ALBERT

Description: Source attribution and process analysis for atmospheric mercury in eastern China simulated by CMAQ-Hg Atmospheric Chemistry and Physics, 15, 8767-8779, 2015 Author(s): J. Zhu, T. Wang, J. Bieser, and V. Matthias The contribution from different emission sources and atmospheric processes to gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), particulate bound mercury (PBM) and mercury deposition in eastern China were quantified using the Community Multi-scale Air Quality (CMAQ-Hg) modeling system run with a nested domain. Natural sources (NAT) and six categories of anthropogenic mercury sources (ANTH) including cement production (CEM), domestic life (DOM), industrial boilers (IND), metal production (MET), coal-fired power plants (PP) and traffic (TRA) were considered for source apportionment. NAT were responsible for 36.6 % of annual averaged GEM concentration, which was regarded as the most important source for GEM in spite of obvious seasonal variation. Among ANTH, the influence of MET and PP on GEM were most evident especially in winter. ANTH dominated the variations of GOM and PBM concentrations with contributions of 86.7 and 79.1 %, respectively. Among ANTH, IND were the largest contributor for GOM (57.5 %) and PBM (34.4 %) so that most mercury deposition came from IND. The effect of mercury emitted from out of China was indicated by a 〉 30 % contribution to GEM concentration and wet deposition. The contributions from nine processes – consisting of emissions (EMIS), gas-phase chemical production/loss (CHEM), horizontal advection (HADV), vertical advection (ZADV), horizontal advection (HDIF), vertical diffusion (VDIF), dry deposition (DDEP), cloud processes (CLDS) and aerosol processes (AERO) – were calculated for process analysis with their comparison in urban and non-urban regions of the Yangtze River delta (YRD). EMIS and VDIF affected surface GEM and PBM concentrations most and tended to compensate each other all the time in both urban and non-urban areas. However, DDEP was the most important removal process for GOM with 7.3 and 2.9 ng m −3 reduced in the surface of urban and non-urban areas, respectively, in 1 day. The diurnal profile variation of processes revealed the transportation of GOM from urban area to non-urban areas and the importance of CHEM/AERO in higher altitudes which partly caused diffusion of GOM downwards to non-urban areas. Most of the anthropogenic mercury was transported and diffused away from urban areas by HADV and VDIF and increased mercury concentrations in non-urban areas by HADV. Natural emissions only influenced CHEM and AERO more significantly than anthropogenic. Local emissions in the YRD contributed 8.5 % more to GEM and ~ 30 % more to GOM and PBM in urban areas compared to non-urban areas.

Description: Seasonal variation of secondary organic aerosol tracers in Central Tibetan Plateau Atmospheric Chemistry and Physics, 15, 8781-8793, 2015 Author(s): R.-Q. Shen, X. Ding, Q.-F. He, Z.-Y. Cong, Q.-Q. Yu, and X.-M. Wang Secondary organic aerosol (SOA) affects the earth's radiation balance and global climate. High-elevation areas are sensitive to global climate change. However, at present, SOA origins and seasonal variations are understudied in remote high-elevation areas. In this study, particulate samples were collected from July 2012 to July 2013 at the remote Nam Co (NC) site, Central Tibetan Plateau and analyzed for SOA tracers from biogenic (isoprene, monoterpenes and β-caryophyllene) and anthropogenic (aromatics) precursors. Among these compounds, isoprene SOA (SOA I ) tracers represented the majority (26.6 ± 44.2 ng m −3 ), followed by monoterpene SOA (SOA M ) tracers (0.97 ± 0.57 ng m −3 ), aromatic SOA (SOA A ) tracer (2,3-dihydroxy-4-oxopentanoic acid, DHOPA, 0.25 ± 0.18 ng m −3 ) and β-caryophyllene SOA tracer (β-caryophyllenic acid, 0.09 ± 0.10 ng m −3 ). SOA I tracers exhibited high concentrations in the summer and low levels in the winter. The similar temperature dependence of SOA I tracers and isoprene emission suggested that the seasonal variation of SOA I tracers at the NC site was mainly influenced by the isoprene emission. The ratio of high-NO x to low-NO x products of SOA I (2-methylglyceric acid to 2-methyltetrols) was highest in the winter and lowest in the summer, due to the influence of temperature and relative humidity. The seasonal variation of SOA M tracers was impacted by monoterpenes emission and gas-particle partitioning. During the summer to the fall, temperature effect on partitioning was the dominant process influencing SOA M tracers' variation; while the temperature effect on emission was the dominant process influencing SOA M tracers' variation during the winter to the spring. SOA M tracer levels did not elevate with increased temperature in the summer, probably resulting from the counteraction of temperature effects on emission and partitioning. The concentrations of DHOPA were 1–2 orders of magnitude lower than those reported in the urban regions of the world. Due to the transport of air pollutants from the adjacent Bangladesh and northeastern India, DHOPA presented relatively higher levels in the summer. In the winter when air masses mainly came from northwestern India, mass fractions of DHOPA in total tracers increased, although its concentrations declined. The SOA-tracer method was applied to estimate secondary organic carbon (SOC) from these four precursors. The annual average of SOC was 0.22 ± 0.29 μgC m −3 , with the biogenic SOC (sum of isoprene, monoterpenes and β-caryophyllene) accounting for 75 %. In the summer, isoprene was the major precursor with its SOC contributions of 81 %. In the winter when the emission of biogenic precursors largely dropped, the contributions of aromatic SOC increased. Our study implies that anthropogenic pollutants emitted in the Indian subcontinent could be transported to the TP and have an impact on SOC over the remote NC.

Description: Influence of biomass burning on CCN number and hygroscopicity during summertime in the eastern Mediterranean Atmospheric Chemistry and Physics Discussions, 15, 21539-21582, 2015 Author(s): A. Bougiatioti, S. Bezantakos, I. Stavroulas, N. Kalivitis, P. Kokkalis, G. Biskos, N. Mihalopoulos, A. Papayannis, and A. Nenes This study investigates the CCN activity and hygroscopic properties of particles influenced by biomass burning in the eastern Mediterranean. Air masses sampled were subject to a range of atmospheric processing (several hours up to 3 days). Values of the hygroscopicity parameter, κ, were derived from cloud condensation nuclei (CCN) measurements and a Hygroscopic Tandem Differential Mobility Analyzer (HTDMA). An Aerosol Chemical Speciation Monitor (ACSM) was also used to determine the chemical composition and mass concentration of non-refractory components of the submicron aerosol fraction. During fire events, the increased organic content (and lower inorganic fraction) of the aerosol decreases the hygroscopicity parameter, κ, for all particle sizes. The reason, however, for this decrease was not the same for all size modes; smaller particle sizes appeared to be richer in less hygroscopic, less CCN-active components due to coagulation processes while larger particles become less hygroscopic during the biomass burning events due to condensation of less hygroscopic gaseous compounds. In addition, smaller particles exhibited considerable chemical dispersion (where hygroscopicity varied up to 100 % for particles of same size); larger particles, however, exhibited considerably less dispersion owing to the effects of aging and retained high levels of CCN activity. These conclusions are further supported by the observed mixing state determined by the HTDMA measurements. ACSM measurements indicate that the bulk composition reflects the hygroscopicity and chemical nature of the largest particles and a large fraction of the CCN concentrations sampled. Based on Positive Matrix Factorization (PMF) analysis of the organic ACSM spectra, CCN concentrations follow a similar trend with the BBOA component, with enhancements of CCN in biomass burning plumes ranging between 65 and 150 %, for supersaturations ranging between 0.2 and 0.7 %. Using multilinear regression, we determine the hygroscopicity of the prime organic aerosol components (BBOA, OOA-BB and OOA); it is found that the total organic hygroscopicity is very close to the inferred hygroscopicity of the oxygenated organic aerosol components. Finally, the transformation of freshly-emitted biomass burning (BBOA) to more oxidized organic aerosol (OOA-BB) can result in a two-fold increase of the inferred organic hygroscopicity. Almost 10 % of the total aerosol hygroscopicity is related to the two biomass burning components (BBOA and OOA-BB), which in turn contribute almost 35 % to the fine-particle organic water of the aerosol. This is important as organic water can contribute to the atmospheric chemistry and the direct radiative forcing.

Description: Measurement-based direct radiative effect by brown carbon over Indo-Gangetic Plain Atmospheric Chemistry and Physics Discussions, 15, 21583-21606, 2015 Author(s): A. Arola, G. L. Schuster, M. R. A. Pitkänen, O. Dubovik, H. Kokkola, A. V. Lindfors, T. Mielonen, T. Raatikainen, S. Romakkaniemi, S. N. Tripathi, and H. Lihavainen The importance of light absorbing organic aerosols, often called brown carbon (BrC), has become evident in recent years. However, there are relatively few measurement-based estimates for the direct radiative effect of BrC so far. In those earlier studies, the AErosol RObotic NETwork (AERONET) measured Aerosol Absorption Optical Depth (AAOD) and Absorption Angstrom Exponent (AAE) have been exploited. However, these two pieces of information are clearly not sufficient to separate properly carbonaceous aerosols from dust, while imaginary indices of refraction would contain more and better justified information for this purpose. This is first time that the direct radiative effect (DRE) of BrC is estimated by exploiting the AERONET-retrieved imaginary indices. We estimated it for four sites in Indo-Gangetic Plain (IGP), Karachi, Lahore, Kanpur and Gandhi College. We found a distinct seasonality, which was generally similar among all the sites, but with slightly different strengths. The monthly warming effect up to 0.5 W m -2 takes place during spring season. On the other hand, BrC results in overall cooling effect in the winter season, which can reach levels close to −1W m -2 . We then estimated similarly also DRE of black carbon and total aerosol, in order to assess the relative significance of BrC radiative effect in the radiative effects of other components. Even though BrC impact seems minor in this context, we demonstrated that it is not insignificant and moreover that it is crucial to perform spectrally resolved radiative transfer calculations to obtain good estimates for DRE of BrC.

Description: Contrail life cycle and properties from 1 year of MSG/SEVIRI rapid-scan images Atmospheric Chemistry and Physics, 15, 8739-8749, 2015 Author(s): M. Vázquez-Navarro, H. Mannstein, and S. Kox The automatic contrail tracking algorithm (ACTA) – developed to automatically follow contrails as they age, drift and spread – enables the study of a large number of contrails and the evolution of contrail properties with time. In this paper we present a year's worth of tracked contrails, from August 2008 to July 2009 in order to derive statistically significant mean values. The tracking is performed using the 5 min rapid-scan mode of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board the Meteosat Second Generation (MSG) satellites. The detection is based on the high spatial resolution of the images provided by the Moderate Resolution Imaging Spectroradiometer on board the Terra satellite (Terra/MODIS), where a contrail detection algorithm (CDA) is applied. The results show the satellite-derived average lifetimes of contrails and contrail-cirrus along with the probability density function (PDF) of other geometric characteristics such as mean coverage, distribution and width. In combination with specifically developed algorithms (RRUMS; Rapid Retrieval of Upwelling irradiance from MSG/SEVIRI and COCS (Cirrus Optical properties derived from CALIOP and SEVIRI), explained below) it is possible to derive the radiative forcing (RF), energy forcing (EF), optical thickness (τ) and altitude of the tracked contrails. Mean values here retrieved are duration, 1 h; length, 130 km; width, 8 km; altitude, 11.7 km; optical thickness, 0.34. Radiative forcing and energy forcing are shown for land/water backgrounds in day/night situations.

Description: Accounting for the effects of sastrugi in the CERES clear-sky Antarctic shortwave angular distribution models Atmospheric Measurement Techniques, 8, 3163-3175, 2015 Author(s): J. Corbett and W. Su The Cloud and the Earth's Radiant Energy System (CERES) instruments on NASA's Terra, Aqua and Soumi NPP satellites are used to provide a long-term measurement of Earth's energy budget. To accomplish this, the radiances measured by the instruments must be inverted to fluxes by the use of a scene-type-dependent angular distribution model (ADM). For permanent snow scenes over Antarctica, shortwave (SW) ADMs are created by compositing radiance measurements over the full viewing zenith and azimuth range. However, the presence of small-scale wind blown roughness features called sastrugi cause the BRDF (bidirectional reflectance distribution function) of the snow to vary significantly based upon the solar azimuth angle and location. This can result in monthly regional biases between −12 and 7.5 Wm −2 in the inverted TOA (top-of-atmosphere) SW flux. The bias is assessed by comparing the CERES shortwave fluxes derived from nadir observations with those from all viewing zenith angles, as the sastrugi affect fluxes inverted from the oblique viewing angles more than for the nadir viewing angles. In this paper we further describe the clear-sky Antarctic ADMs from Su et al. (2015). These ADMs account for the sastrugi effect by using measurements from the Multi-Angle Imaging Spectro-Radiometer (MISR) instrument to derive statistical relationships between radiance from different viewing angles. We show here that these ADMs reduce the bias and artifacts in the CERES SW flux caused by sastrugi, both locally and Antarctic-wide. The regional monthly biases from sastrugi are reduced to between −5 and 7 Wm −2 , and the monthly-mean biases over Antarctica are reduced by up to 0.64 Wm −2 , a decrease of 74 %. These improved ADMs are used as part of the Edition 4 CERES SSF (Single Scanner Footprint) data.

Description: Space-borne observation of methane from atmospheric infrared sounder version 6: validation and implications for data analysis Atmospheric Measurement Techniques Discussions, 8, 8563-8597, 2015 Author(s): X. Xiong, F. Weng, Q. Liu, and E. Olsen Atmospheric Methane (CH 4 ) is generated as a standard product in recent version of the hyperspectral Atmospheric Infrared Sounder (AIRS-V6) aboard NASA's Aqua satellite at the NASA Goddard Earth Sciences Data and Information Services Center (NASA/GES/DISC). Significant improvements in AIRS-V6 was expected but without a thorough validation. This paper first introduced the improvements of CH 4 retrieval in AIRS-V6 and some characterizations, then presented the results of validation using ~ 1000 aircraft profiles from several campaigns spread over a couple of years and in different regions. It was found the mean biases of AIRS CH 4 at layers 343–441 and 441–575 hPa are −0.76 and −0.05 % and the RMS errors are 1.56 and 1.16 %, respectively. Further analysis demonstrates that the errors in the spring and in the high northern latitudes are larger than in other seasons or regions. The error is correlated with Degree of Freedoms (DOFs), particularly in the tropics or in the summer, and cloud amount, suggesting that the "observed" spatiotemporal variation of CH 4 by AIRS is imbedded with some artificial impact from the retrieval sensitivity in addition to its variation in reality, so the variation of information content in the retrievals needs to be taken into account in data analysis of the retrieval products. Some additional filtering (i.e. rejection of profiles with obvious oscillation as well as those deviating greatly from the norm) for quality control is recommended for the users to better utilize AIRS-V6 CH 4 , and their implementation in the future versions of the AIRS retrieval algorithm is under consideration.

Description: Impact of aerosols on the OMI tropospheric NO 2 retrievals over industrialized regions: how accurate is the aerosol correction of cloud-free scenes via a simple cloud model? Atmospheric Measurement Techniques Discussions, 8, 8385-8437, 2015 Author(s): J. Chimot, T. Vlemmix, J. P. Veefkind, J. F. de Haan, and P. F. Levelt The Ozone Monitoring Instrument (OMI) instrument has provided daily global measurements of tropospheric NO 2 for more than a decade. Numerous studies have drawn attention to the complexities related to measurements of tropospheric NO 2 in the presence of aerosols. Fine particles affect the OMI spectral measurements and the length of the average light path followed by the photons. However, they are not explicitly taken into account in the current OMI tropospheric NO 2 retrieval chain. Instead, the operational OMI O 2 -O 2 cloud retrieval algorithm is applied both to cloudy scenes and to cloud free scenes with aerosols present. This paper describes in detail the complex interplay between the spectral effects of aerosols, the OMI O 2 -O 2 cloud retrieval algorithm and the impact on the accuracy of the tropospheric NO 2 retrievals through the computed Air Mass Factor (AMF) over cloud-free scenes. Collocated OMI NO 2 and MODIS Aqua aerosol products are analysed over East China, in industrialized area. In addition, aerosol effects on the tropospheric NO 2 AMF and the retrieval of OMI cloud parameters are simulated. Both the observation-based and the simulation-based approach demonstrate that the retrieved cloud fraction linearly increases with increasing Aerosol Optical Thickness (AOT), but the magnitude of this increase depends on the aerosol properties and surface albedo. This increase is induced by the additional scattering effects of aerosols which enhance the scene brightness. The decreasing effective cloud pressure with increasing AOT represents primarily the absorbing effects of aerosols. The study cases show that the actual aerosol correction based on the implemented OMI cloud model results in biases between −20 and −40 % for the DOMINO tropospheric NO 2 product in cases of high aerosol pollution (AOT ≥ 0.6) and elevated particles. On the contrary, when aerosols are relatively close to the surface or mixed with NO 2 , aerosol correction based on the cloud model results in overestimation of the DOMINO tropospheric NO 2 product, between 10 and 20 %. These numbers are in line with comparison studies between ground-based and OMI tropospheric NO 2 measurements under conditions with high aerosol pollution and elevated particles. This highlights the need to implement an improved aerosol correction in the computation of tropospheric NO 2 AMFs.

Description: Sensitivity of thermal infrared sounders to the chemical and micro-physical properties of UTLS secondary sulphate aerosols Atmospheric Measurement Techniques Discussions, 8, 8439-8481, 2015 Author(s): P. Sellitto and B. Legras Monitoring upper tropospheric-lower stratospheric (UTLS) secondary sulphate aerosols and their chemical and micro-physical properties from satellite nadir observations is crucial to better understand their formation and evolution processes and then to estimate their impact to the UTLS chemistry, and on regional and global radiative balance. Here we present a study aimed at the evaluation of the sensitivity of thermal infrared (TIR) satellite nadir observations to the chemical composition and the size distribution of idealized UTLS sulphate aerosol layers. The extinction properties of sulphuric acid/water droplets, for different sulphuric acid mixing ratios and temperatures, are systematically analysed. The extinction coefficients are derived by means of a Mie code, using refractive indexes taken from the GEISA (Gestion et Étude des Informations Spectroscopiques Atmosphériques: Management and Study of Spectroscopic Information) spectroscopic database and log-normal size distributions with different effective radii and number concentrations. IASI (Infrared Atmospheric Sounding Interferometer) pseudo-observations are generated using forward radiative transfer calculations performed with the 4A (Automatized Atmospheric Absorption Atlas) radiative transfer model, to estimate the impact of the extinction of idealized aerosol layers, at typical UTLS conditions, on the brightness temperature spectra observed by this satellite instrument. We found a marked and typical spectral signature of these aerosol layers between 700 and 1200 cm −1 , due to the absorption bands of the sulphate and bi-sulphate ions and the undissociated sulphuric acid, with the main absorption peaks at 1170 and 905 cm −1 . The dependence of the aerosol spectral signature to the sulphuric acid mixing ratio, and effective number concentration and radius, as well as the role of interferring parameters like the ozone, sulphur dioxide, carbon dioxide and ash absorption, and temperature and water vapour profile uncertainties, are analyzed and critically discussed.

Description: Global cloud top height retrieval using SCIAMACHY limb spectra: model studies and first results Atmospheric Measurement Techniques Discussions, 8, 8295-8352, 2015 Author(s): K.-U. Eichmann, L. Lelli, C. von Savigny, H. Sembhi, and J. P. Burrows Cloud top heights (CTH) were retrieved for the period 1 January 2003 to 7 April 2012 using height-resolved limb spectra measured with the Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on board ENVISAT (ENVIronmental SATellite). In this study, we tested the sensitivity of the colour index method used in the retrieval code SCODA (SCIAMACHY Cloud Detection Algorithm) and the accuracy of the retrieved CTHs in comparison to other methods. Sensitivity studies using the radiative transfer model SCIATRAN showed that the method is capable of generally detecting cloud tops down to about 5 km and very thin cirrus clouds even up to the tropopause. Volcanic particles can also be detected that occasionally reach the lower stratosphere. Low clouds at 2–3 km can only be retrieved under very clean atmospheric conditions, as light scattering of aerosols interferes with the cloud retrieval. Upper tropospheric ice clouds are detectable for cloud optical depths down to about τ N = 0.005, which is in the subvisual range. The detection sensitivity decreases towards the surface. An optical thickness of roughly 0.1 was the lower detection limit for water cloud top heights at 5 km. This value is much lower than thresholds reported for the passive cloud detection in nadir viewing direction. Comparisons with SCIAMACHY nadir cloud top heights, calculated with the Semi-Analytical CloUd Retrieval Algorithm (SACURA), showed a good agreement in the global cloud field distribution. But only opaque clouds (τ N 〉 5) are detectable with the nadir passive retrieval technique in the UV-visible and infrared wavelength range. So due to the frequent occurrence of thin and sub-visual cirrus clouds in the tropics, large cloud top height deviations were detected between both viewing geometries. Also the land/sea contrast seen in nadir retrievals was not detected in limb mode. Co-located cloud top height measurements of the limb viewing Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on ENVISAT for the period from January 2008 to March 2012 were compared, showing good agreement to within 1 km, which is smaller than the vertical field of view of both instruments. Lower stratospheric aerosols from volcanic eruptions occasionally interfered with the cloud retrieval and inhibited detection of tropospheric clouds. Examples of the impact of these events are shown for the volcanoes Kasatochi in August 2008, Sarychev Peak in June 2009, and Nabro in June 2010. Long-lasting aerosol layers were detected after these events in the Northern Hemisphere down to the tropics. Particle top heights up to about 22 km were retrieved in 2009, when the enhanced lower stratospheric aerosol layer persisted for about 7 months. Up to about 82 % of the Northern hemispheric lower stratosphere between 30° and 70° was covered by scattering particles in August 2009 and nearly half in October 2008.

Description: Operation of the Airmodus A11 nano Condensation Nucleus Counter at various inlet pressures, various operation temperatures and design of a new inlet system Atmospheric Measurement Techniques Discussions, 8, 8483-8508, 2015 Author(s): J. Kangasluoma, A. Franchin, J. Duplissy, L. Ahonen, F. Korhonen, M. Attoui, J. Mikkilä, K. Lehtipalo, J. Vanhanen, M. Kulmala, and T. Petäjä Measuring sub-3 nm particles outside of controlled laboratory conditions is a challenging task, as many of the instruments are operated at their limits and are subjected to changing ambient conditions. In this study, we advance the current understanding on the operation of Airmodus A11 nano Condensation Nucleus Counter (nCNC), which consists of a A10 Particle Size Magnifier (PSM) and A20 condensation particle counter (CPC). We explore the effect of the inlet line pressure on the measured particle concentration. We identify two different regions inside the instrument where supersaturation of working fluid can take place. We show the possibility of varying the cut-off of the instrument from 1 to 6 nm, a wider size range than the one usually covered by the PSM. We also present a new inlet system, which allows automated measurements of the background, minimizes the diffusion losses in the sampling line and is equipped with an electrostatic filter to remove ions. Finally, our view of the guidelines for optimal use of the Airmodus nCNC are provided.

Description: Looking beyond stratification: a model-based analysis of the biological drivers of oxygen depletion in the North Sea Biogeosciences Discussions, 12, 12543-12610, 2015 Author(s): F. Große, N. Greenwood, M. Kreus, H. J. Lenhart, D. Machoczek, J. Pätsch, L. A. Salt, and H. Thomas The problem of low oxygen conditions, often referred to as hypoxia, occurs regularly in the North Sea, a temperate European shelf sea. Stratification represents a major process regulating the seasonal dynamics of bottom oxygen. However, lowest oxygen conditions in the North Sea do not occur in the regions of strongest stratification. This suggests that stratification is an important prerequisite for hypoxia, but that the complex interaction between hydrodynamics and the biological processes drives its development. In this study we use the ecosystem model HAMSOM-ECOHAM5 to provide a general characteristic of the different North Sea oxygen regimes, and to quantify the impact of the different physical and biological factors driving the oxygen dynamics below the thermocline and in the bottom layer. We show that the North Sea can be subdivided into three different regimes in terms of oxygen dynamics: (1) a highly productive, non-stratified coastal regime, (2) a productive, seasonally stratified regime with a small sub-thermocline volume, and (3) a productive, seasonally stratified regime with a large sub-thermocline volume, with regime 2 being highly susceptible to hypoxic conditions. Our analysis of the different processes driving the oxygen development reveals that inter-annual variations in the oxygen conditions are caused by variations in primary production, while spatial differences can be attributed to differences in stratification and water depth. In addition, we show that benthic bacteria represent the main oxygen consumers in the bottom layer, consistently accounting for more than 50 % of the overall consumption. By providing these valuable insights, we show that ecosystem models can be a useful tool for the interpretation of observations and the estimation of the impact of anthropogenic drivers on the North Sea oxygen conditions.

Description: Impact of the oceanic geothermal heat flux on a glacial ocean state Climate of the Past Discussions, 11, 3597-3624, 2015 Author(s): M. Ballarotta, F. Roquet, S. Falahat, Q. Zhang, and G. Madec The oceanic geothermal heating (OGH) has a significant impact on the present-day ocean state, but its role during glacial periods, when the ocean circulation and stratification were different from those of today, remains poorly known. In the present study, we analyzed the response of the glacial ocean to OGH, by comparing ocean simulations of the Last Glacial Maximum (LGM, ∼ 21 ka ago) including or not geothermal heating. We found that applying the OGH warmed the Antarctic Bottom Waters (AABW) by ∼ 0.4 °C and increased the abyssal circulation by 15 to 30 % north of 30° S in the deep Pacific and Atlantic basins. The geothermally heated deep waters were then advected toward the Southern Ocean where they upwelled to the surface due to the Ekman transport. The extra heat transport towards Antarctica acted to reduce the amount of sea ice contributing to the freshening of the whole AABW overturning cell. The global amount of salt being conserved, this bottom freshening induced a salinification of the North Atlantic and North Pacific surface and intermediate waters, contributing to the deepening of the North Atlantic Deep Water. This indirect mechanism is responsible for the largest observed warming, found in the North Atlantic deep western boundary current between 2000 and 3000 m (up to 2 °C). The characteristic time scale of the ocean response to the OGH corresponds to an advective time scale (associated with the overturning of the AABW cell) rather than a diffusive time scale. The OGH might facilitate the transition from a glacial to an inter-glacial state but its effect on the deep stratification seems insufficient to drive alone an abrupt climate change.

Description: Woodland Survey of Great Britain 1971–2001 Earth System Science Data, 7, 203-214, 2015 Author(s): C. M. Wood, S. M. Smart, and R. G. H. Bunce The Woodland Survey of Great Britain is a unique data set, consisting of a detailed range of ecological measurements at a national scale, covering a time span of 30 years. A set of 103 woods spread across Britain were first surveyed in 1971, which were again surveyed in 2000–2003 (for convenience referred to subsequently as the "2001 survey"). Standardised methods of describing the trees, shrubs, ground flora, soils and general habitats present were used for both sets of surveys. The sample of 1648 plots spread through 103 woodland sites located across Britain makes it probably the most extensive quantitative ecological woodland survey undertaken in Britain; it is also notable for the range of sites that have been revisited after such a long interval. The data set provides a unique opportunity to explore the effects of a range of potential drivers of woodland change that operated between 1971 and 2001. The data set is available in four discrete parts, which have been assigned the following DOIs: doi:10.5285/4d93f9ac-68e3-49cf-8a41-4d02a7ead81a (Kirby et al., 2013b), doi:10.5285/d6409d40-58fe-4fa7-b7c8-71a105b965b4 (Kirby et al., 2013d), doi:10.5285/fb1e474d-456b-42a9-9a10-a02c35af10d2 (Kirby et al., 2013c), doi:10.5285/2d023ce9-6dbe-4b4f-a0cd-34768e1455ae (Kirby et al., 2013a).

Description: Estimating greenhouse gas emissions from travel – a GIS-based study Geographica Helvetica, 70, 185-192, 2015 Author(s): S. Kuonen Conferences, meetings and congresses are an important part of today's economic and scientific world. But the environmental impact, especially from greenhouse gas emissions associated with travel, can be extensive. Anthropogenic greenhouse gas (GHG) emissions account for the warming of the atmosphere and oceans. This study draws on the need to quantify and reduce greenhouse gas emissions associated with travel activities and aims to give suggestions for organizers and participants on possible ways to reduce greenhouse gas emissions, demonstrated on the example of the European Geography Association (EGEA) Annual Congress 2013 in Wasilkow, Poland. The lack of a comprehensive methodology for the estimation of greenhouse gas emissions from travel led to an outline of a methodology that uses geographic information systems (GIS) to calculate travel distances. The calculation of travel distances in GIS is adapted from actual transportation infrastructure, derived from the open-source platform OpenStreetMap. The methodology also aims to assess the possibilities to reduce GHG emissions by choosing different means of transportation and a more central conference location. The results of the participants of the EGEA congress, who shared their travel data for this study, show that the total travel distance adds up to 238 000 km, with average travel distance of 2429 km per participant. The travel activities of the participants in the study result in total GHG emissions of 39 300 kg CO 2 -eq including both outward and return trip. On average a participant caused GHG emissions of 401 kg CO 2 -eq. In addition, the analysis of the travel data showed differences in travel behaviour depending on the distance between conference site and point of origin. The findings on travel behaviour have then been used to give an estimation of total greenhouse gas emissions from travel for all participants of the conference, which result in a total amount of 79 711 kg CO 2 -eq. The potential for reducing greenhouse gas emissions by substituting short flights with train rides and car rides with bus and train rides is limited. Only 6 % of greenhouse gas emissions could be saved by applying these measures. Further considerable savings could only be made by substituting longer flights (32.6 %) or choosing a more central conference location (26.3 %).

Description: Singular vector based targeted observations of chemical constituents: description and first application of the EURAD-IM-SVA Geoscientific Model Development Discussions, 8, 6267-6307, 2015 Author(s): N. Goris and H. Elbern Measurements of the large dimensional chemical state of the atmosphere provide only sparse snapshots of the state of the system due to their typically insufficient temporal and spatial density. In order to optimize the measurement configurations despite those limitations, the present work describes the identification of sensitive states of the chemical system as optimal target areas for adaptive observations. For this purpose, the technique of singular vector analysis (SVA), which has been proved effective for targeted observations in numerical weather predication, is implemented into the chemical transport model EURAD-IM (EURopean Air pollution and Dispersion – Inverse Model) yielding the EURAD-IM-SVA. Besides initial values, emissions are investigated as critical simulation controlling targeting variables. For both variants, singular vectors are applied to determine the optimal placement for observations and moreover to quantify which chemical compounds have to be observed with preference. Based on measurements of the airship based ZEPTER-2 campaign, the EURAD-IM-SVA has been evaluated by conducting a comprehensive set of model runs involving different initial states and simulation lengths. Since the considered cases are restricted in terms of considered chemical compounds and selected areas, they allow for a retracing of the results and a confirmation of their correctness. Our analysis shows that the optimal placement for observations of chemical species is not entirely determined by mere transport and mixing processes. Rather, a combination of initial chemical concentrations, chemical conversions, and meteorological processes determine the influence of chemical compounds and regions. We furthermore demonstrate that the optimal placement of observations of emission strengths is highly dependent on the location of emission sources and that the benefit of including emissions as target variables outperforms the value of initial value optimisation with growing simulation length. The obtained results confirm the benefit of considering both initial values and emission strengths as target variables and of applying the EURAD-IM-SVA for measurement decision guidance with respect to chemical compounds.

Description: A global scale mechanistic model of the photosynthetic capacity Geoscientific Model Development Discussions, 8, 6217-6266, 2015 Author(s): A. A. Ali, C. Xu, A. Rogers, R. A. Fisher, S. D. Wullschleger, N. G. McDowell, E. C. Massoud, J. A. Vrugt, J. D. Muss, J. B. Fisher, P. B. Reich, and C. J. Wilson Although plant photosynthetic capacity as determined by the maximum carboxylation rate (i.e., V c, max25 ) and the maximum electron transport rate (i.e., J max25 ) at a reference temperature (generally 25 °C) is known to vary substantially in space and time in response to environmental conditions, it is typically parameterized in Earth system models (ESMs) with tabulated values associated to plant functional types. In this study, we developed a mechanistic model of leaf utilization of nitrogen for assimilation (LUNA V1.0) to predict the photosynthetic capacity at the global scale under different environmental conditions, based on the optimization of nitrogen allocated among light capture, electron transport, carboxylation, and respiration. The LUNA model was able to reasonably well capture the observed patterns of photosynthetic capacity in view that it explained approximately 55 % of the variation in observed V c, max25 and 65 % of the variation in observed J max25 across the globe. Our model simulations under current and future climate conditions indicated that V c, max25 could be most affected in high-latitude regions under a warming climate and that ESMs using a fixed V c, max25 or J max25 by plant functional types were likely to substantially overestimate future global photosynthesis.

Description: Uncertainties in calculating precipitation climatology in East Asia Hydrology and Earth System Sciences Discussions, 12, 7765-7783, 2015 Author(s): J. Kim and S. K. Park This study examines the uncertainty in calculating the fundamental climatological characteristics of precipitation in the East Asia region from multiple fine-resolution gridded analysis datasets based on in-situ rain gauge observations. Five observation-based gridded precipitation datasets are used to derive the long-term means, standard deviations in lieu of interannual variability and linear trends over the 28-year period from 1980 to 2007. Both the annual and summer (June–July–August) mean precipitation is examined. The agreement amongst these precipitation datasets are examined using multiple metrics including the signal-to-noise ratio (SNR) defined as the ratio between long-term means and the corresponding standard deviations, and Taylor diagrams which allows examinations of the pattern correlation, the standard deviation, and the centered root mean square error. It is found that the five gauge-based precipitation analysis datasets agree well in the long-term mean and interannual variability in most of the East Asia region including eastern China, Manchuria, South Korea, and Japan, which are densely populated and have fairly high density observation networks. The regions of large inter-dataset variations include Tibetan Plateau, Mongolia, northern Indo-China, and North Korea. The regions of large uncertainties are typically lightly populated and are characterized by severe terrain and/or extreme high elevations. Unlike the long-term mean and interannual variability, agreements between datasets in the linear trend is weak, both for the annual and summer mean values. In most of the East Asia region, the SNR for the linear trend is below 0.5, i.e., the inter-dataset variability exceeds the multi-data ensemble mean. The uncertainty in the spatial distribution of long-term means among these datasets occurs both in the spatial pattern and variability, but the uncertainty for the interannual variability and time trend is much larger in the variability than in the pattern correlation. Thus, care must be taken in using long-term trends calculated from gridded precipitation analysis data for climate studies over the East Asia region.

Description: Qualitative soil moisture assessment in semi-arid Africa – the role of experience and training on inter-rater reliability Hydrology and Earth System Sciences, 19, 3505-3516, 2015 Author(s): M. Rinderer, H. C. Komakech, D. Müller, G. L. B. Wiesenberg, and J. Seibert Soil and water management is particularly relevant in semi-arid regions to enhance agricultural productivity. During periods of water scarcity, soil moisture differences are important indicators of the soil water deficit and are traditionally used for allocating water resources among farmers of a village community. Here we present a simple, inexpensive soil wetness classification scheme based on qualitative indicators which one can see or touch on the soil surface. It incorporates the local farmers' knowledge on the best soil moisture conditions for seeding and brick making in the semi-arid environment of the study site near Arusha, Tanzania. The scheme was tested twice in 2014 with farmers, students and experts (April: 40 persons, June: 25 persons) for inter-rater reliability, bias of individuals and functional relation between qualitative and quantitative soil moisture values. During the test in April farmers assigned the same wetness class in 46 % of all cases, while students and experts agreed on about 60 % of all cases. Students who had been trained in how to apply the method gained higher inter-rater reliability than their colleagues with only a basic introduction. When repeating the test in June, participants were given improved instructions, organized in small subgroups, which resulted in a higher inter-rater reliability among farmers. In 66 % of all classifications, farmers assigned the same wetness class and the spread of class assignments was smaller. This study demonstrates that a wetness classification scheme based on qualitative indicators is a robust tool and can be applied successfully regardless of experience in crop growing and education level when an in-depth introduction and training is provided. The use of a simple and clear layout of the assessment form is important for reliable wetness class assignments.

Description: Nonlinear effects of locally heterogeneous hydraulic conductivity fields on regional stream–aquifer exchanges Hydrology and Earth System Sciences Discussions, 12, 7727-7764, 2015 Author(s): J. Zhu, C. L. Winter, and Z. Wang Computational experiments are performed to evaluate the effects of locally heterogeneous conductivity fields on regional exchanges of water between stream and aquifer systems in the Middle Heihe River Basin (MHRB) of northwestern China. The effects are found to be nonlinear in the sense that simulated discharges from aquifers to streams are systematically lower than discharges produced by a base model parameterized with relatively coarse effective conductivity. A similar, but weaker, effect is observed for stream leakage. The study is organized around three hypotheses: (H1) small-scale spatial variations of conductivity significantly affect regional exchanges of water between streams and aquifers in river basins, (H2) aggregating small-scale heterogeneities into regional effective parameters systematically biases estimates of stream–aquifer exchanges, and (H3) the biases result from slow-paths in groundwater flow that emerge due to small-scale heterogeneities. The hypotheses are evaluated by comparing stream–aquifer fluxes produced by the base model to fluxes simulated using realizations of the MHRB characterized by local (grid-scale) heterogeneity. Levels of local heterogeneity are manipulated as control variables by adjusting coefficients of variation. All models are implemented using the MODFLOW simulation environment, and the PEST tool is used to calibrate effective conductivities defined over 16 zones within the MHRB. The effective parameters are also used as expected values to develop log-normally distributed conductivity ( K ) fields on local grid scales. Stream-aquifer exchanges are simulated with K fields at both scales and then compared. Results show that the effects of small-scale heterogeneities significantly influence exchanges with simulations based on local-scale heterogeneities always producing discharges that are less than those produced by the base model. Although aquifer heterogeneities are uncorrelated at local scales, they appear to induce coherent slow-paths in groundwater fluxes that in turn reduce aquifer–stream exchanges. Since surface water–groundwater exchanges are critical hydrologic processes in basin-scale water budgets, these results also have implications for water resources management.

Description: Near–surface air temperature and snow skin temperature comparison from CREST-SAFE station data with MODIS land surface temperature data Hydrology and Earth System Sciences Discussions, 12, 7665-7687, 2015 Author(s): C. L. Pérez Díaz, T. Lakhankar, P. Romanov, J. Muñoz, R. Khanbilvardi, and Y. Yu Land Surface Temperature (LST) is a key variable (commonly studied to understand the hydrological cycle) that helps drive the energy balance and water exchange between the Earth's surface and its atmosphere. One observable constituent of much importance in the land surface water balance model is snow. Snow cover plays a critical role in the regional to global scale hydrological cycle because rain-on-snow with warm air temperatures accelerates rapid snow-melt, which is responsible for the majority of the spring floods. Accurate information on near-surface air temperature ( T -air) and snow skin temperature ( T -skin) helps us comprehend the energy and water balances in the Earth's hydrological cycle. T -skin is critical in estimating latent and sensible heat fluxes over snow covered areas because incoming and outgoing radiation fluxes from the snow mass and the air temperature above make it different from the average snowpack temperature. This study investigates the correlation between MODerate resolution Imaging Spectroradiometer (MODIS) LST data and observed T -air and T -skin data from NOAA-CREST-Snow Analysis and Field Experiment (CREST-SAFE) for the winters of 2013 and 2014. LST satellite validation is imperative because high-latitude regions are significantly affected by climate warming and there is a need to aid existing meteorological station networks with the spatially continuous measurements provided by satellites. Results indicate that near-surface air temperature correlates better than snow skin temperature with MODIS LST data. Additional findings show that there is a negative trend demonstrating that the air minus snow skin temperature difference is inversely proportional to cloud cover. To a lesser extent, it will be examined whether the surface properties at the site are representative for the LST properties within the instrument field of view.

Description: Does drought alter hydrological functions in forest soils? An infiltration experiment Hydrology and Earth System Sciences Discussions, 12, 7689-7725, 2015 Author(s): K. F. Gimbel, H. Puhlmann, and M. Weiler The water cycle is expected to change in future and severely affect precipitation patterns across central Europe and in other parts of the world, leading to more frequent and severe droughts. Usually, it is assumed that system properties, like soil properties, remain stable and will not be affected by drought events. To study if this assumption is appropriate, we address the effects of drought on the infiltration behavior of forest soils using dye tracer experiments on six sites in three regions across Germany, which were forced into drought conditions. The sites cover clayey, loamy and sandy textured soils. In each region, we compared a deciduous and a coniferous forest stand to address differences between the main tree species. The results of the dye tracer experiments show clear evidence for changes in infiltration behavior at the sites. The infiltration changed at the clayey plots from regular and homogeneous flow to fast preferential flow. Similar behavior was observed at the loamy plots, where large areas in the upper layers remained dry, displaying signs of strong water repellency. This was confirmed by WDPT tests, which revealed, in all except one plot, moderate to severe water repellency. Water repellency was also accountable for the change of regular infiltration to fingered flow in the sandy soils. The results of this study suggest that the "drought-history" or generally the climatic conditions in the past of a soil are more important than the actual antecedent soil moisture status regarding hydrophobicity and infiltration behavior; and also, that drought effects on infiltration need to be considered in hydrological models to obtain realistic predictions concerning water quality and quantity in runoff and groundwater recharge.

Description: State determination of catalytic converters based on an ultra-wideband communication system Journal of Sensors and Sensor Systems, 4, 255-262, 2015 Author(s): I. Motroniuk, R. Stöber, and G. Fischerauer A novel microwave-based approach for monitoring the state of aftertreatment systems such as diesel particulate filters (DPFs), three-way catalytic converters (TWCs), and selective catalytic reduction (SCR) catalysts is proposed. The volume inside the metallic housing of the DPF, TWC, or SCR is considered as a wireless communication channel between two terminals of a communication system. It is shown that, depending on the transmission channel characteristics, the properties of the catalyst, such as the catalyst state, can be inferred. This is done by means of an ultra-wideband (UWB) measurement and the subsequent evaluation and processing of the waveform in the time and frequency domains.

Description: A comparison of chemical mechanisms using tagged ozone production potential (TOPP) analysis Atmospheric Chemistry and Physics, 15, 8795-8808, 2015 Author(s): J. Coates and T. M. Butler Ground-level ozone is a secondary pollutant produced photochemically from reactions of NO x with peroxy radicals produced during volatile organic compound (VOC) degradation. Chemical transport models use simplified representations of this complex gas-phase chemistry to predict O 3 levels and inform emission control strategies. Accurate representation of O 3 production chemistry is vital for effective prediction. In this study, VOC degradation chemistry in simplified mechanisms is compared to that in the near-explicit Master Chemical Mechanism (MCM) using a box model and by "tagging" all organic degradation products over multi-day runs, thus calculating the tagged ozone production potential (TOPP) for a selection of VOCs representative of urban air masses. Simplified mechanisms that aggregate VOC degradation products instead of aggregating emitted VOCs produce comparable amounts of O 3 from VOC degradation to the MCM. First-day TOPP values are similar across mechanisms for most VOCs, with larger discrepancies arising over the course of the model run. Aromatic and unsaturated aliphatic VOCs have the largest inter-mechanism differences on the first day, while alkanes show largest differences on the second day. Simplified mechanisms break VOCs down into smaller-sized degradation products on the first day faster than the MCM, impacting the total amount of O 3 produced on subsequent days due to secondary chemistry.

Description: Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean Atmospheric Chemistry and Physics Discussions, 15, 21607-21669, 2015 Author(s): C. Denjean, F. Cassola, A. Mazzino, S. Triquet, S. Chevaillier, N. Grand, T. Bourrianne, G. Momboisse, K. Sellegri, A. Schwarzenbock, E. Freney, M. Mallet, and P. Formenti This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June–July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco), time of tranport (1–5 days) and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried higher concentration of pollution particles at intermediate altitude (1–3 km) than at elevated altitude (〉 3 km), resulting in scattering Angstrom exponent up to 2.2 within the intermediate altitude. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate light absorption of the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00 ± 0.04. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assimilated to those of native dust in radiative transfer simulations, modeling studies and satellite retrievals over the Mediterranean. Measurements also showed that the coarse mode of mineral dust was conserved even after 5 days of transport in the Mediterranean, which contrasts with the gravitational depletion of large particles observed during the transport of dust plumes over the Atlantic. Simulations with the WRF mesoscale meteorological model highlighted a strong vertical turbulence within the dust layers that could prevent deposition of large particles during their atmospheric transport. This has important implications for the dust radiative effects due to surface dimming, atmospheric heating and cloud formation. The results presented here add to the observational dataset necessary for evaluating the role of mineral dust on the regional climate and rainfall patterns in the western Mediterranean basin.

Description: Identification of particulate organosulfates in three megacities at the middle and lower reaches of the Yangtze River Atmospheric Chemistry and Physics Discussions, 15, 21415-21448, 2015 Author(s): X. K. Wang, S. Rossignol, Y. Ma, L. Yao, M. Y. Wang, J. M. Chen, C. George, and L. Wang PM 2.5 filter samples have been collected in three megacities i.e., Wuhan (WH), Nanjing (NJ), and Shanghai (SH) at the middle and lower reaches of the Yangtze River, respectively. Analysis of those samples using an ultra-high performance liquid chromatography (UHPLC) coupled to an orbitrap mass spectrometer (MS) allowed detection of about two hundred particulate organosulfates (OSs), including dozens of nitrooxy-organosulfates, at each location. While aliphatic OSs represented more than 78 % of the detected OSs at the three locations, aromatic OSs were much less abundant. OSs with two to four isomers accounted for about 50 % of the total OSs on average in these megacities, and the percentage of OSs with six and more isomers in WH was more significant than those in SH and NJ. The average molecular weight, and the degrees of oxidation and saturation of OSs in the WH summer samples were greater than those in WH winter samples. In SH, the average molecular weight and the degree of oxidation of OSs in summer samples were greater than those in winter samples, but the degree of saturation was similar between the two seasons. In summer, the average molecular weight, and the degrees of oxidation and unsaturation of OSs were smallest in WH among the three cities. Between NJ and SH, the average molecular weight and the degree of saturation of OSs were close and the degree of oxidation of OSs in NJ was smaller. Kendrick mass defect diagrams and Van Krevelen diagrams indicated that the characteristics of identified OSs between in NJ and in SH shared better similarity. In addition, the identity and abundance of OSs in SH showed clear seasonal and diurnal variations. OSs in summer were more abundant than they were in winter due to stronger photochemical reactions in summer. The relative abundance of OSs at night was greater than that in the daytime and more nitrooxy-OSs existed at night, probably because of active NO 3 radical chemistry at night. In SH summer samples, OSs with 5 and 10 carbons (C 5 and C 10 ) were the most abundant, indicating the importance of isoprene and monoterpenes as precursors of OSs, whereas the relative abundances of OSs with 8, 9, and more than 14 carbons (C 8 , C 9 , and C 14+ ) were also high in SH winter samples, urging the need to further understand the precursors of OSs.

Description: Trace metal characterization of aerosol particles and cloud water during HCCT 2010 Atmospheric Chemistry and Physics, 15, 8751-8765, 2015 Author(s): K. W. Fomba, D. van Pinxteren, K. Müller, Y. Iinuma, T. Lee, J. L. Collett Jr., and H. Herrmann Trace metal characterization of bulk and size-resolved aerosol and cloud water samples were performed during the Hill Cap Cloud Thuringia (HCCT) campaign. Cloud water was collected at the top of Mt. Schmücke while aerosol samples were collected at two stations upwind and downwind of Mt. Schmücke. Fourteen trace metals including Ti, V, Fe, Mn, Co, Zn, Ni, Cu, As, Sr, Rb, Pb, Cr, and Se were investigated during four full cloud events (FCEs) that fulfilled the conditions of a continuous air mass flow through the three stations. Aerosol particle trace metal concentrations were found to be lower than those observed in the same region during previous field experiments but were within a similar range to those observed in other rural regions in Europe. Fe and Zn were the most abundant elements with concentration ranges of 0.2–111.6 and 1.1–32.1 ng m −3 , respectively. Fe, Mn, and Ti were mainly found in coarse mode aerosols while Zn, Pb, and As were mostly found in the fine mode. Correlation and enrichment factor analysis of trace metals revealed that trace metals such as Ti and Rb were mostly of crustal origin while trace metals such as Zn, Pb, As, Cr, Ni, V, and Cu were of anthropogenic origin. Trace metals such as Fe and Mn were of mixed origins including crustal and combustion sources. Trace metal cloud water concentration decreased from Ti, Mn, Cr, to Co with average concentrations of 9.18, 5.59, 5.54, and 0.46 μg L −1 , respectively. A non-uniform distribution of soluble Fe, Cu, and Mn was observed across the cloud drop sizes. Soluble Fe and Cu were found mainly in cloud droplets with diameters between 16 and 22 μm, while Mn was found mostly in larger drops greater than 22 μm. Fe(III) was the main form of soluble Fe especially in the small and larger drops with concentrations ranging from 2.2 to 37.1 μg L −1 . In contrast to other studies, Fe(II) was observed mainly in the evening hours, implying its presence was not directly related to photochemical processes. Aerosol–cloud interaction did not lead to a marked increase in soluble trace metal concentrations; rather it led to differences in the chemical composition of the aerosol due to preferential loss of aerosol particles through physical processes including cloud drop deposition to vegetative surfaces.

Description: Known and unknown unknowns: the application of ensemble techniques to uncertainty estimation in satellite remote sensing data Atmospheric Measurement Techniques Discussions, 8, 8509-8562, 2015 Author(s): A. C. Povey and R. G. Grainger This paper discusses a best-practice representation of uncertainty in satellite remote sensing data. An estimate of uncertainty is necessary to make appropriate use of the information conveyed by a measurement. Traditional error propagation quantifies the uncertainty in a measurement due to well-understood perturbations in a measurement and auxiliary data – known, quantified "unknowns". The underconstrained nature of most satellite remote sensing observations requires the use of various approximations and assumptions that produce non-linear systematic errors that are not readily assessed – known, unquantifiable "unknowns". Additional errors result from the inability to resolve all scales of variation in the measured quantity – unknown "unknowns". The latter two categories of error are dominant in underconstrained remote sensing retrievals and the difficulty of their quantification limits the utility of existing uncertainty estimates, degrading confidence in such data. This paper proposes the use of ensemble techniques to present multiple self-consistent realisations of a data set as a means of depicting unquantified uncertainties. These are generated using various systems (different algorithms or forward models) believed to be appropriate to the conditions observed. Benefiting from the experience of the climate modelling community, an ensemble provides a user with a more complete representation of the uncertainty as understood by the data producer and greater freedom to consider different realisations of the data.

Description: Improved stratospheric aerosol extinction profiles from SCIAMACHY: validation and sample results Atmospheric Measurement Techniques Discussions, 8, 8353-8383, 2015 Author(s): C. von Savigny, F. Ernst, A. Rozanov, R. Hommel, K.-U. Eichmann, V. Rozanov, J. P. Burrows, and L. W. Thomason Stratospheric aerosol extinction profiles have been retrieved from SCIAMACHY/Envisat measurements of limb-scattered solar radiation. The retrieval is an improved version of an algorithm presented earlier. The retrieved aerosol extinction profiles are compared to co-located aerosol profile measurements with the SAGE II solar occultation instrument at a wavelength of 525 nm. Comparisons were carried out with two versions of the SAGE II data set (version 6.2 and the new version 7.0). In a global average sense the SCIAMACHY and the SAGE II version 7.0 extinction profiles agree to within about 10 % for altitudes above 15 km. Larger relative differences (up to 40 %) are observed at specific latitudes and altitudes. We also find differences between the two SAGE II data versions of up to 40 % for specific latitudes and altitudes. Sample results on the latitudinal and temporal variability of stratospheric aerosol extinction and optical depth during the SCIAMACHY mission period are presented. The results indicate that a series of volcanic eruptions is responsible for the increase in stratospheric aerosol optical depth from 2002 to 2012. Above about 28 km altitude volcanic eruptions are found to have negligible impact in the period 2002 to 2012.

Description: The tropopause inversion layer in baroclinic life cycles experiments: the role of diabatic and mixing processes Atmospheric Chemistry and Physics Discussions, 15, 21495-21537, 2015 Author(s): D. Kunkel, P. Hoor, and V. Wirth Recent studies on the formation of a quasi-permanent layer of enhanced static stability above the thermal tropopause revealed the contributions of dynamical and radiative processes. Dry dynamics lead to the evolution of a tropopause inversion layer (TIL) which is, however, too weak compared to observations and thus diabatic contributions are required. In this study we aim to assess the importance of diabatic as well as mixing processes in the understanding of TIL formation at midlatitudes. The non-hydrostatic model COSMO is applied in an idealized mid-latitude channel configuration to simulate baroclinic life cycles. The effect of individual diabatic, i.e. related to humidity and radiation, and turbulent processes is studied first to estimate the additional contribution of these processes to dry dynamics. In a second step these processes are stepwise included in the model to increase the complexity and finally estimate the relative importance of each process. The results suggest that including turbulence leads to a weaker TIL than in a dry reference simulation. In contrast, the TIL evolves stronger when radiation is included but the temporal occurrence is still comparable to the reference. Using various cloud schemes in the model shows that latent heat release and consecutive increased vertical motions foster an earlier and stronger appearance of the TIL than in all other life cycles. Furthermore, updrafts moisten the upper troposphere and as such increase the radiative effect from water vapor. Particularly, this process becomes more relevant for maintaining the TIL during later stages of the life cycles. Increased convergence of the vertical wind induced by updrafts and by propagating and potentially dissipating inertia-gravity waves further contributes to the enhanced stability of the lower stratosphere. Furthermore, radiative feedback of ice clouds reaching up to the tropopause is identified to potentially further affect the strength of the TIL in the region of the cloud.

Description: Author(s): John Schliemann Coherent states provide a natural connection of quantum systems to their classical limit and are employed in various fields of physics. Here we derive general systematic expansions, with respect to quantum parameters, of expectation values of products of arbitrary operators within both oscillator co… [Phys. Rev. A 92, 022108] Published Mon Aug 10, 2015

Description: Author(s): Xiao Yuan, Qi Zhao, and Xiongfeng Ma The Bell test is one of the most important tools in quantum information science. On the one hand, it enables fundamental tests of the basic physics laws of nature, and on the other hand, it can also be applied in a variety of device-independent tasks such as quantum key distribution and random numbe… [Phys. Rev. A 92, 022107] Published Mon Aug 10, 2015

Description: Author(s): Michael Skotiniotis, Florian Fröwis, Wolfgang Dür, and Barbara Kraus We investigate quantum metrology using a Lie algebraic approach for a class of Hamiltonians, including local and nearest-neighbor interaction Hamiltonians. Using this Lie algebraic formulation, we identify and construct highly symmetric states that admit Heisenberg scaling in precision for phase est… [Phys. Rev. A 92, 022323] Published Mon Aug 10, 2015

Description: Author(s): Seungho Yang and Hyunseok Jeong We investigate how much amount of Greenberger-Horne-Zeilinger (GHZ) entanglement is required in order to prepare a given multipartite state by local operations and classical communication (LOCC). We present a LOCC procedure that asymptotically converts GHZ states into an arbitrary multipartite pure … [Phys. Rev. A 92, 022322] Published Mon Aug 10, 2015

Description: Author(s): Zheng-Yuan Xue, Jian Zhou, and Z. D. Wang To implement a set of universal quantum logic gates based on non-Abelian geometric phases, it is conventional wisdom that quantum systems beyond two levels are required, which is extremely difficult to fulfill for superconducting qubits and appears to be a main reason why only single-qubit gates wer… [Phys. Rev. A 92, 022320] Published Mon Aug 10, 2015

Description: Author(s): A. Walther, L. Rippe, Y. Yan, J. Karlsson, D. Serrano, A. N. Nilsson, S. Bengtsson, and S. Kröll We propose and analyze a high-fidelity readout scheme for a single-instance approach to quantum computing in rare-earth-ion-doped crystals. The scheme is based on using different elements as qubit and readout ions, where the readout ions are doped into the material at a much lower concentration than… [Phys. Rev. A 92, 022319] Published Mon Aug 10, 2015

Description: Author(s): Robert Bennett Radiative corrections to an atom are calculated near a half-space that has arbitrarily shaped small depositions upon its surface. The method is based on calculation of the classical Green's function of the macroscopic Maxwell equations near an arbitrarily perturbed half-space using a Born-series exp… [Phys. Rev. A 92, 022503] Published Mon Aug 10, 2015

Description: Author(s): Yijun Tang, Andrew Sykes, Nathaniel Q. Burdick, John L. Bohn, and Benjamin L. Lev We report the measurement of the deca-heptuplet s -partial-wave scattering length a of two bosonic isotopes of the highly magnetic element dysprosium: a = 112 ( 10 ) a 0 for Dy 162 and a = 92 ( 8 ) a 0 for Dy 164 , where a 0 is the Bohr radius. The scattering lengths are determined by the cross-dimensional relaxation … [Phys. Rev. A 92, 022703] Published Mon Aug 10, 2015

Description: Author(s): Manuel Erhard, Hammam Qassim, Harjaspreet Mand, Ebrahim Karimi, and Robert W. Boyd There exists two prominent methods to transfer information between two spatially separated parties, namely Alice ( A ) and Bob ( B ): quantum teleportation and remote state preparation. However, the difference between these methods is, in the teleportation scheme, the state to be transferred is complete… [Phys. Rev. A 92, 022321] Published Mon Aug 10, 2015

Description: Author(s): J. A. Smith, D. B. Uskov, and L. Kaplan Here, we study the classical information capacity of a quantum channel, assuming linear optical encoding, as a function of available photons and optical modes. We present a formula for general channel capacity and show that this capacity is achieved without requiring the use of entangling operations… [Phys. Rev. A 92, 022324] Published Mon Aug 10, 2015

Description: Author(s): Jens E. Bækhøj and Lars Bojer Madsen The nature of light-induced structures in attosecond transient-absorption spectroscopy of molecular systems is investigated theoretically. It is shown how nuclear dynamics affect these structures. We find that a theoretical three-surface model captures the main characteristics in the calculated spec… [Phys. Rev. A 92, 023407] Published Mon Aug 10, 2015

Description: Author(s): M. V. Frolov, N. L. Manakov, Wei-Hao Xiong, Liang-You Peng, J. Burgdörfer, and Anthony F. Starace We derive an analytic expression for the wavelength scaling of the high-order-harmonic generation (HHG) yield induced by midinfrared driving laser fields. It is based on a quasiclassical description of the returning electron wave packet, which is shown to be largely independent of atomic properties.… [Phys. Rev. A 92, 023409] Published Mon Aug 10, 2015

Description: Author(s): T. Das, B. B. Augstein, C. Figueira de Morisson Faria, L. E. Chipperfield, D. J. Hoffmann, and J. P. Marangos We investigate high-order-harmonic spectra from aligned diatomic molecules in intense driving fields whose components have orthogonal polarizations. We focus on how the driving-field ellipticity influences structural interference patterns in a macroscopic medium. In a previous publication [ Phys. Rev… [Phys. Rev. A 92, 023406] Published Mon Aug 10, 2015

Description: Author(s): P. Bažant, H. Frydrych, G. Alber, and I. Jex Dynamical decoupling is a powerful method for protecting quantum information against unwanted interactions with the help of open-loop control pulses. Realistic control pulses are not ideal and may introduce additional systematic errors. We introduce a class of self-stabilizing pulse sequences capabl… [Phys. Rev. A 92, 022325] Published Mon Aug 10, 2015

Description: Author(s): Jack Wragg, J. S. Parker, and H. W. van der Hart We have developed a two-electron outer region for use within R -matrix theory to describe double ionization processes. The capability of this method is demonstrated for single-photon double ionization of He in the photon energy region between 80 and 180 eV. The cross sections are in agreement with es… [Phys. Rev. A 92, 022504] Published Mon Aug 10, 2015

Description: Author(s): Adam D. Bookatz, Edward Farhi, and Leo Zhou We consider the use of quantum error-detecting codes, together with energy penalties against leaving the code space, as a method for suppressing environmentally induced errors in Hamiltonian-based quantum computation. This method was introduced in Jordan et al. [ Phys. Rev. A 74 , 052322 (2006) ] in t… [Phys. Rev. A 92, 022317] Published Mon Aug 10, 2015

Description: Author(s): Simon C. Davenport and Nigel R. Cooper We study a model of a two-dimensional ultracold atomic gas subjected to an “optical flux lattice”: a laser configuration where Raman-dressed atoms experience a strong artificial magnetic field. This leads to a band structure of narrow energy bands with nonzero Chern numbers. We consider the case of … [Phys. Rev. A 92, 023608] Published Mon Aug 10, 2015

Description: Author(s): Farokh Mivehvar and David L. Feder The coupled dynamics of the atom and photon fields in optical ring cavities with two counterpropagating modes give rise to both spin-orbit interactions as well as long-ranged interactions between atoms of a many-body system. At zero temperature, the interplay between the two-body and cavity-mediated… [Phys. Rev. A 92, 023611] Published Mon Aug 10, 2015

Description: Author(s): Yuki Endo, Daisuke Inotani, Ryo Hanai, and Yoji Ohashi We investigate the possibility that the broken spatial inversion symmetry caused by a trap potential induces a spin-triplet Cooper pair amplitude in an s -wave superfluid Fermi gas. Based on symmetry considerations, we clarify that this phenomenon may occur, when a spin rotation symmetry of the syste… [Phys. Rev. A 92, 023610] Published Mon Aug 10, 2015

Description: Author(s): Tomoki Ozawa, Hannah M. Price, and Iacopo Carusotto We show how the weakly trapped Harper-Hofstadter model can be mapped onto a Harper-Hofstadter model in momentum space. In this momentum-space model, the band dispersion plays the role of the periodic potential, the Berry curvature plays the role of an effective magnetic field, the real-space harmoni… [Phys. Rev. A 92, 023609] Published Mon Aug 10, 2015

Description: Author(s): K. S. Grigoriev, V. A. Makarov, and I. A. Perezhogin Expressions for the electric field at a sum frequency generated by a collinear elliptically polarized Gaussian beam and circularly polarized Laguerre-Gaussian beam in an isotropic chiral nonlinear medium are obtained in quadratures. The amount and locations of C points in the cross section of a sign… [Phys. Rev. A 92, 023814] Published Mon Aug 10, 2015

Description: Author(s): R. Chitra and O. Zilberberg Control and manipulation of quantum engineered systems allows for the utilization of time-dependent parametric modulations for accessing novel out-of-equilibrium phenomena. In the absence of such driving, the dissipative Dicke model exhibits a fascinating out-of-equilibrium many-body phase transitio… [Phys. Rev. A 92, 023815] Published Mon Aug 10, 2015

Description: Author(s): Evgeny N. Bulgakov and Almas F. Sadreev We demonstrate bound states in the first TE and TM diffraction continua (BSC) in a linear periodic array of dielectric spheres in air above the light cone. We classify the BSCs according to the symmetry specified by the azimuthal number m , the Bloch wave vector β directed along the array, and polari… [Phys. Rev. A 92, 023816] Published Mon Aug 10, 2015

Description: Author(s): Diling Zhu, Aymeric Robert, Tom Henighan, Henrik T. Lemke, Matthieu Chollet, J. Mike Glownia, David A. Reis, and Mariano Trigo We present a reconstruction of the transverse acoustic phonon dispersion of germanium from femtosecond time-resolved x-ray diffuse scattering measurements at the Linac Coherent Light Source. We demonstrate an energy resolution of 0.3 meV with a momentum resolution of 0.01 nm − 1 using 10-keV x rays wit… [Phys. Rev. B 92, 054303] Published Mon Aug 10, 2015

Description: Author(s): U. Stockert, S. Hartmann, M. Deppe, N. Caroca-Canales, J. G. Sereni, C. Geibel, and F. Steglich We present measurements of the thermopower S ( T ) on CePd 1 − x Rh x between 2 K and 300 K. For low Rh content, the system behaves as a ferromagnetic Kondo system with a Curie temperature T C of about 6 K, a Kondo scale smaller than T C , and an overall crystal electric field splitting of 210 K. As the Rh con… [Phys. Rev. B 92, 054415] Published Mon Aug 10, 2015

Description: Author(s): Denis D. Sheka, Volodymyr P. Kravchuk, Kostiantyn V. Yershov, and Yuri Gaididei A magnetic helix wire is one of the simplest magnetic systems which manifests properties of both curvature and torsion. Possible equilibrium magnetization states in the helix wire with different anisotropy directions are studied theoretically. There exist two equilibrium states in the helix wire wit… [Phys. Rev. B 92, 054417] Published Mon Aug 10, 2015

Description: Author(s): Mikhail Feygenson, John C. Bauer, Zheng Gai, Carlos Marques, Meigan C. Aronson, Xiaowei Teng, Dong Su, Vesna Stanic, Volker S. Urban, Kevin A. Beyer, and Sheng Dai We have studied the origin of the exchange bias effect in the Au-Fe 3 O 4 dumbbell nanoparticles in two samples with different sizes of the Au seed nanoparticles (4.1 and 2.7 nm) and same size of Fe 3 O 4 nanoparticles (9.8 nm). The magnetization, small-angle neutron-scattering, synchrotron x-ray diffract… [Phys. Rev. B 92, 054416] Published Mon Aug 10, 2015

Description: Author(s): M. Barturen, J. Milano, M. Vásquez-Mansilla, C. Helman, M. A. Barral, A. M. Llois, M. Eddrief, and M. Marangolo In this work we report the appearance of a large perpendicular magnetic anisotropy (PMA) in Fe 1 − x Ga x thin films grown onto ZnSe/GaAs(001). This arising anisotropy is related to the tetragonal metastable phase in as-grown samples recently reported [M. Eddrief et al. , Phys. Rev. B 84 , 161410 (2011) ].… [Phys. Rev. B 92, 054418] Published Mon Aug 10, 2015

Description: Author(s): J. Rychły, J. W. Kłos, M. Mruczkiewicz, and M. Krawczyk We studied a finite Fibonacci sequence of Co and Py stripes aligned side by side and in direct contact with each other. Calculations based on a continuous model, including exchange and dipole interactions, were performed for structures feasible for fabrication and characterization of the main proper… [Phys. Rev. B 92, 054414] Published Mon Aug 10, 2015

Description: Author(s): Manuel Nieto-Vesperinas We put forward the physical meaning of the conservation equation for the helicity on scattering of an electromagnetic field with a generally magnetodielectric bi-isotropic dipolar object. This is the optical theorem for the helicity that, as we find, plays a role for this quantity analogous to that … [Phys. Rev. A 92, 023813] Published Mon Aug 10, 2015

Description: Author(s): Matthew Bradford and Jung-Tsung Shen We investigate numerically the architecture dependence of the characteristics of antibunched photons generated in cavity quantum electrodynamic systems. We show that the quality of antibunching [the smallness of the second-order intensity correlation function at zero time g ( 2 ) ( 0 ) ] and the generation… [Phys. Rev. A 92, 023810] Published Mon Aug 10, 2015

Description: Author(s): Olle Heinonen The magnetization configuration in two stacked micron-size ferromagnetic disks can assume different equilibrium states depending on the interfacial coupling between the disks. Here I examine the magnetization dynamics in response to an out-of-plane field pulse for different equilibrium states. For a… [Phys. Rev. B 92, 054420] Published Mon Aug 10, 2015

Description: Author(s): K. G. Katamadze, N. A. Borshchevskaya, I. V. Dyakonov, A. V. Paterova, and S. P. Kulik We demonstrate the experimental technique for generating a spatial single-mode broadband biphoton field. The method is based on a dispersive optical element which precisely tailors the structure of the type-I spontaneous parametric down-conversion (SPDC) frequency angular spectrum in order to shift … [Phys. Rev. A 92, 023812] Published Mon Aug 10, 2015

Description: Author(s): Philip B. Allen The quasiharmonic (QH) approximation uses harmonic vibrational frequencies ω Q , H ( V ) computed at volumes V near V 0 where the Born-Oppenheimer (BO) energy E el ( V ) is minimum. When this is used in the harmonic free energy, QH approximation gives a good zeroth order theory of thermal expansion and first-o… [Phys. Rev. B 92, 064106] Published Mon Aug 10, 2015

Description: Author(s): Maxim Goryachev, Nikita Kostylev, and Michael E. Tobar The properties of doped and natural impurities in lithium niobate single crystals are studied using the whispering gallery mode method at low temperatures as a function of magnetic field. The study reveals considerable coupling of microwave photon modes to the Fe 3 + spin ensemble in iron-doped and no… [Phys. Rev. B 92, 060406(R)] Published Mon Aug 10, 2015

Description: Author(s): Takashi Kikkawa, Ken-ichi Uchida, Shunsuke Daimon, Zhiyong Qiu, Yuki Shiomi, and Eiji Saitoh The longitudinal spin Seebeck effect (LSSE) in Pt / Y 3 Fe 5 O 12 ( YIG ) junction systems has been investigated at various magnetic fields and temperatures. We found that the LSSE voltage in a Pt/YIG-slab system is suppressed by applying high magnetic fields and this suppression is critically enhanced at low… [Phys. Rev. B 92, 064413] Published Mon Aug 10, 2015

Description: Author(s): Stavros Komineas and Nikos Papanicolaou We study the dynamics of skyrmions in Dzyaloshinskii-Moriya materials with easy-axis anisotropy. An important link between topology and dynamics is established through the construction of unambiguous conservation laws obtained earlier in connection with magnetic bubbles and vortices. In particular, … [Phys. Rev. B 92, 064412] Published Mon Aug 10, 2015

Description: Author(s): Wen-ju Gu, Zhen Yi, Li-hui Sun, and Da-hai Xu In the paper we study the nonlinear mechanical cooling processes in an intrinsic quadratically optomechanical coupling system without linearizing the optomechanical interaction. We apply scattering theory to calculate the transition rates between different mechanical Fock states using the resolvent … [Phys. Rev. A 92, 023811] Published Mon Aug 10, 2015

Description: Author(s): Markus Schmitt and Stefan Kehrein The notion of a dynamical quantum phase transition (DQPT) was recently introduced [Heyl et al. , Phys. Rev. Lett. 110 , 135704 (2013) ] as the nonanalytic behavior of the Loschmidt echo at critical times in the thermodynamic limit. In this work the quench dynamics in the ground state sector of the two… [Phys. Rev. B 92, 075114] Published Mon Aug 10, 2015

Description: Author(s): S. E. Korshunov We show that a physical realization of the phase diagram proposed by Minnhagen et al. [ Phys. Rev. B 78 , 184432 (2008) ] for the so-called generalized fully frustrated XY model on a square lattice can be achieved in arrays of superconductor-ferromagnet-superconductor junctions near the transition of t… [Phys. Rev. B 92, 064506] Published Mon Aug 10, 2015

Description: Author(s): Yuhe Zhang, G. J. Sreejith, and J. K. Jain The possibility of realizing bosonic fractional quantum Hall effect in ultracold atomic systems suggests a new route to producing and manipulating anyons, by introducing auxiliary bosons of a different species that capture quasiholes and thus inherit their nontrivial braiding properties. States with… [Phys. Rev. B 92, 075116] Published Mon Aug 10, 2015

Description: Author(s): H. Y. Yuan and X. R. Wang We report a counterintuitive finding that notches in an otherwise homogeneous magnetic nanowire can boost current-induced domain wall (DW) propagation. DW motion in notch-modulated wires can be classified into three phases: (1) A DW is pinned around a notch when the current density is below the depi… [Phys. Rev. B 92, 054419] Published Mon Aug 10, 2015

Description: Author(s): Yannic Utz, Franziska Hammerath, Satoshi Nishimoto, Christian Hess, Neela Sekhar Beesetty, Romuald Saint-Martin, Alexandre Revcolevschi, Bernd Büchner, and Hans-Joachim Grafe The S = 1 / 2 antiferromagnetic Heisenberg spin chain compound Sr 2 CuO 3 doped with 1 % and 2 % of Ni impurities has been studied by means of Cu 63 nuclear magnetic resonance. A strong decrease of the spin-lattice relaxation rate T 1 − 1 at low temperatures points toward a spin gap, while a stretching exponent … [Phys. Rev. B 92, 060405(R)] Published Mon Aug 10, 2015

Description: Author(s): Y. Wang, K. Wohlfeld, B. Moritz, C. J. Jia, M. van Veenendaal, K. Wu, C.-C. Chen, and T. P. Devereaux Using cluster perturbation theory, we explain the origin of the strongly dispersive feature found at high binding energy in the spectral function of the Hubbard model. By comparing the Hubbard and t − J − 3 s model spectra, we show that this dispersion does not originate from either coupling to spin fluc… [Phys. Rev. B 92, 075119] Published Mon Aug 10, 2015

Description: Author(s): Kengo Fushiya, Ryoichi Miyazaki, Ryuji Higashinaka, Akira Yamada, Masaichiro Mizumaki, Satoshi Tsutsui, Kiyofumi Nitta, Tomoya Uruga, Bunya Suemitsu, Hideyuki Sato, and Yuji Aoki We have measured x-ray absorption spectra at the Sm L 3 edge to investigate the Sm-ion valence of ( S m x L a 1 − x ) O s 4 S b 12 , in which field-insensitive heavy-fermion behavior appears at low temperatures for x = 1 . It has been found that the Sm-ion valance shifts to 2 + with La ion substitution; from v = + 2.78 ( x = 1 ) … [Phys. Rev. B 92, 075118] Published Mon Aug 10, 2015

Description: Author(s): J.-Q. Yan, M. A. McGuire, A. F. May, D. Parker, D. G. Mandrus, and B. C. Sales Mo 3 Sb 7 single crystals lightly doped with Cr, Ru, or Te are studied in order to explore the interplay between superconductivity, magnetism, and the cubic-tetragonal structural transition. The structural transition at 53 K is extremely sensitive to Ru or Te substitution which introduces additional el… [Phys. Rev. B 92, 064507] Published Mon Aug 10, 2015

Description: Author(s): Su-Yang Xu, Chang Liu, I. Belopolski, S. K. Kushwaha, R. Sankar, J. W. Krizan, T.-R. Chang, C. M. Polley, J. Adell, T. Balasubramanian, K. Miyamoto, N. Alidoust, Guang Bian, M. Neupane, H.-T. Jeng, C.-Y. Huang, W.-F. Tsai, T. Okuda, A. Bansil, F. C. Chou, R. J. Cava, H. Lin, and M. Z. Hasan A three-dimensional (3D) Dirac semimetal is a novel state of quantum matter which has recently attracted much attention as an apparent 3D version of graphene. In this paper, we report results on the electronic structure of the 3D Dirac semimetal Na 3 Bi at a surface that reveals its nontrivial ground … [Phys. Rev. B 92, 075115] Published Mon Aug 10, 2015

Description: Author(s): Christophe Mora, Cătălin Paşcu Moca, Jan von Delft, and Gergely Zaránd We generalize Nozières' Fermi-liquid theory for the low-energy behavior of the Kondo model to that of the single-impurity Anderson model. In addition to the electrons' phase shift at the Fermi energy, the low-energy Fermi-liquid theory is characterized by four Fermi-liquid parameters: the two given … [Phys. Rev. B 92, 075120] Published Mon Aug 10, 2015

Description: Author(s): S. Thiess, T.-L. Lee, C. Aruta, C. T. Lin, F. Venturini, N. B. Brookes, B. C. C. Cowie, and J. Zegenhagen We analyzed the valence band (VB) of the 90 K high-temperature superconductor YBa 2 Cu 3 O 7 − δ by photoelectron spectroscopy under standing-wave excitation employing hard x rays. Precisely positioning the standing-wave intensity in the unit cell allows selectively probing the VB yield from the CuO chains… [Phys. Rev. B 92, 075117] Published Mon Aug 10, 2015

Description: Author(s): Tamene R. Dasa and Valeri S. Stepanyuk The continuous reduction of magnetic units to ultrasmall length scales inspires efforts to look for a suitable means of controlling magnetic states. In this study, we show two surface charge alteration techniques for tuning the interlayer exchange coupling of ferromagnetic layers separated by parama… [Phys. Rev. B 92, 075412] Published Mon Aug 10, 2015

Description: Author(s): Jun Kang, Hasan Sahin, H. Duygu Ozaydin, R. Tugrul Senger, and François M. Peeters The electronic properties, carrier mobility, and strain response of TiS 3 nanoribbons ( TiS 3 NRs) are investigated by first-principles calculations. We found that the electronic properties of TiS 3 NRs strongly depend on the edge type ( a or b ). All a - TiS 3 NRs are metallic with a magnetic ground state, … [Phys. Rev. B 92, 075413] Published Mon Aug 10, 2015

Description: Author(s): Beom Hyun Kim and Jeroen van den Brink The recent discovery that resonant inelastic x-ray scattering can probe single-magnon (SM) dispersions in transition metal (TM) oxides when the x-ray energy is tuned to the TM L edge has put this technique on a par with inelastic neutron scattering. It is generally presumed that selection rules forb… [Phys. Rev. B 92, 081105(R)] Published Mon Aug 10, 2015

Description: Author(s): Erik G. C. P. van Loon, Mikhail I. Katsnelson, and Mikhail Lemeshko We use the dual boson approach to reveal the phase diagram of the Fermi-Hubbard model with long-range dipole-dipole interactions. By using a large-scale finite-temperature calculation on a 64 × 64 square lattice we demonstrate the existence of a novel phase, possessing an “ultralong-range” order. The … [Phys. Rev. B 92, 081106(R)] Published Mon Aug 10, 2015

Description: Author(s): Jing Wang, Biao Lian, Xiao-Liang Qi, and Shou-Cheng Zhang Motivated by the possibility of experimental detection of the topological magnetoelectric effect the authors put forth a theoretical proposal for its realization in the zero plateau quantum anomalous Hall state of a ferromagnet-topological insulator heterostructure. [Phys. Rev. B 92, 081107(R)] Published Mon Aug 10, 2015

Description: Author(s): Chen Fang, Yige Chen, Hae-Young Kee, and Liang Fu We theoretically study three-dimensional topological semimetals (TSMs) with nodal lines protected by crystalline symmetries. Compared to TSMs with point nodes, e.g., Weyl semimetals and Dirac semimetals, where the conduction and the valence bands touch at discrete points, in these TSMs the two bands… [Phys. Rev. B 92, 081201(R)] Published Mon Aug 10, 2015

Description: Author(s): Susanne Mueller, Atindra Nath Pal, Matija Karalic, Thomas Tschirky, Christophe Charpentier, Werner Wegscheider, Klaus Ensslin, and Thomas Ihn We have investigated low-temperature electronic transport on InAs/GaSb double quantum wells, a system which promises to be electrically tunable from a normal to a topological insulator. Hall bars of 50 μ m in length down to a few micrometers gradually develop a pronounced resistance plateau near charg… [Phys. Rev. B 92, 081303(R)] Published Mon Aug 10, 2015

Description: Author(s): Linhu Li and Shu Chen We study topological properties of phase transition points of topological quantum phase transitions by assigning a topological invariant defined on a closed circle or surface surrounding the phase transition point in the parameter space of momentum and transition driving parameter. By applying our s… [Phys. Rev. B 92, 085118] Published Mon Aug 10, 2015

Description: Author(s): Tommy Li The quantum transmission problem for a particle moving in a quantum point contact in the presence of a Rashba spin-orbit interaction and applied magnetic field is solved semiclassically. A strong Rashba interaction and parallel magnetic field form emergent Dirac states at the center of the constrict… [Phys. Rev. B 92, 085302] Published Mon Aug 10, 2015

Description: Author(s): Hyun-Jung Kim and Jun-Hyung Cho The search for one-dimensional electron systems with a giant Rashba-type spin splitting is of importance for the application of spin transport. Here we report, based on a first-principles density-functional-theory calculation, that Bi zigzag chains formed on a heterogeneous GaAs(110) surface have a … [Phys. Rev. B 92, 085303] Published Mon Aug 10, 2015

Description: Author(s): Benjamin Schröder, Thorsten Weber, Sergey V. Yalunin, Thomas Kiel, Christian Matyssek, Murat Sivis, Sascha Schäfer, Felix von Cube, Stephan Irsen, Kurt Busch, Claus Ropers, and Stefan Linden We report the spatial mapping of surface plasmons on conical gold nanotips by electron energy loss spectroscopy. We observe standing-wave patterns resulting from reflections of the fundamental surface-plasmon mode at the nanotip apex. The experimental results are in very good agreement with numerica… [Phys. Rev. B 92, 085411] Published Mon Aug 10, 2015

Description: Author(s): J. Zhong, H. L. Ma, S. P. Hu, X. G. Wu, H. B. Sun, G. S. Li, C. Y. He, Y. Zheng, C. B. Li, Q. M. Chen, H. W. Li, Y. H. Wu, and P. W. Luo Excited states of the odd-odd nucleus Tb 158 have been studied via the Sm 154 ( Li 7 , 3 n ) Tb 158 reaction at a beam energy of 27 MeV. The new level scheme of Tb 158 involving a positive parity rotational band is established up to excitation energy ∼ 2.3 MeV and spin ∼ 17 ℏ . By comparing with the rotational bands… [Phys. Rev. C 92, 024308] Published Mon Aug 10, 2015

Description: Author(s): Babak Sadigh, Paul Erhart, and Daniel Åberg We conduct a detailed investigation of the polaron self-interaction (pSI) error in standard approximations to the exchange-correlation (XC) functional within density-functional theory (DFT). The pSI leads to delocalization error in the polaron wave function and energy, as calculated from the Kohn-Sh… [Phys. Rev. B 92, 075202] Published Mon Aug 10, 2015

Description: Author(s): S. Momota, I. Tanihata, A. Ozawa, M. Notani, K. Yoshida, K. Morimoto, T. Yamaguchi, T. Onishi, A. Yoshida, Y. X. Watanabe, Z. Liu, and A. Ono Transverse momentum ( P T ) distributions of projectilelike fragments produced at intermediate energy are investigated. P T distributions of fragments with mass A F = 10 – 37 , produced from an Ar 40 beam with E = 95 MeV / nucleon and a Be target, are observed as a function of fragment velocity by using the Rikagak… [Phys. Rev. C 92, 024608] Published Mon Aug 10, 2015

Description: Author(s): Neul Ha, Takaaki Mano, Ying-Lin Chou, Yu-Nien Wu, Shun-Jen Cheng, Juanita Bocquel, Paul M. Koenraad, Akihiro Ohtake, Yoshiki Sakuma, Kazuaki Sakoda, and Takashi Kuroda Making use of droplet epitaxy, we systematically controlled the height of self-assembled GaAs quantum dots by more than one order of magnitude. The photoluminescence spectra of single quantum dots revealed the strong dependence of the spectral linewidth on the dot height. Tall dots with a height of … [Phys. Rev. B 92, 075306] Published Mon Aug 10, 2015

Description: Author(s): Jinghua Fu Event-by-event correlations between v n and ɛ m , n for different collision centralities are studied with hydrodynamics. For the more central collisions v n is better correlated with ɛ m , n defined with relatively larger radial weight power m , like m = n + 1 . For the more peripheral collisions, v n prefers ɛ m , n … [Phys. Rev. C 92, 024904] Published Mon Aug 10, 2015

Description: Author(s): S. Velle and L. P. Csernai We study an exact rotating and expanding solution of the fluid dynamical model of heavy ion reactions, that take into account the rate of slowing down of the rotation due to the longitudinal and transverse expansion of the system. The parameters of the model are set on the basis of realistic 3+1D fl… [Phys. Rev. C 92, 024905] Published Mon Aug 10, 2015

Description: Author(s): S. N. Gninenko and N. V. Krasnikov The decay K L → invisible has never been experimentally tested. In the Standard Model (SM), its branching ratio for the decay into two neutrinos is helicity suppressed and predicted to be Br ( K L → ν ν ¯ ) ≲ 10 − 10 . We consider several natural extensions of the SM, such as two-Higgs-doublet (2HDM), 2HDM and ligh… [Phys. Rev. D 92, 034009] Published Mon Aug 10, 2015

Description: Author(s): Ophélia Fabre, Simon Prunet, and Jean-Philippe Uzan The standard cosmological model does not determine the spatial topology of the Universe. This article revisits the signature of a nontrivial topology on the properties of the cosmic microwave background anisotropies. We show that the correlation function of the coefficients of the expansion of the t… [Phys. Rev. D 92, 043003] Published Mon Aug 10, 2015

Description: Author(s): D. Falcone and L. Oliver We reexamine lepton mixing in gauge models by considering two theories within the type I seesaw mechanism, the extended Standard Model, i.e. S U ( 2 ) L × U ( 1 ) Y with singlet right-handed heavy neutrinos, and the left-right model, S U ( 2 ) L × S U ( 2 ) R × U ( 1 ) B − L . The former is often used as a simple heuristic approac… [Phys. Rev. D 92, 033004] Published Mon Aug 10, 2015

Description: Author(s): Mohammad Khazaei, Masao Arai, Taizo Sasaki, Ahmad Ranjbar, Yunye Liang, and Seiji Yunoki MXenes are a set of two-dimensional transition metal carbides and nitrides that offer many potential applications in energy storage and electronic devices. As an important parameter to design new electronic devices, we investigate the work functions of bare MXenes and their functionalized ones with … [Phys. Rev. B 92, 075411] Published Mon Aug 10, 2015