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  • 101. Gama, C.
    et al.
    Ribeiro, Isabel
    SMHI, Research Department, Air quality.
    Lange, A. C.
    Vogel, A.
    Ascenso, A.
    Seixasa, V
    Elbern, H.
    Borrego, C.
    Friese, E.
    Monteiro, A.
    Performance assessment of CHIMERE and EURAD-IM' dust modules2019In: Atmospheric Pollution Research, E-ISSN 1309-1042, Vol. 10, no 4, p. 1336-1346Article in journal (Refereed)
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  • 102. Geels, Camilla
    et al.
    Andersson, Camilla
    SMHI, Research Department, Air quality.
    Hanninen, Otto
    Lanso, Anne Sofie
    Schwarze, Per E.
    Skjoth, Carsten Ambelas
    Brandt, Jorgen
    Future Premature Mortality Due to O-3, Secondary Inorganic Aerosols and Primary PM in Europe - Sensitivity to Changes in Climate, Anthropogenic Emissions, Population and Building Stock2015In: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 12, no 3, p. 2837-2869Article in journal (Refereed)
    Abstract [en]

    Air pollution is an important environmental factor associated with health impacts in Europe and considerable resources are used to reduce exposure to air pollution through emission reductions. These reductions will have non-linear effects on exposure due, e.g., to interactions between climate and atmospheric chemistry. By using an integrated assessment model, we quantify the effect of changes in climate, emissions and population demography on exposure and health impacts in Europe. The sensitivity to the changes is assessed by investigating the differences between the decades 2000-2009, 2050-2059 and 2080-2089. We focus on the number of premature deaths related to atmospheric ozone, Secondary Inorganic Aerosols and primary PM. For the Nordic region we furthermore include a projection on how population exposure might develop due to changes in building stock with increased energy efficiency. Reductions in emissions cause a large significant decrease in mortality, while climate effects on chemistry and emissions only affects premature mortality by a few percent. Changes in population demography lead to a larger relative increase in chronic mortality than the relative increase in population. Finally, the projected changes in building stock and infiltration rates in the Nordic indicate that this factor may be very important for assessments of population exposure in the future.

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  • 103. Geels, Camilla
    et al.
    Winther, Morten
    Andersson, Camilla
    SMHI, Research Department, Air quality.
    Jalkanen, Jukka-Pekka
    Brandt, Jorgen
    Frohn, Lise M.
    Im, Ulas
    Leung, Wing
    SMHI, Professional Services.
    Christensen, Jesper H.
    Projections of shipping emissions and the related impact on air pollution and human health in the Nordic region2021In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 21, no 16, p. 12495-12519Article in journal (Refereed)
    Abstract [en]

    International initiatives have successfully brought down the emissions, and hence also the related negative impacts on environment and human health, from shipping in Emission Control Areas (ECAs). However, the question remains as to whether increased shipping in the future will counteract these emission reductions. The overall goal of this study is to provide an up-to-date view on future ship emissions and provide a holistic view on atmospheric pollutants and their contribution to air quality in the Nordic (and Arctic) area. The first step has been to set up new and detailed scenarios for the potential developments in global shipping emissions, including different regulations and new routes in the Arctic. The scenarios include a Baseline scenario and two additional SOx Emission Control Areas (SE-CAs) and heavy fuel oil (HFO) ban scenarios. All three scenarios are calculated in two variants involving Business-As-Usual (BAU) and High-Growth (HiG) traffic scenarios. Additionally a Polar route scenario is included with new ship traffic routes in the future Arctic with less sea ice. This has been combined with existing Current Legislation scenarios for the land-based emissions (ECLIPSE V5a) and used as input for two Nordic chemistry transport models (DEHM and MATCH). Thereby, the current (2015) and future (2030, 2050) air pollution levels and the contribution from shipping have been simulated for the Nordic and Arctic areas. Population exposure and the number of premature deaths attributable to air pollution in the Nordic area have thereafter been assessed by using the health assessment model EVA (Economic Valuation of Air pollution). It is estimated that within the Nordic region approximately 9900 persons died prematurely due to air pollution in 2015 (corresponding to approximately 37 premature deaths for every 100 000 inhabitants). When including the projected development in both shipping and land-based emissions, this number is estimated to decrease to approximately 7900 in 2050. Shipping alone is associated with about 850 premature deaths during present day conditions (as a mean over the two models), decreasing to approximately 600 cases in the 2050 BAU scenario. Introducing a HFO ban has the potential to lower the number of cases associated with emissions from shipping to approximately 550 in 2050, while the SECA scenario has a smaller impact. The "worst-case" scenario of no additional regulation of shipping emissions combined with a high growth in the shipping traffic will, on the other hand, lead to a small increase in the relative impact of shipping, and the number of premature deaths related to shipping is in that scenario projected to be around 900 in 2050. This scenario also leads to increased deposition of nitrogen and black carbon in the Arctic, with potential impacts on environment and climate.

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    Projections of shipping emissions and the related impact on air pollution and human health in the Nordic region
  • 104. Genberg, J.
    et al.
    Hyder, M.
    Stenstrom, K.
    Bergström, Robert
    SMHI, Research Department, Air quality.
    Simpson, D.
    Fors, E. O.
    Jonsson, J. A.
    Swietlicki, E.
    Source apportionment of carbonaceous aerosol in southern Sweden2011In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 11, no 22, p. 11387-11400Article in journal (Refereed)
    Abstract [en]

    A one-year study was performed at the Vavihill background station in southern Sweden to estimate the anthropogenic contribution to the carbonaceous aerosol. Weekly samples of the particulate matter PM10 were collected on quartz filters, and the amounts of organic carbon, elemental carbon, radiocarbon (C-14) and levoglucosan were measured. This approach enabled source apportionment of the total carbon in the PM10 fraction using the concentration ratios of the sources. The sources considered in this study were emissions from the combustion of fossil fuels and biomass, as well as biogenic sources. During the summer, the carbonaceous aerosol mass was dominated by compounds of biogenic origin (80 %), which are associated with biogenic primary and secondary organic aerosols. During the winter months, biomass combustion (32 %) and fossil fuel combustion (28 %) were the main contributors to the carbonaceous aerosol. Elemental carbon concentrations in winter were about twice as large as during summer, and can be attributed to biomass combustion, probably from domestic wood burning. The contribution of fossil fuels to elemental carbon was stable throughout the year, although the fossil contribution to organic carbon increased during the winter. Thus, the organic aerosol originated mainly from natural sources during the summer and from anthropogenic sources during the winter. The result of this source apportionment was compared with results from the EMEP MSC-W chemical transport model. The model and measurements were generally consistent for total atmospheric organic carbon, however, the contribution of the sources varied substantially. E.g. the biomass burning contributions of OC were underestimated by the model by a factor of 2.2 compared to the measurements.

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  • 105. Genberg, J.
    et al.
    van der Gon, H. A. C. Denier
    Simpson, D.
    Swietlicki, E.
    Areskoug, H.
    Beddows, D.
    Ceburnis, D.
    Fiebig, M.
    Hansson, H. C.
    Harrison, R. M.
    Jennings, S. G.
    Saarikoski, S.
    Spindler, G.
    Visschedijk, A. J. H.
    Wiedensohler, A.
    Yttri, K. E.
    Bergström, Robert
    SMHI, Research Department, Air quality.
    Light-absorbing carbon in Europe - measurement and modelling, with a focus on residential wood combustion emissions2013In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 17, p. 8719-8738Article in journal (Refereed)
    Abstract [en]

    The atmospheric concentration of elemental carbon (EC) in Europe during the six-year period 2005-2010 has been simulated with the EMEP MSC-W model. The model bias compared to EC measurements was less than 20% for most of the examined sites. The model results suggest that fossil fuel combustion is the dominant source of EC in most of Europe but that there are important contributions also from residential wood burning during the cold seasons and, during certain episodes, also from open biomass burning (wildfires and agricultural fires). The modelled contributions from open biomass fires to ground level concentrations of EC were small at the sites included in the present study, <3% of the long-term average of EC in PM10. The modelling of this EC source is subject to many uncertainties, and it was likely underestimated for some episodes. EC measurements and modelled EC were also compared to optical measurements of black carbon (BC). The relationships between EC and BC (as given by mass absorption cross section, MAC, values) differed widely between the sites, and the correlation between observed EC and BC is sometimes poor, making it difficult to compare results using the two techniques and limiting the comparability of BC measurements to model EC results. A new bottom-up emission inventory for carbonaceous aerosol from residential wood combustion has been applied. For some countries the new inventory has substantially different EC emissions compared to earlier estimates. For northern Europe the most significant changes are much lower emissions in Norway and higher emissions in neighbouring Sweden and Finland. For Norway and Sweden, comparisons to source-apportionment data from winter campaigns indicate that the new inventory may improve model-calculated EC from wood burning. Finally, three different model setups were tested with variable atmospheric lifetimes of EC in order to evaluate the model sensitivity to the assumptions regarding hygroscopicity and atmospheric ageing of EC. The standard ageing scheme leads to a rapid transformation of the emitted hydrophobic EC to hygroscopic particles, and generates similar results when assuming that all EC is aged at the point of emission. Assuming hydrophobic emissions and no ageing leads to higher EC concentrations. For the more remote sites, the observed EC concentration was in between the modelled EC using standard ageing and the scenario treating EC as hydrophobic. This could indicate too-rapid EC ageing in the model in relatively clean parts of the atmosphere.

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  • 106.
    Gidhagen, Lars
    SMHI, Research Department, Air quality.
    Coastal upwelling in the Baltic - a presentation of satellite and in situ measurements of sea surface temperatures indicating coastal upwelling Part l and ll1984Report (Other academic)
    Abstract [en]

    Satellite data (AVHRR) and in situ data of sea surface temperatures have been used to describe wind-induced upwelling along the Swedish coast of the Baltic.

    The satellite data, transformed to isotherm charts  points out three sections of the coast where the upwelling is especially intense. The cold upwelled water, normally found within 10 - 20 kilometres from the coast, sometimes spreads out in finger-like filaments. There are indications of propagation of upwelling fronts and centers, which may be associated with coastal-trapped waves. .

    Ten years of insitu measurements of sea surface temperature have been used for a statistical compilation of upwelling events. The statistics reveal that upwelling is a common feature along certain sections of the coast, occuring for about one fourth to one third of the time. Some information of time- scales and temperature anomalies associated with the upwelling events are also given. A wind analysis shows a correlation between upwelling and winds parallell to the shoreline, in accordance with the Ekman theory of upwelling generation.

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    Coastal upwelling in the Baltic - a presentation of satellite and in situ measurements of sea surface temperatures indicating coastal upwelling Part l
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    Coastal upwelling in the Baltic - a presentation of satellite and in situ measurements of sea surface temperatures indicating coastal upwelling Part ll
  • 107.
    Gidhagen, Lars
    SMHI, Research Department, Air quality.
    COASTAL UPWELLING IN THE BALTIC SEA - SATELLITE AND INSITU MEASUREMENTS OF SEA-SURFACE TEMPERATURES INDICATING COASTAL UPWELLING1987In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 24, no 4, p. 449-462Article in journal (Refereed)
  • 108.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Lovenheim, Boel
    Johansson, Christer
    Modeling Effects of Climate Change on Air Quality and Population Exposure in Urban Planning Scenarios2012In: Advances in Meteorology, ISSN 1687-9309, E-ISSN 1687-9317, article id 240894Article in journal (Refereed)
    Abstract [en]

    We employ a nested system of global and regional climate models, linked to regional and urban air quality chemical transport models utilizing detailed inventories of present and future emissions, to study the relative impact of climate change and changing air pollutant emissions on air quality and population exposure in Stockholm, Sweden. We show that climate change only marginally affects air quality over the 20-year period studied. An exposure assessment reveals that the population of Stockholm can expect considerably lower NO2 exposure in the future, mainly due to reduced local NOx emissions. Ozone exposure will decrease only slightly, due to a combination of increased concentrations in the city centre and decreasing concentrations in the suburban areas. The increase in ozone concentration is a consequence of decreased local NOx emissions, which reduces the titration of the long-range transported ozone. Finally, we evaluate the consequences of a planned road transit project on future air quality in Stockholm. The construction of a very large bypass road (including one of the largest motorway road tunnels in Europe) will only marginally influence total population exposure, this since the improved air quality in the city centre will be complemented by deteriorated air quality in suburban, residential areas.

  • 109.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Funquist, Lennart
    SMHI, Research Department, Oceanography.
    Murthy, Ray
    SMHI.
    Calculations of horizontal exchange coefficients using Eulerian time series current meter data from the Baltic Sea1986Report (Other academic)
    Abstract [en]

    A method is described which relates observed eularian current fluctuations to horizontal exchange coefficients. The method is applied to current meter time series from the southern and the central parts of the Baltic Proper and from the Bothnian Sea.

    Energy spectras suggest that current fluctuations with a time scale shorter than 24 hours can be considered as turbulence in large scale circulation models and parameterized by an exchange coefficient.

    The horizontal exchange is found to be horizontally uniform. The calculated exchange coefficients have a vertical variation ranging from 10-50 m s in the surface layer to 1-3 m s below 70 metres . Inertial or near-inertial oscillations are the most important physical processes that produce horizontal exchange.

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  • 110.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Johansson, C
    Langner, Joakim
    SMHI, Research Department, Air quality.
    Foltescu, Valter
    SMHI.
    Urban scale modeling of particle number concentration in Stockholm2005In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 39, no 9, p. 1711-1725Article in journal (Refereed)
    Abstract [en]

    A three-dimensional dispersion model has been implemented over the urban area of Stockholm (35 x 35 km) to assess the spatial distribution of number concentrations of particles in the diameter range 3-400 nm. Typical number concentrations in the urban background of Stockholm is 10 000 cm(-3), while they are three times higher close to a major highway outside the city and seven times higher within a densely trafficked street canyon site in the city center. The model, which includes an aerosol module for calculating the particle number losses due to coagulation and dry deposition, has been run for a 10-day period. Model results compare well with measured data, both in levels and in temporal variability. Coagulation was found to be of little importance in terms of time averaged concentrations, contributing to losses of only a few percent as compared to inert particles, while dry deposition yield particle number losses of up to 25% in certain locations. Episodic losses of up to 10% due to coagulation and 50% due to deposition, are found some kilometers downwind of major roads, rising in connection with low wind speed and suppressed turbulent mixing. Removal due to coagulation and deposition will thus be more significant for the simulation of extreme particle number concentrations during peak episodes. The study shows that dispersion models with proper aerosol dynamics included may be used to assess particle number concentrations in Stockholm, where ultrafine particles principally originate from traffic emissions. Emission factors may be determined from roadside measurements, but ambient temperature must be considered, as it has a strong influence on particle number emissions from vehicles. (c) 2005 Elsevier Ltd. All rights reserved.

  • 111.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Johansson, C
    Langner, Joakim
    SMHI, Research Department, Air quality.
    Olivares, G
    Simulation of NOx and ultrafine particles in a street canyon in Stockholm, Sweden2004In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 38, no 14, p. 2029-2044Article in journal (Refereed)
    Abstract [en]

    A computational fluid dynamic (CFD) model has been used to assess the concentrations of NO, and particle number in a street canyon in Stockholm with a high traffic volume. Comparisons of a simulated 11-week long time series of NOx with measurements (both sides of the street, urban background excluded) show good agreement, especially if emissions are distributed to be three times higher along the side of the street where the traffic is uphill, as compared to the downhill side. The simulation of number concentrations of inert particles indicates a similar asymmetry in emissions. A month-long measurement of particle size distribution (7-450 nm) at street level indicates that the ratio of nucleation size mode particle (7-20 nm) to total particle number (7-450 nm) is decreasing for increased particle surface area. Given the strong dominance of the locally generated particles over the urban background, this is interpreted as a local change in the size distribution. The results of a monodisperse aerosol dynamic model, coupled to the CFD model that simulates also the turbulence generated by vehicle movements, show that coagulation and deposition may reduce total particle inside the canyon with approximately 30% during low wind speeds. Most of the removal occurs shortly after emission, before the particles reach the leeward curb-side. Losses between the leeward curb-side and other locations in the street, e.g. roof levels, is estimated to be smaller, less than 10%. Coagulation is the dominating removal process under low wind speed conditions and deposition for higher wind speeds, the summed removal being smaller for high wind velocities. Deposition is enhanced over the road surface due to the velocities generated by vehicle movements. Although coagulation and deposition removal is most effective on the smallest ultrafine particles, this effect is not sufficient to explain the observed change in size distribution. It is suggested that also the formation of particles in the exhaust plumes is influenced by a larger particle surface area in the ambient air. (C) 2004 Elsevier Ltd. All rights reserved.

  • 112.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Johansson, C
    Omstedt, Gunnar
    SMHI, Research Department, Air quality.
    Langner, Joakim
    SMHI, Research Department, Air quality.
    Olivares, G
    Model simulations of NOx and ultrafine particles close to a Swedish highway2004In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 38, no 24, p. 6730-6740Article in journal (Refereed)
    Abstract [en]

    Based on the results from a 6-week monitoring campaign in an area close to a major highway north of Stockholm, Sweden, NOx emission factors representative for vehicle speeds of 100-120 km per h were determined to 0.61 g/veh-km for light duty and to 7.1 g/veh,km for heavy duty vehicles. The corresponding factors for particle number were 1.4 x 10(14) and 52 x 10(14) particles/veh,km, determined for an ambient temperature interval of +7 to +17 degreesC. The removal effects of coagulation and dry deposition on total number concentrations were assessed by numerical model simulations. Velocity and turbulence fields, including those produced by the vehicles, were simulated in a Computational Fluid Dynamics (CFD) model. Coagulation was found to be of little importance over the first 100 m downwind of the highway. The high friction velocities over the road surface created by vehicle movements enhanced deposition locally, contributing to the removal of approximately 10% of the particles originally emitted. Beyond a point 10 m downwind of the highway the removal rate was low and the ultrafine particles were almost inert while being advected over the next hundred meters. As a consequence, it seems reasonable to use monitored data from stations close to highways to estimate emission factors for particle number, assuming that the particles are inert. Those "effective" emission factors should be applicable for urban models with a larger spatial resolution.

  • 113.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Johansson, C
    Strom, J
    Kristensson, A
    Swietlicki, E
    Pirjola, L
    Hansson, H C
    Model simulation of ultrafine particles inside a road tunnel2003In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 37, no 15, p. 2023-2036Article in journal (Refereed)
    Abstract [en]

    A monodispersive aerosol dynamic model, coupled to a 3D hydrodynamical grid model, has been used to study the dynamics of ultrafine particles inside a road tunnel in Stockholm, Sweden. The model results were compared to measured data of particle number concentrations, traffic intensity and tunnel ventilation rate. Coagulation and depositional losses to the tunnel walls were shown to be important processes during traffic peak hours, together contributing to losses of 77% of the particles smaller than 10nm and 41% of the particles of size 10-29nm. Particle growth due to water uptake or the presence of a micron-sized, resuspended particle fraction did not have any significant effect on the number of particles lost due to coagulation. Model simulation of particle number concentration response to temporal variations in traffic flow showed that constant emission factors could be used to reproduce the concentration variations of the particles larger than 29nm, while vehicle-speed-dependent factors are suggested to reproduce the variation of the smallest fractions. The emission factors for particle number concentrations estimated from the model simulation are in general higher and show a larger contribution from light-duty vehicles than what has been reported from a tunnel in California. The model study shows that combined measurements and model simulations in road tunnels can be used to improve the determinations of vehicle emission factors for ultrafine particles under realistic driving conditions. (C) 2003 Elsevier Science Ltd. All rights reserved.

  • 114.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Johansson, Christer
    Institutionen för tillämpad miljövetenskap (ITM), Stockholms universitet.
    Törnquist, Lars
    NORDIC - A database for evaluation of dispersion models on the local, urban and regional scale2004Report (Other academic)
    Abstract [en]

    The EU directives together with the Swedish environmental legislation will require the Swedish municipalities to assess how they comply with given air quality standards. Model tools will be an important and necessary complement to measurements. Air pollution originates only partly from local sources within a particular municipality and there is often an important part that is transported over long distances, even from outside Sweden. Therefore model tools that aspire to simulate total concentrations of a pollutant, have to involve sources and dispersion on different scales, starting with the entire Europe and going down to the microscale of an individual street.

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  • 115.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Johansson, H.
    Omstedt, Gunnar
    SMHI, Research Department, Air quality.
    SIMAIR-Evaluation tool for meeting the EU directive on air pollution limits2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 5, p. 1029-1036Article in journal (Refereed)
    Abstract [en]

    Almost all Swedish cities need to determine air pollution levels especially PM10-close to major streets. SIMAIR is an internet tool that can be used by all Swedish municipalities to assess PM10, NO(2), CO and benzene levels and how they compare to the EU directive. SIMAIR is delivered to the municipalities with all required input data pre-loaded and is meant to be used prior to decisions if and where, monitoring campaigns are required. The system includes a road and vehicle database with emission factors and a model to calculate non tailpipe PM10 emissions. Regional and urban background contributions are pre-calculated and stored as hourly values oil a 1 x 1 km(2) grid. The local contribution is calculated by the user, selecting either an open road or a street canyon environment. A comparison between measured and simulated concentrations in four street locations shows that SIMAIR is able to Calculate statistics of yearly mean values, 90-percentile and 98-percentile daily mean values and the number of days exceeding the limit value that are well within +/- 50% that EU requires for model estimates of yearly mean values. In comparison, all Values except one are within +/- 25% which is the quality objective for fixed measurements according to the EU directive. The SIMAIR model system is also able to separate the percentual contribution of the long-range transport from Outside the city, the city contribution and the local contribution from the traffic of an individual street. (C) 2008 Elsevier Ltd. All rights reserved.

  • 116.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Kahelin, H
    Schmidt-Thome, P
    Johansson, C
    Anthropogenic and natural levels of arsenic in PM10 in Central and Northern Chile2002In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 36, no 23, p. 3803-3817Article in journal (Refereed)
    Abstract [en]

    A few copper and gold smelters in Chile are behind a large fraction of global arsenic emissions, raising concerns for increased concentrations of arsenic in PM10 in Central and Northern Chile. This concern is amplified by the fact that Northern Chile soils and rivers in general are characterized by a high arsenic content. A monitoring and modeling study has been performed to quantify the regional impact of the smelter emissions. Measured atmospheric arsenic concentrations from 2.4 to 30.7 ng m(-3) were found at seven rural stations, located tens to hundreds of kilometers away from the nearest smelter. Analyses of topsoil and subsoil samples taken from PM 10 monitoring stations revealed levels up to 291 mg kg(-1), the highest values found in the northern Atacama desert in Chile. An absolute principal component analysis of selected trace elements in PM10 shows that the regional impact of anthropogenic smelter emissions on airborne arsenic concentrations is more important than the effect of soil dust resuspension. The dominance of the smelter emissions is larger in Central Chile than in the northern parts. The impact of resuspended soil dust on airborne arsenic levels in rural areas was estimated not to exceed 5 ng m(-3). The model calculations support the dominant role of anthropogenic emissions and give spatial and temporal variations in atmospheric concentrations consistent with the monitored levels at five of the seven stations. At two of the northernmost stations indications were found of unidentified sources other than the smelters and the resuspended soil dust, contributing to about 5 ng m(-3) of total arsenic levels. The study confirms that a strong control or elimination of arsenic emissions from the smelters would lead to arsenic in PM10 levels in Northern and Central Chile comparable to non-polluted areas in other countries. (C) 2002 Elsevier Science Ltd. All rights reserved.

  • 117.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Krecl, Patricia
    Targino, Admir Creso
    Polezer, Gabriela
    Godoi, Ricardo H. M.
    Felix, Erika
    Cipoli, Yago A.
    Charres, Isabella
    Malucelli, Francisco
    Wolf, Alyson
    Alonso, Marcelo
    Segersson, David
    SMHI, Research Department, Air quality.
    Castelhano, Francisco J.
    Amorim, Jorge Humberto
    SMHI, Research Department, Air quality.
    Mendonca, Francisco
    An integrated assessment of the impacts of PM2.5 and black carbon particles on the air quality of a large Brazilian city2021In: Air quality, atmosphere and health, ISSN 1873-9318, E-ISSN 1873-9326Article in journal (Refereed)
    Abstract [en]

    Data on airborne fine particle (PM2.5) emissions and concentrations in cities are valuable for traffic and air quality managers, urban planners, health practitioners, researchers, and ultimately for legislators and decision makers. Emissions and ambient concentrations of PM2.5 and black carbon (BC) were assessed in the city of Curitiba, southern Brazil. The methodology combined a month-long monitoring campaign with both fixed and mobile instruments, development of emission inventories, and dispersion model simulations on different scales. The mean urban background PM2.5 concentrations during the campaign were 7.3 mu g m(-3) in Curitiba city center, but three- to fourfold higher (25.3 mu g m(-3)) in a residential area on the city's outskirts, indicating the presence of local sources, possibly linked to biomass combustion. BC concentrations seemed to be more uniformly distributed over the city, with mean urban background concentrations around 2 mu g m(-3), half of which due to local traffic emissions. Higher mean BC concentrations (3-5 mu g m(-3)) were found along busy roads. The dispersion modeling also showed high PM2.5 and BC concentrations along the heavily transited ring road. However, the lack of in situ data over these peripheral areas prevented the verification of the model output. The vehicular emission factors for PM2.5 and BC from the literature were found not to be suitable for Curitiba's fleet and needed to be adjusted. The integrated approach of this study can be implemented in other cities, as long as an open data policy and a close cooperation among regional, municipal authorities and academia can be achieved.

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    An integrated assessment of the impacts of PM2.5 and black carbon particles on the air quality of a large Brazilian city
  • 118.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    Amorim, Jorge Humberto
    SMHI, Research Department, Air quality.
    Asker, Christian
    SMHI, Research Department, Air quality.
    Belušić, Danijel
    SMHI, Research Department, Climate research - Rossby Centre.
    Carvalho, Ana Cristina
    SMHI, Research Department, Air quality.
    Engardt, Magnuz
    Hundecha, Yeshewatesfa
    SMHI, Research Department, Hydrology.
    Körnich, Heiner
    SMHI, Research Department, Meteorology.
    Lind, Petter
    SMHI, Research Department, Climate research - Rossby Centre.
    Lindstedt, David
    SMHI, Research Department, Climate research - Rossby Centre.
    Olsson, Esbjörn
    SMHI, Research Department, Meteorology.
    Rosberg, Jörgen
    SMHI, Research Department, Hydrology.
    Segersson, David
    SMHI, Research Department, Air quality.
    Strombäck, Lena
    SMHI, Research Department, Hydrology.
    Towards climate services for European cities: Lessons learnt from the Copernicus project Urban SIS2020In: Urban Climate, E-ISSN 2212-0955, Vol. 31, article id 100549Article in journal (Refereed)
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  • 119.
    Gidhagen, Lars
    et al.
    SMHI, Research Department, Air quality.
    Omstedt, Gunnar
    SMHI, Research Department, Air quality.
    Pershagen, Goran
    Willers, Saskia
    Bellander, Tom
    High-resolution modeling of residential outdoor particulate levels in Sweden2013In: Journal of Exposure Science and Environmental Epidemiology, ISSN 1559-0631, E-ISSN 1559-064X, Vol. 23, no 3, p. 306-314Article in journal (Refereed)
    Abstract [en]

    Large-scale exposure assessments that include both between- and within-city differences in air pollution levels are lacking. The objective of this study was to model long-term particle exposure for the whole of Sweden, separating long-range transport from local sources, which were further separated into combustion and road dust. Annual regional, urban and local traffic PM exposure contributions were modeled for 26,000 addresses from a national survey, using a European scale model, an urban model and a local traffic model. Total PM10 was overall dominated by the regional contribution, ranging from 3.5 mu g/m(3) (northernmost) to 13.5 mu g/m(3) (southernmost). Local traffic and urban sources contributed nationally on average to 16% of total PM10, but for urban populations this contribution was larger (for Stockholm around 30%). Generalized to the Swedish adult population, the average residential exposure contributions from regional, urban and local traffic PM10 were 10.2, 1.3 and 0.2 mu g/m(3), respectively. Corresponding exposure to PM, was 5.1, 0.5 and 0.03 mu g/m(3), respectively. Long-range transport dominates average Swedish residential PM1 and PM10 levels, but for urban populations the contributions from urban and local traffic sources are important and may even dominate for residences close to heavily trafficked roads. The study shows the importance of considering both national and city-scale gradients. The approach to exposure modeling at home addresses of a Swedish cohort includes both the regional scale and the urban and local traffic contributions to total PM exposure. With this we can resolve both between- and within-city gradients in national exposure assessments. The within-city exposure is further divided into a submicron (combustion) and a supermicron (road dust generated by studded tires) part. This gives new possibilities to study health impacts of different particles generated in Scandinavian cities. Journal of Exposure Science and Environmental Epidemiology (2013) 23, 306-314; doi:10.1038/jes.2012.122; published online 23 January 2013

  • 120. Gramsch, Ernesto
    et al.
    Gidhagen, Lars
    SMHI, Research Department, Air quality.
    Wahlin, Peter
    Oyola, Pedro
    Moreno, Francisco
    Predominance of soot-mode ultrafine particles in Santiago de Chile: Possible sources2009In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 43, no 14, p. 2260-2267Article in journal (Refereed)
    Abstract [en]

    A monitoring campaign was performed in Santiago de Chile during a winter month of 2003 and 2006 (July) using several instruments to measure the size distribution of particulate material. For the first time, the size distribution of ultrafine particles was measured in Santiago, and an estimation of its sources was done by analyzing its temporal variation. The study was performed in three sites: one of them is located in the eastern part of Santiago, a sector with low particle concentration and about 100 m from a busy street. The other site is located in the western part, which is the sector that has the highest concentration of fine and coarse particle matter during winter, also located far from a street. The third site is located within 5 in from the busiest street in Santiago. In all stations traffic is the dominating source for fine and ultrafine particles and the size distribution is peaked towards 60-100 nm (soot mode). Only in the site near the street, it is possible to see a clear peak towards smaller sizes (10-30 nm). The size distribution measurements presented here indicate that aerosol dynamics play a more important role for the Santiago case as compared to cleaner cities in Europe. Changes in the particle size during different hours of the day reflect both variations in meteorological mixing conditions as well as effects of aerosol dynamic processes such as coagulation, condensation and dry deposition. A relative increase in the number of the larger ultrafine particles (d >= 70 nm), as compared to the number of smaller particles (d < 70 nm) correlated with wind speed is an indication of pollution transport with aged particles from other parts of the city. (C) 2009 Elsevier Ltd. All rights reserved.

  • 121. Gramsch, Ernesto
    et al.
    Munoz, Alicia
    Langner, Joakim
    SMHI, Research Department, Air quality.
    Morales, Luis
    Soto, Cristian
    Perez, Patricio
    Rubio, Maria A.
    Black carbon transport between Santiago de Chile and glaciers in the Andes Mountains2020In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 232, article id 117546Article in journal (Refereed)
  • 122. Grote, Ruediger
    et al.
    Samson, Roeland
    Alonso, Rocio
    Amorim, Jorge Humberto
    SMHI, Research Department, Air quality.
    Carinanos, Paloma
    Churkina, Galina
    Fares, Silvano
    Le Thiec, Didier
    Niinemets, Ulo
    Mikkelsen, Teis Norgaard
    Paoletti, Elena
    Tiwary, Abhishek
    Calfapietra, Carlo
    Functional traits of urban trees: air pollution mitigation potential2016In: Frontiers in Ecology and the Environment, ISSN 1540-9295, E-ISSN 1540-9309, Vol. 14, no 10, p. 543-550Article in journal (Refereed)
  • 123. Haapanala, Paivi
    et al.
    Raisanen, Petri
    Kahnert, Michael
    SMHI, Research Department, Air quality.
    Nousiainen, Timo
    Sensitivity of the shortwave radiative effect of dust on particle shape: Comparison of spheres and spheroids2012In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 117, article id D08201Article in journal (Refereed)
    Abstract [en]

    The sensitivity of direct shortwave radiative effects of dust (DRE) to assumed particle shape is investigated. Radiative transfer simulations are conducted using optical properties of either spheres, mass-equivalent spheroids (mass-conserving case), or (mass-equivalent) spheroids whose number concentration is modified so that they have the same midvisible optical thickness (tau(545 nm)) as spheres (tau-conserving case). The impact of particle shape on DRE is investigated for different dust particle effective radii, optical thickness of the dust cloud, solar zenith angle, and spectral surface albedo (ocean, grass, and desert). It is found that the influence of particle shape on the DRE is strongest over ocean. It also depends very strongly on the shape distribution of spheroids used, to a degree that the results for two distributions of spheroids may deviate more from each other than from those for spheres. Finally, the effects of nonsphericity largely depend on whether the mass- or tau-conserving case is considered. For example, when using a shape distribution of spheroids recommended in a recent study for approximating the single-scattering properties of dust, the DRE at the surface differs at most 5% from that from spherical particles in the mass-conserving case. This stems from compensating nonsphericity effects on optical thickness, asymmetry parameter, and single-scattering albedo. However, in the tau-conserving case, the negative DRE at the surface can be up to 15% weaker for spheroids than spheres.

  • 124. Haapanala, Paivi
    et al.
    Raisanen, Petri
    McFarquhar, Greg M.
    Tiira, Jussi
    Macke, Andreas
    Kahnert, Michael
    SMHI, Research Department, Air quality.
    DeVore, John
    Nousiainen, Timo
    Disk and circumsolar radiances in the presence of ice clouds2017In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 17, no 11, p. 6865-6882Article in journal (Refereed)
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  • 125. Han, Z.
    et al.
    Sakurai, T.
    Ueda, H.
    Carmichael, G. R.
    Streets, D.
    Hayami, H.
    Wang, Z.
    Holloway, T.
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Hozumi, Y.
    Park, S. U.
    Kajino, M.
    Sartelet, K.
    Fung, C.
    Bennet, Cecilia
    SMHI, Research Department, Air quality.
    Thongboonchoo, N.
    Tang, Y.
    Chang, A.
    Matsuda, K.
    Amann, M.
    MICS-Asia II: Model intercomparison and evaluation of ozone and relevant species2008In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 42, no 15, p. 3491-3509Article in journal (Refereed)
    Abstract [en]

    Eight regional Eulerian chemical transport models (CTMs) are compared with each other and with an extensive set of observations including ground-level concentrations from EANET, ozone soundings from JMA and vertical profiles from the TRACE-P experiment to evaluate the models' abilities in simulating O(3) and relevant species (SO(2), NO, NO(2), HNO(3) and PAN) in the troposphere of East Asia and to look for similarities and differences among model performances. Statistical analysis is conducted to help estimate the consistency and discrepancy between model simulation and observation in terms of various species, seasons, locations, as well as attitude ranges. In general, all models show a good skill of simulating SO(2) for both ground level and the lower troposphere, although two of the eight models systematically overpredict SO(2) concentration. The model skills for O(3) vary largely with region and season. For ground-level O(3), model results are best correlated with observations in July 2001. Comparing with O(3) soundings measured in the afternoon reveals the best consistency among models in March 2001 and the largest disparity in O(3) magnitude in July 2001, although most models produce the best correlation in July as well. In terms of the statistics for the four flights of TRACE-P experiment, most models appear to be able to accurately capture the variability in the lower troposphere. The model performances for NO(x) are relatively poor, with lower correlation and with almost all models tending to underpredict NO(x) levels, due to larger uncertainties in either emission estimates or complex chemical mechanism represented. All models exhibit larger RMSE at altitudes < 2 km than 2-5.5 kin, mainly due to a consistent tendency of these models towards underprediction of the magnitude of intense plumes that often originate from near surface. Relatively lower correlation at altitudes 2-5.5 km may be attributed to the models' limitation in representing convection or potential chemical processes. Most of the key features in species distribution have been consistently reproduced by the participating models, such as the O(3) enhancement in the western Pacific Ocean in March and in northeast Asia in July, respectively, although the absolute model values may differ considerably from each other. Large differences are found among models in the southern parts of the domain for all the four periods, including southern China and northern parts of some Southeast Asia countries where the behaviors of chemical components and the ability of these models are still not clearly known because of a lack of observational databases. (C) 2007 Elsevier Ltd. All rights reserved.

  • 126. Hayami, Hiroshi
    et al.
    Sakurai, T.
    Han, Z.
    Ueda, H.
    Carmichael, G. R.
    Streets, D.
    Holloway, T.
    Wang, Z.
    Thongboonchoo, N.
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Bennet, Cecilia
    SMHI, Research Department, Air quality.
    Fung, C.
    Chang, A.
    Park, S. U.
    Kajino, M.
    Sartelet, K.
    Matsuda, K.
    Amann, M.
    MICS-Asia II: Model intercomparison and evaluation of particulate sulfate, nitrate and ammonium2008In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 42, no 15, p. 3510-3527Article in journal (Refereed)
    Abstract [en]

    Eight chemical transport models participate in a model intercomparison study for East Asia, MICS-Asia II. This paper analyzes calculated results for particulate matter of sulfate, nitrate and ammonium through comparisons with each other and with monthly measurements at EANET (the acid deposition monitoring network in East Asia) and daily measurements at Fukue, Japan. To the EANET measurements, model ensemble means better agree with model individual results for sulfate and total ammonium, although total nitrate is consistently and considerably underestimated. To measurements at Fukue, the models show better agreement than for the EANET measurements. This is likely because Fukue is centered in many of the model domains, whereas the EANET stations are mostly in Southeast Asia and Russia. Moreover, it would be important that Fukue is in Northeast Asia, where the emission inventory is more reliable than Southeast Asia. The model-model comparisons are made in view of the total amount in the atmosphere, vertical profile, coefficient of variation in surface concentrations, and transformation changes with distance. All the models show reasonable tendencies in vertical profiles and composition ratios. However, total amounts in the atmosphere are discrepant among the models. The consistency of the total amount in the atmosphere would influence source-receptor analysis. It seems that model results would be consistent, if the models take into account the primitive processes like emission, advection/diffusion, chemical transformation and dry/wet deposition, no matter the processes are modeled simply or comprehensively. Through the comparison study, we learned that it would be difficult to find any problems from one comparison (model-observation comparison with one data or many but at one station or in a short period). Modelers tend to examine model performances only from model-observation comparisons. However, taking budget in a certain or whole model domain would be important, before the models are applied to source-receptor analysis. (C) 2007 Elsevier Ltd. All rights reserved.

  • 127. Hedberg, E
    et al.
    Gidhagen, Lars
    SMHI, Research Department, Air quality.
    Johansson, C
    Source contributions to PM10 and arsenic concentrations in Central Chile using positive matrix factorization2005In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 39, no 3, p. 549-561Article in journal (Refereed)
    Abstract [en]

    Sampling of particles (PM10) was conducted during a one-year period at two rural sites in Central Chile, Quillota and Linares. The samples were analyzed for elemental composition. The data sets have undergone source-recepior analyses in order to estimate the sources and their abundance's in the PM10 size fraction. by using the factor analytical method positive matrix factorization (PMF). The analysis showed that PM10 was dominated by soil resuspension at both sites during the summer months, while during winter traffic dominated the particle mass at Quillota and local wood burning dominated the particle mass at Linares. Two copper smelters impacted the Quillota station, and contributed to 10% and 16% of PM10 as an average during summer and winter. respectively. One smelter impacted Linares by 8% and 19% of PM10 in the summer and winter, respectively. For arsenic the two smelters accounted for 87% of the monitored arsenic levels at Quillota and at Linares one smelter contributed with 72% of the measured mass. In comparison with PMF, the use of a dispersion model tended to overestimate the smelter contribution to arsenic levels at both sites. The robustness of the PMF model was tested by using randomly reduced data sets, where 85%, 70%, 50% and 33% of the samples were included. In this way the ability of the model to reconstruct the sources initially found by the original data set could be tested. On average for all sources the relative standard deviation increased from 7% to 25% for the variables identifying the sources, when decreasing the data set from 85% to 33% of the samples, indicating that the solution initially found was very stable to begin with. But it was also noted that sources due to industrial or combustion processes were more sensitive for the size of the data set, compared to the natural sources as local soil and sea spray sources. (C) 2004 Elsevier Ltd. All rights reserved.

  • 128. Hiemstra, J.A.
    et al.
    Saaroni, H.
    Amorim, Jorge Humberto
    SMHI, Research Department, Air quality.
    The Urban Heat Island: Thermal Comfort and the Role of Urban Greening2017In: The Urban Forest - Cultivating Green Infrastructure for People and the Environment / [ed] D. Pearlmutter, C. Calfapietra, R. Samson, L. O'Brien, S.K. Ostoić, G. Sanesi, R.A. del Amo, Springer International Publishing , 2017, p. 7-19Chapter in book (Refereed)
  • 129. Hillring, B
    et al.
    Krieg, Roland
    SMHI, Research Department, Air quality.
    Wind energy potential in southern Sweden - Example of planning methodology1998In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 13, no 4, p. 471-479Article in journal (Refereed)
    Abstract [en]

    This study presents a planning model for Swedish activities in the field of wind power. Models and results of calculations of the land-based wind energy potential with the Wind Atlas Analysis and Application Programme, WA(s)P, are described and analysed in a geographical information systems (GIS) called the ArcView(R) GIS system. One county in southern Sweden was chosen as a case study to present the methods used. The results from that case study indicate a great wind energy potential but there are nevertheless many factors limiting that potential. The study calls for a further development of planning tools in the field. Important areas for the future are the development of knowledge in market issues, wind power technology, environmental issues, and public opinion on constructing wind turbines. (C) 1998 Elsevier Science Ltd. All rights reserved.

  • 130. Hirtl, Marcus
    et al.
    Arnold, Delia
    Baro, Rocio
    Brenot, Hugues
    Coltelli, Mauro
    Eschbacher, Kurt
    Hard-Stremayer, Helmut
    Lipok, Florian
    Maurer, Christian
    Meinhard, Dieter
    Mona, Lucia
    Mulder, Marie D.
    Papagiannopoulos, Nikolaos
    Pernsteiner, Michael
    Plu, Matthieu
    Robertson, Lennart
    SMHI, Research Department, Air quality.
    Rokitansky, Carl-Herbert
    Scherllin-Pirscher, B.
    Sievers, Klaus
    Sofiev, Mikhail
    de Cerff, Wim Jan Som
    Steinheimer, Martin
    Stuefer, Martin
    Theys, Nicolas
    Uppstu, Andreas
    Wagenaar, Saskia
    Winkler, Roland
    Wotawa, Gerhard
    Zobl, Fritz
    Zopp, Raimund
    A volcanic-hazard demonstration exercise to assess and mitigate the impacts of volcanic ash clouds on civil and military aviation2020In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 20, no 6, p. 1719-1739Article in journal (Refereed)
    Download full text (pdf)
    A volcanic-hazard demonstration exercise to assess and mitigate the impacts of volcanic ash clouds on civil and military aviation
  • 131. Hole, Lars
    et al.
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Climate change impact on atmospheric nitrogen deposition in northwestern Europe: A model study2008In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 37, no 1, p. 9-17Article in journal (Refereed)
    Abstract [en]

    A high-resolution chemical transport model, driven by meteorology representing current and future climate, was used to investigate the effects of possible future changes in climate on nitrogen deposition in northwestern Europe. The model system was able to resolve the climatology of precipitation and chemical properties observed in northern Europe during the 1980s, albeit with some underestimation of the temporal and spatial variability of meteorological parameters and chemical components. The results point toward a substantial increase (30% or more) in nitrogen deposition over western Norway as a consequence of increasing precipitation but more moderate changes for other areas. Deposition of oxidized nitrogen will increase more than the deposition of reduced nitrogen. Over Sweden, oxidized nitrogen will increase only marginally and reduced nitrogen will decrease, although annual precipitation is expected to increase here as well. This is probably because more reduced nitrogen will be removed further west in Scandinavia because of the strong increase in precipitation along the Norwegian coast. The total deposition of oxidized nitrogen over Norway is expected to increase from 96 Gg N y(-1) during the current climate to 107 Gg N y(-1) by 2100 due only to changes in climate. The corresponding values for Sweden are more modest, from 137 Gg N y(-1) to 139 Gg N y(-1).

  • 132. Holloway, Tracey
    et al.
    Sakurai, Tatsuya
    Han, Zhiwei
    Ehlers, Susanna
    Spak, Scott N.
    Horowitz, Larry W.
    Carmichael, Gregory R.
    Streets, David G.
    Hozumi, Y.
    Ueda, Hiromasa
    Park, S. U.
    Fung, Christopher
    Kajino, M.
    Thongboonchoo, Narisara
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Bennet, Cecilia
    SMHI, Research Department, Air quality.
    Hayami, Hiroshi
    Sartelet, Karine
    Wang, Zifa
    Matsuda, K.
    Amann, Markus
    MICS-Asia II: Impact of global emissions on regional air quality in Asia2008In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 42, no 15, p. 3543-3561Article in journal (Refereed)
    Abstract [en]

    This study quantifies the seasonality and geographic variability of global pollutant inflow to Asia. Asia is often looked to as a major source of intercontinental air pollution transport with rising emissions and efficient pollutant export processes. However, the degree to which foreign emissions have been imported to Asia has not been thoroughly examined. The Model Inter-Comparison Study for Asia (MICS-Asia) is an international collaboration to study air pollution transport and chemistry in Asia. Using the global atmospheric chemistry Model of Ozone and Related Tracers (MOZART v. 2.4), and comparing results with a suite of regional models participating in MICS-Asia, we find that imported O-3 contributes significantly throughout Asia. The choice of upper boundary condition is found to be particularly important for O-3, even for surface concentrations. Both North America and Europe contribute to ground-level O-3 concentrations throughout the region, though the seasonality of these two sources varies. North American contributions peak at over 10% of monthly mean O-3 during winter months in East Asia, compared to Europe's spring- and autumn-maxima (5-8%). In comparison to observed data from the Acid Deposition Monitoring Network in East Asia (EANET), MOZART concentrations for 03 generally fall within the range of the MICS models, but MOZART is unable to capture the fine spatial variability of shorter-lived species as well as the regional models. (C) 2007 Elsevier Ltd. All rights reserved.

  • 133.
    Holmin Fridell, Sofi
    et al.
    SMHI, Core Services.
    Jones, Jörgen
    SMHI, Professional Services.
    Bennet, Cecilia
    SMHI, Research Department, Air quality.
    Södergren, Helena
    SMHI, Professional Services.
    Kindell, Sven
    SMHI, Professional Services.
    Andersson, Stefan
    SMHI, Research Department, Air quality.
    Jakobsson, Mattias
    SMHI, Professional Services.
    Luftkvaliteten i Sverige år 20302013Report (Other academic)
    Abstract [sv]

    Sveriges luftkvalitet påverkas av lokala och nationella utsläppskällor såväl som av emissioner från Europa. Utsläppen av många luftföroreningar har minskat under de senaste årtiondena tack vare kontinuerligt skärpta emissionskrav. Trots kraftiga minskningar av utsläppen både i Sverige och övriga Europa har inte luftkvaliteten i våra städer, med avseende på kvävedioxid (NO2), ozon (O3) och partiklar (PM10), förbättrats avsevärt det senaste decenniet. Inte heller har t.ex. surheten i Sveriges skogsmarker minskat sedan 1980-talet (Naturvårdsverket, a).SMHI genomförde under 2011 och 2012 en kartläggning av luftmiljö och deposition fram till år 2020 (Andersson et al, 2011 och Omstedt et al, 2012a). I detta fortsättningsprojekt har kartläggningen gjorts ytterligare 10 år framåt i tiden, till år 2030. Studien behandlar både lokal luftkvalitet och beräkningar av bakgrundshalter och deposition.Lokala beräkningar har utförts för 46 gator/vägar i eller i nära anslutning till tätortsmiljö. Beräkningarna omfattar halter av kvävedioxid och partiklar (PM10 och PM2.5). Deposition redovisas för svavel- och kväveföreningar uppdelat på total-, våt- samt torrdeposition.Lufthalter inklusive AOT40 redovisas för ozon.Lokalt uppvisar PM10 flest överskridandena av miljökvalitetsnormerna och miljökvalitetsmålet Frisk luft. Årsmedelvärdet varierar mellan de studerade gatumiljöerna från knappt 10 till 37 μg m–3, och 90-percentilen från knappt 17 till 80 μg m–3. Miljökvalitetsmålet för PM10 beräknas överskridas i 42 av de 46 studerade trafikmiljöerna.PM2.5-halterna ligger väl under miljökvalitetsnormen för samtliga studerade trafikmiljöer. Miljökvalitetsmålet överskrids i åtta av de 42 studerade trafikmiljöerna. Årsmedelvärdet varierar mellan4 och 12 μg m–3.För NO2 varierar årsmedelvärdet i de studerade städerna mellan 6 och 25 μg m–3, 98-percentilen av dygnsmedelvärden mellan 12 och 46 μg m–3 och 98-percentilen av timmedelvärdet mellan 16 och 67 μg m–3. Miljökvalitetsnormerna beräknas inte överskridas i någon av de studerade trafikmiljöerna. Miljökvalitetsmålet Frisk luft för NO2 avseende 98-percentil timmedelvärden överskrids i 4 av de 46 studerade miljöerna. För årsmedelvärden noteras inget överskridande av målet.För fyra gator har en känslighetsanalys genomförts där trafikökningen har hållits oförändrad jämfört med år 2008. Uteblivna trafikökningar till år 2030 jämfört med 2008 leder till minskade haltnivåer mellan 3 och 11 % för PM10 och NO2. PM2.5 påverkas endast marginellt av förändrade trafikflöden.Som följd av minskade emissioner kommer deposition av svavel och oxiderat kväve att minska till år 2030. Depositionen kommer vara fortsatt störst i södra Sverige. Depositionen av reducerat kväve kommer på de flesta platser vara oförändrad.Luftkvaliteten med avseende på marknära ozon kommer att förbättras i Sverige fram till år 2030. Halterna av ozon kommer fortsatt att ligga under miljökvalitetsmålet för ozons påverkan på grödor och skog.De största osäkerheterna i denna studie antas finnas i emissionsdata, trafikökningar på enskilda gator, fordonssammansättningen (t.ex. andelen dieselbilar) och andelen bilar med dubbdäck. I studien används meteorologin för år 2008 vilket gör att erhållna resultat inte inkluderarvariabilitet i meteorologin.

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  • 134. Huijnen, V.
    et al.
    Eskes, H. J.
    Poupkou, A.
    Elbern, H.
    Boersma, K. F.
    Foret, G.
    Sofiev, M.
    Valdebenito, A.
    Flemming, J.
    Stein, O.
    Gross, A.
    Robertson, Lennart
    SMHI, Research Department, Air quality.
    D'Isidoro, M.
    Kioutsioukis, I.
    Friese, E.
    Amstrup, B.
    Bergström, Robert
    SMHI, Research Department, Air quality.
    Strunk, A.
    Vira, J.
    Zyryanov, D.
    Maurizi, A.
    Melas, D.
    Peuch, V-H
    Zerefos, C.
    Comparison of OMI NO2 tropospheric columns with an ensemble of global and European regional air quality models2010In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 10, no 7, p. 3273-3296Article in journal (Refereed)
    Abstract [en]

    We present a comparison of tropospheric NO2 from OMI measurements to the median of an ensemble of Regional Air Quality (RAQ) models, and an intercomparison of the contributing RAQ models and two global models for the period July 2008 - June 2009 over Europe. The model forecasts were produced routinely on a daily basis in the context of the European GEMS ("Global and regional Earth-system (atmosphere) Monitoring using Satellite and in-situ data") project. The tropospheric vertical column of the RAQ ensemble median shows a spatial distribution which agrees well with the OMI NO2 observations, with a correlation r=0.8. This is higher than the correlations from any one of the individual RAQ models, which supports the use of a model ensemble approach for regional air pollution forecasting. The global models show high correlations compared to OMI, but with significantly less spatial detail, due to their coarser resolution. Deviations in the tropospheric NO2 columns of individual RAQ models from the mean were in the range of 20-34% in winter and 40-62% in summer, suggesting that the RAQ ensemble prediction is relatively more uncertain in the summer months. The ensemble median shows a stronger seasonal cycle of NO2 columns than OMI, and the ensemble is on average 50% below the OMI observations in summer, whereas in winter the bias is small. On the other hand the ensemble median shows a somewhat weaker seasonal cycle than NO2 surface observations from the Dutch Air Quality Network, and on average a negative bias of 14%. Full profile information was available for two RAQ models and for the global models. For these models the retrieval averaging kernel was applied. Minor differences are found for area-averaged model columns with and without applying the kernel, which shows that the impact of replacing the a priori profiles by the RAQ model profiles is on average small. However, the contrast between major hotspots and rural areas is stronger for the direct modeled vertical columns than the columns where the averaging kernels are applied, related to a larger relative contribution of the free troposphere and the coarse horizontal resolution in the a priori profiles compared to the RAQ models. In line with validation results reported in the literature, summertime concentrations in the lowermost boundary layer in the a priori profiles from the DOMINO product are significantly larger than the RAQ model concentrations and surface observations over the Netherlands. This affects the profile shape, and contributes to a high bias in OMI tropospheric columns over polluted regions. The global models indicate that the upper troposphere may contribute significantly to the total column and it is important to account for this in comparisons with RAQ models. A combination of upper troposphere model biases, the a priori profile effects and DOMINO product retrieval issues could explain the discrepancy observed between the OMI observations and the ensemble median in summer.

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  • 135.
    Häggkvist, Kenneth
    et al.
    SMHI, Professional Services.
    Persson, Christer
    SMHI, Research Department, Air quality.
    Robertson, Lennart
    SMHI, Research Department, Air quality.
    Spridningsberäkningar rörande gasutsläpp från ett antal källor inom SSAB Luleå-verken1986Report (Other academic)
  • 136. Im, Ulas
    et al.
    Christensen, Jesper H.
    Nielsen, Ole-Kenneth
    Sand, Maria
    Makkonen, Risto
    Geels, Camilla
    Andersson, Camilla
    SMHI, Research Department, Air quality.
    Kukkonen, Jaakko
    Lopez-Aparicio, Susana
    Brandt, Jorgen
    Contributions of Nordic anthropogenic emissions on air pollution and premature mortality over the Nordic region and the Arctic2019In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 19, no 20, p. 12975-12992Article in journal (Refereed)
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  • 137. Im, Ulas
    et al.
    Tsigaridis, Kostas
    Faluvegi, Gregory
    Langen, Peter L.
    French, Joshua P.
    Mahmood, Rashed
    Thomas, Manu
    SMHI, Research Department, Air quality.
    von Salzen, Knut
    Thomas, Daniel C.
    Whaley, Cynthia H.
    Klimont, Zbigniew
    Skov, Henrik
    Brandt, Jorgen
    Present and future aerosol impacts on Arctic climate change in the GISS-E2.1 Earth system model2021In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 21, no 13, p. 10413-10438Article in journal (Refereed)
    Abstract [en]

    The Arctic is warming 2 to 3 times faster than the global average, partly due to changes in short-lived climate forcers (SLCFs) including aerosols. In order to study the effects of atmospheric aerosols in this warming, recent past (1990-2014) and future (2015-2050) simulations have been carried out using the GISS-E2.1 Earth system model to study the aerosol burdens and their radiative and climate impacts over the Arctic (> 60 degrees N), using anthropogenic emissions from the Eclipse V6b and the Coupled Model Inter-comparison Project Phase 6 (CMIP6) databases, while global annual mean greenhouse gas concentrations were prescribed and kept fixed in all simulations. Results showed that the simulations have underestimated observed surface aerosol levels, in particular black carbon (BC) and sulfate (SO42-), by more than 50 %, with the smallest biases calculated for the atmosphere-only simulations, where winds are nudged to reanalysis data. CMIP6 simulations performed slightly better in reproducing the observed surface aerosol concentrations and climate parameters, compared to the Eclipse simulations. In addition, simulations where atmosphere and ocean are fully coupled had slightly smaller biases in aerosol levels compared to atmosphere-only simulations without nudging. Arctic BC, organic aerosol (OA), and SO(4)(2-)burdens decrease significantly in all simulations by 10 %-60% following the reductions of 7 %-78% in emission projections, with the Eclipse ensemble showing larger reductions in Arctic aerosol burdens compared to the CMIP6 ensemble. For the 2030-2050 period, the Eclipse ensemble simulated a radiative forcing due to aerosol-radiation interactions (RFARI) of -0.39 +/- 0.01Wm(-2), which is -0.08Wm(-2) larger than the 1990-2010 mean forcing (-0.32Wm(-2)), of which -0.24 +/- 0.01Wm(-2) was attributed to the anthropogenic aerosols. The CMIP6 ensemble simulated a RFARI of --0.35 to -0.40Wm(-2) for the same period, which is -0.01 to -0.06Wm(-2) larger than the 1990-2010 mean forcing of 0.35Wm(-2). The scenarios with little to no mitigation (worst-case scenarios) led to very small changes in the RFARI, while scenarios with medium to large emission mitigations led to increases in the negative RFARI, mainly due to the decrease in the positive BC forcing and the decrease in the negative SO42- forcing. The anthropogenic aerosols accounted for -0.24 to -0.26Wm(-2) of the net RFARI in 2030-2050 period, in Eclipse and CMIP6 ensembles, respectively. Finally, all simulations showed an increase in the Arctic surface air temperatures throughout the simulation period. By 2050, surface air temperatures are projected to increase by 2.4 to 2.6 degrees C in the Eclipse ensemble and 1.9 to 2.6 degrees C in the CMIP6 ensemble, compared to the 1990-2010 mean. Overall, results show that even the scenarios with largest emission reductions leads to similar impact on the future Arctic surface air temperatures and sea-ice extent compared to scenarios with smaller emission reductions, implying reductions of greenhouse emissions are still necessary to mitigate climate change.

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    Present and future aerosol impacts on Arctic climate change in the GISS-E2.1 Earth system model
  • 138.
    Jansson, Anna
    et al.
    SMHI, Core Services.
    Persson, Christer
    SMHI, Research Department, Air quality.
    Strandberg, Gustav
    SMHI, Research Department, Climate research - Rossby Centre.
    2D meso-scale re-analysis of precipitation, temperature and wind over Europe - ERAMESAN: Time period 1980-20042007Report (Other academic)
    Abstract [en]

    The need for long time series of gridded meteorological data with a fine spatial and temporal resolution has increased in recent years. The requirements for this type of gridded meteorological data fields arise from many different areas of the society, in connection to atmospheric environment studies of air quality and deposition and trends in these parameters, regional climate change, wind energy, hydrological studies etc. The aim of the present project is to investigate the possibility of producing historical, high quality and time consistent, meso-scale re analyses for the whole of Europe regarding precipitation, 2 m temperature and wind for at least 25 years back in time.The MESAN analysis system (Häggmark et al., 2000) at SMHI was chosen as a basis for the reanalysis and the system was adjusted to cover the whole of Europe. In order to find the most appropriate first guess fields to be used in the MESAN system, a pilot study was performed. ERA- 40 data from ECMWF was selected as best possible first guess fields for the re analysis. The performed re-analysis, which is denoted ERAMESAN, includes gridded data covering all Europe with a time resolution of 6 h and a spatial resolution of 0.1º (11 km) in a rotated latitude longitude coordinate system for the time-period 1980-2004. All analyses are archived in GRIB-format and stored on disc at SMHI. The dataset is also available within the EUMETNET optional programme Showcase EUROGRID.A partial validation for the years 1998-2000, using a cross validation procedure with independent observations (5.5% of the total amount of stations), shows an improvement in ERAMESAN compared to the ERA-40 data for all studied parameters with regard to root mean square deviation, mean absolute deviation and mean bias deviation for all seasons. The deviations are roughly of the order of 15% smaller compared to what is obtained from ERA-40. The frequency distribution of large precipitation amounts per day and high wind speeds are substantially better described in ERAMESAN compared to ERA-40. However, the tendency to underestimate the frequency of very large precipitation amounts or high wind speeds, compared to observations, can be seen also for ERAMESAN. It is important to be aware of this limitation when using ERAMESAN data for practical applications concerning evaluation of risks for extreme wind speeds or very large precipitation amounts or in e.g. wind energy studies.

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  • 139. Jenkin, M. E.
    et al.
    Khan, M. A. H.
    Shallcross, D. E.
    Bergström, Robert
    SMHI, Research Department, Air quality.
    Simpson, D.
    Murphy, K. L. C.
    Rickard, A. R.
    The CRI v2.2 reduced degradation scheme for isoprene2019In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 212, p. 172-182Article in journal (Refereed)
  • 140. Johansson, Christer
    et al.
    Norman, Michael
    Gidhagen, Lars
    SMHI, Research Department, Air quality.
    Spatial & temporal variations of PM10 and particle number concentrations in urban air2007In: Environmental Monitoring & Assessment, ISSN 0167-6369, E-ISSN 1573-2959, Vol. 127, no 1-3, p. 477-487Article in journal (Refereed)
    Abstract [en]

    The size of particles in urban air varies over four orders of magnitude (from 0.001 mu m to 10 mu m in diameter). In many cities only particle mass concentrations (PM10, i.e. particles < 10 mu m diameter) is measured. In this paper we analyze how differences in emissions, background concentrations and meteorology affect the temporal and spatial distribution of PM10 and total particle number concentrations (PNC) based on measurements and dispersion modeling in Stockholm, Sweden. PNC at densely trafficked kerbside locations are dominated by ultrafine particles (< 0.1 mu m diameter) due to vehicle exhaust emissions as verified by high correlation with NOx. But PNC contribute only marginally to PM10, due to the small size of exhaust particles. Instead wear of the road surface is an important factor for the highest PM10 concentrations observed. In Stockholm, road wear increases drastically due to the use of studded tires and traction sand on streets during winter; up to 90% of the locally emitted PM10 may be due to road abrasion. PM10 emissions and concentrations, but not PNC, at kerbside are controlled by road moisture. Annual mean urban background PM10 levels are relatively uniformly distributed over the city, due to the importance of long range transport. For PNC local sources often dominate the concentrations resulting in large temporal and spatial gradients in the concentrations. Despite these differences in the origin of PM10 and PNC, the spatial gradients of annual mean concentrations due to local sources are of equal magnitude due to the common source, namely traffic. Thus, people in different areas experiencing a factor of 2 different annual PM10 exposure due to local sources will also experience a factor of 2 different exposure in terms of PNC. This implies that health impact studies based solely on spatial differences in annual exposure to PM10 may not separate differences in health effects due to ultrafine and coarse particles. On the other hand, health effect assessments based on time series exposure analysis of PM10 and PNC, should be able to observe differences in health effects of ultrafine particles versus coarse particles.

  • 141. Johansson, Julia M.
    et al.
    Watne, Agot K.
    Karlsson, Per Erik
    Karlsson, Gunilla Pihl
    Danielsson, Helena
    Andersson, Camilla
    SMHI, Research Department, Air quality.
    Pleijel, Hakan
    The European heat wave of 2018 and its promotion of the ozone climate penalty in southwest Sweden2020In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 25, p. 39-50Article in journal (Refereed)
    Abstract [en]

    The ozone concentration ([O-3]), temperature (T) and vapour pressure deficit (VPD) during the 2018 heat wave (HW) was compared with conditions from 2013-2017. The study included one coastal and two inland sites in southwest Sweden. The positive relationship between [O-3] and T was stronger in 2018. The average daytime T from April-September was higher by 2.0-2.4 degrees C in 2018. The VPD was strongly and positively affected by the 2018 HW. The daytime mean [O-3] was enhanced by 7-12% in 2018. The relationship between hourly daytime [O-3] and T, as well as that between the daily maximum [O-3] and daily maximum T, was steeper in 2018. The stronger promotion of [O-3] by T in 2018 was possibly partly a result of dry conditions causing stomatal closure of vegetation and thus a weaker O-3 sink. If HWs like that in 2018 become more common, they can be expected to promote higher [O-3] and risk larger health and ecosystem effects.

  • 142. Jonsson, Oskar
    et al.
    Andersson, Camilla
    SMHI, Research Department, Air quality.
    Forsberg, Bertil
    Johansson, Christer
    Air pollution episodes in Stockholm regional background air due to sources in Europe and their effects on human population2013In: Boreal environment research, ISSN 1239-6095, E-ISSN 1797-2469, Vol. 18, no 3-4, p. 280-302Article in journal (Refereed)
    Abstract [en]

    Using air quality measurements, we categorized air pollution according to source sectors in a rural background environment in southern Sweden based on hourly air-mass backward trajectories during 1997-2010. Concentrations of fine (PM2.5) and sum of fine and coarse particulate matter (PM10), accumulation mode particle number, black carbon and surface ozone were 4.0, 3.9, 4.5, 6.8 and 1.3 times higher, respectively, in air masses from the southeast as compared with those in air masses from the cleanest sector in the northwest, consistent with air-mass transport over areas with relatively high emissions of primary particulate matter (PM) and secondary PM precursors. The highest ultrafine particle numbers were associated with clean air from the northwest. We estimate that almost 7.8% and 0.6% higher premature human mortality is caused by PM2.5 and ozone exposure, respectively, when air originates from the southeast as compared with that when air originates from the northwest. Reductions of emissions in eastern Europe would reduce the highest air pollution concentrations and associated health risks. However, since air masses from the southwest are more frequent, emissions in the western part of Europe are more important for annual mean premature mortality.

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  • 143. Jonsson, P
    et al.
    Bennet, Cecilia
    SMHI, Research Department, Air quality.
    Eliasson, I
    Lindgren, E S
    Suspended particulate matter and its relations to the urban climate in Dar es Salaam, Tanzania2004In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 38, no 25, p. 4175-4181Article in journal (Refereed)
    Abstract [en]

    Relationships between sources and levels of particulate matter and climatic parameters (urban heat island intensity, wind speed, temperature and relative humidity) were investigated in the coastal city of Dar es Salaam, Tanzania's largest city. Measurements were made during the wet and dry seasons of 2001 at an urban and a rural site. Five elements were used to represent different sources: K in fine particles (biomass), Zn in fine particles (industry), Cl in coarse particles (sea spray), Ti in coarse particles (soil) and Pb in fine particles (traffic). The concentrations of these elements varied considerably between the urban and rural site during both the wet and dry season, with the urban site in the dry season having the highest concentrations. Diurnal differences are also apparent, although not as straightforward. In an attempt to explain these differences, correlations between all elements and the climatic parameters were investigated. The results show that the nocturnal urban heat island intensity was positively correlated and wind speed negatively correlated with particulate levels, presumably due to the increased atmospheric stability. (C) 2004 Elsevier Ltd. All rights reserved.

  • 144.
    Kahnert, Michael
    SMHI, Research Department, Air quality.
    Boundary symmetries in linear differential and integral equation problems applied to the self-consistent Green's function formalism of acoustic and electromagnetic scattering2006In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 265, no 2, p. 383-393Article in journal (Refereed)
    Abstract [en]

    Explicit symmetry relations for the Green's function subject to homogeneous boundary conditions are derived for arbitrary linear differential or integral equation problems in which the boundary surface has a set of symmetry elements. For corresponding homogeneous problems subject to inhomogeneous boundary conditions implicit symmetry relations involving the Green's function are obtained. The usefulness of these symmetry relations is illustrated by means of a recently developed self-consistent Green's function formalism of electromagnetic and acoustic scattering problems applied to the exterior scattering problem. One obtains explicit symmetry relations for the volume Green's function, the surface Green's function, and the interaction operator, and the respective symmetry relations are shown to be equivalent. This allows us to treat boundary symmetries of volume-integral equation methods, boundary-integral equation methods, and the T matrix formulation of acoustic and electromagnetic scattering under a common theoretical framework. By specifying a specific expansion basis the coordinate-free symmetry relations of, e.g., the surface Green's function can be brought into the form of explicit symmetry relations of its expansion coefficient matrix. For the specific choice of radiating spherical wave functions the approach is illustrated by deriving unitary reducible representations of non-cubic finite point groups in this basis, and by deriving the corresponding explicit symmetry relations of the coefficient matrix., The reducible representations can be reduced by group-theoretical techniques, thus bringing the coefficient matrix into block-diagonal form, which can greatly reduce ill-conditioning problems in numerical applications. (c) 2006 Elsevier B.V. All rights reserved.

  • 145.
    Kahnert, Michael
    SMHI, Research Department, Air quality.
    Electromagnetic scattering by nonspherical particles: Recent advances2010In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 111, no 11, p. 1788-1790Article in journal (Other academic)
    Abstract [en]

    This note gives a short introduction to the reprint of the article "Numerical methods in electromagnetic scattering theory" by Kahnert, M (JQSRT 2003:79-80:775-824). Some of the most important developments in the field since the publication of this article are briefly reviewed. A list of typos that have been identified in the original article is given in the appendix. (C) 2009 Elsevier Ltd. All rights reserved.

  • 146.
    Kahnert, Michael
    SMHI, Research Department, Air quality.
    Information constraints in variational data assimilation2018In: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 144, no 716, p. 2230-2244Article in journal (Refereed)
  • 147.
    Kahnert, Michael
    SMHI, Research Department, Air quality.
    Irreducible representations of finite groups in the T-matrix formulation of the electromagnetic scattering problem2005In: Optical Society of America. Journal A: Optics, Image Science, and Vision, ISSN 1084-7529, E-ISSN 1520-8532, Vol. 22, no 6, p. 1187-1199Article in journal (Refereed)
    Abstract [en]

    For particles with discrete geometrical symmetries, a group-theoretical method is presented for transforming the matrix quantities in the T-matrix description of the electromagnetic scattering problem from the reducible basis of vector spherical wave functions into a new basis in which all matrix quantities become block diagonal. The notorious ill-conditioning problems in the inversion of the Q matrix are thus considerably alleviated, and the matrix inversion becomes numerically more expedient. The method can be applied to any point group. For the specific example of the D-6h group, it is demonstrated that computations in the new basis are faster by a factor of 3.6 as compared with computations that use the reducible basis. Most importantly, the method is capable of extending the range of size parameters for which convergent results can be obtained by 50%. (c) 2005 Optical Society of America

  • 148.
    Kahnert, Michael
    SMHI, Research Department, Air quality.
    Light scattering by particles with boundary symmetries2008In: Light Scattering Reviews 3: Light Scattering and Reflection / [ed] Kokhanovsky, Alexander, Berlin: Springer , 2008, p. 69-107Chapter in book (Refereed)
  • 149.
    Kahnert, Michael
    SMHI, Research Department, Air quality.
    Modelling radiometric properties of inhomogeneous mineral dust particles: Applicability and limitations of effective medium theories2015In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 152, p. 16-27Article in journal (Refereed)
    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.

  • 150.
    Kahnert, Michael
    SMHI, Research Department, Air quality.
    Modelling the optical and radiative properties of freshly emitted light absorbing carbon within an atmospheric chemical transport model2010In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 10, no 3, p. 1403-1416Article in journal (Refereed)
    Abstract [en]

    Light absorbing carbon (LAC) aerosols have a complex, fractal-like aggregate structure. Their optical and radiative properties are notoriously difficult to model, and approximate methods may introduce large errors both in the interpretation of aerosol remote sensing observations, and in quantifying the direct radiative forcing effect of LAC. In this paper a numerically exact method for solving Maxwell's equations is employed for computing the optical properties of freshly emitted, externally mixed LAC aggregates. The computations are performed at wavelengths of 440 nm and 870 nm, and they cover the entire size range relevant for modelling these kinds of aerosols. The method for solving the electromagnetic scattering and absorption problem for aggregates proves to be sufficiently stable and fast to make accurate multiple-band computations of LAC optical properties feasible. The results from the electromagnetic computations are processed such that they can readily be integrated into a chemical transport model (CTM), which is a prerequisite for constructing robust observation operators for chemical data assimilation of aerosol optical observations. A case study is performed, in which results obtained with the coupled optics/CTM model are employed as input to detailed radiative transfer computations at a polluted European location. It is found that the still popular homogeneous sphere approximation significantly underestimates the radiative forcing at top of atmosphere as compared to the results obtained with the aggregate model. Notably, the LAC forcing effect predicted with the aggregate model is less than that one obtains by assuming a prescribed mass absorption cross section for LAC.

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