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  • 251.
    Carlsson, Bengt
    SMHI, Forskningsavdelningen, Hydrologi.
    Hydrokemiska data från de svenska fältforskningsområdena1985Rapport (Annet vitenskapelig)
    Abstract [sv]

    En viktig uppgift för SMHI är att övervaka och fortlöpande geupplysningar om hydrologiska data i Sverige. I och med övertagandet1979 av ansvaret för de av NFR upprättade FältForsknings~mrådena (FFO) har även hydrokemin kommit att utgöra ennaturlig del av SMHis verksamhetsområde.Denna rapport utgör en första publicering av de hydrokemiskadata med korresponderande vattenföringsdata, som idag, 1985,finns på SMHI i FFO-arkivet. Materialet presenteras här iform av tidsdiagram samt en tabell över de analyserade variablernasmedelvärden. Ytterligare en del äldre material frånIHD-områden finns fortfarande utspritt på andra institutionermen skall så småningom läggas in i FFO-arkivet. Rapporteninnehåller också en kortfattad beskrivning av varje område.Inga försök till utvärdering har gjorts. Dock har observeratsen viss skillnad i haltnivå för bl a Cl och N0 2 från IHDperioden1965-75 (analyserade av MISU) jämfört med perioden1979-84 (analyserade av SMHI). Orsaken skall utredas. Avsiktenär att på ett överskådligt sätt redovisa vilka data, somfinns tillgängliga för forskningsändamål.

  • 252.
    Carlsson, Bengt
    SMHI, Forskningsavdelningen, Hydrologi.
    Some facts about the Torne and Kalix River Basins. A contribution to the NEWBALTIC II workshop in Abisko June 19991999Rapport (Annet vitenskapelig)
    Abstract [en]

    The Torne and Kalix rivers rise in the uppermost north west part of Sweden and their basins are situated between approximately 65°50N and 69°N as shown in Figure 1. The size basin of the two river basins is about 58 000 km2 of which 14 500 km2 (25%) is situated in Finland and 350 km 2 (0.6%) in Norway. The remaining, 43 150km2, makes up 9.7% of the area of Sweden. Data presented in this paper originate from Swedish measurements. Finnish data of snow and evaporation from the east of the Torne River basin can be find in the FinnishHydrological Yearbook (1994), which also includes some statistics for the period 1961-90.

    The density of population is very low, about three people per square kilometre. People are mostly living in the river valleys near the coast, the towns of Haparanda, Torneo and Kalix, or in ore-mining centres like Kiruna.

    Most of the basin can be characterised as a flat forest and mire area. The mountains in the north west part compose only 7-8 % of the total drainage basin. The runoff regime is thus characterised by a flow maximum produced by the snowmelt in the forest and swamp region. The mountains are very old. They were formed during the paleozoic era 300 000 000 years ago. As can be seen in Figure 3 at least 1/3 of the basin area is situated below 200masl andalso about 1/3 above the 500m elevation line.

    Topography is further described in Figure 3.

    As can be seen from Table I, the Torne River is number two and the Kalix River number 10 in drainage area order of the Swedish rivers. Due to dominating south-west winds and orographic effects, the Abisko region has a proportionately low precipitation. The specific runoff of the Torne River is thus lower then other Swedish rivers in this part of Sweden.

  • 253.
    Carlsson, Bengt
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Bergström, Sten
    SMHI, Forskningsavdelningen, Hydrologi.
    The TELFLOOD project: Rainfall – Runoff Modelling and forecasting1998Rapport (Annet vitenskapelig)
    Abstract [en]

    The aim of the TELFLOOD project is to improve methods for hydrological forecasting in steep

    catchments. The hydrological modelling task of SMHI has been to improve the HBV model and to

    develop and test routines for model updating and forecasting.

    A new response routine, based on the variable contributing area concept, has been developed and

    proved to be successful in several experimental basins in Sweden, Italy and Ireland

    . The technique

    uses the contributing area in a way that is consistent with the procedure for soil moisture accounting

    and does not require further free parameters. Model improvements are significant to the standard

    HBV-96 version, in particular as concems minor floods after dry periods.

    A new updating routine, based on state corrections of the storages of the HBV model, was

    developed and tested. For some events it proved to be more efficient than the standard method

    based on input corrections.

  • 254.
    Carlsson, Bengt
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Bergström, Sten
    SMHI, Samhälle och säkerhet.
    Andréasson, Johan
    SMHI, Affärsverksamhet.
    Hellström, Sara-Sofia
    SMHI, Samhälle och säkerhet.
    Framtidens översvämningsrisker2006Rapport (Annet vitenskapelig)
    Abstract [sv]

    På uppdrag av Länsförsäkringsbolagens Forskningsfond har en studie av framtidens översvämningsrisker i Sverige genomförts. Arbetet har koncentrerats till Dalälven, och de stora sjöarna Vänern, Mälaren och Hjälmaren, men en del landsomfattande analyser har också genomförts. Metodiken baserades på två globala klimatmodeller, två antaganden om framtida utsläpp av växthusgaser och en regional klimatmodell för dynamisk nedskalning till svenska förhållanden. De regionala klimatscenarierna har vidarebearbetats med hjälp av den hydrologiska HBV-modellen och de beräknade vattenflödena och vattenstånden behandlades statistiskt med frekvensanalys. Resultaten visar att den framtida riskexponeringen ändras olika i olika delar av landet. Situationen tycks förvärras speciellt i Vänerområdet och längs Göta älv. Det blir också högre risker för översvämningar i de västliga delarna av fjällkedjan. Riskerna för skyfall, som kan skapa allvarliga lokala översvämningar, ökar sannolikt, även om det är svårt att urskilja ett gemensamt mönster i klimatscenarierna. Studien har också behandlat osäkerheterna i bedömningen av översvämningsriskerna. Det är tydligt att osäkerheten i de globala klimatscenarierna svara för en stor del av osäkerheterna i slutresultaten, men det finns också osäkerheter orsakade av valet av strategi för att överföra klimatförändringssignalen från klimatmodeller till den hydrologiska modellen.

  • 255.
    Carlsson, Bengt
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Lindström, Göran
    SMHI, Forskningsavdelningen, Hydrologi.
    HBV-modellen och flödesprognoser2001Rapport (Annet vitenskapelig)
    Abstract [sv]
    • Olika uppdateringsmetoder för HBV-modellen har utvecklats och jämförts. Metoderna har utvärderats i simuleringsexperiment där modellkörningar med observerade data användes som meteorologisk prognos. De olika uppdateringsmetoder som testats är dels autoregressiva, dvs de bygger på en korrektion av uppmätt fel före prognosens början, dels sådana som bygger på en uppdatering av indata dvs nederbörd och temperatur och slutligen sådana där modellens tillståndsvariabler uppdateras. Resultaten visar att alla metoderna medför en förbättrad avrinningsprognos. Ingen av metoderna kan dock sägas vara den bästa vid alla tillfällen. AR-metoden gav bäst resultat vid högsta flöden, t ex i samband med snösmältning, medan uppdatering av modellens tillstånd gav något bättre resultat vid regnflöden. Om en modell skall användas för prognoser i samband med höga flöden är det viktigt att man redan vid kalibreringen tar hänsyn till detta och kalibrerar med hänsyn till just toppflöden, som annars systematiskt kommer att underskattas.
    • Effekten av en uppdatering avklingar jämförelsevis snabbt. Vid långtidsprognoser är det troligt att en kombination av nu testade metoder och uppdatering av t ex snömagasin och de faktorer som speciellt påverkar snösmältningen, dvs. temperatur och kanske t o m modellens graddagfaktor, skulle ge en bättre prognos.
  • 256.
    Carlsson, Bengt
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Sanner, Håkan
    SMHI, Samhälle och säkerhet.
    Influence of river regulation on runoff to the Gulf of Bothnia: Gulf of Bothnia Year 19911994Rapport (Annet vitenskapelig)
  • 257.
    Carlsson, Bengt
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Sanner, Håkan
    SMHI.
    Modelling influence of river regulation on runoff to the Gulf of Bothnia1996Inngår i: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 27, nr 5, s. 337-350Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Runoff from a land area of approximately 490,000 km(2) enters the Gulf of Bothnia. This runoff is of essential importance for the flushing of the Gulf. a change in the volume of runoff effects the residence time. There are many natural as well as man made changes in the runoff, both in the form of long-term changes over many years and those occurring within one year. The most significant man made changes come from hydropower regulation. This report describes the effect on runoff from the development of the hydropower plants in Sweden and Finland by means of comparing recorded regulated runoff and simulated natural runoff. A recent time period, 1980-91, and a time period before regulation, 1925-36, were simulated. The monthly magnitudes of the redistributed flows were found to be on average 1,700 m(3)/s. The maximum redistributed monthly flow in May - June reached 5,000-6,000 m(3)/s.

  • 258.
    Carlund, Thomas
    et al.
    SMHI, Samhälle och säkerhet.
    Håkansson, Bertil
    SMHI, Forskningsavdelningen, Oceanografi.
    Land, P
    Aerosol optical depth over the Baltic Sea derived from AERONET and SeaWiFS measurements2005Inngår i: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 26, nr 2, s. 233-245Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three years of data on aerosol optical depth (tau(a)) from the Aerosol Robotic Network (AERONET) station on the island of Gotland in the Baltic Sea have been analysed and compared with Sea-viewing Wide Field of view Sensor (SeaWiFS) data. Normally, the atmosphere over Gotland could be considered as clear, with a daily median value Of tau(a) at 500 nm of about 0.08. The median value of Angstrom's wavelength exponent (alpha) for wavelengths between 440 nm and 870 nm was 1.37, indicating that the dominant aerosol is more of a continental than of a pure maritime type. SeaWiFS GAC level 2 data on tau(a) and alpha were compared to data from the ground-based AERONET station. For the 37 cases of simultaneous satellite and ground-based measurements under cloud-free skies it was found that, on average, the value of tau(a)(865 nm) from SeaWiFS was about 0.02 higher than tau(a)(870 nm) from the AERONET station. At the same time approximate tau(a)(440 nm) from SeaWiFS was about 0.03 lower than tau(a)(440 nm) of AERONET. alpha(510, 865) from SeaWiFS was, on average, 1.2 lower than alpha(500, 870) from the AERONET measurements. These results cannot explain the very frequent occurences of negative values of normalized water-leaving radiance at 412 nm and 443 nm in the SeaWiFS reprocessing #3 data.

  • 259.
    Carlund, Thomas
    et al.
    SMHI, Samhälle och säkerhet.
    Landelius, Tomas
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Josefsson, Weine
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Comparison and uncertainty of aerosol optical depth estimates derived from spectral and broadband measurements2003Inngår i: Journal of applied meteorology (1988), ISSN 0894-8763, E-ISSN 1520-0450, Vol. 42, nr 11, s. 1598-1610Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An experimental comparison of spectral aerosol optical depth tau(a,lambda) derived from measurements by two spectral radiometers [a LI-COR, Inc., LI-1800 spectroradiometer and a Centre Suisse d'Electronique et de Microtechnique (CSEM) SPM2000 sun photometer] and a broadband field pyrheliometer has been made. The study was limited to three wavelengths ( 368, 500, and 778 nm), using operational calibration and optical depth calculation procedures. For measurements taken on 32 days spread over 1 yr, the rms difference in tau(a,lambda) derived from the two spectral radiometers was less than 0.01 at 500 and 778 nm. For wavelengths shorter than 500 nm and longer than 950 nm, the performance of the LI-1800 in its current configuration did not permit accurate determinations of tau(a,lambda). Estimates of spectral aerosol optical depth from broadband pyrheliometer measurements using two models of the Angstromngstrom turbidity coefficient were examined. For the broadband method that was closest to the sun photometer results, the mean (rms) differences in tau(a,lambda) were 0.014 (0.028), 0.014 (0.019), and 0.013 ( 0.014) at 368, 500, and 778 nm. The mean differences are just above the average uncertainties of the sun photometer tau(a,lambda) values (0.012, 0.011, and 0.011) for the same wavelengths, as determined through a detailed uncertainty analysis. The amount of atmospheric water vapor is a necessary input to the broadband methods. If upper-air sounding data are not available, water vapor from a meteorological forecast model yields significantly better turbidity results than does using estimates from surface measurements of air temperature and relative humidity.

  • 260. Carmichael, G R
    et al.
    Calori, G
    Hayami, H
    Uno, I
    Cho, S Y
    Engardt, Magnuz
    SMHI, Forskningsavdelningen, Luftmiljö.
    Kim, S B
    Ichikawa, Y
    Ikeda, Y
    Woo, J H
    Ueda, H
    Amann, M
    The MICS-Asia study: model intercomparison of long-range transport and sulfur deposition in East Asia2002Inngår i: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 36, nr 2, s. 175-199Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An intercomparison study involving eight long-range transport models for sulfur deposition in East Asia has been initiated, The participating models included Eulerian and Lagrangian frameworks, with a wide variety of vertical resolutions and numerical approaches. Results from this study, in which models used common data sets for emissions, meteorology, and dry, wet and chemical conversion rates, are reported and discussed. Model results for sulfur dioxide and sulfate concentrations, wet deposition amounts, for the period January and May 1993, are compared with observed quantities at 18 surface sites in East Asia. At many sites the ensemble of models is found to have high skill in predicting observed quantities. At other sites all models show poor predictive capabilities. Source-receptor relationships estimated by the models are also compared. The models show a high degree of consistency in identifying the main source-receptor relationships, as well as in the relative contributions of wet/dry pathways for removal. But at some locations estimated deposition amounts can vary by a factor or 5. The influence of model structure and parameters on model performance is discussed. The main factors determining the deposition fields are the emissions and underlying meteorological fields. Model structure in terms of vertical resolution is found to be more important than the parameterizations used for chemical conversion and removal, as these processes are highly coupled and often work in compensating directions. (C) 2002 Elsevier Science Ltd. All rights reserved.

  • 261. Carmichael, G R
    et al.
    Hayami, H
    Calori, G
    Uno, I
    Cho, S Y
    Engardt, Magnuz
    SMHI, Forskningsavdelningen, Luftmiljö.
    Kim, S B
    Ichikawa, Y
    Ikeda, Y
    Ueda, H
    Amann, M
    Model intercomparison study of long range transport and sulfur deposition in East Asia (MICS-ASIA)2001Inngår i: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 130, nr 1-4, s. 51-62Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To help improve the use of models in science & policy analysis in Asia it is necessary to have a better understanding of model performance and uncertainties. Towards this goal an intercomparison exercise has been initiated as a collaborative study of scientists interested in long-range transport in East Asia. An overview of this study is presented in this paper. The study consists of a set of prescribed test calculations with carefully controlled experiments. Models used the same domain, emission inventory, model parameters, meteorological conditions, etc. Two periods (January and May 1993) were selected to reflect long-range transport conditions under two distinct seasons. During these periods measurements of sulfur concentrations and deposition were made throughout the study region using identical sampling and analysis protocols. The intercomparison activity consists of four tasks (Blind Test, Fixed Parameter Test, Source Receptor test, and Tuning Test). All participants were asked to do Task A, and as many of the other tasks as possible. To date seven different models have participated in this study. Results and key findings are presented.

  • 262. Carmichael, G. R.
    et al.
    Sakurai, T.
    Streets, D.
    Hozumi, Y.
    Ueda, H.
    Park, S. U.
    Fung, C.
    Han, Z.
    Kajino, M.
    Engardt, Magnuz
    SMHI, Forskningsavdelningen, Luftmiljö.
    Bennet, Cecilia
    SMHI, Forskningsavdelningen, Luftmiljö.
    Hayami, H.
    Sartelet, K.
    Holloway, T.
    Wang, Z.
    Kannari, A.
    Fu, J.
    Matsuda, K.
    Thongbooncho, N.
    Amann, M.
    MICS-Asia II: The model intercomparison study for Asia Phase II methodology and overview of findings2008Inngår i: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 42, nr 15, s. 3468-3490Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Results from the Model Intercomparison Study Asia Phase II (MICS-Asia II) are presented. Nine different regional modeling groups simulated chemistry and transport of ozone (O-3), secondary aerosol, acid deposition, and associated precursors, using common emissions and boundary conditions derived from a global model. Four-month-long periods, representing 2 years and three seasons (i.e., March, July, and December in 2001, and March in 2002), are analyzed. New observational data, obtained under the EANET (the Acid Deposition Monitoring Network in East Asia) monitoring program, were made available for this study, and these data provide a regional database to compare with model simulations. The analysis focused around seven subject areas: O-3 and related precursors, aerosols, acid deposition, global inflow of pollutants and precursor to Asia, model sensitivities to aerosol parameterization, analysis of emission fields, and detailed analyses of individual models, each of which is presented in a companion paper in this issue of Atmospheric Environment. This overview discusses the major findings of the study, as well as information on common emissions, meteorological conditions, and observations. (C) 2007 Elsevier Ltd. All rights reserved.

  • 263.
    Caron, Louis-Philippe
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre. Climate Forecasting Unit, Institut Cátála de Ciènces del clima (IC3).
    Boudreault, Mathieu
    Bruyere, Cindy L.
    Changes in large-scale controls of Atlantic tropical cyclone activity with the phases of the Atlantic multidecadal oscillation2015Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 44, nr 7-8, s. 1801-1821Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Atlantic tropical cyclone activity is known to oscillate between multi-annual periods of high and low activity. These changes have been linked to the Atlantic multidecadal oscillation (AMO), a mode of variability in Atlantic sea surface temperature which modifies the large-scale conditions of the tropical Atlantic. Cyclone activity is also modulated at higher frequencies by a series of other climate factors, with some of these influences appearing to be more consistent than others. Using the HURDAT2 database and a second set of tropical cyclone data corrected for possible missing storms in the earlier part of the record, we investigate, through Poisson regressions, the relationship between a series of climate variables and a series of metrics of seasonal Atlantic cyclone activity during both phases of the AMO. We find that, while some influences, such as El Nino Southern oscillation, remain present regardless of the AMO phase, other climate factors show an influence during only one of the two phases. During the negative phase, Sahel precipitation and the North Atlantic oscillation (NAO) are measured to play a role, while during the positive phase, the 11-year solar cycle and dust concentration over the Atlantic appear to be more important. Furthermore, we show that during the negative phase of the AMO, the NAO influences all our measures of tropical cyclone activity, and we go on to provide evidence that this is not simply due to changes in steering current, the mechanism by which the NAO is usually understood to impact Atlantic cyclone activity. Finally, we conclude by demonstrating that our results are robust to the sample size as well as to the choice of the statistical model.

  • 264. Caron, Louis-Philippe
    et al.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Analysing present, past and future tropical cyclone activity as inferred from an ensemble of Coupled Global Climate Models2008Inngår i: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 60, nr 1, s. 80-96Artikkel i tidsskrift (Fagfellevurdert)
  • 265. Caron, Louis-Philippe
    et al.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Understanding and simulating the link between African easterly waves and Atlantic tropical cyclones using a regional climate model: the role of domain size and lateral boundary conditions2012Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 39, nr 1-2, s. 113-135Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using a suite of lateral boundary conditions, we investigate the impact of domain size and boundary conditions on the Atlantic tropical cyclone and african easterly Wave activity simulated by a regional climate model. Irrespective of boundary conditions, simulations closest to observed climatology are obtained using a domain covering both the entire tropical Atlantic and northern African region. There is a clear degradation when the high-resolution model domain is diminished to cover only part of the African continent or only the tropical Atlantic. This is found to be the result of biases in the boundary data, which for the smaller domains, have a large impact on TC activity. In this series of simulations, the large-scale Atlantic atmospheric environment appears to be the primary control on simulated TC activity. Weaker wave activity is usually accompanied by a shift in cyclogenesis location, from the MDR to the subtropics. All ERA40-driven integrations manage to capture the observed interannual variability and to reproduce most of the upward trend in tropical cyclone activity observed during that period. When driven by low-resolution global climate model (GCM) integrations, the regional climate model captures interannual variability (albeit with lower correlation coefficients) only if tropical cyclones form in sufficient numbers in the main development region. However, all GCM-driven integrations fail to capture the upward trend in Atlantic tropical cyclone activity. In most integrations, variations in Atlantic tropical cyclone activity appear uncorrelated with variations in African easterly wave activity.

  • 266. Caron, Louis-Philippe
    et al.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Doblas-Reyes, Francisco
    Multi-year prediction skill of Atlantic hurricane activity in CMIP5 decadal hindcasts2014Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 42, nr 9-10, s. 2675-2690Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using a statistical relationship between simulated sea surface temperature and Atlantic hurricane activity, we estimate the skill of a CMIP5 multi-model ensemble at predicting multi-annual level of Atlantic hurricane activity. The series of yearly-initialized hindcasts show positive skill compared to simpler forecasts such as persistence and climatology as well as non-initialized forecasts and return anomaly correlation coefficients of similar to 0.6 and similar to 0.8 for five and nine year forecasts, respectively. Some skill is shown to remain in the later years and making use of those later years to create a lagged-ensemble yields, for individual models, results that approach that obtained by the multi-model ensemble. Some of the skill is shown to come from persisting rather than predicting the climate shift that occur in 1994-1995. After accounting for that shift, the anomaly correlation coefficient for five-year forecasts is estimated to drop to 0.4, but remains statistically significant up to lead years 3-7. Most of the skill is shown to come from the ability of the forecast systems at capturing change in Atlantic sea surface temperature, although the failure of most systems at reproducing the observed slow down in warming over the tropics in recent years leads to an underestimation of hurricane activity in the later period.

  • 267.
    Caron, Louis-Philippe
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Vaillancourt, Paul A.
    Winger, Katja
    On the relationship between cloud-radiation interaction, atmospheric stability and Atlantic tropical cyclones in a variable-resolution climate model2013Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 40, nr 5-6, s. 1257-1269Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We compare two 28-year simulations performed with two versions of the Global Environmental Multiscale model run in variable-resolution mode. The two versions differ only by small differences in their radiation scheme. The most significant modification introduced is a reduction in the ice effective radius, which is observed to increase absorption of upwelling infrared radiation and increase temperature in the upper troposphere. The resulting change in vertical lapse rate is then observed to drive a resolution-dependent response of convection, which in turn modifies the zonal circulation and induces significant changes in simulated Atlantic tropical cyclone activity. The resulting change in vertical lapse rate and its implication in the context of anthropogenic climate change are discussed.

  • 268.
    Caron, Louis-Philippe
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jones, Colin
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Winger, Katja
    Impact of resolution and downscaling technique in simulating recent Atlantic tropical cylone activity2011Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 37, nr 5-6, s. 869-892Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using the global environmental multiscale (GEM) model, we investigate the impact of increasing model resolution from 2A degrees to 0.3A degrees on Atlantic tropical cyclone activity. There is a clear improvement in the realism of Atlantic storms with increased resolution, in part, linked to a better representation of African easterly waves. The geographical distribution of a Genesis Potential Index, composed of large-scales fields known to impact cyclone formation, coincides closely in the model with areas of high cyclogenesis. The geographical distribution of this index also improves with resolution. We then compare two techniques for achieving local high resolution over the tropical Atlantic: a limited-area model driven at the boundaries by the global 2A degrees GEM simulation and a global variable resolution model (GVAR). The limited-area domain and high-resolution part of the GVAR model coincide geographically, allowing a direct comparison between these two downscaling options. These integrations are further compared with a set of limited-area simulations employing the same domain and resolution, but driven at the boundaries by reanalysis. The limited-area model driven by reanalysis produces the most realistic Atlantic tropical cyclone variability. The GVAR simulation is clearly more accurate than the limited-area version driven by GEM-Global. Degradation in the simulated interannual variability is partly linked to the models failure to accurately reproduce the impact of atmospheric teleconnections from the equatorial Pacific and Sahel on Atlantic cyclogenesis. Through the use of a smaller limited-area grid, driven by GEM-Global 2A degrees, we show that an accurate representation of African Easterly Waves is crucial for simulating Atlantic tropical cyclone variability.

  • 269. Carril, A. F.
    et al.
    Menendez, C. G.
    Remedio, A. R. C.
    Robledo, F.
    Soerensson, A.
    Tencer, B.
    Boulanger, J. -P
    de Castro, M.
    Jacob, D.
    Le Treut, H.
    Li, L. Z. X.
    Penalba, O.
    Pfeifer, S.
    Rusticucci, M.
    Salio, P.
    Samuelsson, Patrick
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Sanchez, E.
    Zaninelli, P.
    Performance of a multi-RCM ensemble for South Eastern South America2012Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 39, nr 12, s. 2747-2768Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ability of four regional climate models to reproduce the present-day South American climate is examined with emphasis on La Plata Basin. Models were integrated for the period 1991-2000 with initial and lateral boundary conditions from ERA-40 Reanalysis. The ensemble sea level pressure, maximum and minimum temperatures and precipitation are evaluated in terms of seasonal means and extreme indices based on a percentile approach. Dispersion among the individual models and uncertainties when comparing the ensemble mean with different climatologies are also discussed. The ensemble mean is warmer than the observations in South Eastern South America (SESA), especially for minimum winter temperatures with errors increasing in magnitude towards the tails of the distributions. The ensemble mean reproduces the broad spatial pattern of precipitation, but overestimates the convective precipitation in the tropics and the orographic precipitation along the Andes and over the Brazilian Highlands, and underestimates the precipitation near the monsoon core region. The models overestimate the number of wet days and underestimate the daily intensity of rainfall for both seasons suggesting a premature triggering of convection. The skill of models to simulate the intensity of convective precipitation in summer in SESA and the variability associated with heavy precipitation events (the upper quartile daily precipitation) is far from satisfactory. Owing to the sparseness of the observing network, ensemble and observations uncertainties in seasonal means are comparable for some regions and seasons.

  • 270. Casanueva, A.
    et al.
    Kotlarski, S.
    Herrera, S.
    Fernandez, J.
    Gutierrez, J. M.
    Boberg, F.
    Colette, A.
    Christensen, O. B.
    Goergen, K.
    Jacob, D.
    Keuler, K.
    Nikulin, Grigory
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Teichmann, C.
    Vautard, R.
    Daily precipitation statistics in a EURO-CORDEX RCM ensemble: added value of raw and bias-corrected high-resolution simulations2016Inngår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 47, nr 3-4, s. 719-737Artikkel i tidsskrift (Fagfellevurdert)
  • 271.
    Cato, Ingemar
    et al.
    Geological Survey of Sweden (SGU),.
    Håkansson, Bertil
    SMHI, Forskningsavdelningen, Oceanografi.
    Hallberg, Ola
    Geological Survey of Sweden (SGU),.
    Kjellin, Bernt
    Geological Survey of Sweden (SGU),.
    Andersson, Pia
    SMHI, Samhälle och säkerhet.
    Erlandsson, Cecilia
    Geological Survey of Sweden (SGU),.
    Axe, Philip
    SMHI, Forskningsavdelningen, Oceanografi.
    A new approach to state the areas of oxygen deficits in the Baltic Sea2008Rapport (Annet vitenskapelig)
    Abstract [en]

    Sediment and near bottom water oxygen data was evaluated to look for correspondence in anoxic conditions. The SGU and SMHI monitoring data showed high correlation, although the actual data tested proved to be few, coincidence in space was promising. The conclusion drawn from the evaluation is that anoxic postglacial sediments were generally overlaid by near bottom anoxic waters. Hence, it is suggested that the spatial distribution of postglacial clays in the sea-bottom surface can be used, together with near bottom waters oxygen data, to improve spatial distribution in mapping oxygen deficits.Time series of oxygen deficit volume and area was calculated from near bottom data from several sub basins in the southern and central Baltic Proper. In general, hypoxic and anoxic water conditions increased over time but perturbations of improved oxygen conditions linked to major inflow events occurs especially in the Bornholm, Eastern and Western Gotland Basins.The high spatial variability of the postglacial sediments in the Western Gotland Basin compared to other basins indicates that it is indeed sensitive to the area coverage of anoxic waters. In addition, the relatively weak stratification and high variability over time of oxygen deficit make this basin favourable for oxygen improvement engineering methods.In coastal waters several bays along the Östergötland and Småland archipelagos should be further evaluated before selected for ecological engineering methods to improve oxygen conditions.

  • 272. Cavazos, Tereza
    et al.
    Luna-Nino, Rosa
    Cerezo-Mota, Ruth
    Fuentes Franco, Ramon
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Mendez, Matias
    Pineda Martinez, Luis Felipe
    Valenzuela, Ernesto
    Climatic trends and regional climate models intercomparison over the CORDEX-CAM (Central America, Caribbean, and Mexico) domain2019Inngår i: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An intercomparison of three regional climate models (RCMs) (PRECIS-HadRM3P, RCA4, and RegCM4) was performed over the Coordinated Regional Dynamical Experiment (CORDEX)-Central America, Caribbean, and Mexico (CAM) domain to determine their ability to reproduce observed temperature and precipitation trends during 1980-2010. Particular emphasis was given to the North American monsoon (NAM) and the mid-summer drought (MSD) regions. The three RCMs show negative (positive) temperature (precipitation) biases over the mountains, where observations have more problems due to poor data coverage. Observations from the Climate Research Unit (CRU) and ERA-Interim show a generalized warming over the domain. The most significant warming trend (>= 0.34 degrees C/decade) is observed in the NAM, which is moderately captured by the three RCMs, but with less intensity; each decade from 1970 to 2016 has become warmer than the previous ones, especially during the summer (mean and extremes); this warming appears partially related to the positive Atlantic Multidecadal Oscillation (+AMO). CRU, GPCP, and CHIRPS show significant decreases of precipitation (less than -15%/decade) in parts of the southwest United States and northwestern Mexico, including the NAM, and a positive trend (5-10%/decade) in June-September in eastern Mexico, the MSD region, and northern South America, but longer trends (1950-2017) are not statistically significant. RCMs are able to moderately simulate some of the recent trends, especially in winter. In spite of their mean biases, the RCMs are able to adequately simulate inter-annual and seasonal variations. Wet (warm) periods in regions affected by the MSD are significantly correlated with the +AMO and La Nina events (+AMO and El Nino). Summer precipitation trends from GPCP show opposite signs to those of CRU and CHIRPS over the Mexican coasts of the southern Gulf of Mexico, the Yucatan Peninsula, and Cuba, possibly due to data limitations and differences in grid resolutions.

  • 273. Cederwall, K
    et al.
    Brandt, Maja
    SMHI, Forskningsavdelningen, Hydrologi.
    Workshop 6 (synthesis): linking between flood risks and land use changes2002Inngår i: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 45, nr 8, s. 181-182Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Land use changes, such as deforestation, are increasing the world's vulnerability to flooding. Detailed knowledge of the local situation is essential for risk assessment and design of effective flood prevention measures and governs the infrastructure and engineering measures implemented. However extreme floods in large catchments can overwhelm both natural capacity and constructed flood management measures.

  • 274. Ceola, S.
    et al.
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Baratti, E.
    Bloeschl, G.
    Capell, Réne
    SMHI, Forskningsavdelningen, Hydrologi.
    Castellarin, A.
    Freer, J.
    Han, D.
    Hrachowitz, M.
    Hundecha, Yeshewatesfa
    SMHI, Forskningsavdelningen, Hydrologi.
    Hutton, C.
    Lindström, Göran
    SMHI, Forskningsavdelningen, Hydrologi.
    Montanari, A.
    Nijzink, R.
    Parajka, J.
    Toth, E.
    Viglione, A.
    Wagener, T.
    Virtual laboratories: new opportunities for collaborative water science2015Inngår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, nr 4, s. 2101-2117Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reproducibility and repeatability of experiments are the fundamental prerequisites that allow researchers to validate results and share hydrological knowledge, experience and expertise in the light of global water management problems. Virtual laboratories offer new opportunities to enable these prerequisites since they allow experimenters to share data, tools and pre-defined experimental procedures (i.e. protocols). Here we present the outcomes of a first collaborative numerical experiment undertaken by five different international research groups in a virtual laboratory to address the key issues of reproducibility and repeatability. Moving from the definition of accurate and detailed experimental protocols, a rainfall-runoff model was independently applied to 15 European catchments by the research groups and model results were collectively examined through a web-based discussion. We found that a detailed modelling protocol was crucial to ensure the comparability and reproducibility of the proposed experiment across groups. Our results suggest that sharing comprehensive and precise protocols and running the experiments within a controlled environment (e.g. virtual laboratory) is as fundamental as sharing data and tools for ensuring experiment repeatability and reproducibility across the broad scientific community and thus advancing hydrology in a more coherent way.

  • 275. Cerezo-Mota, Ruth
    et al.
    Cavazos, Tereza
    Arritt, Raymond
    Torres-Alavez, Abraham
    Sieck, Kevin
    Nikulin, Grigory
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Moufouma-Okia, Wilfram
    Antonio Salinas-Prieto, Jose
    CORDEX-NA: factors inducing dry/wet years on the North American Monsoon region2016Inngår i: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 36, nr 2, s. 824-836Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The output of four regional climate models (RCMs) from the Coordinated Regional Climate Downscaling Experiment (CORDEX)-North America (NA) region was analysed for the 1990-2008 period, with particular interest on the mechanisms associated with wet and dry years over the North American Monsoon (NAM) core region. All RCMs (RCA3.5, HadGEM3-RA, REMO, and RegCM4) were forced by the ERA-Interim reanalysis. Model precipitation was compared against several observational gridded data sets at different time scales. Most RCMs capture well the annual cycle of precipitation and outperform ERA-Interim, which is drier than the observations. RCMs underestimate (overestimate) the precipitation over the coastal plains (mountains) and have some problems to reproduce the interannual variability of the monsoon. To further investigate this, two extreme summers that showed the largest consistency among observations and RCMs were chosen: one wet (1990) and one dry (2005). The impact of the passage of tropical cyclones, the size of the Western Hemisphere Warm Pool (WHWP), the Intertropical Convergence Zone (ITCZ) position, and the initial intensity of the land-sea thermal contrast (LSTC) were analysed. During the wet year, the LSTC was stronger than the 2005 dry monsoon season and there were a larger number of hurricanes near the Gulf of California, the WHWP was more extended, and the ITCZ was located in a more northerly position than in 2005. All these processes contributed to a wetter NAM season. During the dry year, the LSTC was weaker, with a later onset, probably due to a previous very wet winter. The inverse precipitation relationship between winter and summer in the monsoon region was well captured by most of the RCMs. RegCM4 showed the largest biases and HadGEM3-RA the smallest ones.

  • 276. Chadwick, R.
    et al.
    Martin, G. M.
    Copsey, D.
    Bellon, G.
    Caian, Mihaela
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Codron, F.
    Rio, C.
    Roehrig, R.
    Examining the West African Monsoon circulation response to atmospheric heating in a GCM dynamical core2017Inngår i: Journal of Advances in Modeling Earth Systems, ISSN 1942-2466, Vol. 9, nr 1, s. 149-167Artikkel i tidsskrift (Fagfellevurdert)
  • 277. Chen, Hans W.
    et al.
    Zhang, Qiong
    Körnich, Heiner
    SMHI, Forskningsavdelningen, Meteorologi.
    Chen, Deliang
    A robust mode of climate variability in the Arctic: The Barents Oscillation2013Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, nr 11, s. 2856-2861Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Barents Oscillation (BO) is an anomalous wintertime atmospheric circulation pattern in the Northern Hemisphere that has been linked to the meridional flow over the Nordic Seas. There are speculations that the BO has important implications for the Arctic climate; however, it has also been suggested that the pattern is an artifact of Empirical Orthogonal Function (EOF) analysis due to an eastward shift of the Arctic Oscillation/North Atlantic Oscillation (AO/NAO). In this study, EOF analyses are performed to show that a robust pattern resembling the BO can be found during different time periods, even when the AO/NAO is relatively stationary. This BO has a high and stable temporal correlation with the geostrophic zonal wind over the Barents Sea, while the contribution from the AO/NAO is small. The surface air temperature anomalies over the Barents Sea are closely associated with this mode of climate variability.

  • 278. Cheymol, Anne
    et al.
    De Backer, Hugo
    Josefsson, Weine
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Stuebi, Rene
    Comparison and validation of the aerosol optical depth obtained with the Langley plot method in the UV-B from Brewer Ozone Spectrophotometer measurements2006Inngår i: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 111, nr D16, artikkel-id D16202Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    [ 1] The Aerosol Optical Depths (AODs) retrieved from Brewer Ozone Spectrophotometer measurements with a method previously developed (Cheymol and De Backer, 2003) are now validated by comparisons between AODs from six Brewer spectrophotometers and two CSEM SPM2000 sunphotometers: two Brewer spectrophotometers 016 and 178 at Uccle in Belgium; one Brewer spectrophotometer 128 and one sunphotometer CSEM SPM2000 at Norrkoping in Sweden; and three Brewer instruments 040, 072, 156 at Arosa and one CSEM SPM2000 sunphotometer at Davos in Switzerland. The comparison between AODs from Brewer spectrophotometer 128 at 320.1 nm and sunphotometer SPM2000 at 368 nm at Norrkoping shows that the AODs obtained from the Brewer measurements with the Langley Plot Method (LPM) are very accurate if the neutral density filter spectral transmittances are well known: with the measured values of these filters, the correlation coefficient, the slope, and the intercept of the regression line are 0.98, 0.85 +/- 0.004, and 0.02 +/- 0.0014, respectively. The bias observed is mainly owing to the wavelength difference between the two instruments. The comparison between AODs from different Brewer spectrophotometers confirm that AODs will be in very good agreement if they are measured with several Brewer instruments at the same place: At Uccle, the correlation coefficient, slope, and intercept of the regression line are 0.98, 1.02 +/- 0.003, and 0.06 +/- 0.001, respectively; at Arosa, the comparisons between the AODs from three Brewer spectrophotometers 040, 072, and 156 give a correlation coefficient, a slope, and an intercept of the regression line above 0.94, 0.98 and below 0.04, respectively.

  • 279. Christensen, J H
    et al.
    Räisänen, Jouni
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Iversen, T
    Bjorge, D
    Christensen, O B
    Rummukainen, Markku
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    A synthesis of regional climate change simulations - A Scandinavian perspective2001Inngår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 28, nr 6, s. 1003-1006Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Four downscaling experiments of regional climate change for the Nordic countries have been conducted with three different regional climate models (RCMs). A short synthesis of the outcome of the suite of experiments is presented as an ensemble, reflecting the different driving atmosphere-ocean general circulation model (AOGCM) conditions, RCM model resolution and domain size, and choice of emission scenarios. This allows the sources of uncertainties in the projections to be assessed. At the same time analysis of the climate change signal for temperature and precipitation over the period 1990-2050 reveals strong similarities. In particular, all experiments in the suite simulate changes in the precipitation distribution towards a higher frequency of heavy precipitation.

  • 280. Christensen, Jens H.
    et al.
    Carter, Timothy R.
    Rummukainen, Markku
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Amanatidis, Georgios
    Evaluating the performance and utility of regional climate models: the PRUDENCE project2007Inngår i: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 81, s. 1-6Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    This special issue of Climatic Change contains a series of research articles documenting coordinated work carried out within a 3-year European Union project 'Prediction of Regional scenarios and Uncertainties for Defining European Climate change risks and Effects' (PRUDENCE). The main objective of the PRUDENCE project was to provide high resolution climate change scenarios for Europe at the end of the twenty-first century by means of dynamical downscaling (regional climate modelling) of global climate simulations. The first part of the issue comprises seven overarching PRUDENCE papers on: (1) the design of the model simulations and analyses of climate model perfort-natice, (2 and 3) evaluation and intercomparison of simulated climate changes, (4 and 5) specialised analyses of impacts on water resources and on other sectors including agriculture, ecosystems, energy, and transport, (6) investigation of extreme weather events and (7) implications of the results for policy. A paper summarising the related MICE (Modelling the Impact of Climate Extremes) project is also included. The second part of the issue contains 12 articles that focus in more detail on some of the themes summarised in the overarching papers. The PRUDENCE results represent the first comprehensive, continental-scale intercomparison and evaluation of high resolution climate models and their applications, bringing together climate modelling, impact research and social sciences expertise on climate change.

  • 281. Christensen, Jens Hesselbjerg
    et al.
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Giorgi, Filippo
    Lenderink, Geert
    Rummukainen, Markku
    SMHI, Samhälle och säkerhet.
    Weight assignment in regional climate models2010Inngår i: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 44, nr 2-3, s. 179-194Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An important new development within the European ENSEMBLES project has been to explore performance-based weighting of regional climate models (RCMs). Until now, although no weighting has been applied in multi-RCM analyses, one could claim that an assumption of 'equal weight' was implicitly adopted. At the same time, different RCMs generate different results, e. g. for various types of extremes, and these results need to be combined when using the full RCM ensemble. The process of constructing, assigning and combining metrics of model performance is not straightforward. Rather, there is a considerable degree of subjectivity both in the choice of metrics and on how these may be combined into weights. We explore the applicability of combining a set of 6 specifically designed RCM performance metrics to produce one aggregated model weight with the purpose of combining climate change information from the range of RCMs used within ENSEMBLES. These metrics capture aspects of model performance in reproducing large-scale circulation patterns, meso-scale signals, daily temperature and precipitation distributions and extremes, trends and the annual cycle. We examine different aggregation procedures that generate different inter-model spreads of weights. The use of model weights is sensitive to the aggregation procedure and shows different sensitivities to the selected metrics. Generally, however, we do not find compelling evidence of an improved description of mean climate states using performance-based weights in comparison to the use of equal weights. We suggest that model weighting adds another level of uncertainty to the generation of ensemble-based climate projections, which should be suitably explored, although our results indicate that this uncertainty remains relatively small for the weighting procedures examined.

  • 282. Christensen, Ole Bossing
    et al.
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Zorita, Eduardo
    Projected Change-Atmosphere2015Kapittel i bok, del av antologi (Annet vitenskapelig)
    Abstract [en]

    This chapter builds on the comprehensive summary of climate change scenarios in the first BACC assessment published in 2008. This chapter first addresses the dynamical downscaling of general circulation model (GCM) results to the regional scale, focussing on results from 13 regional climate model (RCM) simulations in the ENSEMBLES project as this European-scale ensemble simulation is also relevant for the Baltic Sea region and many studies on temperature, precipitation, wind speed and snow amounts have been performed. This chapter then reviews statistical downscaling studies that use large-scale atmospheric variables (predictors) to estimate possible future change in several smaller scale fields (predictands), with the greatest emphasis given to hydrological variables (such as precipitation and run-off). For the Baltic Sea basin, the findings of the statistical downscaling studies are generally in line with studies employing dynamical downscaling.

  • 283. Clausen, Niels-Erik
    et al.
    Pryor, Sara C.
    Larsén, Xiaoli Guo
    Hyvönen, Reijo
    Venäläinen, Ari
    Suvilampi4, Elina
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Barthelmie, Rebecca
    Are we facing increasing extreme winds in the future?2009Konferansepaper (Annet vitenskapelig)
  • 284. Colette, Augustin
    et al.
    Andersson, Camilla
    SMHI, Forskningsavdelningen, Luftmiljö.
    Baklanov, Alexander
    Bessagnet, Bertrand
    Brandt, Jorgen
    Christensen, Jesper H.
    Doherty, Ruth
    Engardt, Magnuz
    SMHI, Forskningsavdelningen, Luftmiljö.
    Geels, Camilla
    Giannakopoulos, Christos
    Hedegaard, Gitte B.
    Katragkou, Eleni
    Langner, Joakim
    SMHI, Forskningsavdelningen, Luftmiljö.
    Lei, Hang
    Manders, Astrid
    Melas, Dimitris
    Meleux, Frederik
    Rouil, Laurence
    Sofiev, Mikhail
    Soares, Joana
    Stevenson, David S.
    Tombrou-Tzella, Maria
    Varotsos, Konstantinos V.
    Young, Paul
    Is the ozone climate penalty robust in Europe?2015Inngår i: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 10, nr 8, artikkel-id 084015Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ozone air pollution is identified as one of the main threats bearing upon human health and ecosystems, with 25 000 deaths in 2005 attributed to surface ozone in Europe (IIASA 2013 TSAP Report #10). In addition, there is a concern that climate change could negate ozone pollution mitigation strategies, making them insufficient over the long run and jeopardising chances to meet the long term objective set by the European Union Directive of 2008 (Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008) (60 ppbv, daily maximum). This effect has been termed the ozone climate penalty. One way of assessing this climate penalty is by driving chemistry-transport models with future climate projections while holding the ozone precursor emissions constant (although the climate penalty may also be influenced by changes in emission of precursors). Here we present an analysis of the robustness of the climate penalty in Europe across time periods and scenarios by analysing the databases underlying 11 articles published on the topic since 2007, i.e. a total of 25 model projections. This substantial body of literature has never been explored to assess the uncertainty and robustness of the climate ozone penalty because of the use of different scenarios, time periods and ozone metrics. Despite the variability of model design and setup in this database of 25 model projection, the present meta-analysis demonstrates the significance and robustness of the impact of climate change on European surface ozone with a latitudinal gradient from a penalty bearing upon large parts of continental Europe and a benefit over the North Atlantic region of the domain. Future climate scenarios present a penalty for summertime (JJA) surface ozone by the end of the century (2071-2100) of at most 5 ppbv. Over European land surfaces, the 95% confidence interval of JJA ozone change is [0.44; 0.64] and [0.99; 1.50] ppbv for the 2041-2070 and 2071-2100 time windows, respectively.

  • 285. Colette, Augustin
    et al.
    Andersson, Camilla
    SMHI, Forskningsavdelningen, Luftmiljö.
    Manders, Astrid
    Mar, Kathleen
    Mircea, Mihaela
    Pay, Maria-Teresa
    Raffort, Valentin
    Tsyro, Svetlana
    Cuvelier, Cornelius
    Adani, Mario
    Bessagnet, Bertrand
    Bergström, Robert
    SMHI, Forskningsavdelningen, Luftmiljö.
    Briganti, Gino
    Butler, Tim
    Cappelletti, Andrea
    Couvidat, Florian
    D'Isidoro, Massimo
    Doumbia, Thierno
    Fagerli, Hilde
    Granier, Claire
    Heyes, Chris
    Klimont, Zig
    Ojha, Narendra
    Otero, Noelia
    Schaap, Martijn
    Sindelarova, Katarina
    Stegehuis, Annemiek I.
    Roustan, Yelva
    Vautard, Robert
    van Meijgaard, Erik
    Vivanco, Marta Garcia
    Wind, Peter
    EURODELTA-Trends, a multi-model experiment of air quality hindcast in Europe over 1990-20102017Inngår i: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 10, nr 9, s. 3255-3276Artikkel i tidsskrift (Fagfellevurdert)
  • 286. Colette, Augustin
    et al.
    Schucht, Simone
    Ciarelli, Giancarlo
    Létinois, Laurent
    Meleux, Frédérik
    Andersson, Camilla
    SMHI, Forskningsavdelningen, Luftmiljö.
    Cuvelier, C.
    Manders, A.
    Mar, K.A.
    Mircea, M.
    Pay, T.
    Raffort, V.
    Tsyro, S.
    Adani, M.
    Bergström, Robert
    SMHI, Forskningsavdelningen, Luftmiljö.
    Bessagnet, G
    Briganti, A.
    Cappelletti, A.
    Couvidat, F.
    D'Isidoro, M.
    Fagerli, H.
    Ojha, N.
    Otero, N.
    Wind, P.
    Long-term air quality trends in Europe Fine Particulate Matter (PM2.5) Health Impacts.2018Rapport (Annet vitenskapelig)
  • 287. Conley, Daniel J.
    et al.
    Bjorck, Svante
    Bonsdorff, Erik
    Carstensen, Jacob
    Destouni, Georgia
    Gustafsson, Bo G.
    Hietanen, Susanna
    Kortekaas, Marloes
    Kuosa, Harri
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    Mueller-Karulis, Baerbel
    Nordberg, Kjell
    Norkko, Alf
    Nuernberg, Gertrud
    Pitkanen, Heikki
    Rabalais, Nancy N.
    Rosenberg, Rutger
    Savchuk, Oleg P.
    Slomp, Caroline P.
    Voss, Maren
    Wulff, Fredrik
    Zillen, Lovisa
    Hypoxia-Related Processes in the Baltic Sea2009Inngår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, nr 10, s. 3412-3420Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Hypoxia, a growing worldwide problem, has been intermittently present in the modern Baltic Sea since its formation ca. 8000 cal. yr BP. However, both the spatial extent and intensity of hypoxia have increased with anthropogenic eutrophication due to nutrient inputs. Physical processes, which control stratification and the renewal of oxygen in bottom waters, are important constraints on the formation and maintenance of hypoxia. Climate controlled inflows of saline water from the North Sea through the Danish Straits is a critical controlling factor governing the spatial extent and duration of hypoxia. Hypoxia regulates the biogeochemical cycles of both phosphorus (P) and nitrogen (N) in the water column and sediments. Significant amounts of P are currently released from sediments, an order of magnitude larger than anthropogenic inputs. The Baltic Sea is unique for coastal marine ecosystems experiencing N losses in hypoxic waters below the halocline. Although benthic communities in the Baltic Sea are naturally constrained by salinity gradients, hypoxia has resulted in habitat loss over vast areas and the elimination of benthic fauna, and has severely disrupted benthic food webs. Nutrient load reductions are needed to reduce the extent, severity, and effects of hypoxia.

  • 288. Conley, Daniel J.
    et al.
    Carstensen, Jacob
    Aigars, Juris
    Axe, Philip
    SMHI, Forskningsavdelningen, Oceanografi.
    Bonsdorff, Erik
    Eremina, Tatjana
    Haahti, Britt-Marie
    Humborg, Christoph
    Jonsson, Per
    Kotta, Jonne
    Lannegren, Christer
    Larsson, Ulf
    Maximov, Alexey
    Medina, Miguel Rodriguez
    Lysiak-Pastuszak, Elzbieta
    Remeikaite-Nikiene, Nijole
    Walve, Jakob
    Wilhelms, Sunhild
    Zillen, Lovisa
    Hypoxia Is Increasing in the Coastal Zone of the Baltic Sea2011Inngår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 45, nr 16, s. 6777-6783Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hypoxia is a well-described phenomenon in the offshore waters of the Baltic Sea with both the spatial extent and intensity of hypoxia known to have increased due to anthropogenic eutrophication, however, an unknown amount of hypoxia is present in the coastal zone. Here we report on the widespread unprecedented occurrence of hypoxia across the coastal zone of the Baltic Sea. We have identified 115 sites that have experienced hypoxia during the period 1955-2009 increasing the global total to ca. 500 sites, with the Baltic Sea coastal zone containing over 20% of all known sites worldwide. Most sites experienced episodic hypoxia, which is a precursor to development of seasonal hypoxia. The Baltic Sea coastal zone displays an alarming trend with hypoxia steadily increasing with time since the 1950s effecting nutrient biogeochemical processes, ecosystem services, and coastal habitat.

  • 289. Corrales-Suastegui, Arturo
    et al.
    Fuentes Franco, Ramon
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Pavia, Edgar G.
    The mid-summer drought over Mexico and Central America in the 21st century2019Inngår i: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The southern Mexico and Central America (SMCA) region shows a dominant well-defined precipitation annual cycle. The rainy season usually begins in May and ends in October, with a relatively dry period in July and August known as the mid-summer drought (MSD); notable exceptions are the Caribbean coast of Honduras and Costa Rica. This MSD phenomenon is expected to be affected as the SMCA experiences an enhanced differential warming between the Pacific and Atlantic Oceans (PO-AO) towards the end of the 21st century. Previous studies have suggested that this differential warming will induce a strengthening of the westward Caribbean low-level jet (CLLJ) and that this heightened CLLJ will shift precipitation westwards, falling on the PO instead that within the SMCA region causing a severe drought. In this work we examine this scenario with a new model, the Rossby Center Regional Climate Model (RCA4), for the COordinated Regional climate Downscaling EXperiment (CORDEX) Central America domain, forced with different general circulation models (GCMs) and for different representative concentration paths (RCPs). We consider 25-year periods as "present conditions" (1981-2005) and "future scenario" (2071-2095), focusing on the "extended summer" season (May-October). Results suggest that in the future the spatial extension of the MSD will decrease and that in certain areas the MSD will be more intense but less frequent compared to present conditions. Also, the oceanic differential warming, the intensification of the CLLJ, and the reduction in regional precipitation in the future scenario, suggested by previous works, were verified in this study.

  • 290. Couvreux, F.
    et al.
    Roehrig, R.
    Rio, C.
    Lefebvre, M. -P
    Caian, Mihaela
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Komori, T.
    Derbyshire, S.
    Guichard, F.
    Favot, F.
    D'Andrea, F.
    Bechtold, P.
    Gentine, P.
    Representation of daytime moist convection over the semi-arid Tropics by parametrizations used in climate and meteorological models2015Inngår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 141, nr 691, s. 2220-2236Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A case of daytime development of deep convection over tropical semi-arid land is used to evaluate the representation of convection in global and regional models. The case is based on observations collected during the African Monsoon Multidisciplinary Analysis (AMMA) field campaign and includes two distinct transition phases, from clear sky to shallow cumulus and from cumulus to deep convection. Different types of models, run with identical initial and boundary conditions, are intercompared: a reference large-eddy simulation (LES), single-column model (SCM) version of four different Earth system models that participated in the Coupled Model Intercomparison Project 5 exercise, the SCM version of the European Centre for Medium-range Weather Forecasts operational forecast model, the SCM version of a mesoscale model and a bulk model. Surface fluxes and radiative heating are prescribed preventing any atmosphere-surface and cloud-radiation coupling in order to simplify the analyses so that it focuses only on convective processes. New physics packages are also evaluated within this framework. As the LES correctly reproduces the observed growth of the boundary layer, the gradual development of shallow clouds, the initiation of deep convection and the development of cold pools, it provides a basis to evaluate in detail the representation of the diurnal cycle of convection by the other models and to test the hypotheses underlying convective parametrizations. Most SCMs have difficulty in representing the timing of convective initiation and rain intensity, although substantial modifications to boundary-layer and deep-convection parametrizations lead to improvements. The SCMs also fail to represent the mid-level troposphere moistening during the shallow convection phase, which we analyse further. Nevertheless, beyond differences in timing of deep convection, the SCM models reproduce the sensitivity to initial and boundary conditions simulated in the LES regarding boundary-layer characteristics, and often the timing of convection triggering.

  • 291. Crewell, S
    et al.
    Bloemink, H
    Feijt, A
    Garcia, S G
    Jolivet, D
    Krasnov, O A
    van Lammeren, A
    Lohnert, J
    van Meijgaard, E
    Meywerk, J
    Quante, M
    Pfeilsticker, K
    Schmidt, S
    Scholl, T
    Simmer, C
    Schroder, M
    Trautmann, T
    Venema, V
    Wendisch, M
    Willén, Ulrika
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    The BALTEX Bridge Campaign - An integrated approach for a better understanding of clouds2004Inngår i: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 85, nr 10, s. 1565-+Artikkel i tidsskrift (Fagfellevurdert)
  • 292.
    Crochemore, Louise
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Ramos, Maria-Helena
    Pappenberger, Florian
    Bias correcting precipitation forecasts to improve the skill of seasonal streamflow forecasts2016Inngår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 20, nr 9, s. 3601-3618Artikkel i tidsskrift (Fagfellevurdert)
  • 293.
    Crochemore, Louise
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Ramos, Maria-Helena
    Pappenberger, Florian
    Perrin, Charles
    Seasonal streamflow forecasting by conditioning climatology with precipitation indices2017Inngår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 21, nr 3, s. 1573-1591Artikkel i tidsskrift (Fagfellevurdert)
  • 294. Cuxart, J
    et al.
    Holtslag, A A M
    Beare, R J
    Bazile, E
    Beljaars, A
    Cheng, A
    Conangla, L
    Ek, M
    Freedman, F
    Hamdi, R
    Kerstein, A
    Kitagawa, H
    Lenderink, G
    Lewellen, D
    Mailhot, J
    Mauritsen, T
    Perov, Veniamin
    SMHI, Forskningsavdelningen, Meteorologi.
    Schayes, G
    Steeneveld, G J
    Svensson, G
    Taylor, P
    Weng, W
    Wunsch, S
    Xu, K M
    Single-column model intercomparison for a stably stratified atmospheric boundary layer2006Inngår i: Boundary-layer Meteorology, ISSN 0006-8314, E-ISSN 1573-1472, Vol. 118, nr 2, s. 273-303Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The parameterization of the stably stratified atmospheric boundary layer is a difficult issue, having a significant impact on medium-range weather forecasts and climate integrations. To pursue this further, a moderately stratified Arctic case is simulated by nineteen single-column turbulence schemes. Statistics from a large-eddy simulation intercomparison made for the same case by eleven different models are used as a guiding reference. The single-column parameterizations include research and operational schemes from major forecast and climate research centres. Results from first-order schemes, a large number of turbulence kinetic energy closures, and other models were used. There is a large spread in the results; in general, the operational schemes mix over a deeper layer than the research schemes, and the turbulence kinetic energy and other higher-order closures give results closer to the statistics obtained from the large-eddy simulations. The sensitivities of the schemes to the parameters of their turbulence closures are partially explored.

  • 295. Dahl, M
    et al.
    Pers, Charlotta
    SMHI, Forskningsavdelningen, Hydrologi.
    Comparison of four models simulating phosphorus dynamics in Lake Vanern, Sweden2004Inngår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 8, nr 6, s. 1153-1163Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper compares four water quality models applied to Lake Vanern, Sweden. The comparison is focused on phosphorus, the primary limiting nutrient in Lake Vanern. Two of the models, FYRISA and HBV-NP, are simple and were developed as parts of catchment models. Two other models, called LEEDS and MOM are more comprehensive lake models. The models were calibrated using data from the period 1985-1992 and validated using data from the period 1993-2000. The fit to calibration data is similar for the FYRISA, HBV-NP, and LEEDS models, and slightly worse for the BIOLA model. All models fit the validation data almost as well as the calibration data. The models behaviour was tested in two representative scenarios. An increase of emissions by 40% from a pulp and paper mill has a negligible effect on the water quality, while a decrease in phosphorus load by 14% (accomplished by better waste-water treatment in rural households) gives a considerable decrease in phosphorus concentration in the lake. Still, the results of the scenarios vary between the models.

  • 296.
    Dahlgren, Per
    et al.
    SMHI, Forskningsavdelningen, Meteorologi.
    Gustafsson, Nils
    SMHI, Forskningsavdelningen, Meteorologi.
    Assimilating host model information into a limited area model2012Inngår i: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 64, artikkel-id 15836Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose to add an extra source of information to the data-assimilation of the regional HIgh Resolution Limited Area Model (HIRLAM) model, constraining larger scales to the host model providing the lateral boundary conditions. An extra term, J(k), measuring the distance to the large-scale vorticity of the host model, is added to the cost-function of the variational data-assimilation. Vorticity is chosen because it is a good representative of the large-scale flow and because vorticity is a basic control variable of the HIRLAM variational data-assimilation. Furthermore, by choosing only vorticity, the remaining model variables, divergence, temperature, surface pressure and specific humidity will be allowed to adapt to the modified vorticity field in accordance with the internal balance constraints of the regional model. The error characteristics of the J(k) term are described by the horizontal spectral densities and the vertical eigenmodes (eigenvectors and eigenvalues) of the host model vorticity forecast error fields, expressed in the regional model geometry. The vorticity field, provided by the European Centre for Medium-range Weather Forecasts (ECMWF) operational model, was assimilated into the HIRLAM model during an experiment period of 33 d in winter with positive impact on forecast verification statistics for upper air variables and mean sea level pressure.

  • 297.
    Dahlgren, Per
    et al.
    SMHI, Forskningsavdelningen, Meteorologi.
    Landelius, Tomas
    SMHI, Forskningsavdelningen, Atmosfärisk fjärranalys.
    Kållberg, Per
    SMHI, Forskningsavdelningen, Meteorologi.
    Gollvik, Stefan
    SMHI, Forskningsavdelningen, Meteorologi.
    A high-resolution regional reanalysis for Europe. Part 1: Three-dimensional reanalysis with the regional HIgh-Resolution Limited-Area Model (HIRLAM)2016Inngår i: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 142, nr 698, s. 2119-2131Artikkel i tidsskrift (Fagfellevurdert)
  • 298. Danielssen, D S
    et al.
    Edler, Lars
    SMHI, Forskningsavdelningen, Oceanografi.
    Fonselius, Stig
    SMHI, Forskningsavdelningen, Oceanografi.
    Hernroth, L
    Ostrowski, M
    Svendsen, E
    Talpsepp, L
    Oceanographic variability in the Skagerrak and Northern Kattegat, May-June, 19901997Inngår i: ICES Journal of Marine Science, ISSN 1054-3139, E-ISSN 1095-9289, Vol. 54, nr 5, s. 753-773Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Skagerrak Experiment (SKAGEX), was a large, international, ICES-supported joint venture, carried out in the Skagerrak-Kattegat area on four different surveys in the period 1990-1991. It involved some 20 institutes and, at times, up to 17 research vessels. The main aim of the Experiment was to identify and quantify the different water masses entering and leaving the Skagerrak area and their variation over lime. It also aimed to investigate the mechanisms that drive the circulation and to study their effects on biological processes. The aim was to be attained mostly through extensive synoptic observations. This paper focuses on the variability in physical, chemical and biological parameters during the first part of SKAGEX, 24 May-20 June 1990. During the first half of the period of investigation, the main outflow from the Skagerrak, represented by the Norwegian Coastal Current, was barotropic with daily mean velocities varying from 10-40 cm s(-1). During the second half a clear baroclinic current component developed, giving rise to near surface velocities of up to 100 cm s(-1). A pronounced feature in the Skagerrak during the study was the counter-clockwise circulation of the Norwegian Coastal Current at times of strong northwesterly winds. During such conditions this surface water reached as far as the Danish coast south of 57 degrees N and upwelling along the Norwegian coast was also found. During northerly winds upwelling also occurred along the Swedish coast. The nutrient-rich Jutland Coastal Water, originating from the German Eight, was never found to reach the inner part of the Skagerrak during this first part of SKAGEX. It was partly blocked or diluted by other water-masses. A large ''ridge'' of nutrient-rich Atlantic water was found in the central Skagerrak throughout the investigation. It is shown that this elongated ''ridge'' was associated with the deepest (>500 m) area of the Skagerrak. Within this area, high subsurface chlorophyll concentrations were always found and, due to the persistence of the supply of nutrients, it is concluded that this phenomenon could be one of the main reasons for the high productivity of the Skagerrak. (C) 1997 International Council for the Exploration of the Sea.

  • 299. Danielsson, A.
    et al.
    Jönsson, Anette
    SMHI, Samhälle och säkerhet.
    Rahm, Lars
    SMHI, Forskningsavdelningen, Oceanografi.
    Resuspension patterns in the Baltic proper2007Inngår i: Journal of Sea Research, ISSN 1385-1101, E-ISSN 1873-1414, Vol. 57, nr 4, s. 257-269Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Waves induce resuspension of surface sediments and contribute to the long-term mobilisation of particulate matter from erosion to accumulation bottoms. This has a major impact on the nutrient cycle in shallow seas by enhancing degradation, microbial production and recycling. The Baltic Sea represents such an area. The aim of this work is to analyse the spatial and temporal resuspension patterns in the Baltic Sea. To estimate the bottom friction velocity, modelled wave data are used in combination with data on grain size. This new data set is compared to a resuspension threshold of friction velocity to estimate the events of resuspension. The variation in bottom friction velocity, resuspension frequency and duration are related to wind climate, fetch, water depth and sediment type. Substantial resuspension can be found down to 40-60 m, with durations from one day to as much as two weeks. The highest winds in the area are highly anisotropic with a dominance of S-SW-W winds and the highest resuspension frequencies are found along the shallow eastern coasts. A seasonal pattern is observed with relatively high friction velocities and high resuspension frequencies during winter. There is also a variation depending on grain size, where sediments with fine and medium sand have a considerably higher percentage of resuspension events than bottoms with other dominant grain sizes. Five sub-areas are identified, characterised by different sediment types, resuspension and wind characteristics. If, in the future, wind speed increases as predicted, resuspension of sediments will also increase with effects on the nutrient cycle. (c) 2006 Elsevier B.V. All rights reserved.

  • 300. de Brugh, J. M. J. Aan
    et al.
    Schaap, M.
    Vignati, E.
    Dentener, F.
    Kahnert, Michael
    SMHI, Forskningsavdelningen, Luftmiljö.
    Sofiev, M.
    Huijnen, V.
    Krol, M. C.
    The European aerosol budget in 20062011Inngår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 11, nr 3, s. 1117-1139Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the aerosol budget over Europe in 2006 calculated with the global transport model TM5 coupled to the size-resolved aerosol module M7. Comparison with ground observations indicates that the model reproduces the observed concentrations quite well with an expected slight underestimation of PM10 due to missing emissions (e.g. resuspension). We model that a little less than half of the anthropogenic aerosols emitted in Europe are exported and the rest is removed by deposition. The anthropogenic aerosols are removed mostly by rain (95%) and only 5% is removed by dry deposition. For the larger natural aerosols, especially sea salt, a larger fraction is removed by dry processes (sea salt: 70%, mineral dust: 35%). We model transport of aerosols in the jet stream in the higher atmosphere and an import of Sahara dust from the south at high altitudes. Comparison with optical measurements shows that the model reproduces the Angstrom parameter very well, which indicates a correct simulation of the aerosol size distribution. However, we underestimate the aerosol optical depth. Because the surface concentrations are close to the observations, the shortage of aerosol in the model is probably at higher altitudes. We show that the discrepancies are mainly caused by an overestimation of wet-removal rates. To match the observations, the wet-removal rates have to be scaled down by a factor of about 5. In that case the modelled ground-level concentrations of sulphate and sea salt increase by 50% (which deteriorates the match), while other components stay roughly the same. Finally, it is shown that in particular events, improved fire emission estimates may significantly improve the ability of the model to simulate the aerosol optical depth. We stress that discrepancies in aerosol models can be adequately analysed if all models would provide (regional) aerosol budgets, as presented in the current study.

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