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  • 61. Ots, Riinu
    et al.
    Young, Dominique E.
    Vieno, Massimo
    Xu, Lu
    Dunmore, Rachel E.
    Allan, James D.
    Coe, Hugh
    Williams, Leah R.
    Herndon, Scott C.
    Ng, Nga L.
    Hamilton, Jacqueline F.
    Bergström, Robert
    SMHI, Forskningsavdelningen, Luftmiljö.
    Di Marco, Chiara
    Nemitz, Eiko
    Mackenzie, Ian A.
    Kuenen, Jeroen J. P.
    Green, David C.
    Reis, Stefan
    Heal, Mathew R.
    Simulating secondary organic aerosol from missing diesel-related intermediate-volatility organic compound emissions during the Clean Air for London (ClearfLo) campaign2016Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 16, nr 10, s. 6453-6473Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present high-resolution (5aEuro-kmaEuro-aEuro parts per thousand x aEuro-5aEuro-km) atmospheric chemical transport model (ACTM) simulations of the impact of newly estimated traffic-related emissions on secondary organic aerosol (SOA) formation over the UK for 2012. Our simulations include additional diesel-related intermediate-volatility organic compound (IVOC) emissions derived directly from comprehensive field measurements at an urban background site in London during the 2012 Clean Air for London (ClearfLo) campaign. Our IVOC emissions are added proportionally to VOC emissions, as opposed to proportionally to primary organic aerosol (POA) as has been done by previous ACTM studies seeking to simulate the effects of these missing emissions. Modelled concentrations are evaluated against hourly and daily measurements of organic aerosol (OA) components derived from aerosol mass spectrometer (AMS) measurements also made during the ClearfLo campaign at three sites in the London area. According to the model simulations, diesel-related IVOCs can explain on average aEuro parts per thousand aEuro-30aEuro-% of the annual SOA in and around London. Furthermore, the 90th percentile of modelled daily SOA concentrations for the whole year is 3.8aEuro-A mu gaEuro-m(-3), constituting a notable addition to total particulate matter. More measurements of these precursors (currently not included in official emissions inventories) is recommended. During the period of concurrent measurements, SOA concentrations at the Detling rural background location east of London were greater than at the central London location. The model shows that this was caused by an intense pollution plume with a strong gradient of imported SOA passing over the rural location. This demonstrates the value of modelling for supporting the interpretation of measurements taken at different sites or for short durations.

  • 62.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    Numerical solutions of the macroscopic Maxwell equations for scattering by non-spherical particles: A tutorial review2016Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 178, s. 22-37Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Numerical solution methods for electromagnetic scattering by non-spherical particles comprise a variety of different techniques, which can be traced back to different assumptions and solution strategies applied to the macroscopic Maxwell equations. One can distinguish between time- and frequency-domain methods; further, one can divide numerical techniques into finite-difference methods (which are based on approximating the differential operators), separation-of-variables methods (which are based on expanding the solution in a complete set of functions, thus approximating the fields), and volume integral-equation methods (which are usually solved by discretisation of the target volume and invoking the long-wave approximation in each volume cell). While existing reviews of the topic often tend to have a target audience of program developers and expert users, this tutorial review is intended to accommodate the needs of practitioners as well as novices to the field. The required conciseness is achieved by limiting the presentation to a selection of illustrative methods, and by omitting many technical details that are not essential at a first exposure to the subject. On the other hand, the theoretical basis of numerical methods is explained with little compromises in mathematical rigour; the rationale is that a good grasp of numerical light scattering methods is best achieved by understanding their foundation in Maxwell's theory. (C) 2015 Elsevier Ltd. All rights reserved.

  • 63. Andersson, Emma
    et al.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    Coupling aerosol optics to the MATCH (v5.5.0) chemical transport model and the SALSA (v1) aerosol microphysics module2016Inngår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 9, nr 5, s. 1803-1826Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new aerosol-optics model is implemented in which realistic morphologies and mixing states are assumed, especially for black carbon particles. The model includes both external and internal mixing of all chemical species, it treats externally mixed black carbon as fractal aggregates, and it accounts for inhomogeneous internal mixing of black carbon by use of a novel "core-grey-shell" model. Simulated results of aerosol optical properties, such as aerosol optical depth, backscattering coefficients and the Angstrom exponent, as well as radiative fluxes are computed with the new optics model and compared with results from an older optics-model version that treats all particles as externally mixed homogeneous spheres. The results show that using a more detailed description of particle morphology and mixing state impacts the aerosol optical properties to a degree of the same order of magnitude as the effects of aerosol-microphysical processes. For instance, the aerosol optical depth computed for two cases in 2007 shows a relative difference between the two optics models that varies over the European region between 28 and 18 %, while the differences caused by the inclusion or omission of the aerosol-microphysical processes range from 50 to 37 %. This is an important finding, suggesting that a simple optics model coupled to a chemical transport model can introduce considerable errors affecting radiative fluxes in chemistry-climate models, compromising comparisons of model results with remote sensing observations of aerosols, and impeding the assimilation of satellite products for aerosols into chemical-transport models.

  • 64. Lacressonniere, Gwendoline
    et al.
    Foret, Gilles
    Beekmann, Matthias
    Siour, Guillaume
    Engardt, Magnuz
    SMHI, Forskningsavdelningen, Luftmiljö.
    Gauss, Michael
    Watson, Laura
    Andersson, Camilla
    SMHI, Forskningsavdelningen, Luftmiljö.
    Colette, Augustin
    Josse, Beatrice
    Marecal, Virginie
    Nyiri, Agnes
    Vautard, Robert
    Impacts of regional climate change on air quality projections and associated uncertainties2016Inngår i: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 136, nr 2, s. 309-324Artikkel i tidsskrift (Fagfellevurdert)
  • 65. Markakis, Konstantinos
    et al.
    Valari, Myrto
    Engardt, Magnuz
    SMHI, Forskningsavdelningen, Luftmiljö.
    Lacressonniere, Gwendoline
    Vautard, Robert
    Andersson, Camilla
    SMHI, Forskningsavdelningen, Luftmiljö.
    Mid-21st century air quality at the urban scale under the influence of changed climate and emissions - case studies for Paris and Stockholm2016Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 16, nr 4, s. 1877-1894Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ozone, PM10 and PM2.5 concentrations over Paris, France and Stockholm, Sweden were modelled at 4 and 1 km horizontal resolutions respectively for the present and 2050 periods employing decade-long simulations. We account for large-scale global climate change (RCP-4.5) and fine-resolution bottom-up emission projections developed by local experts and quantify their impact on future pollutant concentrations. Moreover, we identify biases related to the implementation of regional-scale emission projections by comparing modelled pollutant concentrations between the fine-and coarse-scale simulations over the study areas. We show that over urban areas with major regional contribution (e.g. the city of Stockholm) the bias related to coarse-scale projections may be significant and lead to policy misclassification. Our results stress the need to better understand the mechanism of bias propagation across the modelling scales in order to design more successful local-scale strategies. We find that the impact of climate change is spatially homogeneous in both regions, implying strong regional influence. The climate benefit for ozone (daily mean and maximum) is up to 5% for Paris and 2% for Stockholm city. The climate benefit on PM2.5 and PM10 in Paris is between 5 and 10 %, while for Stockholm we estimate mixed trends of up to 3% depending on season and size class. In Stockholm, emission mitigation leads to concentration reductions up to 15% for daily mean and maximum ozone and 20% for PM. Through a sensitivity analysis we show that this response is entirely due to changes in emissions at the regional scale. On the contrary, over the city of Paris (VOC-limited photochemical regime), local mitigation of NO x emissions increases future ozone concentrations due to ozone titration inhibition. This competing trend between the respective roles of emission and climate change, results in an increase in 2050 daily mean ozone by 2.5% in Paris. Climate and not emission change appears to be the most influential factor for maximum ozone concentration over the city of Paris, which may be particularly interesting from a health impact perspective.

  • 66. Borrego, C.
    et al.
    Amorim, Jorge Humberto
    SMHI, Forskningsavdelningen, Luftmiljö.
    Tchepel, O.
    Dias, D.
    Rafael, S.
    Sa, E.
    Pimentel, C.
    Fontes, T.
    Fernandes, P.
    Pereira, S. R.
    Bandeira, J. M.
    Coelho, M. C.
    Urban scale air quality modelling using detailed traffic emissions estimates2016Inngår i: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 131, s. 341-351Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The atmospheric dispersion of NOx and PM10 was simulated with a second generation Gaussian model over a medium-size south-European city. Microscopic traffic models calibrated with GPS data were used to derive typical driving cycles for each road link, while instantaneous emissions were estimated applying a combined Vehicle Specific Power/Co-operative Programme for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe (VSP/EMEP) methodology. Site-specific background concentrations were estimated using time series analysis and a low-pass filter applied to local observations. Air quality modelling results are compared against measurements at two locations for a 1 week period. 78% of the results are within a factor of two of the observations for 1-h average concentrations, increasing to 94% for daily averages. Correlation significantly improves when background is added, with an average of 0.89 for the 24 h record. The results highlight the potential of detailed traffic and instantaneous exhaust emissions estimates, together with filtered urban background, to provide accurate input data to Gaussian models applied at the urban scale. (C) 2016 Elsevier Ltd. All rights reserved.

  • 67. Sand, M.
    et al.
    Berntsen, T. K.
    von Salzen, K.
    Flanner, M. G.
    Langner, Joakim
    SMHI, Forskningsavdelningen, Luftmiljö.
    Victor, D. G.
    Response of Arctic temperature to changes in emissions of short-lived climate forcers2016Inngår i: Nature Climate Change, ISSN 1758-678X, E-ISSN 1758-6798, Vol. 6, nr 3, s. 286-+Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is growing scientific(1,2) and political(3,4) interest in the impacts of climate change and anthropogenic emissions on the Arctic. Over recent decades temperatures in the Arctic have increased at twice the global rate, largely as a result of ice-albedo and temperature feedbacks(5-8). Although deep cuts in global CO2 emissions are required to slow this warming, there is also growing interest in the potential for reducing short-lived climate forcers (SLCFs; refs 9,10). Politically, action on SLCFs may be particularly promising because the benefits of mitigation are seen more quickly than for mitigation of CO2 and there are large co-benefits in terms of improved air quality(11). This Letter is one of the first to systematically quantify the Arctic climate impact of regional SLCFs emissions, taking into account black carbon (BC), sulphur dioxide (SO2), nitrogen oxides (NOx), volatile organic compounds (VOCs), organic carbon (OC) and tropospheric ozone (O-3), and their transport processes and transformations in the atmosphere. This study extends the scope of previous works(2,12) by including more detailed calculations of Arctic radiative forcing and quantifying the Arctic temperature response. We find that the largest Arctic warming source is from emissions within the Asian nations owing to the large absolute amount of emissions. However, the Arctic is most sensitive, per unit mass emitted, to SLCFs emissions from a small number of activities within the Arctic nations themselves. Astringent, but technically feasible mitigation scenario for SLCFs, phased in from 2015 to 2030, could cut warming by 0.2 (+/- 0.17) K in 2050.

  • 68.
    Andersson, Stefan
    et al.
    SMHI, Affärsverksamhet.
    Arvelius, Johan
    SMHI, Affärsverksamhet.
    Verbova, Marina
    SMHI, Affärsverksamhet.
    Omstedt, Gunnar
    SMHI, Forskningsavdelningen, Luftmiljö.
    Torstensson, Martin
    SMHI, Affärsverksamhet.
    Identifiering av potentiella riskområden för höga halter av benso(a)pyren Nationell kartering av emissioner och halter av B(a)P från vedeldning i småhusområden2015Rapport (Annet vitenskapelig)
    Abstract [sv]

    Den här studien är en kartläggning och screening av emissioner och halter av benso(a)pyren (B(a)P) i Sverige. Syftet är att identifiera potentiella riskområden för överskridande av miljökvalitetsnormen (MKN). Ett övervägande bidrag till haltnivåerna till B(a)P är emissioner från den småskaliga vedeldningen, varför studien går ut på att beräkna och fördela emissionerna från uppvärmning av småhus. Metodiken består översiktligt av tre delar; beräkning av kommunvisa emissioner av B(a)P i Sverige, fördelning av dessa årsemissioner inom kommunerna på ett raster om 1 km × 1 km samt beräkning av årsmedelhalter utifrån detta emissionsraster. För att beräkna kommunvisa årsemissioner av B(a)P utnyttjas statistik från MSB över antalet eldstäder, modellerade värden på småhusens energibehov från ENLOSS, antaganden om eldvanor och emissionsfaktorer per typ av eldstad. De kommunvisa emissionerna fördelas sedan inom kommunen i ett grid om 1 km × 1 km utgående från antal kvadratmeter boyta småhus per km2 från fastighetsregistret. För pannor används dessutom tätortsvis statistik från Energimarknadsinspektionen över antal anslutna småhus till fjärrvärmenät, som vi enligt egen fördelning applicerar tätortsvis. Slutligen beräknas årsmedelhalter av B(a)P utifrån emissionsrastret på 1 km × 1 km utgående från linjära samband mellan emissioner och halter från tidigare genomförda lokalskaliga spridningsberäkningar med SIMAIR-ved i Västerbottenprojektet. Huvudslutsatserna från studien är följande: • De högsta årsemissionerna av B(a)P från vedpannor, som står för i särklass högst emission per enhet och därmed har störst påverkan på den lokala luftkvaliteten, beräknas för Skellefteå (18 200 g år–1) följt av Örnsköldsvik (13 600 g år–1), Gotland (13 500 g år–1), Sundsvall (12 900 g år–1) och Hudiksvall (12 300 g år–1). • Utifrån ett linjärt antagande mellan emissioner och halter fås kommunvisa årsmedelhalter av B(a)P 2012 på 0.03 – 1.03 ng m–3 för haltmåttet kartans högsta värde (KHV). Motsvarande värden för kartans ytmedelvärde (KYM) är 0.01 – 0.25 ng m–3. • Beräkningarna indikerar att det föreligger risk för överskridande av MKN (>1.0 ng m–3) i vissa enskilda gridrutor i tätorterna Sollefteå och Laholm (avseende årsmedelhalt av B(a)P uttryckt som KHV). Höga årsmedelhalter (>0.8 ng m–3) fås även för Kramfors, Säffle, Arvidsjaur, Boden, Skellefteå och Trollhättan. Detta är kommuner med en stor andel vedpannor i förhållande till lokaleldstäder. • Merparten (273 av 290) av kommunerna i Sverige har haltnivåer (KHV) högre än miljökvalitetsmålet Frisk luft (>0.1 ng m–3). Här är påverkan även betydande för utsläpp från trivseleldning med lokaleldstäder. • Studien ska ses som en översiktlig kartläggning och screening av emissioner och halter av B(a)P från småskaliga vedeldningen. Beräkningarna kan anses representera ett ”worst case”. • Den i särklass största osäkerheten vad gäller indata är statistiken från MSB över antalet eldstäder per kommun, samt hur eldstäderna fördelas mellan olika kommuner i gemensamma räddningstjänstområden. Detaljeringsgraden av underlaget samt klassificeringen av eldstäderna kan variera betydligt mellan olika kommuner/räddningstjänstförbund. För kommuner som enligt beräkningarna har haltnivåer som överskrider eller är nära att överskrida MKN rekommenderas, i ett första steg, att en noggrannare granskning/inventering görs av indata som används i beräkningarna, i synnerhet antalet eldstäder. In this report methods and results are presented from downscaling of about 40 climate

  • 69. Simpson, David
    et al.
    Bartnicki, Jerzy
    Jalkanen, Jukka-Pekka
    Hansson, Hans-Christen
    Hertel, Ole
    Langner, Joakim
    SMHI, Forskningsavdelningen, Luftmiljö.
    Pryor, Sara C.
    Environmental Impacts-Atmospheric Chemistry2015Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    This chapter addresses sources and trends of atmospheric pollutants and deposition in relation to the Baltic Sea region. Air pollution is shown to have important effects, including significant contributions to nitrogen loading of the Baltic Sea area, ecosystem impacts due to acidifying and eutrophying pollutants and ozone, and human health impacts. Compounds such as sulphate and ozone also have climate impacts. Emission changes have been very significant over the past 100 years, although very different for land-and sea-based sources. Land-based emissions generally peaked around 1980-1990 and have since reduced due to emissions control measures. Emissions from shipping have been steadily increasing for decades, but recent measures have reduced sulphur and particulate emissions. Future developments depend strongly on policy developments. Changes in concentration and deposition of the acidifying components generally follow emission changes within the European area. Mean ozone levels roughly doubled during the twentieth century across the northern hemisphere, but peak levels have reduced in many regions in the past 20 years. The main changes in air pollution in the Baltic Sea region are due to changes in emissions rather than to climate change.

  • 70. Silva, F. C.
    et al.
    Borrego, C.
    Keizer, J. J.
    Amorim, Jorge Humberto
    SMHI, Forskningsavdelningen, Luftmiljö.
    Verheijen, F. G. A.
    Effects of moisture content on wind erosion thresholds of biochar2015Inngår i: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 123, s. 121-128Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Biochar, i.e. pyrolysed biomass, as a soil conditioner is gaining increasing attention in research and industry, with guidelines and certifications being developed for biochar production, storage and handling, as well as for application to soils. Adding water to biochar aims to reduce its susceptibility to become airborne during and after the application to soils, thereby preventing, amongst others, human health issues from inhalation. The Bagnold model has previously been modified to explain the threshold friction velocity of coal particles at different moisture contents, by adding an adhesive effect. However, it is unknown if this model also works for biochar particles. We measured the threshold friction velocities of a range of biochar particles (woody feedstock) under a range of moisture contents by using a wind tunnel, and tested the performance of the modified Bagnold model. Results showed that the threshold friction velocity can be significantly increased by keeping the gravimetric moisture content at or above 15% to promote adhesive effects between the small particles. For the specific biochar of this study, the modified Bagnold model accurately estimated threshold friction velocities of biochar particles up to moisture contents of 10%. (C) 2015 Elsevier Ltd. All rights reserved.

  • 71. Watson, Laura
    et al.
    Lacressonniere, Gwendoline
    Gauss, Michael
    Engardt, Magnuz
    SMHI, Forskningsavdelningen, Luftmiljö.
    Andersson, Camilla
    SMHI, Forskningsavdelningen, Luftmiljö.
    Josse, Beatrice
    Marecal, Virginie
    Nyiri, Agnes
    Sobolowski, Stefan
    Siour, Guillaume
    Vautard, Robert
    The impact of meteorological forcings on gas phase air pollutants over Europe2015Inngår i: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 119, s. 240-257Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The impact of meteorological forcings on gas phase air pollutants (ozone and nitrogen dioxide) over Europe was studied using four offline chemistry transport models (CTMs) as part of the IMPACT2C project. This study uses long (20- and 30-year) simulations to evaluate the present-day performance of the CTMs, which is a necessary first step before undertaking any analysis of future air quality impacts. Two sets of meteorological forcings were used for each model: reanalysis of past observation data (ERA-Interim) and Global Climate Model (GCM) output. The results for the simulations forced by reanalysis data were assessed in relation to AirBase v7 measurement data, and it was determined that all four models slightly overpredict annual O-3 values (mean biases range between 0.7 and 6.6 ppb) and three out of the four models underpredict observed annual NO2 (mean biases range between -3.1 and -5.2 ppb). The simulations forced by climate models result in spatially averaged monthly concentrations of O-3 that are generally between 0 and 5 ppb higher than the values obtained from simulations forced by reanalysis data; therefore it was concluded that the use of climate models introduces an additional bias to the results, but this bias tends not to be significant in the majority of cases. The bias in O-3 results appears to be correlated mainly to differences in temperature and boundary layer height between the two types of simulations, whereas the less significant bias in NO2 is negatively correlated to temperature and boundary layer height. It is also clear that the selection of chemical boundary conditions is an important factor in determining the variability of O-3 model results. These results will be used as a baseline for the interpretation of future work, which will include an analysis of future climate scenarios upon European air quality. (C) 2015 Elsevier Ltd. All rights reserved.

  • 72. Astrom, Christofer
    et al.
    Ebi, Kristie L.
    Langner, Joakim
    SMHI, Forskningsavdelningen, Luftmiljö.
    Forsberg, Bertil
    Developing a Heatwave Early Warning System for Sweden: Evaluating Sensitivity of Different Epidemiological Modelling Approaches to Forecast Temperatures2015Inngår i: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 12, nr 1, s. 254-267Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Over the last two decades a number of heatwaves have brought the need for heatwave early warning systems (HEWS) to the attention of many European governments. The HEWS in Europe are operating under the assumption that there is a high correlation between observed and forecasted temperatures. We investigated the sensitivity of different temperature mortality relationships when using forecast temperatures. We modelled mortality in Stockholm using observed temperatures and made predictions using forecast temperatures from the European Centre for Medium-range Weather Forecasts to assess the sensitivity. We found that the forecast will alter the expected future risk differently for different temperature mortality relationships. The more complex models seemed more sensitive to inaccurate forecasts. Despite the difference between models, there was a high agreement between models when identifying risk-days. We find that considerations of the accuracy in temperature forecasts should be part of the design of a HEWS. Currently operating HEWS do evaluate their predictive performance; this information should also be part of the evaluation of the epidemiological models that are the foundation in the HEWS. The most accurate description of the relationship between high temperature and mortality might not be the most suitable or practical when incorporated into a HEWS.

  • 73.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    Modelling radiometric properties of inhomogeneous mineral dust particles: Applicability and limitations of effective medium theories2015Inngår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 152, s. 16-27Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of inhomogeneous mineralogical composition on the optical properties of mineral dust particles is investigated. More specifically, spheres composed of a non-absorbing mineral with multiple spherical hematite inclusions are considered. The size of the particles, the number of inclusions, and the hematite volume fraction are varied, and the differential and integral optical properties are compared to those computed for homogeneous spheres. The effective refractive index of the homogeneous spheres is obtained (i) by use of four conventional effective medium approximations; and (ii) by freely varying the real and imaginary parts of the refractive index until a best-fit of the scattering matrix elements is achieved for all scattering angles and particle sizes. Among the integral radiometric observables, the single scattering albedo is most sensitive to particle inhomogeneity, while the extinction and scattering efficiency and the asymmetry parameter are rather insensitive. The phase function, the degree of linear polarisation, the linear depolarisation, and, indeed, all elements of the scattering matrix are strongly modulated by particle inhomogeneity. None of the effective medium approaches, not even the best-fit method, are able to reproduce the single scattering albedo and the scattering matrix elements over the entire range of particle sizes. (C) 2014 Elsevier Ltd. All rights reserved.

  • 74.
    Andersson, Camilla
    et al.
    SMHI, Forskningsavdelningen, Luftmiljö.
    Bergström, Robert
    SMHI, Forskningsavdelningen, Luftmiljö.
    Bennet, Cecilia
    SMHI, Forskningsavdelningen, Luftmiljö.
    Robertson, Lennart
    SMHI, Forskningsavdelningen, Luftmiljö.
    Thomas, Manu
    SMHI, Forskningsavdelningen, Luftmiljö.
    Korhonen, H.
    Lehtinen, K. E. J.
    Kokkola, H.
    MATCH-SALSA - Multi-scale Atmospheric Transport and CHemistry model coupled to the SALSA aerosol microphysics model - Part 1: Model description and evaluation2015Inngår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 8, nr 2, s. 171-189Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have implemented the sectional aerosol dynamics model SALSA (Sectional Aerosol module for Large Scale Applications) in the European-scale chemistry-transport model MATCH (Multi-scale Atmospheric Transport and Chemistry). The new model is called MATCH-SALSA. It includes aerosol microphysics, with several formulations for nucleation, wet scavenging and condensation. The model reproduces observed higher particle number concentration (PNC) in central Europe and lower concentrations in remote regions. The modeled PNC size distribution peak occurs at the same or smaller particle size as the observed peak at four measurement sites spread across Europe. Total PNC is underestimated at northern and central European sites and accumulation-mode PNC is underestimated at all investigated sites. The low nucleation rate coefficient used in this study is an important reason for the underestimation. On the other hand, the model performs well for particle mass (including secondary inorganic aerosol components), while elemental and organic carbon concentrations are underestimated at many of the sites. Further development is needed, primarily for treatment of secondary organic aerosol, in terms of biogenic emissions and chemical transformation. Updating the biogenic secondary organic aerosol (SOA) scheme will likely have a large impact on modeled PM2.5 and also affect the model performance for PNC through impacts on nucleation and condensation.

  • 75. Eckhardt, S.
    et al.
    Quennehen, B.
    Olivie, D. J. L.
    Berntsen, T. K.
    Cherian, R.
    Christensen, J. H.
    Collins, W.
    Crepinsek, S.
    Daskalakis, N.
    Flanner, M.
    Herber, A.
    Heyes, C.
    Hodnebrog, O.
    Huang, L.
    Kanakidou, M.
    Klimont, Z.
    Langner, Joakim
    SMHI, Forskningsavdelningen, Luftmiljö.
    Law, K. S.
    Lund, M. T.
    Mahmood, R.
    Massling, A.
    Myriokefalitakis, S.
    Nielsen, I. E.
    Nojgaard, J. K.
    Quaas, J.
    Quinn, P. K.
    Raut, J. -C
    Rumbold, S. T.
    Schulz, M.
    Sharma, S.
    Skeie, R. B.
    Skov, H.
    Uttal, T.
    von Salzen, K.
    Stohl, A.
    Current model capabilities for simulating black carbon and sulfate concentrations in the Arctic atmosphere: a multi-model evaluation using a comprehensive measurement data set2015Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, nr 16, s. 9413-9433Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The concentrations of sulfate, black carbon (BC) and other aerosols in the Arctic are characterized by high values in late winter and spring (so-called Arctic Haze) and low values in summer. Models have long been struggling to capture this seasonality and especially the high concentrations associated with Arctic Haze. In this study, we evaluate sulfate and BC concentrations from eleven different models driven with the same emission inventory against a comprehensive pan-Arctic measurement data set over a time period of 2 years (2008-2009). The set of models consisted of one Lagrangian particle dispersion model, four chemistry transport models (CTMs), one atmospheric chemistry-weather forecast model and five chemistry climate models (CCMs), of which two were nudged to meteorological analyses and three were running freely. The measurement data set consisted of surface measurements of equivalent BC (eBC) from five stations (Alert, Barrow, Pallas, Tiksi and Zeppelin), elemental carbon (EC) from Station Nord and Alert and aircraft measurements of refractory BC (rBC) from six different campaigns. We find that the models generally captured the measured eBC or rBC and sulfate concentrations quite well, compared to previous comparisons. However, the aerosol seasonality at the surface is still too weak in most models. Concentrations of eBC and sulfate averaged over three surface sites are underestimated in winter/spring in all but one model (model means for January-March underestimated by 59 and 37% for BC and sulfate, respectively), whereas concentrations in summer are overestimated in the model mean (by 88 and 44% for July-September), but with overestimates as well as underestimates present in individual models. The most pronounced eBC underestimates, not included in the above multi-site average, are found for the station Tiksi in Siberia where the measured annual mean eBC concentration is 3 times higher than the average annual mean for all other stations. This suggests an underestimate of BC sources in Russia in the emission inventory used. Based on the campaign data, biomass burning was identified as another cause of the modeling problems. For sulfate, very large differences were found in the model ensemble, with an apparent anti-correlation between modeled surface concentrations and total atmospheric columns. There is a strong correlation between observed sulfate and eBC concentrations with consistent sulfate/eBC slopes found for all Arctic stations, indicating that the sources contributing to sulfate and BC are similar throughout the Arctic and that the aerosols are internally mixed and undergo similar removal. However, only three models reproduced this finding, whereas sulfate and BC are weakly correlated in the other models. Overall, no class of models (e.g., CTMs, CCMs) performed better than the others and differences are independent of model resolution.

  • 76. Sofiev, M.
    et al.
    Berger, U.
    Prank, M.
    Vira, J.
    Arteta, J.
    Belmonte, J.
    Bergmann, K. -C
    Cheroux, F.
    Elbern, H.
    Friese, E.
    Galan, C.
    Gehrig, R.
    Khvorostyanov, D.
    Kranenburg, R.
    Kumar, U.
    Marecal, V.
    Meleux, F.
    Menut, L.
    Pessi, A. -M
    Robertson, Lennart
    SMHI, Forskningsavdelningen, Luftmiljö.
    Ritenberga, O.
    Rodinkova, V.
    Saarto, A.
    Segers, A.
    Severova, E.
    Sauliene, I.
    Siljamo, P.
    Steensen, B. M.
    Teinemaa, E.
    Thibaudon, M.
    Peuch, V. -H
    MACC regional multi-model ensemble simulations of birch pollen dispersion in Europe2015Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, nr 14, s. 8115-8130Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the first ensemble modelling experiment in relation to birch pollen in Europe. The seven-model European ensemble of MACC-ENS, tested in trial simulations over the flowering season of 2010, was run through the flowering season of 2013. The simulations have been compared with observations in 11 countries, all members of the European Aeroallergen Network, for both individual models and the ensemble mean and median. It is shown that the models successfully reproduced the timing of the very late season of 2013, generally within a couple of days from the observed start of the season. The end of the season was generally predicted later than observed, by 5 days or more, which is a known feature of the source term used in the study. Absolute pollen concentrations during the season were somewhat underestimated in the southern part of the birch habitat. In the northern part of Europe, a record-low pollen season was strongly overestimated by all models. The median of the multi-model ensemble demonstrated robust performance, successfully eliminating the impact of outliers, which was particularly useful since for most models this was the first experience of pollen forecasting.

  • 77. Arnold, S. R.
    et al.
    Emmons, L. K.
    Monks, S. A.
    Law, K. S.
    Ridley, D. A.
    Turquety, S.
    Tilmes, S.
    Thomas, J. L.
    Bouarar, I.
    Flemming, J.
    Huijnen, V.
    Mao, J.
    Duncan, B. N.
    Steenrod, S.
    Yoshida, Y.
    Langner, Joakim
    SMHI, Forskningsavdelningen, Luftmiljö.
    Long, Y.
    Biomass burning influence on high-latitude tropospheric ozone and reactive nitrogen in summer 2008: a multi-model analysis based on POLMIP simulations2015Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, nr 11, s. 6047-6068Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have evaluated tropospheric ozone enhancement in air dominated by biomass burning emissions at high latitudes (>50 degrees N) in July 2008, using 10 global chemical transport model simulations from the POLMIP multimodel comparison exercise. In model air masses dominated by fire emissions, Delta O-3/Delta CO values ranged between 0.039 and 0.196 ppbv ppbv(-1) (mean: 0.113 ppbv ppbv(-1)) in freshly fire-influenced air, and between 0.140 and 0.261 ppbv ppb(-1) (mean: 0.193 ppbv) in more aged fire-influenced air. These values are in broad agreement with the range of observational estimates from the literature. Model Delta PAN/Delta CO enhancement ratios show distinct groupings according to the meteorological data used to drive the models. ECMWF-forced models produce larger Delta PAN/Delta CO values (4.47 to 7.00 pptv ppbv(-1)) than GEOS5-forced models (1.87 to 3.28 pptv ppbv(-1)), which we show is likely linked to differences in efficiency of vertical transport during poleward export from mid-latitude source regions. Simulations of a large plume of biomass burning and anthropogenic emissions exported from towards the Arctic using a Lagrangian chemical transport model show that 4-day net ozone change in the plume is sensitive to differences in plume chemical composition and plume vertical position among the POLMIP models. In particular, Arctic ozone evolution in the plume is highly sensitive to initial concentrations of PAN, as well as oxygenated VOCs (acetone, acetaldehyde), due to their role in producing the peroxyacetyl radical PAN precursor. Vertical displacement is also important due to its effects on the stability of PAN, and subsequent effect on NOx abundance. In plumes where net ozone production is limited, we find that the lifetime of ozone in the plume is sensitive to hydrogen peroxide loading, due to the production of HOx from peroxide photolysis, and the key role of HO2 + O-3 in controlling ozone loss. Overall, our results suggest that emissions from biomass burning lead to large-scale photochemical enhancement in high-latitude tropospheric ozone during summer.

  • 78. van der Gon, H. A. C. Denier
    et al.
    Bergström, Robert
    SMHI, Forskningsavdelningen, Luftmiljö.
    Fountoukis, C.
    Johansson, C.
    Pandis, S. N.
    Simpson, D.
    Visschedijk, A. J. H.
    Particulate emissions from residential wood combustion in Europe revised estimates and an evaluation2015Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, nr 11, s. 6503-6519Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Currently residential wood combustion (RWC) is increasing in Europe because of rising fossil fuel prices but also due to climate change mitigation policies. However, especially in small-scale applications, RWC may cause high emissions of particulate matter (PM). Recently we have developed a new high-resolution (7 x 7 km) anthropogenic carbonaceous aerosol emission inventory for Europe. The inventory indicated that about half of the total PM2.5 emission in Europe is carbonaceous aerosol and identified RWC as the largest organic aerosol source in Europe. The inventory was partly based on national reported PM emissions. Use of this organic aerosol inventory as input for two chemical transport models (CTMs), PMCAMx and EMEP MSC-W, revealed major underestimations of organic aerosol in winter time, especially for regions dominated by RWC. Interestingly, this was not universal but appeared to differ by country. In the present study we constructed a revised bottom-up emission inventory for RWC accounting for the semivolatile components of the emissions. The revised RWC emissions are higher than those in the previous inventory by a factor of 2-3 but with substantial inter-country variation. The new emission inventory served as input for the CTMs and a substantially improved agreement between measured and predicted organic aerosol was found. The revised RWC inven-tory improves the model-calculated organic aerosol significantly. Comparisons to Scandinavian source apportionment studies also indicate substantial improvements in the modelled wood-burning component of organic aerosol. This suggests that primary organic aerosol emission inventories need to be revised to include the semivolatile organic aerosol that is formed almost instantaneously due to dilution and cooling of the flue gas or exhaust. Since RWC is a key source of fine PM in Europe, a major revision of the emission estimates as proposed here is likely to influence source-receptor matrices and modelled source apportionment. Since usage of biofuels in small combustion units is a globally significant source, the findings presented here are also relevant for regions outside of Europe.

  • 79. Emmons, L. K.
    et al.
    Arnold, S. R.
    Monks, S. A.
    Huijnen, V.
    Tilmes, S.
    Law, K. S.
    Thomas, J. L.
    Raut, J. -C
    Bouarar, I.
    Turquety, S.
    Long, Y.
    Duncan, B.
    Steenrod, S.
    Strode, S.
    Flemming, J.
    Mao, J.
    Langner, Joakim
    SMHI, Forskningsavdelningen, Luftmiljö.
    Thompson, A. M.
    Tarasick, D.
    Apel, E. C.
    Blake, D. R.
    Cohen, R. C.
    Dibb, J.
    Diskin, G. S.
    Fried, A.
    Hall, S. R.
    Huey, L. G.
    Weinheimer, A. J.
    Wisthaler, A.
    Mikoviny, T.
    Nowak, J.
    Peischl, J.
    Roberts, J. M.
    Ryerson, T.
    Warneke, C.
    Helmig, D.
    The POLARCAT Model Intercomparison Project (POLMIP): overview and evaluation with observations2015Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, nr 12, s. 6721-6744Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A model intercomparison activity was inspired by the large suite of observations of atmospheric composition made during the International Polar Year (2008) in the Arctic. Nine global and two regional chemical transport models participated in this intercomparison and performed simulations for 2008 using a common emissions inventory to assess the differences in model chemistry and transport schemes. This paper summarizes the models and compares their simulations of ozone and its precursors and presents an evaluation of the simulations using a variety of surface, balloon, aircraft and satellite observations. Each type of measurement has some limitations in spatial or temporal coverage or in composition, but together they assist in quantifying the limitations of the models in the Arctic and surrounding regions. Despite using the same emissions, large differences are seen among the models. The cloud fields and photolysis rates are shown to vary greatly among the models, indicating one source of the differences in the simulated chemical species. The largest differences among models, and between models and observations, are in NOy partitioning (PAN vs. HNO3) and in oxygenated volatile organic compounds (VOCs) such as acetaldehyde and acetone. Comparisons to surface site measurements of ethane and propane indicate that the emissions of these species are significantly underestimated. Satellite observations of NO2 from the OMI (Ozone Monitoring Instrument) have been used to evaluate the models over source regions, indicating anthropogenic emissions are underestimated in East Asia, but fire emissions are generally overestimated. The emission factors for wildfires in Canada are evaluated using the correlations of VOCs to CO in the model output in comparison to enhancement factors derived from aircraft observations, showing reasonable agreement for methanol and acetaldehyde but underestimate ethanol, propane and acetone, while overestimating ethane emission factors.

  • 80.
    Thomas, Manu Anna
    et al.
    SMHI, Forskningsavdelningen, Luftmiljö.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    Andersson, Camilla
    SMHI, Forskningsavdelningen, Luftmiljö.
    Kokkola, H.
    Hansson, Ulf
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Langner, Joakim
    SMHI, Forskningsavdelningen, Luftmiljö.
    Devasthale, Abhay
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Integration of prognostic aerosol-cloud interactions in a chemistry transport model coupled offline to a regional climate model2015Inngår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 8, nr 6, s. 1885-1898Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To reduce uncertainties and hence to obtain a better estimate of aerosol (direct and indirect) radiative forcing, next generation climate models aim for a tighter coupling between chemistry transport models and regional climate models and a better representation of aerosol-cloud interactions. In this study, this coupling is done by first forcing the Rossby Center regional climate model (RCA4) with ERA-Interim lateral boundaries and sea surface temperature (SST) using the standard cloud droplet number concentration (CDNC) formulation (hereafter, referred to as the 'stand-alone RCA4 version' or 'CTRL' simulation). In the stand-alone RCA4 version, CDNCs are constants distinguishing only between land and ocean surface. The meteorology from this simulation is then used to drive the chemistry transport model, Multiple-scale Atmospheric Transport and Chemistry (MATCH), which is coupled online with the aerosol dynamics model, Sectional Aerosol module for Large Scale Applications (SALSA). CDNC fields obtained from MATCH-SALSA are then fed back into a new RCA4 simulation. In this new simulation (referred to as 'MOD' simulation), all parameters remain the same as in the first run except for the CDNCs provided by MATCH-SALSA. Simulations are carried out with this model setup for the period 2005-2012 over Europe, and the differences in cloud microphysical properties and radiative fluxes as a result of local CDNC changes and possible model responses are analysed. Our study shows substantial improvements in cloud microphysical properties with the input of the MATCH-SALSA derived 3-D CDNCs compared to the stand-alone RCA4 version. This model setup improves the spatial, seasonal and vertical distribution of CDNCs with a higher concentration observed over central Europe during boreal summer (JJA) and over eastern Europe and Russia during winter (DJF). Realistic cloud droplet radii (CD radii) values have been simulated with the maxima reaching 13 mu m, whereas in the stand-alone version the values reached only 5 mu m. A substantial improvement in the distribution of the cloud liquid-water paths (CLWP) was observed when compared to the satellite retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) for the boreal summer months. The median and standard deviation values from the 'MOD' simulation are closer to observations than those obtained using the stand-alone RCA4 version. These changes resulted in a significant decrease in the total annual mean net fluxes at the top of the atmosphere (TOA) by -5 W m(-2) over the domain selected in the study. The TOA net fluxes from the 'MOD' simulation show a better agreement with the retrievals from the Clouds and the Earth's Radiant Energy System (CERES) instrument. The aerosol indirect effects are estimated in the 'MOD' simulation in comparison to the pre-industrial aerosol emissions (1900). Our simulations estimated the domain averaged annual mean total radiative forcing of -0.64 W m(-2) with a larger contribution from the first indirect aerosol effect (-0.57 W m(-2)) than from the second indirect aerosol effect (-0.14 W m(-2)).

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