability of both types of sensors than currently envisaged.

Description: Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau Mathieu Casado, Amaelle Landais, Valérie Masson-Delmotte, Christophe Genthon, Erik Kerstel, Samir Kassi, Laurent Arnaud, Ghislain Picard, Frederic Prie, Olivier Cattani, Hans-Christian Steen-Larsen, Etienne Vignon, and Peter Cermak Atmos. Chem. Phys., 16, 8521-8538, doi:10.5194/acp-16-8521-2016, 2016 Climatic conditions in Concordia are very cold (−55 °C in average) and very dry, imposing difficult conditions to measure the water vapour isotopic composition. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces (down to 20 ppmv). Here we present the results results of a first campaign of measurement of isotopic composition of water vapour in Concordia, the site where the 800 000 years long ice core was drilled.

Description: Surface Renewal as a Significant Mechanism for Dust Emission Jie Zhang, Zhenjiao Teng, Ning Huang, Lei Guo, and Yaping Shao Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-421,2016 Manuscript under review for ACP (discussion: open, 0 comments) In spite of the tremendous efforts, many questions remain unanswered regarding dust emission mechanisms. A series of wind-tunnel experiments are carried out on dust emissions from different soil surfaces to better understand relevant mechanisms. Here are some interesting results that demonstrate the importance of surface renewal mechanism which was normally neglected in previous researches and is strongly recommended to be considered in future dust models.

Description: Variations in O 3 , CO, and CH 4 over the Bay of Bengal during the summer monsoon season: Ship-borne measurements and model simulations Imran A. Girach, Narendra Ojha, Prabha R. Nair, Andrea Pozzer, Yogesh K. Tiwari, K. Ravi Kumar, and Jos Lelieveld Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-595,2016 Manuscript under review for ACP (discussion: open, 0 comments) This study presents first ship-borne measurements of trace gases over the Bay of Bengal during summer monsoon. The observed variations in trace gases are shown to be due to dynamics/transport and en-route photochemistry. Analysis of meteorological and chemical fields shows that significantly lower ozone during rainfall is associated with the downdrafts. A regional model reproduces the observed variations and revealed the rapid transport of ozone across the Bay of Bengal during an event.

Description: Chemical Characteristics of Marine Fine Aerosols over Sea and at Offshore Islands during Three Cruise Sampling Campaigns in the Taiwan Strait– Sea Salts and Anthropogenic Particles Tsung-Chang Li, Chung-Shin Yuan, Chung-Hsuang Hung, Hsun-Yu Lin, Hu-Ching Huang, and Chon-Lin Lee Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-384,2016 Manuscript under review for ACP (discussion: open, 0 comments) This manuscript is significant because it is important to establish data on the background physicochemical characteristics of atmospheric fine particles, as well as their spatial distributions and seasonal variations given various meteorological conditions, and the results of this study will be very much valuable for clarifying the transportation PM 2.5 over sea and at the offshore islands at the Taiwan Strait, which can further fill the the important blank for the global atmospheric research.

Description: On the role of tropopause folds in summertime tropospheric ozone over the eastern Mediterranean and the Middle East Dimitris Akritidis, Andrea Pozzer, Prodromos Zanis, Evangelos Tyrlis, Bojan Škerlak, Michael Sprenger, and Jos Lelieveld Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-547,2016 Manuscript under review for ACP (discussion: open, 0 comments) We investigate the contribution of tropopause folds in the summertime tropospheric ozone pool over the eastern Mediterranean and the Middle East. For this purpose we use the EMAC atmospheric chemistry climate model and a fold identification algorithm. A clear increase of ozone is found in the middle troposphere due to fold activity. The interannual variability of near surface ozone over the eastern Mediterranean is related to that of both tropopause folds and ozone in the free troposphere.

Description: Effect of tropical cyclones on the stratosphere–troposphere exchange observed using satellite observations over the north Indian Ocean M. Venkat Ratnam, S. Ravindra Babu, S. S. Das, G. Basha, B. V. Krishnamurthy, and B. Venkateswararao Atmos. Chem. Phys., 16, 8581-8591, doi:10.5194/acp-16-8581-2016, 2016 The impact of cyclones that occurred over the north Indian Ocean during 2007–2013 on the STE process is quantified using satellite observations. It is shown that cyclones have a significant impact on the tropopause structure, ozone and water vapour budget, and consequentially STE in the UTLS region. The cross-tropopause mass flux from the stratosphere to the troposphere for cyclonic storms is found to be 0.05 ± 0.29 × 10 −3  kg m −2 , and for very severe cyclonic storms it is 0.5 ± 1.07 × 10 −3  kg m −2 .

Description: Turbulence kinetic energy budget during the afternoon transition – Part 2: A simple TKE model Erik Nilsson, Marie Lothon, Fabienne Lohou, Eric Pardyjak, Oscar Hartogensis, and Clara Darbieu Atmos. Chem. Phys., 16, 8873-8898, doi:10.5194/acp-16-8873-2016, 2016 A new simple model for turbulence kinetic energy (TKE) and its budget is presented for the sheared convective atmospheric boundary layer. It is used to study effects of buoyancy and shear on TKE evolution during the afternoon transition, especially near the surface. We also find a region of weak turbulence during unstable afternoon conditions below the inversion top, which we refer to as a "pre-residual layer".

Description: Turbulence kinetic energy budget during the afternoon transition – Part 1: Observed surface TKE budget and boundary layer description for 10 intensive observation period days Erik Nilsson, Fabienne Lohou, Marie Lothon, Eric Pardyjak, Larry Mahrt, and Clara Darbieu Atmos. Chem. Phys., 16, 8849-8872, doi:10.5194/acp-16-8849-2016, 2016 The evolution of near-surface turbulence kinetic energy (TKE) and its budget in the afternoon transition has been studied based on field measurements. The study shows that TKE transport is an important budget term that needs to be taken into account in modeling of TKE. A non-local parametrization of dissipation using a TKE–length scale model which takes into account of boundary layer depth also gave improved results compared to a local parametrization.

Description: Ice nucleation efficiency of AgI: review and new insights Claudia Marcolli, Baban Nagare, André Welti, and Ulrike Lohmann Atmos. Chem. Phys., 16, 8915-8937, doi:10.5194/acp-16-8915-2016, 2016 Silver iodide is one of the best-investigated ice nuclei. It has relevance for the atmosphere since it is used for glaciogenic cloud seeding. Nevertheless, many open questions remain. This paper gives an overview of silver iodide as an ice nucleus and tries to identify the factors that influence the ice nucleation ability of silver iodide.

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. Discuss., doi:10.5194/acp-2016-560,2016 Manuscript under review for ACP (discussion: open, 0 comments) A 1-km gridded and comprehensive biomass burning emission inventory is developed for mainland China in 2012, based on the county-level activity data and updated source-specific emission factors. Several important parameters for emissions estimation are investigated. This paper presents the detailed emission inventory for air quality modelling and supports the development of a targeted control strategy for biomass pollution.

Description: How stratospheric are deep stratospheric intrusions? LUAMI 2008 Thomas Trickl, Hannes Vogelmann, Andreas Fix, Andreas Schäfler, Martin Wirth, Bertrand Calpini, Gilbert Levrat, Gonzague Romanens, Arnoud Apituley, Keith M. Wilson, Robert Begbie, Jens Reichardt, Holger Vömel, and Michael Sprenger Atmos. Chem. Phys., 16, 8791-8815, doi:10.5194/acp-16-8791-2016, 2016 A rather homogeneous deep stratospheric intrusion event was mapped by vertical sounding over central Europe and by model calculations along the transport path. The very low minimum H 2 O mixing ratios demonstrate almost negligible mixing with tropospheric air during the downward transport. The vertical distributions of O 3 and aerosol were transferred from the source region to Europe without major change. A rather shallow outflow from the stratosphere was found.

Description: Controls on phase composition and ice water content in a convection-permitting model simulation of a tropical mesoscale convective system Charmaine N. Franklin, Alain Protat, Delphine Leroy, and Emmanuel Fontaine Atmos. Chem. Phys., 16, 8767-8789, doi:10.5194/acp-16-8767-2016, 2016 Simulations of tropical convection are used to investigate the processes that control the phase composition of tropical clouds. It is shown that the growth of ice is less dependent on vertical velocity than is liquid water, with the control on ice water content being the ice sizes and available liquid water. Results show that in the purely ice region of convective updraughts, the buoyancy is controlled by the ice sizes, demonstrating the importance of microphysical processes on convective dynamics.

Description: Relative humidity-dependent viscosity of secondary organic material from toluene photo-oxidation and possible implications for organic particulate matter over megacities Mijung Song, Pengfei F. Liu, Sarah J. Hanna, Rahul A. Zaveri, Katie Potter, Yuan You, Scot T. Martin, and Allan K. Bertram Atmos. Chem. Phys., 16, 8817-8830, doi:10.5194/acp-16-8817-2016, 2016 To improve predictions of air quality, visibility, and climate change, knowledge of the viscosities and diffusion rates within organic particulate matter consisting of secondary organic material (SOM) is required. Most qualitative and quantitative measurements of viscosity and diffusion rates within organic particulate matter have focused on SOM particles generated from biogenic volatile organic compounds (VOCs) such as α -pinene and isoprene. In this study, we quantify the relative humidity (RH)-dependent viscosities at 295 ± 1 K of SOM produced by photo-oxidation of toluene, an anthropogenic VOC. The viscosities of toluene-derived SOM were 2  ×  10 −1 to  ∼  6  ×  10 6  Pa s from 30 to 90 % RH, and greater than  ∼  2  ×  10 8  Pa s (similar to or greater than the viscosity of tar pitch) for RH  ≤  17 %. These viscosities correspond to Stokes–Einstein-equivalent diffusion coefficients for large organic molecules of  ∼  2  ×  10 −15  cm 2  s −1 for 30 % RH, and lower than  ∼  3  ×  10 −17  cm 2  s −1 for RH  ≤  17 %. Based on these estimated diffusion coefficients, the mixing time of large organic molecules within 200 nm toluene-derived SOM particles is 0.1–5 h for 30 % RH, and higher than  ∼  100 h for RH  ≤  17 %. As a starting point for understanding the mixing times of large organic molecules in organic particulate matter over cities, we applied the mixing times determined for toluene-derived SOM particles to the world's top 15 most populous megacities. If the organic particulate matter in these megacities is similar to the toluene-derived SOM in this study, in Istanbul, Tokyo, Shanghai, and São Paulo, mixing times in organic particulate matter during certain periods of the year may be very short, and the particles may be well-mixed. On the other hand, the mixing times of large organic molecules in organic particulate matter in Beijing, Mexico City, Cairo, and Karachi may be long and the particles may not be well-mixed in the afternoon (15:00–17:00 LT) during certain times of the year.

Description: Air–surface exchange of gaseous mercury over permafrost soil: an investigation at a high-altitude (4700 m a.s.l.) and remote site in the central Qinghai-Tibet Plateau Zhijia Ci, Fei Peng, Xian Xue, and Xiaoshan Zhang Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-515,2016 Manuscript under review for ACP (discussion: open, 0 comments) We performed filed measurements and controlled field experiments to examine the flux, temporal variation and influencing factors of air–surface Hg(0) exchange at a high-altitude and remote site in the central Qinghai-Tibet Plateau. We found that the environmental conditions greatly influenced the air–surface Hg dynamics. Our results have important implications to the Hg biogeochemical cycle in the soils of Qinghai-Tibet Plateau under the rapid climate warming and environmental change.

Description: Aerosol source apportionment from 1-year measurements at the CESAR tower in Cabauw, the Netherlands Patrick Schlag, Astrid Kiendler-Scharr, Marcus Johannes Blom, Francesco Canonaco, Jeroen Sebastiaan Henzing, Marcel Moerman, André Stephan Henry Prévôt, and Rupert Holzinger Atmos. Chem. Phys., 16, 8831-8847, doi:10.5194/acp-16-8831-2016, 2016 This work provides chemical composition data of atmospheric aerosols acquired during 1 year in the rural site of Cabauw, the Netherlands. In some periods, we found unexpected high particle mass concentrations exceeding the WHO limits. Using these composition data, we found that reducing ammonia emissions in this region would largely reduce the main aerosol component ammonium nitrate, whereas the local mitigation of the organics turned out to be difficult due to the lack of a designated source.

Description: Assessment of cloud related fine mode AOD enhancements based on AERONET SDA product A. Arola, T. F. Eck, H. Kokkola, M. R. A. Pitkänen, and S. Romakkaniemi Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-600,2016 Manuscript under review for ACP (discussion: open, 0 comments) One of the issues that hinder the measurement-based assessment of aerosol-cloud interactions by remote sensing methods is that typically aerosols and clouds cannot be measured simultaneously by passive remote sensing methods. AERONET includes so-called SDA product that provides the fine mode AOD also in mixed cloud-aerosol observations. These measurements have not been yet fully exploited in studies of aerosol-cloud interactions. We applied SDA for this kind of analysis.

Description: Global combustion sources of organic aerosols: model comparison with 84 AMS factor-analysis data sets Alexandra P. Tsimpidi, Vlassis A. Karydis, Spyros N. Pandis, and Jos Lelieveld Atmos. Chem. Phys., 16, 8939-8962, doi:10.5194/acp-16-8939-2016, 2016 In this work we use a global chemistry climate model together with a comprehensive global AMS data set in order to provide valuable insights into the temporal and geographical variability of the contribution of the emitted particles and the chemically processed organic material from combustion sources to total OA. This study reveals the high importance of SOA from anthropogenic sources on global OA concentrations and identifies plausible sources of discrepancy between models and measurements.

Description: Modeling investigation of light absorbing aerosols in the central Amazon during the wet season Qiaoqiao Wang, Jorge Saturno, Xuguang Chi, David Walter, Jost V. Lavric, Daniel Moran- Zuloaga, Florian Ditas, Christopher Pöhlker, Joel Brito, Samara Carbone, Paulo Artaxo, and Meinrat O. Andreae Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-586,2016 Manuscript under review for ACP (discussion: open, 0 comments) We use a chemical transport model to interpret observed aerosol concentrations and absorption over the Amazon basin during the wet season. With daily temporal resolution for open fire emissions and modified aerosol optical properties, our model successfully captures the observed variation of aerosol concentrations and absorption over the Amazon basin. The simulation indicates important influence of open fire mainly from northern South America and from Northern Africa in the wet season.

Description: Influence of enhanced Asian NO x emissions on ozone in the Upper Troposphere and Lower Stratosphere (UTLS) in chemistry climate model simulations Chaitri Roy, Suvarna Fadnavis, Rolf Müller, Ayantika Dey Chaudhary, and Felix Ploeger Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-582,2016 Manuscript under review for ACP (discussion: open, 0 comments) In the monsoon season, Asian NO x emissions are rapidly transported to the UTLS and can impact ozone in the UTLS. From chemistry climate model simulations, we show that increasing Asian NO x emissions have led to enhanced ozone radiative forcing over South east Asia which leads to significant warming over the Tibetan plateau and increase precipitations over India. However, a further increase in NO x emissions elicited negative precipitation via ozone heating over the Tibetan plateau.

Description: HCOOH distributions from IASI for 2008–2014: comparison with ground-based FTIR measurements and a global chemistry-transport model Matthieu Pommier, Cathy Clerbaux, Pierre-François Coheur, Emmanuel Mahieu, Jean-François Müller, Clare Paton-Walsh, Trissevgeni Stavrakou, and Corinne Vigouroux Atmos. Chem. Phys., 16, 8963-8981, doi:10.5194/acp-16-8963-2016, 2016 This work presents for the first time 7 years of formic acid (HCOOH) measurements recorded by the satellite instrument, IASI. The comparison of the data set with ground-based FTIR measurements and a CTM shows the interannual and the seasonal variation are well captured. Global distributions are provided, highlighting the long-range transport of tropospheric HCOOH over the oceans and the detection of source regions e.g. over India, USA, and Africa.

Description: Current Understanding of the Driving Mechanisms for Spatiotemporal Variations of Atmospheric Speciated Mercury: A Critical Review Huiting Mao, Irene Cheng, and Leiming Zhang Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-563,2016 Manuscript under review for ACP (discussion: open, 0 comments) Understanding of spatial and temporal variations of atmospheric speciated mercury can advance our knowledge of mercury cycling in various environments. This review summarized spatiotemporal variations of TGM/GEM, GOM, and PBM in various environments including oceans, continents, high elevation, the free troposphere, and low to high latitudes. Remaining questions/issues and recommendations were provided for future research on spatiotemporal variations of atmospheric Hg.

Description: Linking variations in sea spray aerosol particle hygroscopicity to composition during two microcosm experiments Sara D. Forestieri, Gavin C. Cornwell, Taylor M. Helgestad, Kathryn A. Moore, Christopher Lee, Gordon A. Novak, Camille M. Sultana, Xiaofei Wang, Timothy H. Bertram, Kimberly A. Prather, and Christopher D. Cappa Atmos. Chem. Phys., 16, 9003-9018, doi:10.5194/acp-16-9003-2016, 2016 Hygroscopic growth factors at 85 % relative humidity (GF(85 %)) were quantified along with particle composition for primary sea spray aerosol (SSA) particles generated in marine aerosol reference tanks (MARTs) from seawater in which two independent phytoplankton blooms were induced. The observed 5 to 15 % depression in the GF(85 %) values (relative to pure sea salt) is consistent with the large observed volume fractions of non-refractory organic matter (NR-OM) comprising the SSA.

Description: Space based observation of volcanic iodine monoxide Anja Schönhardt, Andreas Richter, Nicolas Theys, and John P. Burrows Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-619,2016 Manuscript under review for ACP (discussion: open, 0 comments) Iodine monoxide, IO, has been observed in satellite measurements following the eruption of the Kasatochi volcano, Alaska, in 2008. Large IO columns are detected by SCIAMACHY on ENVISAT and GOME-2 on MetOp-A for several days. IO amounts are approximately one order of magnitude smaller than those of BrO. Details in the spatial distributions differ between IO, BrO and sulphur dioxide, SO 2 . The total mass of IO in the volcanic plume is determined to be on the order of 10 Mg.

Description: Los Angeles megacity: a high-resolution land–atmosphere modelling system for urban CO 2 emissions Sha Feng, Thomas Lauvaux, Sally Newman, Preeti Rao, Ravan Ahmadov, Aijun Deng, Liza I. Díaz-Isaac, Riley M. Duren, Marc L. Fischer, Christoph Gerbig, Kevin R. Gurney, Jianhua Huang, Seongeun Jeong, Zhijin Li, Charles E. Miller, Darragh O'Keeffe, Risa Patarasuk, Stanley P. Sander, Yang Song, Kam W. Wong, and Yuk L. Yung Atmos. Chem. Phys., 16, 9019-9045, doi:10.5194/acp-16-9019-2016, 2016 We developed a high-resolution land–atmosphere modelling system for urban CO 2 emissions over the LA Basin. We evaluated various model configurations, FFCO 2 products, and the impact of the model resolution. FFCO 2 emissions outpace the atmospheric model resolution to represent the CO 2 concentration variability across the basin. A novel forward model approach is presented to evaluate the surface measurement network, reinforcing the importance of using high-resolution emission products.

Description: Emissions of NO, NO 2 , and PM from inland water transportation Ralf Kurtenbach, Kai Vaupel, Jörg Kleffmann, Ulrich Klenk, Eberhard Schmidt, and Peter Wiesen Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-587,2016 Manuscript under review for ACP (discussion: open, 0 comments) Real world emissions from inland water transport were investigated at the river Rhine: –obtained NO x and PM emission indices are prerequisite for improving emission inventories, –obtained NO 2 /NO x emission ratio points to ship diesel engines without after-treatment systems as main emitter, –NO x emissions of all investigated motor ship types are above the threshold values of national German guidelines, –the need for the implementation of efficient NO x reduction technique is discussed.

Description: Daytime formation of nitrous acid at a coastal remote site in Cyprus indicating a common ground source of atmospheric HONO and NO Hannah Meusel, Uwe Kuhn, A.Andreas Reifs, Chinmay Malik, Hartwig Harder, Monica Martinez, Jan Schuladen, Birger Bohn, Uwe Parchatka, John N. Crowley, Horst Fischer, Thorsten Hoffmann, Ruud Janssen, Oscar Hartogensis, M.Michael Pikridas, Mihalis Vrekoussis, Efstratios Bourtsoukidis, Bettina Weber, Jos Lelieveld, Jonathan Williams, Ulrich Pöschl, Yafang Cheng, and Hang Su Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-554,2016 Manuscript under review for ACP (discussion: open, 0 comments) There are many studies which show discrepancies between modelled and measured nitrous acid (HONO, precursor of OH radical) in the troposphere but with no satisfactory explanation. Ideal conditions to study the unknown sources of HONO were found on Cyprus, a remote Mediterranean island. Trace gas measurements, budget analysis indicate a common source of NO and HONO, which is not related with anthropogenic acitivity but most likely derive from biologic activity in soils and subsequent emission.

Description: Model-based aviation advice on distal volcanic ash clouds by assimilating aircraft in situ measurements Guangliang Fu, Arnold Heemink, Sha Lu, Arjo Segers, Konradin Weber, and Hai-Xiang Lin Atmos. Chem. Phys., 16, 9189-9200, doi:10.5194/acp-16-9189-2016, 2016 Assimilating aircraft in situ measurements can significantly improve aviation advice on distal part of volcanic ash plume.

Description: A multi-model intercomparison of halogenated very short-lived substances (TransCom-VSLS): linking oceanic emissions and tropospheric transport for a reconciled estimate of the stratospheric source gas injection of bromine R. Hossaini, P. K. Patra, A. A. Leeson, G. Krysztofiak, N. L. Abraham, S. J. Andrews, A. T. Archibald, J. Aschmann, E. L. Atlas, D. A. Belikov, H. Bönisch, L. J. Carpenter, S. Dhomse, M. Dorf, A. Engel, W. Feng, S. Fuhlbrügge, P. T. Griffiths, N. R. P. Harris, R. Hommel, T. Keber, K. Krüger, S. T. Lennartz, S. Maksyutov, H. Mantle, G. P. Mills, B. Miller, S. A. Montzka, F. Moore, M. A. Navarro, D. E. Oram, K. Pfeilsticker, J. A. Pyle, B. Quack, A. D. Robinson, E. Saikawa, A. Saiz-Lopez, S. Sala, B.-M. Sinnhuber, S. Taguchi, S. Tegtmeier, R. T. Lidster, C. Wilson, and F. Ziska Atmos. Chem. Phys., 16, 9163-9187, doi:10.3334/CDIAC/hippo_012, 2016 The first concerted multi-model intercomparison of halogenated very short-lived substances (VSLS) has been performed, within the framework of the ongoing Atmospheric Tracer Transport Model Intercomparison Project (TransCom). Eleven global models or model variants participated (nine chemical transport models and two chemistry–climate models) by simulating the major natural bromine VSLS, bromoform (CHBr 3 ) and dibromomethane (CH 2 Br 2 ), over a 20-year period (1993–2012). Except for three model simulations, all others were driven offline by (or nudged to) reanalysed meteorology. The overarching goal of TransCom-VSLS was to provide a reconciled model estimate of the stratospheric source gas injection (SGI) of bromine from these gases, to constrain the current measurement-derived range, and to investigate inter-model differences due to emissions and transport processes. Models ran with standardised idealised chemistry, to isolate differences due to transport, and we investigated the sensitivity of results to a range of VSLS emission inventories. Models were tested in their ability to reproduce the observed seasonal and spatial distribution of VSLS at the surface, using measurements from NOAA's long-term global monitoring network, and in the tropical troposphere, using recent aircraft measurements – including high-altitude observations from the NASA Global Hawk platform. The models generally capture the observed seasonal cycle of surface CHBr 3 and CH 2 Br 2 well, with a strong model–measurement correlation ( r   ≥  0.7) at most sites. In a given model, the absolute model–measurement agreement at the surface is highly sensitive to the choice of emissions. Large inter-model differences are apparent when using the same emission inventory, highlighting the challenges faced in evaluating such inventories at the global scale. Across the ensemble, most consistency is found within the tropics where most of the models (8 out of 11) achieve best agreement to surface CHBr 3 observations using the lowest of the three CHBr 3 emission inventories tested (similarly, 8 out of 11 models for CH 2 Br 2 ). In general, the models reproduce observations of CHBr 3 and CH 2 Br 2 obtained in the tropical tropopause layer (TTL) at various locations throughout the Pacific well. Zonal variability in VSLS loading in the TTL is generally consistent among models, with CHBr 3 (and to a lesser extent CH 2 Br 2 ) most elevated over the tropical western Pacific during boreal winter. The models also indicate the Asian monsoon during boreal summer to be an important pathway for VSLS reaching the stratosphere, though the strength of this signal varies considerably among models. We derive an ensemble climatological mean estimate of the stratospheric bromine SGI from CHBr 3 and CH 2 Br 2 of 2.0 (1.2–2.5) ppt,  ∼  57 % larger than the best estimate from the most recent World Meteorological Organization (WMO) Ozone Assessment Report. We find no evidence for a long-term, transport-driven trend in the stratospheric SGI of bromine over the simulation period. The transport-driven interannual variability in the annual mean bromine SGI is of the order of ±5 %, with SGI exhibiting a strong positive correlation with the El Niño–Southern Oscillation (ENSO) in the eastern Pacific. Overall, our results do not show systematic differences between models specific to the choice of reanalysis meteorology, rather clear differences are seen related to differences in the implementation of transport processes in the models.

Description: Large XCH 4 anomaly in summer 2013 over northeast Asia observed by GOSAT Misa Ishizawa, Osamu Uchino, Isamu Morino, Makoto Inoue, Yukio Yoshida, Kazuo Mabuchi, Tomoko Shirai, Yasunori Tohjima, Shamil Maksyutov, Hirofumi Ohyama, Shuji Kawakami, Atsushi Takizawa, and Dmitry Belikov Atmos. Chem. Phys., 16, 9149-9161, doi:10.5194/acp-16-9149-2016, 2016 Greenhouse gases Observing SATellite (GOSAT) was launched to monitor CO 2 and CH 4 concentrations from the space. This paper analyses an extremely high XCH 4 event over Northeast Asia observed by GOSAT in the summer of 2013. Results indicate that the high XCH 4 event was caused by fast transport of CH 4 -rich air from East China to Japan due to anomalies of north Pacific high-pressure system over East Asia. This study demonstrates the capability of GOSAT to detect an XCH 4 event on a synoptic scale.

Description: Technical Note: Simultaneous fully dynamic characterization of multiple input-output relationships in climate models Ben Kravitz, Douglas G. MacMartin, Philip J. Rasch, and Hailong Wang Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-653,2016 Manuscript under review for ACP (discussion: open, 0 comments) We introduce system identification techniques to climate science wherein multiple dynamic input-output relationships can be simultaneously characterized in a single simulation. This method, involving multiple small perturbations (in space and time) of an input field while monitoring output fields to quantify responses, allows for identification of different timescales of climate response to forcing without substantially pushing the climate far away from a steady state.

Description: Influence of seed aerosol surface area and oxidation rate on vapor wall deposition and SOA mass yields: a case study with α -pinene ozonolysis Theodora Nah, Renee C. McVay, Xuan Zhang, Christopher M. Boyd, John H. Seinfeld, and Nga L. Ng Atmos. Chem. Phys., 16, 9361-9379, doi:10.5194/acp-16-9361-2016, 2016 The influence of seed aerosol surface area and oxidation rate on SOA formation in α-pinene ozonolysis is studied. SOA growth rate and mass yields are independent of seed surface area, consistent with the condensation of SOA-forming vapors being dominated by quasi-equilibrium growth. Faster α-pinene oxidation rates and higher SOA mass yields are observed at increasing O 3  concentrations, indicating that a faster α-pinene oxidation rate leads to rapidly produced SOA-forming oxidation products.

Description: Real-time detection of highly oxidized organosulfates and BSOA marker compounds during the F–BEACh 2014 field study Martin Brüggemann, Laurent Poulain, Andreas Held, Torsten Stelzer, Christoph Zuth, Stefanie Richters, Anke Mutzel, Dominik van Pinxteren, Yoshiteru Iinuma, Sarmite Katkevica, René Rabe, Hartmut Herrmann, and Thorsten Hoffmann Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-650,2016 Manuscript under review for ACP (discussion: open, 0 comments) Using complementary mass spectrometric techniques during a field study in Central Europe, characteristic contributors to the organic aerosol mass were identified. Besides common marker compounds for biogenic secondary organic aerosol, highly oxidized sulfur-species were detected in the particle phase. High time-resolution measurements revealed correlations between these organosulfates and particulate sulfate as well as gas-phase peroxyradicals, giving hints to underlying formation mechanisms.

Description: Introduction to the SPARC Reanalysis Intercomparison Project (S-RIP) and overview of the reanalysis systems Masatomo Fujiwara, Jonathon S. Wright, Gloria L. Manney, Lesley J. Gray, James Anstey, Thomas Birner, Sean Davis, Edwin P. Gerber, V. Lynn Harvey, Michaela I. Hegglin, Cameron R. Homeyer, John A. Knox, Kirstin Krüger, Alyn Lambert, Craig S. Long, Patrick Martineau, Beatriz M. Monge-Sanz, Michelle L. Santee, Susann Tegtmeier, Simon Chabrillat, David G. H. Tan, David R. Jackson, Saroja Polavarapu, Gilbert P. Compo, Rossana Dragani, Wesley Ebisuzaki, Yayoi Harada, Chiaki Kobayashi, Will McCarty, Kazutoshi Onogi, Steven Pawson, Adrian Simmons, Krzysztof Wargan, Jeffrey S. Whitaker, and Cheng-Zhi Zou Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-652,2016 Manuscript under review for ACP (discussion: open, 0 comments) We introduce the SPARC Reanalysis Intercomparison Project (S-RIP), review key concepts and elements of atmospheric reanalysis systems, and summarize the technical details of and differences among eleven of these systems. Our primary objective is to collect these items into a single reference that supports and streamlines scientific studies and intercomparisons of reanalysis products. We also address several common misunderstandings and points of confusion regarding reanalysis data sets.

Description: The major stratospheric final warming in 2016: Dispersal of vortex air and termination of Arctic chemical ozone loss Gloria L. Manney and Zachary D. Lawrence Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-633,2016 Manuscript under review for ACP (discussion: open, 0 comments) The 2015/16 Arctic winter stratosphere was the coldest on record through late February, raising the possibility of extensive chemical ozone loss. However, a major final sudden stratospheric warming in early March curtailed ozone destruction. We used Aura MLS satellite trace gas data and MERRA-2 meteorological data to show the details of transport, mixing, and dispersal of chemically-processed air during the major final warming, and how these processes limited Arctic chemical ozone loss.

Description: STEFLUX, a tool for investigating stratospheric intrusions: application to two WMO/GAW global stations Davide Putero, Paolo Cristofanelli, Michael Sprenger, Bojan Škerlak, Laura Tositti, and Paolo Bonasoni Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-514,2016 Manuscript under review for ACP (discussion: open, 0 comments) The aim of this paper is to present STEFLUX, a tool to obtain a fast-computing identification of the stratospheric intrusions (SI) occurring at a specific location and during a specified time window. STEFLUX results are hereby compared to the SI observations at two high-mountain WMO/GAW global stations in Nepal and Italy, representative of two hot-spots for climate change. Furthermore, the climatology of SI at the two stations is assessed, and the impact of several climate factors investigated.

Description: Conditions for super-adiabatic droplet growth after entrainment mixing Fan Yang, Raymond Shaw, and Huiwen Xue Atmos. Chem. Phys., 16, 9421-9433, doi:10.5194/acp-16-9421-2016, 2016 When dry air is mixed into a cloud, droplets evaporate. If the diluted cloud mixture continues to rise, the remaining droplets will grow. In this work we show theoretically and computationally that a critical height exists, above which the droplets in a mixed, diluted cloud volume become larger than those in an undiluted volume. An environment that is humid and aerosol free is most favorable for producing such large droplets, which may contribute to the onset of precipitation formation.

Description: Co-benefits of global and regional greenhouse gas mitigation for US air quality in 2050 Yuqiang Zhang, Jared H. Bowden, Zachariah Adelman, Vaishali Naik, Larry W. Horowitz, Steven J. Smith, and J. Jason West Atmos. Chem. Phys., 16, 9533-9548, doi:10.5194/acp-16-9533-2016, 2016 Reducing greenhouse gas (GHG) emissions can also improve air quality. We estimate the co-benefits of global GHG mitigation for US air quality in 2050 at fine resolution by downscaling from a previous global study. Foreign GHG mitigation under RCP4.5 contributes more to the US O 3 reduction (76 % of the total) than domestic mitigation and contributes 26 % of the PM2.5 reduction. Therefore, the US gains significantly greater air quality co-benefits by coordinating GHG controls internationally.

Description: Development and Assessment of a High Spatial Resolution (4.4 km) MISR Aerosol Product Using AERONET-DRAGON Data Michael J. Garay, Olga V. Kalashnikova, and Michael A. Bull Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-569,2016 Manuscript under review for ACP (discussion: open, 0 comments) Satellite data from the MISR instrument was used to produce aerosol optical depth (AOD) retrievals at 4.4 km spatial resolution – a factor of 16 improvement relative to the currently operational 17.6 km product. Retrievals were compared with high-spatial resolution ground based observations made by AERONET-DRAGON deployments around the globe. It was found that the 4.4 km MISR retrievals performed significantly better than the 17.6 km retrievals in comparisons made at over 100 individual sites.

Description: Trends in normalized difference vegetation index (NDVI) associated with urban development in northern West Siberia Igor Esau, Victoria V. Miles, Richard Davy, Martin W. Miles, and Anna Kurchatova Atmos. Chem. Phys., 16, 9563-9577, doi:10.5194/acp-16-9563-2016, 2016 Vegetation cover in the remote and cold areas of northern West Siberia is rapidly changing. Analysis of summer maximum vegetation productivity index collected over 15 years (2000–2014) by Terra/Aqua satellites revealed “greening” over the northern (tundra/tundra-forest) and widespread “browning” over the southern (taiga) parts of the region. The vegetation changes around 28 urbanized areas were different. Many Siberian cities become greener even against wider browning trends at the background.

Description: Understanding Severe Winter Haze Pollution in the North-Central North China Plain in 2014 Zhicong Yin, Huijun Wang, and Huopo Chen Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-641,2016 Manuscript under review for ACP (discussion: open, 0 comments) The winter haze days over the North-Central North China Plain in 2014 was the highest in the past 30 years. Taking the anti-cyclone circulation over North China as an intermediary, the positive phases of the East Atlantic/West Russia, the Western Pacific and the Eurasia patterns led to a larger number of haze days in 2014. The related external forcing included pre-autumn Arctic sea ice, winter and pre-autumn surface temperature, and pre-autumn sea surface temperature in Pacific.

Description: Single-particle investigation of summertime and wintertime Antarctic sea spray aerosols using low-Z particle EPMA, Raman microspectrometry, and ATR-FTIR imaging techniques Hyo-Jin Eom, Dhrubajyoti Gupta, Hye-Rin Cho, HeeJin Hwang, SoonDo Hur, Yeontae Gim, and Chul-Un Ro Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-584,2016 Manuscript under review for ACP (discussion: open, 0 comments) Summertime and wintertime Antarctic sea spray aerosol (SSA) samples having a drastic chlorophyll-a level contrast were investigated on a single particle basis. X-ray analysis showed that the contents of C, O, Ca, S, and Si were more elevated, whereas Cl was more depleted for the summertime sample. The combined application of RMS and ATR-FTIR imaging showed Mg hydrate salts of alanine and Mg salts of fatty acids were major organic species in nascent Antarctic SSAs.

Description: Multi-model simulations of aerosol and ozone radiative forcing for the period 1990–2015 Gunnar Myhre, Wenche Aas, Ribu Cherian, William Collins, Greg Faluvegi, Mark Flanner, Piers Forster, Øivind Hodnebrog, Zbigniew Klimont, 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. Discuss., doi:10.5194/acp-2016-594,2016 Manuscript under review for ACP (discussion: open, 0 comments) 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 stronger positive than reported in IPCC AR5.

Description: On the simultaneous deployment of two single-particle mass spectrometers at an urban background and a roadside site during SAPUSS Manuel Dall'Osto, David C. S. Beddows, Eoin J. McGillicuddy, Johanna K. Esser-Gietl, Roy M. Harrison, and John C. Wenger Atmos. Chem. Phys., 16, 9693-9710, doi:10.5194/acp-16-9693-2016, 2016 The aerosol time-of-flight mass spectrometer (ATOFMS) provides size resolved information on the chemical composition of single particles with high time resolution. Within SAPUSS (Solving Aerosol Problems by Using Synergistic Strategies), continuous measurements of ambient particles were made simultaneously at two urban locations in the city of Barcelona (Spain). We find that organic nitrogen is a considerable fraction of the single particles detected, especially at the traffic-dominated site.

Description: A method for the direct measurement of surface tension of collected atmospherically relevant aerosol particles using atomic force microscopy Andrew D. Hritz, Timothy M. Raymond, and Dabrina D. Dutcher Atmos. Chem. Phys., 16, 9761-9769, doi:10.5194/acp-16-9761-2016, 2016 In this manuscript, we present a novel, first-principles method for the determination of surface tension of collected liquid aerosol particles. The method uses an atomic force microscope with a specially designed probe to directly measure the surface tension, a physical parameter required for Kohler theory. The measurements were verified using a standard, check-standard and then applied to a dry and humidified oxidized α-pinene aerosol system.

Description: A model study of the pollution effects of the first 3 months of the Holuhraun volcanic fissure: comparison with observations and air pollution effects Birthe Marie Steensen, Michael Schulz, Nicolas Theys, and Hilde Fagerli Atmos. Chem. Phys., 16, 9745-9760, doi:10.5194/acp-16-9745-2016, 2016 The Bardarbunga volcanic fissure during the second half of 2014 caused large amounts of SO 2 emission. The paper studies the effects of this increase in pollution levels over Europe during the first 3 months of the eruption with a dispersion model. The model results are compared to satellite and surface concentration observations. The biggest differences are found in Iceland and on the coast of northern Norway. For the average pollution levels over Europe, Iceland is located too far away.

Description: Estimating N 2 O 5 uptake coefficients using ambient measurements of NO 3 , N 2 O 5 , ClNO 2 and particle-phase nitrate G. J. Phillips, J. Thieser, M. J. Tang, N. Sobanski, G. Schuster, J. Fachinger, F. Drewnick, S. Borrmann, H. Bingemer, J. Lelieveld, and J. N. Crowley Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-693,2016 Manuscript under review for ACP (discussion: open, 0 comments) We use trace gas measurements (N 2 O 5 , ClNO 2 , NO 3 ) and particle properties (surface area, nitrate contant etc) to derive uptake coefficients (the probability of removal from the gas-phase on a per-collision basis) for the interaction of N 2 O 5 with ambient aerosol and also the efficiency of formation of ClNO 2 . The uptake coefficients show high variability but are reasonably well captured by parameterisations based on laboratory measurements.

Description: Regional and global temperature response to anthropogenic SO 2 emissions from China in three climate models Matthew Kasoar, Apostolos Voulgarakis, Jean-François Lamarque, Drew T. Shindell, Nicolas Bellouin, William J. Collins, Greg Faluvegi, and Kostas Tsigaridis Atmos. Chem. Phys., 16, 9785-9804, doi:10.5194/acp-16-9785-2016, 2016 Computer models are our primary tool to investigate how fossil-fuel emissions are affecting the climate. Here, we used three different climate models to see how they simulate the response to removing sulfur dioxide emissions from China. We found that the models disagreed substantially on how large the climate effect is from the emissions in this region. This range of outcomes is concerning if scientists or policy makers have to rely on any one model when performing their own studies.

Description: Different pathways of the formation of highly oxidized multifunctional organic compounds (HOMs) from the gas-phase ozonolysis of β -caryophyllene Stefanie Richters, Hartmut Herrmann, and Torsten Berndt Atmos. Chem. Phys., 16, 9831-9845, doi:10.5194/acp-16-9831-2016, 2016 New reaction pathways of highly oxidized multifunctional organic compounds (HOMs) from the ozonolysis of the sesquiterpene (C 15 H 24 ) beta-caryophyllene were elucidated based on experiments using isotopically labelled ozone and H/D exchange experiments. These new insights in reaction pathways of unsaturated RO 2 radicals are responsible for the production of about two-thirds of the detected HOMs from beta-caryophyllene and extend the knowledge of HOM formation mechanisms in the atmosphere.

Description: Atmospheric aerosols in Rome, Italy: Sources, dynamics and spatial variations during two seasons Caroline Struckmeier, Frank Drewnick, Friederike Fachinger, Gian Paolo Gobbi, and Stephan Borrmann Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-664,2016 Manuscript under review for ACP (discussion: open, 0 comments) The characteristics of ambient aerosol during two seasons (spring/autumn) and at two locations (suburban/urban) in Rome were investigated. We distinguished regionally advected and locally produced organic aerosol from different sources, including cooking, traffic, biomass burning, but also from locally emitted cigarette smoke, for which we propose a new marker peak for identification in aerosol mass spectra. The impact of Saharan dust advection events on local aerosol concentration was studied.

Description: Measurements of non-volatile aerosols with a VTDMA and their correlations with carbonaceous aerosols in Guangzhou, China Heidi H. Y. Cheung, Haobo Tan, Hanbing Xu, Fei Li, Cheng Wu, Jian Z. Yu, and Chak K. Chan Atmos. Chem. Phys., 16, 8431-8446, doi:10.5194/acp-16-8431-2016, 2016 We present simultaneous measurements of aerosol volatility and carbonaceous matters in Guangzhou, China, in Feb and Mar 2014 using a VTDMA and OC / EC analyzer. Low volatility particles with no significant evaporation at 300° C in the VTDMA contributed 5–15 % of number concentrations of the 40–300 nm particles. Mass closure suggests that non-volatile organic carbon, in addition to elemental carbon, was one of the components of the non-volatile residuals measured by the VTDMA in this study.

Description: Implementation of warm-cloud processes in a source-oriented WRF/Chem model to study the effect of aerosol mixing state on fog formation in the Central Valley of California Hsiang-He Lee, Shu-Hua Chen, Michael J. Kleeman, Hongliang Zhang, Steven P. DeNero, and David K. Joe Atmos. Chem. Phys., 16, 8353-8374, doi:10.5194/acp-16-8353-2016, 2016 A source-oriented CCN module was implemented in a source-oriented chemistry model to study the effect of aerosol mixing state on fog formation. The fraction of aerosols activating into CCN at a supersaturation of 0.5 % in the Central Valley decreased from 94 % in the internal mixture model to 80 % in the source-oriented model. The internal mixture model predicted greater CCN activation than the source-oriented model due to artificial coating of hydrophobic particles with hygroscopic components.

Description: The incorporation of an organic soil layer in the Noah-MP land surface model and its evaluation over a boreal aspen forest Liang Chen, Yanping Li, Fei Chen, Alan Barr, Michael Barlage, and Bingcheng Wan Atmos. Chem. Phys., 16, 8375-8387, doi:10.5194/acp-16-8375-2016, 2016 This work is the first time that Noah-MP is used to investigate the impact of parameterizing organic soil at a boreal forest site. Including an organic soil parameterization significantly improved performance of the model in surface energy and hydrology simulations due to the lower thermal conductivity and greater porosity of the organic soil. It substantially modified the partition between direct soil evaporation and vegetation transpiration in the simulation.

Description: Investigation of processes controlling summertime gaseous elemental mercury oxidation at midlatitudinal marine, coastal, and inland sites Zhuyun Ye, Huiting Mao, Che-Jen Lin, and Su Youn Kim Atmos. Chem. Phys., 16, 8461-8478, doi:10.5194/acp-16-8461-2016, 2016 In this study, a state-of-the-art chemical mechanism was incorporated into a box model to investigate the atmospheric Hg cycling in different environments. As a result, for each of the three environments, GOM diurnal cycles of over half the selected cases were reasonably represented by the box model. A realistic model can be a powerful tool, providing important information on atmospheric Hg cycling and implications for policy makers.

Description: A study of the influence of forest gaps on fire–atmosphere interactions Michael T. Kiefer, Warren E. Heilman, Shiyuan Zhong, Joseph J. Charney, and Xindi Bian Atmos. Chem. Phys., 16, 8499-8509, doi:10.5194/acp-16-8499-2016, 2016 Studies of fire–atmosphere interactions in horizontally heterogeneous forests are limited in number. This study considers the sensitivity of fire-perturbed variables (e.g., vertical velocity, turbulent kinetic energy) to gaps in forest cover using ARPS-CANOPY, an atmospheric numerical model with a canopy sub-model. Results show that the atmosphere is most sensitive to the fire when the gap is centered on the fire and least sensitive when the gap is upstream of the fire.

Description: Differential column measurements using compact solar-tracking spectrometers Jia Chen, Camille Viatte, Jacob K. Hedelius, Taylor Jones, Jonathan E. Franklin, Harrison Parker, Elaine W. Gottlieb, Paul O. Wennberg, Manvendra K. Dubey, and Steven C. Wofsy Atmos. Chem. Phys., 16, 8479-8498, doi:10.5194/acp-16-8479-2016, 2016 This paper helps establish a range of new applications for compact solar-tracking Fourier transform spectrometers, and shows the capability of differential column measurements for determining urban emissions. By accurately measuring the differences in the integrated column amounts of carbon dioxide and methane across local and regional sources in California, we directly observe the mass loading of the atmosphere due to the influence of emissions in the intervening locale.

Description: On the climatological probability of the vertical propagation of stationary planetary waves Khalil Karami, Peter Braesicke, Miriam Sinnhuber, and Stefan Versick Atmos. Chem. Phys., 16, 8447-8460, doi:10.5194/acp-16-8447-2016, 2016 We introduce a diagnostic tool to assess in a climatological framework the optimal propagation conditions for stationary planetary waves. Analyzing 50 winters using NCEP/NCAR reanalysis data we demonstrate several problematic features of the refractive index of Rossby waves. We introduced the Rossby waves membership value function to calculate the optimal propagation conditions for Rossby waves. Sensitivity of our diagnostic tool to strong and weak vortex regimes are examined.

Description: Investigation of aerosol indirect effects on monsoon clouds using ground-based measurements over a high-altitude site in Western Ghats Vasudevan Anil Kumar, Govindan Pandithurai, Parakkatt Parambil Leena, Kundan K. Dani, Palani Murugavel, Sunil M. Sonbawne, Rohit D. Patil, and Rajamma Sukumaran Maheskumar Atmos. Chem. Phys., 16, 8423-8430, doi:10.5194/acp-16-8423-2016, 2016 The effect of atmospheric aerosols on cloud properties is not very well understood in the Indian region, especially over Western Ghats, which is influenced by natural and anthropogenic aerosols. Collocated measurements of aerosol and cloud properties were used to estimate aerosol indirect effects using two methods: one with cloud drop number concentration and the other with cloud droplet size. Discrepancy between both methods is discussed, and the necessity of dispersion offset is emphasized.

Description: Effects of daily meteorology on the interpretation of space-based remote sensing of NO 2 Joshua L. Laughner, Azimeh Zare, and Ronald C. Cohen Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-536,2016 Manuscript under review for ACP (discussion: open, 0 comments) Satellite measurements of the atmosphere provide global information on pollutants that play an important role in air quality. These measurements require assumed knowledge about the vertical profile of these pollutants, which are often simulated at coarse resolution in space and time. We find that simulating these inputs with better spatial and temporal resolution alters individual measurements by up to 40 %, the average measurement by up to 10 %, and increases derived emissions by up to 100 %.

Description: Observations of PAN and its confinement in the Asian summer monsoon anticyclone in high spatial resolution Jörn Ungermann, Mandfred Ern, Martin Kaufmann, Rolf Müller, Reinhold Spang, Felix Ploeger, Bärbel Vogel, and Martin Riese Atmos. Chem. Phys., 16, 8389-8403, doi:10.5194/acp-16-8389-2016, 2016 This paper presents an analysis of temperature and the trace gases PAN and O 3 in the Asian Summer Monsoon (ASM) region. The positive PAN anomaly consisting of polluted air is confined vertically within the main ASM anticyclone, whereas a recently shed eddy exhibits enhanced PAN VMRs for 1 to 2 km above the thermal tropopause. This implies that eddy shedding provides a very rapid horizontal transport pathway of Asian pollution into the extratropical lowermost stratosphere.

Description: Two mechanisms of stratospheric ozone loss in the Northern hemisphere, studied using data assimilation of Odin/SMR atmospheric observations Kazutoshi Sagi, Kristell Pérot, Donal Murtagh, and Yvan Orsolini Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-511,2016 Manuscript under review for ACP (discussion: open, 0 comments) We assess and quantify the ozone loss driven by NO x triggered by stratospheric warmings and the halogens-induced ozone loss using data assimilation results over a decade. To illustrate the difference between halogen-induced loss and NO x -induced loss, we compared a relatively cold and stable winter 2010/2011 and a composite calculation of four winters, 2003/2004, 2005/2006, 2008/2009 and 2012/2013, which were all affected by a major mid-winter sudden stratospheric warming event.

Description: Chemical analysis of refractory stratospheric aerosol particles collected within the arctic vortex and inside polar stratospheric clouds Martin Ebert, Ralf Weigel, Konrad Kandler, Gebhard Günther, Sergej Molleker, Jens-Uwe Grooß, Bärbel Vogel, Stephan Weinbruch, and Stephan Borrmann Atmos. Chem. Phys., 16, 8405-8421, doi:10.5194/acp-16-8405-2016, 2016 Stratospheric aerosol particles were collected within the arctic vortex in late winter. The chemical composition of refractory particles were analyzed by scanning electron microscopy. More than 750 refractory particles with diameters above 500 nm were found consisting of silicates, Fe- and Ca-rich particles and metal mixtures. The detection of refractory particles in the late winter polar stratosphere has strong implications for the formation of polar stratospheric clouds and ozone depletion.

Description: A missing source of aerosols in Antarctica – beyond long-range transport, phytoplankton, and photochemistry Michael R. Giordano, Lars E. Kalnajs, Anita Avery, James D. Goetz, Sean M. Davis, and Peter F. DeCarlo Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-606,2016 Manuscript under review for ACP (discussion: open, 0 comments) 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 spring to summer add additional sulfate.

Description: A Backscatter Lidar Forward Operator for Particle-Representing Atmospheric Chemistry Models Armin Geisinger, Andreas Behrendt, Volker Wulfmeyer, Jens Strohbach, Jochen Förstner, Roland Potthast, and Ina Mattis Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-609,2016 Manuscript under review for ACP (discussion: open, 0 comments) Hereby, we present a new backscatter lidar forward operator which allows for a quantitative comparison of atmospheric chemistry models and backscatter lidar measurements. We applied the operator on model predictions of the 2010 Eyjafjallajökull eruption where the model obviously overestimated the ash concentration. Uncertainties of the operator were minimized by applying averaging algorithms and performing sensitivity studies. Further steps towards quantitative model validation were identified.

Description: Evidence of horizontal and vertical transport of water in the Southern Hemisphere Tropical Tropopause Layer (TTL) from high-resolution balloon observations Sergey M. Khaykin, Jean-Pierre Pommereau, Emmanuel D. Riviere, Gerhard Held, Felix Ploeger, Melanie Ghysels, Nadir Amarouche, Jean-Paul Vernier, Frank G. Wienhold, and Dmitry Ionov Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-588,2016 Manuscript under review for ACP (discussion: open, 0 comments) The study makes use of a series of field experiments conducted in Brazil and aimed at studying the processes controlling the composition of tropical lower stratosphere. High-resolution balloon-borne measurements together with global-coverage satellite observations and weather radar acquisitions are analyzed using trajectory and transport modeling in order to evaluate the contribution of different transport pathways to the stratospheric water budget.

Description: Why do GCMs overestimate the aerosol cloud lifetime effect? A comparison of CAM5 and a CRM Cheng Zhou and Joyce E. Penner Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-612,2016 Manuscript under review for ACP (discussion: open, 0 comments) 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 and a cloud resolving model 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: Tropical temperature variability and Kelvin wave activity in the UTLS from GPS RO measurements Barbara Scherllin-Pirscher, William J. Randel, and Joowan Kim Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-576,2016 Manuscript under review for ACP (discussion: open, 0 comments) Tropical temperature variability and associated Kelvin wave activity is investigated from 10 km to 30 km using 13 years of high-resolution observational data. Strongest temperature variability is found in the tropical tropopause region between approximately 16 km and 20 km, where peaks of Kelvin wave activity are irregularly distributed in time. Detailed knowledge of dynamical processes in the tropical tropopause region is an essential part to better understand climate variability and change.

Description: Size-resolved aerosol and cloud condensation nuclei (CCN) properties in the remote marine South China Sea, Part 1: Observations and source classification Samuel A. Atwood, Jeffrey S. Reid, Sonia M. Kreidenweis, Donald R. Blake, Haflidi H. Jonsson, Nofel D. Lagrosas, Peng Lynch, Elizabeth A. Reid, Walter R. Sessions, and James B. Simpas Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-645,2016 Manuscript under review for ACP (discussion: open, 0 comments) Aerosol particles were measured by ship in remote marine regions of the South China Sea as part of the 2012 7 Southeast Asian Studies (7SEAS) experiments. As the particle populations changed throughout the experiment, the distribution of particle sizes and the amount of water that collected on them changed as well. These changes were associated with various impacts from smoke, sea salt, and pollution sources, and impact how clouds form and precipitation occurs in the region.

Description: Long-range atmospheric transport of volatile monocarboxylic acids with Asian dust over high mountain snow site, central Japan Tomoki Mochizuki, Kimitaka Kawamura, Kazuma Aoki, and Nobuo Sugimoto Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-623,2016 Manuscript under review for ACP (discussion: open, 0 comments) High abundances of formic and acetic acids in the snow pit samples (6 m in depth) collected at snowfield site near Mt. Tateyama, central Japan. Formic and acetic acids are highly abundant in the snow with dust layers in which Ca was enriched. We propose that alkaline metals in Asian dusts largely titrate gaseous organic acids during long-range atmospheric transport.

Description: Large-Scale Vertical Velocity, Diabatic Heating and Drying Profiles Associated with Seasonal and Diurnal Variations of Convective Systems Observed in the GoAmazon2014/5 Experiment Shuaiqi Tang, Shaocheng Xie, Yunyan Zhang, Minghua Zhang, Courtney Schumacher, Hannah Upton, Michael P. Jensen, Karen L. Johnson, Meng Wang, Maike Ahlgrimm, Zhe Feng, Patrick Minnis, and Mandana Thieman Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-644,2016 Manuscript under review for ACP (discussion: open, 0 comments) Data observed during the Green Ocean Amazon (GoAmazon2014/5) experiment are used to derive the large-scale fields in this study. The morning propagating convective systems are active during the wet season but rare during the dry season. The afternoon convections are active in both seasons, with heating and moistening in the lower level corresponding to the vertical convergence of eddy fluxes. Case study shows distinguish large-scale environments for three types of convective systems in Amazonia.

Description: Can we detect regional methane anomalies? A comparison between three observing systems Cindy Cressot, Isabelle Pison, Peter J. Rayner, Philippe Bousquet, Audrey Fortems-Cheiney, and Frédéric Chevallier Atmos. Chem. Phys., 16, 9089-9108, doi:10.5194/acp-16-9089-2016, 2016 Several hypothesis have been made to attribute current trends in atmospheric methane to particular regions. In this context, this work aims at evaluating how well anomalies in methane emissions can be detected at the regional scale with currently available observing systems: two space-borne instruments and a surface network. Our results show that inter-annual analyses of methane emissions inferred by atmospheric inversions should always include an uncertainty assessment.

Description: A high-resolution regional emission inventory of atmospheric mercury and its comparison with multi-scale inventories: a case study of Jiangsu, China Hui Zhong, Yu Zhao, Marilena Muntean, Lei Zhang, and Jie Zhang Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-540,2016 Manuscript under review for ACP (discussion: open, 0 comments) A better understanding of the discrepancies in multi-scale emission inventories could provide indications for their limitations and further improvements. We develop a bottom-up inventory of Hg emissions for Jiangsu China. Compared to the national and global inventories, largest total Hg emissions and fraction of Hg 2+ are estimated. The crucial parameters responsible for the differences include Hg contents in coals/materials, abatement rates of emission control devices and activity levels.

Description: Radiative effects of inter-annually varying versus inter-annually invariant aerosol emissions from fires Benjamin S. Grandey, Hsiang-He Lee, and Chien Wang Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-599,2016 Manuscript under review for ACP (discussion: open, 0 comments) Wildfires emit organic carbon aerosols, small particles suspended in the atmosphere. These aerosols may cool the climate system via interactions with sunlight and clouds. We have used a global climate model to investigate the cooling effects of these aerosols. We find that ignoring inter-annual variability of the emissions may lead to an overestimation of the cooling effect of the aerosols emitted by fires.

Description: The importance of plume rise on the concentrations and atmospheric impacts of biomass burning aerosol Carolin Walter, Saulo R. Freitas, Christoph Kottmeier, Isabel Kraut, Daniel Rieger, Heike Vogel, and Bernhard Vogel Atmos. Chem. Phys., 16, 9201-9219, doi:10.5194/acp-16-9201-2016, 2016 Buoyancy produced by vegetation fires can lead to substantial plume rise with consequences for the dispersion of aerosol emitted by the fires. To study this effect a 1-D plume rise model was included into the regional online integrated model system COSMO-ART. Comparing model results and satellite data for a case study of 2010 Canadian wildfires shows, that the plume rise model outperforms prescribed emission height. The radiative impact of the aerosol leads to a pronounced temperature change.

Description: Wildfire influences on the variability and trend of summer surface ozone in the mountainous western United States Xiao Lu, Lin Zhang, Xu Yue, Jiachen Zhang, Daniel A. Jaffe, Andreas Stohl, Yuanhong Zhao, and Jingyuan Shao Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-646,2016 Manuscript under review for ACP (discussion: open, 0 comments) Increasing wildfire activities in the mountainous western US may present a challenge for the region to attain a recently revised ozone air quality standard in summer. We quantify the wildfire influence on the ozone variability, trends, and number of high ozone days over this region in summers 1989–2010 using a Lagrangian dispersion model and statistical regression models.

Description: Theoretical analysis of mixing in liquid clouds – Part 3: Inhomogeneous mixing Mark Pinsky, Alexander Khain, and Alexei Korolev Atmos. Chem. Phys., 16, 9273-9297, doi:10.5194/acp-16-9273-2016, 2016 An idealized diffusion--evaporation model of time-dependent mixing between cloud and non-cloud volumes is analyzed. It is shown that the evolution of microphysical variables and the final equilibrium stage are unambiguously determined by two non-dimensional parameters. Delimitation between the types of mixing on the plane of these parameters is carried out. The definitions of homogeneous and inhomogeneous mixings are reconsidered and clarified. Results are compared with the classical concept.

Description: Theoretical investigation of mixing in warm clouds – Part 2: Homogeneous mixing Mark Pinsky, Alexander Khain, Alexei Korolev, and Leehi Magaritz-Ronen Atmos. Chem. Phys., 16, 9255-9272, doi:10.5194/acp-16-9255-2016, 2016 The evolution of monodisperse and polydisperse droplet size distributions (DSDs) during homogeneous mixing is analyzed. It is shown that the classic conceptual scheme, according to which homogeneous mixing leads to a decrease in the droplet mass under constant droplet concentration, is valid only in cases of initially very narrow DSDs. In cases of wide DSDs a decrease of both mass and concentration take place such that the characteristic droplet sizes remain nearly constant.

Description: Speciation of OH reactivity above the canopy of an isoprene-dominated forest J. Kaiser, K. M. Skog, K. Baumann, S. B. Bertman, S. B. Brown, W. H. Brune, J. D. Crounse, J. A. de Gouw, E. S. Edgerton, P. A. Feiner, A. H. Goldstein, A. Koss, P. K. Misztal, T. B. Nguyen, K. F. Olson, J. M. St. Clair, A. P. Teng, S. Toma, P. O. Wennberg, R. J. Wild, L. Zhang, and F. N. Keutsch Atmos. Chem. Phys., 16, 9349-9359, doi:10.5194/acp-16-9349-2016, 2016 OH reactivity can be used to assess the amount of reactive carbon in an air mass. “Missing” reactivity is commonly found in forested environments and is attributed to either direct emissions of unmeasured volatile organic compounds or to unmeasured/underpredicted oxidation products. Using a box model and measurements from the 2013 SOAS campaign, we find only small discrepancies in measured and calculated reactivity. Our results suggest the discrepancies stem from unmeasured direct emissions.

Description: Tropospheric ozone seasonal and long-term variability as seen by lidar and surface measurements at the JPL-Table Mountain Facility, California Maria Jose Granados-Muñoz and Thierry Leblanc Atmos. Chem. Phys., 16, 9299-9319, doi:10.5194/acp-16-9299-2016, 2016 Tropospheric ozone DIAL measurements between 2000 and 2015 and surface ozone data from 2013 to 2015 measured at JPL Table Mountain Facility are presented for the first time. Tropospheric ozone variability and trends in the southwestern USA are analyzed observing an increasing ozone trend in the upper troposphere. The influence of the origin of air masses arriving at JPL-TMF and tropopause folds above the site on ozone vertical structure and variability are also observed.

Description: Adjusting particle-size distributions to account for aggregation in tephra-deposit model forecasts Larry G. Mastin, Alexa R. Van Eaton, and Adam J. Durant Atmos. Chem. Phys., 16, 9399-9420, doi:10.5194/acp-16-9399-2016, 2016 During volcanic eruptions, fine ash settles out of the atmosphere to form deposits. Particle aggregation makes it difficult for models to calculate where fine ash will fall. In this study we show that the Ash3d dispersion model can accurately predict where fine ash will land if one assumes a Gaussian size distribution of aggregates, ~ 0.18–0.23 mm in diameter and 600 kg m −3 in density. This aggregation scheme has optimally reproduced deposits for four well-documented eruptions.

Description: Stratospheric gravity waves at Southern Hemisphere orographic hotspots: 2003–2014 AIRS/Aqua observations Lars Hoffmann, Alison W. Grimsdell, and M. Joan Alexander Atmos. Chem. Phys., 16, 9381-9397, doi:10.7289/V5J1012Q, 2016 We present a 12-year record (2003-2014) of stratospheric gravity wave activity at Southern Hemisphere orographic hotspots as observed by the AIRS/Aqua satellite instrument. We introduce a method to discriminate between gravity waves from orographic or other sources and propose a simple model to predict the occurrence of mountain waves using zonal wind thresholds. The prediction model can help to disentangle upper level wind effects from low level source and other influences.

Description: The Dynamical Impact of Rossby Wave Breaking upon UK PM10 Concentration C. P. Webber, H. F. Dacre, W. J. Collins, and G. Masato Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-571,2016 Manuscript under review for ACP (discussion: open, 0 comments) The influence of synoptic meteorology on UK PM10 concentration ([PM10]) is analysed. ERA-Interim reanalysis data is used to detect upper tropospheric wave breaking that explains much of the UK winter synoptic meteorological variability. Wave breaking is shown to positively impact UK [PM10], with a persistent Omega block feature resulting in the greatest probability of exceeding a hazardous UK [PM10]. The meteorological dynamics of UK PM10 exceedances are better understood following this study.

Description: Estimation of the advection effects induced by surface heterogeneities in the surface energy budget Joan Cuxart, Burkhard Wrenger, Daniel Martínez-Villagrasa, Joachim Reuder, Marius O. Jonassen, Maria A. Jiménez, Marie Lothon, Fabienne Lohou, Oscar Hartogensis, Jens Dünnermann, Laura Conangla, and Anirban Garai Atmos. Chem. Phys., 16, 9489-9504, doi:10.5194/acp-16-9489-2016, 2016 Estimations of the effect of thermal advection in the surface energy budget are provided. Data from the experimental campaign BLLAST, held in Southern France in summer 2011, are used, including airborne data by drones and surface-based instrumentation. Model data outputs and satellite information are also inspected. Surface heterogeneities of the order of the kilometer or larger seem to have little effect on the budget, whereas hectometer-scale structures may contribute significantly to it.

Description: Spectroscopic evidence of large aspherical β -NAT particles involved in denitrification in the December 2011 Arctic stratosphere Wolfgang Woiwode, Michael Höpfner, Lei Bi, Michael C. Pitts, Lamont R. Poole, Hermann Oelhaf, Sergej Molleker, Stephan Borrmann, Marcus Klingebiel, Gennady Belyaev, Andreas Ebersoldt, Sabine Griessbach, Jens-Uwe Grooß, Thomas Gulde, Martina Krämer, Guido Maucher, Christof Piesch, Christian Rolf, Christian Sartorius, Reinhold Spang, and Johannes Orphal Atmos. Chem. Phys., 16, 9505-9532, doi:10.5194/acp-16-9505-2016, 2016 The analysis of spectral signatures of a polar stratospheric cloud in airborne infrared remote sensing observations in the Arctic in combination with further collocated measurements supports the view that the observed cloud consisted of highly aspherical nitric acid trihydrate particles. A characteristic "shoulder-like" spectral signature may be exploited for identification of large, highly aspherical nitric acid trihydrate particles involved in denitrification of the polar winter stratosphere.

Description: Observing Entrainment Mixing, Photochemical Ozone Production, and Regional Methane Emissions by Aircraft Using a Simple Mixed-Layer Model Justin F. Trousdell, Stephen A. Conley, Andy Post, and Ian C. Faloona Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-635,2016 Manuscript under review for ACP (discussion: open, 0 comments) In-situ data from two flight campaigns in California’s San Joaquin Valley, an area characterized by complex terrain and patchy sources, is used to estimate important aspects of air pollution meteorology including rates of: vertical mixing, photochemical production of ozone, and the surface emission of non-reactive gases. Shown is the utility of airborne studies to help constrain crucial elements of air pollution modeling including: vertical mixing, horizontal advection, and emission inventories.

Description: Integrated studies of a regional ozone pollution synthetically affected by subtropical high and typhoon system in the Yangtze River Delta region, China Lei Shu, Min Xie, Tijian Wang, Pulong Chen, Yong Han, Shu Li, Bingliang Zhuang, Mengmeng Li, and Da Gao Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-581,2016 Manuscript under review for ACP (discussion: open, 0 comments) Severe high ozone episodes usually have close relations to synoptic systems. A regional continuous ozone pollution episode is detected over the Yangtze River Delta region in August 2013. By means of observational analysis and model simulations, it is found that the Western Pacific subtropical high and Typhoon Utor play an important role.

Description: Impacts of the July 2012 Siberian Fire Plume on Air Quality in the Pacific Northwest Andrew 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. Discuss., doi:10.5194/acp-2016-302,2016 Manuscript under review for ACP (discussion: open, 0 comments) We present a case study of an intense wildfire smoke plume from Siberia that affected the air quality across the Pacific Northwest on July 6–10, 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: Parameterization of single-scattering albedo (SSA) and absorption Ångström exponent (AAE) with EC / OC for aerosol emissions from biomass burning Rudra P. Pokhrel, Nick L. Wagner, Justin M. Langridge, Daniel A. Lack, Thilina Jayarathne, Elizabeth A. Stone, Chelsea E. Stockwell, Robert J. Yokelson, and Shane M. Murphy Atmos. Chem. Phys., 16, 9549-9561, doi:10.5194/acp-16-9549-2016, 2016 This paper gives first multi-wavelength estimates of SSA and AAE of emissions from combustion of Indonesian peat. In addition, it demonstrates that SSA of biomass burning emissions can be parameterized with EC / (EC+OC) and that this parameterization is quantitatively superior to previously published parameterizations based on MCE. It also shows that EC / (EC+OC) parameterization accurately predicts SSA during the first few hours of aging of a biomass burning plume.

Description: Particulate-Phase Mercury Emissions during Biomass Burning and Impact on Resulting Deposition: a Modelling Assessment Francesco De Simone, Sergio Cinnirella, Christian N. Gencarelli, Francesco Carbone, Ian M. Hedgecock, and Nicola Pirrone Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-685,2016 Manuscript under review for ACP (discussion: open, 0 comments) Biomass Burning (BB) releases of Hg, usually considered to be Hg(0), are a significant global source of atmospheric Hg. However there is experimental evidence that a fraction of this Hg is bound to particulate matter, Hg(P). This modelling study shows how increasing fractions of Hg(P) reduce the availability of Hg to the global pool, raising Hg exposure for those regions characterized by high BB, with implications for the sub-Arctic and also rice-growing areas in South-East Asia.

Description: Variation in global chemical composition of PM 2.5 : emerging results from SPARTAN Graydon Snider, Crystal L. Weagle, Kalaivani K. Murdymootoo, Amanda Ring, Yvonne Ritchie, Emily Stone, Ainsley Walsh, Clement Akoshile, Nguyen Xuan Anh, Rajasekhar Balasubramanian, Jeff Brook, Fatimah D. Qonitan, Jinlu Dong, Derek Griffith, Kebin He, Brent N. Holben, Ralph Kahn, Nofel Lagrosas, Puji Lestari, Zongwei Ma, Amit Misra, Leslie K. Norford, Eduardo J. Quel, Abdus Salam, Bret Schichtel, Lior Segev, Sachchida Tripathi, Chien Wang, Chao Yu, Qiang Zhang, Yuxuan Zhang, Michael Brauer, Aaron Cohen, Mark D. Gibson, Yang Liu, J. Vanderlei Martins, Yinon Rudich, and Randall V. Martin Atmos. Chem. Phys., 16, 9629-9653, doi:10.5194/acp-16-9629-2016, 2016 We examine the chemical composition of fine particulate matter (PM 2.5 ) collected on filters at traditionally undersampled, globally dispersed urban locations. Several PM 2.5 chemical components (e.g. ammonium sulfate, ammonium nitrate, and black carbon) vary by more than an order of magnitude between sites while aerosol hygroscopicity varies by a factor of 2. Enhanced anthropogenic dust fractions in large urban areas are apparent from high Zn : Al ratios.

Description: Hydroxyl radical in/on illuminated polar snow: formation rates, lifetimes, and steady-state concentrations Zeyuan Chen, Liang Chu, Edward S. Galbavy, Keren Ram, and Cort Anastasio Atmos. Chem. Phys., 16, 9579-9590, doi:10.5194/acp-16-9579-2016, 2016 We made the first measurements of the concentrations of hydroxyl radical ( • OH), a dominant environmental oxidant, in snow grains. Concentrations of • OH in snow at Summit, Greenland, are comparable to values reported for midlatitude cloud and fog drops, even though impurity levels in the snow are much lower. At these concentrations, the lifetimes of organics and bromide in Summit snow are approximately 3 days and 7 h, respectively, suggesting that OH is a major oxidant for both species.

Description: Technical note: Intercomparison of three AATSR Level 2 (L2) AOD products over China Yahui Che, Yong Xue, Linlu Mei, Jie Guang, Lu She, Jianping Guo, Yincui Hu, Hui Xu, Xingwei He, Aojie Di, and Cheng Fan Atmos. Chem. Phys., 16, 9655-9674, doi:10.5194/acp-16-9655-2016, 2016 Remotely sensed data could provide continuous spatial coverage of aerosol property over the pan-Eurasian area for PEEX program. The AATSR data can be used to retrieve aerosol optical depth (AOD). The Aerosol_cci project provides users with three AOD retrieval algorithms for AATSR data. Because China is vast in territory and has great differences in terms of land surfaces, the combination of the AERONET and CARSNET data can validate the Level 2 AOD products from AATSR data more comprehensively.

Description: Evaluation of regional isoprene emission factors and modeled fluxes in California Pawel K. Misztal, Jeremy C. Avise, Thomas Karl, Klaus Scott, Haflidi H. Jonsson, Alex B. Guenther, and Allen H. Goldstein Atmos. Chem. Phys., 16, 9611-9628, doi:10.5194/acp-16-9611-2016, 2016 In this study, for the first time regional BVOC models are compared with direct regional measurements of fluxes from aircraft, allowing assessment of model accuracy at scales relevant to air quality modeling. We directly assess modeled isoprene emission inventories which are important for regional air quality simulations of ozone and secondary particle concentrations.

Description: Physics of Stratocumulus Top (POST): turbulence characteristics Imai Jen-La Plante, Yongfeng Ma, Katarzyna Nurowska, Hermann Gerber, Djamal Khelif, Katarzyna Karpinska, Marta K. Kopec, Wojciech Kumala, and Szymon P. Malinowski Atmos. Chem. Phys., 16, 9711-9725, doi:10.5194/acp-16-9711-2016, 2016 Using airborne data from of Physics of Stratocumulus Top campaign we analysed turbulence at the interface between free troposphere and cloud top. We found turbulence in temperature inversion capping cloud as well as in adjacent cloud top layer very anisotropic. Eddies are elongated horizontally by wind shear and flattened by static stability. These properties of turbulence at the cloud top were overlooked so far, which explains problems with understanding of entrainment at stratocumulus top.

Description: Impact of crop field burning and mountains on heavy haze in the North China Plain: a case study Xin Long, Xuexi Tie, Junji Cao, Rujin Huang, Tian Feng, Nan Li, Suyu Zhao, Jie Tian, Guohui Li, and Qiang Zhang Atmos. Chem. Phys., 16, 9675-9691, doi:10.5194/acp-16-9675-2016, 2016 We studied the impact of crop field burning (CFB) on air pollution in North China Plain (NCP) using MODIS observations and the numerical model WRF-CHEM. The CFB plume emitted in southern NCP and went through a long-range transport to northern NCP. The long-range transport and the effect of mountains obviously enhanced the PM 2.5 pollution in northern NCP. The prohibition of CFB should be strict not just in or around Beijing, but also on the ulterior crop growth areas of southern NCP.

Description: Tracking city CO 2 emissions from space using a high-resolution inverse modelling approach: a case study for Berlin, Germany Dhanyalekshmi Pillai, Michael Buchwitz, Christoph Gerbig, Thomas Koch, Maximilian Reuter, Heinrich Bovensmann, Julia Marshall, and John P. Burrows Atmos. Chem. Phys., 16, 9591-9610, doi:10.5194/acp-16-9591-2016, 2016 Approximately 70 % of total CO 2 emissions arise from cities; however, there exist large uncertainties in quantifying urban emissions. The present study investigates the potential of a satellite mission like CarbonSat to retrieve the city emissions via inverse modelling techniques. The study makes a valid conclusion that an instrument like CarbonSat has high potential to provide important information on city emissions when exploiting the observations using a high-resolution modelling system.

Description: Tropospheric observations of CFC-114 and CFC-114a with a focus on long-term trends and emissions Johannes C. Laube, Norfazrin Mohd Hanif, Patricia Martinerie, Eileen Gallacher, Paul J. Fraser, Ray Langenfelds, Carl A. M. Brenninkmeijer, Jakob Schwander, Emmanuel Witrant, Jia-Lin Wang, Chang-Feng Ou-Yang, Lauren J. Gooch, Claire E. Reeves, William T. Sturges, and David E. Oram Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-610,2016 Manuscript under review for ACP (discussion: open, 0 comments) Chlorofluorocarbons (CFCs) are ozone depleting substances as well as strong greenhouse gases, and the control of their production and use under the Montreal Protocol has had demonstrable benefits to both mitigation of increasing surface UV radiation and climate forcing. A global ban on consumption came into force in 2010, but there is evidence of continuing emissions of certain CFCs from a range of sources. One compound has received little attention in the literature, namely CFC-114 (C 2 Cl 2 F 4 ). Of particular interest here is the differentiation between CFC-114 (CClF 2 CClF 2 ) and its asymmetric isomeric form CFC-114a (CF 3 CCl 2 F) as atmospheric long-term measurements in the peer-reviewed literature to date have been assumed to represent the sum of both isomers with a time-invariant isomeric speciation. Here we report the first long-term measurements of the two isomeric forms separately, and find that they have different origins and trends in the atmosphere. Air samples collected at Cape Grim (41° S), Australia, during atmospheric background conditions since 1978, combined with samples collected from deep polar snow (firn) enable us to obtain a near-complete record of both gases since their initial production and release in the 1940s. Both isomers were present in the unpolluted atmosphere in comparably small amounts before 1960. The mixing ratio of CFC-114 doubled from 7.9 to 14.8 parts per trillion (ppt) between the start of the Cape Grim record in 1978 and the end of our record in 2014, while over the same time CFC-114a trebled from 0.35 to 1.03 ppt. Mixing ratios of both isomers are slowly decreasing by the end of this period. This is consistent with measurements of recent aircraft-based samples showing no significant interhemispheric mixing ratio gradient. We also find that the fraction of CFC-114a mixing ratio relative to that of CFC-114 increased from 4.3 % to 6.9 % over the 37-year period. This contradicts the current tacit assumption used in international climate change and ozone depletion assessments that both isomers have been largely co-emitted and that their atmospheric concentration ratio has remained approximately constant in time. Complementary observations of air collected in Taiwan indicate a persisting source of CFC-114a in South East Asia which may have been contributing to the changing balance between the two isomers. In addition we present top-down global annual emission estimates of CFC-114 and CFC-114a derived from these measurements using a two-dimensional atmospheric chemistry-transport model. In general, the emissions for both compounds grew steadily during the 1980s, followed by a substantial reduction from the late 1980s onwards, which is consistent with the reduction of emission in response to the Montreal Protocol, and broadly consistent with bottom-up estimates derived by industry. However, we find that small but significant emissions of both isomers remain in 2014. Moreover the inferred changes to the ratio of emissions of the two isomers since the 1990s also indicate that the sources of the two gases are, in part, independent.

Description: Biogenic cloud nuclei in the central Amazon during the transition from wet to dry season James D. Whitehead, Eoghan Darbyshire, Joel Brito, Henrique M. J. Barbosa, Ian Crawford, Rafael Stern, Martin W. Gallagher, Paul H. Kaye, James D. Allan, Hugh Coe, Paulo Artaxo, and Gordon McFiggans Atmos. Chem. Phys., 16, 9727-9743, doi:10.5194/acp-16-9727-2016, 2016 We present measurements of aerosols during the transition from wet to dry seasons at a pristine rainforest site in central Amazonia. By excluding pollution episodes, we focus on natural biogenic aerosols. Submicron aerosols are dominated by organic material, similar to previous wet season measurements. Larger particles are dominated by biological material, mostly fungal spores, with higher concentrations at night. This study provides important data on the nature of particles above the Amazon.

Description: Optical, physical and chemical properties of aerosols transported to a coastal site in the Western Mediterranean: Focus on primary marine aerosols Marine Claeys, Greg Roberts, Marc Mallet, Jovanna Arndt, Karine Sellegri, Jean Sciare, John Wenger, and Bastien Sauvage Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-602,2016 Manuscript under review for ACP (discussion: open, 0 comments) For a period of five days (summer 2013), the mass concentration of primary marine aerosols was dominant compared to other aerosols measured in a ground-based measuring site in Corsica Island. The characteristics of primary marine aerosols such as their size distribution, their optical properties and their direct radiative effect were studied in function of their ageing and their region of emission. These characteristics were compared to two other periods dominated by different aerosol regime.