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  • 1601. Wang, Jia
    et al.
    Kwok, Ron
    Saucier, F. J.
    Hutchings, J
    Ikeda, M
    Hibler III, W
    Haapala, J
    Coon, M.D.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Eicken, H
    Tanaka, N
    Prentki, D
    Johnsson, W
    Working toward improved small‐scale sea ice‐ocean modeling in the Arctic seas2003In: EOS: Transactions, ISSN 0096-3941, E-ISSN 2324-9250, Vol. 84, no 34, p. 325-330Article in journal (Refereed)
  • 1602.
    Wang, Shiyu
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Hordoir, Robinson
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Development and evaluation of a new regional coupled atmosphere-ocean model in the North Sea and Baltic Sea2015In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 67, article id 24284Article in journal (Refereed)
    Abstract [en]

    A new regional coupled model system for the North Sea and the Baltic Sea is developed, which is composed of the regional setup of ocean model NEMO, the Rossby Centre regional climate model RCA4, the sea ice model LIM3 and the river routing model CaMa-Flood. The performance of this coupled model system is assessed using a simulation forced with ERA-Interim reanalysis data at the lateral boundaries during the period 1979-2010. Compared to observations, this coupled model system can realistically simulate the present climate. Since the active coupling area covers the North Sea and Baltic Sea only, the impact of the ocean on the atmosphere over Europe is small. However, we found some local, statistically significant impacts on surface parameters like 2m air temperature and sea surface temperature (SST). A precipitation-SST correlation analysis indicates that both coupled and uncoupled models can reproduce the air-sea relationship reasonably well. However, the coupled simulation gives slightly better correlations even when all seasons are taken into account. The seasonal correlation analysis shows that the air-sea interaction has a strong seasonal dependence. Strongest discrepancies between the coupled and the uncoupled simulations occur during summer. Due to lack of air-sea interaction, in the Baltic Sea in the uncoupled atmosphere-standalone run the correlation between precipitation and SST is too small compared to observations, whereas the coupled run is more realistic. Further, the correlation analysis between heat flux components and SST tendency suggests that the coupled model has a stronger correlation. Our analyses show that this coupled model system is stable and suitable for different climate change studies.

  • 1603. Wang, Zhan
    et al.
    Belusic, Danijel
    SMHI, Research Department, Climate research - Rossby Centre.
    Huang, Yi
    Siems, Steven T.
    Manton, Michael J.
    Understanding Orographic Effects on Surface Observations at Macquarie Island2016In: Journal of Applied Meteorology and Climatology, ISSN 1558-8424, E-ISSN 1558-8432, Vol. 55, no 11, p. 2377-2395Article in journal (Refereed)
  • 1604. Wang, Zifa
    et al.
    Xie, Fuying
    Sakurai, T.
    Ueda, H.
    Han, Zhiwei
    Carmichael, G. R.
    Streets, D.
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Holloway, T.
    Hayami, H.
    Kajino, M.
    Thongboonchoo, N.
    Bennet, Cecilia
    SMHI, Research Department, Air quality.
    Park, S. U.
    Fung, C.
    Chang, A.
    Sartelet, K.
    Amann, M.
    MICS-Asia II: Model inter-comparison and evaluation of acid deposition2008In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 42, no 15, p. 3528-3542Article in journal (Refereed)
    Abstract [en]

    This paper focuses on the comparison of chemical deposition of eight regional chemical models used in Model Inter-Comparison Study for Asia (MICS-Asia) II. Monthly-mean depositions of chemical species simulated by these models, including dry deposition of SO(2), HNO(3), NH(3), Sulfate, nitrate and ammonium and wet deposition of SO(4)(2-), NO(3)(-) and NH(4)(+), have been provided for four periods (March, July, December 2001 and March 2002) in this work. Observations at 37 sites of the Acid Deposition Monitoring Network in East Asia (EANET) are compared with SO(4)(2-), NO(3)(-) and NH(4)(+) wet deposition model results. Significant correlations appeared between the observation and computed ensemble mean of participant models. Also, differences among modeled sulfur and nitrogen dry depositions have been studied at the EANET sites. Based on the analysis of acid deposition for various species from different models, total depositions of sulfur (SO(2) and sulfate) and nitrogen (nitrate and ammonium) have been evaluated as the ensemble mean of the eight models. In general, all models capture the observed spatial distribution' of sulfur and nitrogen deposition, although the absolute values may differ from measurements. High deposition often occurs in eastern China, Japan, the Republic of Korea, Thailand, Vietnam, Philippines and other parts of Southeast Asia. The magnitude of model bias is quite large for many of the models. In examining the reasons for model-measurement disagreement, we find that differences in chemical processes, deposition parameterization, and modeled precipitation are the main reasons for large model disparities. (C) 2008 Elsevier Ltd. All rights reserved.

  • 1605. Watson, Laura
    et al.
    Lacressonniere, Gwendoline
    Gauss, Michael
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Andersson, Camilla
    SMHI, Research Department, Air quality.
    Josse, Beatrice
    Marecal, Virginie
    Nyiri, Agnes
    Sobolowski, Stefan
    Siour, Guillaume
    Szopa, Sophie
    Vautard, Robert
    Impact of emissions and+2 degrees C climate change upon future ozone and nitrogen dioxide over Europe2016In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 142, p. 271-285Article in journal (Refereed)
  • 1606. Watson, Laura
    et al.
    Lacressonniere, Gwendoline
    Gauss, Michael
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Andersson, Camilla
    SMHI, Research Department, Air quality.
    Josse, Beatrice
    Marecal, Virginie
    Nyiri, Agnes
    Sobolowski, Stefan
    Siour, Guillaume
    Vautard, Robert
    The impact of meteorological forcings on gas phase air pollutants over Europe2015In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 119, p. 240-257Article in journal (Refereed)
    Abstract [en]

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

  • 1607. Weichselgartner, Juergen
    et al.
    Arheimer, Berit
    SMHI, Research Department, Hydrology.
    Evolving Climate Services into Knowledge-Action Systems2019In: Weather, Climate, and Society, ISSN 1948-8327, E-ISSN 1948-8335, Vol. 11, no 2, p. 385-399Article in journal (Refereed)
  • 1608. Weigel, Benjamin
    et al.
    Andersson, Helén
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Blenckner, Thorsten
    Snickars, Martin
    Bonsdorff, Erik
    Long-term progression and drivers of coastal zoobenthos in a changing system2015In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 528, p. 141-159Article in journal (Refereed)
    Abstract [en]

    Coastal zones are facing climate-driven change coupled with escalating eutrophication. With increasing shifts in hydrographic conditions during the past few decades, a focal task is to understand how environmental drivers affect zoobenthic communities, which play a crucial role in ecosystem functioning. By using long-term data, spanning 40 yr (1973 to 2013) in the northern Baltic Sea, we showed a disparity in zoobenthic responses with pronounced changes in community composition and a trend towards decreased biomass in sheltered areas, while biomasses increased in exposed areas of the coastal zone. We used generalized additive modeling to show that bottom oxygen saturation, sea surface temperature and organic load of the sediments were the main environmental drivers behind contrasting patterns in biomass progression. Oxygen saturation alone explained over one third of the deviation in the biomass developments in sheltered areas, while exposed areas were mainly limited by organic content of the sediments. We analyzed high-resolution climate-scenario simulations, following the Intergovernmental Panel on Climate Change scenarios for the Baltic Sea region in combination with different nutrient load scenarios, for the end of the 21st century. The scenario outcomes showed negative trends in bottom oxygen concentrations throughout the coastal and archipelago zone along with overall increasing temperatures and primary production, and decreasing salinity. Our results suggest that these projected future conditions will strengthen the observed pattern in decreasing zoobenthic production in the immediate coastal zones. Moreover, the potential intensification of unfavorable conditions ex-panding seaward may lead to an expansion of biomass loss to more exposed sites.

  • 1609. Wells, Mark L.
    et al.
    Trainer, Vera L.
    Smayda, Theodore J.
    Karlson, Bengt
    SMHI, Research Department, Oceanography.
    Trick, Charles G.
    Kudela, Raphael M.
    Ishikawa, Akira
    Bernard, Stewart
    Wulff, Angela
    Anderson, Donald M.
    Cochlan, William P.
    Harmful algal blooms and climate change: Learning from the past and present to forecast the future2015In: Harmful Algae, ISSN 1568-9883, E-ISSN 1878-1470, Vol. 49, p. 68-93Article in journal (Refereed)
    Abstract [en]

    Climate change pressures will influence marine planktonic systems globally, and it is conceivable that harmful algal blooms may increase in frequency and severity. These pressures will be manifest as alterations in temperature, stratification, light, ocean acidification, precipitation-induced nutrient inputs, and grazing, but absence of fundamental knowledge of the mechanisms driving harmful algal blooms frustrates most hope of forecasting their future prevalence. Summarized here is the consensus of a recent workshop held to address what currently is known and not known about the environmental conditions that favor initiation and maintenance of harmful algal blooms. There is expectation that harmful algal bloom (HAB) geographical domains should expand in some cases, as will seasonal windows of opportunity for harmful algal blooms at higher latitudes. Nonetheless there is only basic information to speculate upon which regions or habitats HAB species may be the most resilient or susceptible. Moreover, current research strategies are not well suited to inform these fundamental linkages. There is a critical absence of tenable hypotheses for how climate pressures mechanistically affect HAB species, and the lack of uniform experimental protocols limits the quantitative cross-investigation comparisons essential to advancement. A HAB "best practices" manual would help foster more uniform research strategies and protocols, and selection of a small target list of model HAB species or isolates for study would greatly promote the accumulation of knowledge. Despite the need to focus on keystone species, more studies need to address strain variability within species, their responses under multifactorial conditions, and the retrospective analyses of long-term plankton and cyst core data; research topics that are departures from the norm. Examples of some fundamental unknowns include how larger and more frequent extreme weather events may break down natural biogeographic barriers, how stratification may enhance or diminish HAB events, how trace nutrients (metals, vitamins) influence cell toxicity, and how grazing pressures may leverage, or mitigate HAB development. There is an absence of high quality time-series data in most regions currently experiencing HAB outbreaks, and little if any data from regions expected to develop HAB events in the future. A subset of observer sites is recommended to help develop stronger linkages among global, national, and regional climate change and HAB observation programs, providing fundamental datasets for investigating global changes in the prevalence of harmful algal blooms. Forecasting changes in HAB patterns over the next few decades will depend critically upon considering harmful algal blooms within the competitive context of plankton communities, and linking these insights to ecosystem, oceanographic and climate models. From a broader perspective, the nexus of HAB science and the social sciences of harmful algal blooms is inadequate and prevents quantitative assessment of impacts of future HAB changes on human wellbeing. These and other fundamental changes in HAB research will be necessary if HAB science is to obtain compelling evidence that climate change has caused alterations in HAB distributions, prevalence or character, and to develop the theoretical, experimental, and empirical evidence explaining the mechanisms underpinning these ecological shifts. (C) 2015 Elsevier B.V. All rights reserved.

  • 1610. Wells, M.L
    et al.
    Karlson, Bengt
    SMHI, Research Department, Oceanography.
    Harmful Algal Blooms in a Changing Ocean2018In: Global Ecology and Oceanography of Harmful Algal Blooms, Ecological Studies, vol. 232: Presents the key research areas of the international GEOHAB programme / [ed] Glibert, P.M., Berdalet, E., Burford, M.A., Pitcher, G.C., Zhou, M. (Eds.), Springer International Publishing , 2018, 1, p. 77-90Chapter in book (Other academic)
  • 1611.
    Wern, Lennart
    et al.
    SMHI, Core Services.
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Sveriges vindklimat 1901-2008: Analys av trend i geostrofisk vind2009Report (Other academic)
    Abstract [sv]

    En studie har gjorts hur vinden har varierat i Sverige under perioden 1901 - 2008. Eftersom det saknas långa homogena mätserier av vindhastighet i Sverige har vi utgått från tryckmätningar och beräknatden s.k. geostrofiska vinden i elva trianglar som täcker Sverige. Eftersom bara tre observationer per dag (morgon, middag och kväll) har funnits att tillgå så kan det ha blåst mer mellan observationerna.Ett stort arbete har lagts ner på att kontrollera och rätta felaktiga observationer. Mellan åren 1951 och 2008 har varje observerat värde jämförts med ett interpolerat värde. Om skillnaden varit mer än 4 - 5 hPa har en karta analyserats för att kunna avgöra om det i databasen lagrade värdet varit korrekt. Kanske tusen tryckkartor har analyserats. Även två närliggande stationers observationer har jämförts till exempel Bromma och Observatoriekullen. Före 1951 har granskningsarbetet varit begränsat eftersom digitaliserade data saknas för fler stationer än de som ingår i denna undersökning.Förändringen av vindklimatet i elva trianglar som täcker huvuddelen av Sverige har studerats medhjälp av flera olika mått, bland annat:- Årets högsta vindhastighet- Årets medelvindhastighet- Antal fall på minst 25 m/s under året- Potentiell vindenergi under åretÅrets högsta geostrofiska vindhastighet har även jämförts med högsta havsvattenstånd och skogsskador.I det studerade materialet inträffade den absolut högsta geostrofiska vindhastigheten den 13 januari 1984 i den sydligaste triangeln Göteborg - Visby - Lund. Då beräknades den geostrofiska vindhastigheten till 66 m/s och vindriktningen var 235°.Denna undersökning visar bland annat att:- Årets högsta vindhastighet har ökat i fem trianglar och minskat i sex trianglar sedan 1951. Den sammanvägde trenden i Sverige visar på en svag ökning som inte är statistiskt signifikant.- Antal tillfällen per år då vindhastigheten varit minst 25 m/s har minskat i sju av de elva trianglarna sedan 1951.- Medelvindhastigheten har minskat i tio av de elva trianglarna sedan 1951. För fyra trianglar i norra Sverige är denna minskning statistiskt signifikant. Sammantaget för Sverige har medelvindhastigheten minskat med 4 %.- På samma sätt har den potentiella vindenergin minskat i dessa tio trianglar sedan 1951-talet. Minskningen är statistiskt signifikant i de fyra nordliga trianglarna. Sammantaget för Sverige har energin minskat med 7 %.

  • 1612.
    Wern, Lennart
    et al.
    SMHI, Core Services.
    Kindell, Sven
    SMHI, Professional Services.
    Robertson, Lennart
    SMHI, Research Department, Air quality.
    Luktberäkningar för AB ELMO i Flen1986Report (Other academic)
  • 1613.
    Wern, Lennart
    et al.
    SMHI, Core Services.
    Omstedt, Gunnar
    SMHI, Research Department, Air quality.
    Spridningsberäkningar för Volvos planerade bilfabrik i Uddevalla - energicentralen1985Report (Other academic)
  • 1614.
    Wesslander, Karin
    et al.
    SMHI, Core Services.
    Andersson, Lars
    SMHI, Core Services.
    Axe, Philip
    SMHI, Research Department, Oceanography.
    Johansson, Johannes
    SMHI, Core Services.
    Linders, Johanna
    SMHI, Core Services.
    Nexelius, Nils
    SMHI, Core Services.
    Skjevik, Ann-Turi
    SMHI, Core Services.
    Swedish National Report on Eutrophication Status in the Skagerrak, Kattegat and the Sound - OSPAR ASSESSMENT 20162017Report (Other academic)
    Abstract [en]

    The Swedish OSPAR waters were assessed by applying the OSPAR Common Procedure for the time period 2006 – 2014. The Swedish parts of Skagerrak, Kattegat and the Sound constitute the outer part of the transition zone between the estuarine Baltic Sea and the oceanic North Sea and were investigated for nutrients, chlorophyll-a,oxygen, macrophytes, phytoplankton and zoobenthos. The conclusion from the overall assessment of the Swedish OSPAR waters was that only Skagerrak open sea could be classified as a Non-Problem Area and all other assessment units were classified as Problem Areas.  Atmospheric input of nitrogen significantly decreased in both Skagerrak and Kattegat and the land based input of total nutrients also decreased in Skagerrak, Kattegat as well as the Sound. However, the short-term trend of nitrogen input to the Sound was positive. Skagerrak is governed by trans-boundary transports from the North Sea of mainly nitrogen but also phosphorus. Kattegat receives trans-boundary nutrients from both the Baltic Sea through the Sound and from Skagerrak and transports nutrients towards the coast and the western part of the basin.  Overall, concentrations of DIN, DIP, TN and chlorophyll-a decreased in most areas, however, no significant trends were found for DIP. Increasing concentrations were found in silicate, POC and TP. The Secchi depth increased in most areas. Oxygen deficiency was mainly a problem in the fjords and the Kattegat open sea.  In Skagerrak coastal waters winter nutrients were only elevated in the fjords. Concentrations of DIN generally decreased significantly and there were tendencies of decreasing DIP. This pattern was also supported by the total nitrogen while total phosphorus increased. Secchi depth was improving and there was a significant positive trend of increasing depths. However, zoobenthos were still in bad condition and phytoplankton indicator species were often elevated. Chlorophyll-a concentrations were generally decreasing but still elevated in the inner coastal waters. There were also problems with algal toxins such as DST (Diarrhetic Shellfish Toxin) and PST (Paralystic Shellfish Toxin) infections in the area. According to the OSPAR classification scheme, a unit with no evident increased nutrient enrichment can be classified as a Problem Area but the cause might be due to trans-boundary transport from adjacent areas. In the open area of Kattegat there were still problems with oxygen deficiency, especially in the southern parts, even though the trend was significantly positive for the assessment period 2006 – 2014. Concentrations of chlorophyll-a and DIN decreased significantly, however, DIN levels were still generally elevated, especially in the southern parts of Kattegat while DIP was closer to the assessment level. In Kattegat coastal waters winter nutrients were elevated in all assessment units, except from the inner coastal waters, even though there was a general pattern of decreasing going trends. Chlorophyll-a was mainly elevated in the Sound and the estuaries. Secchi depth is generally improving and a significant increase was seen in the Sound. Also in Kattegat, zoobenthos were in bad condition and phytoplankton indicator species were often elevated. 

  • 1615. Westra, S.
    et al.
    Fowler, H. J.
    Evans, J. P.
    Alexander, L. V.
    Berg, Peter
    SMHI, Research Department, Climate research - Rossby Centre.
    Johnson, F.
    Kendon, E. J.
    Lenderink, G.
    Roberts, N. M.
    Future changes to the intensity and frequency of short-duration extreme rainfall2014In: Reviews of geophysics, ISSN 8755-1209, E-ISSN 1944-9208, Vol. 52, no 3, p. 522-555Article, review/survey (Refereed)
    Abstract [en]

    Evidence that extreme rainfall intensity is increasing at the global scale has strengthened considerably in recent years. Research now indicates that the greatest increases are likely to occur in short-duration storms lasting less than a day, potentially leading to an increase in the magnitude and frequency of flash floods. This review examines the evidence for subdaily extreme rainfall intensification due to anthropogenic climate change and describes our current physical understanding of the association between subdaily extreme rainfall intensity and atmospheric temperature. We also examine the nature, quality, and quantity of information needed to allow society to adapt successfully to predicted future changes, and discuss the roles of observational and modeling studies in helping us to better understand the physical processes that can influence subdaily extreme rainfall characteristics. We conclude by describing the types of research required to produce a more thorough understanding of the relationships between local-scale thermodynamic effects, large-scale atmospheric circulation, and subdaily extreme rainfall intensity.

  • 1616.
    Wetterhall, Fredrik
    et al.
    SMHI, Research Department, Hydrology.
    Bardossy, Andras
    Chen, Deliang
    Halldin, Sven
    Xu, Chong-Yu
    Daily precipitation-downscaling techniques in three Chinese regions2006In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 42, no 11, article id W11423Article in journal (Refereed)
    Abstract [en]

    [ 1] Four methods of statistical downscaling of daily precipitation were evaluated on three catchments located in southern, eastern, and central China. The evaluation focused on seasonal variation of statistical properties of precipitation and indices describing the precipitation regime, e. g., maximum length of dry spell and maximum 5-day precipitation, as well as interannual and intra-annual variations of precipitation. The predictors used in this study were mean sea level pressure, geopotential heights at 1000, 850, 700, and 500 hPa, and specific humidity as well as horizontal winds at 850, 700, and 500 hPa levels from the NCEP/NCAR reanalysis with 2.5 degrees x 2.5 degrees resolution for 1961 - 2000. The predictand was daily precipitation from 13 stations. Two analogue methods, one using principal components analysis (PCA) and the other Teweles-Wobus scores (TWS), a multiregression technique with a weather generator producing precipitation (SDSM) and a fuzzy-rule-based weather-pattern-classification method (MOFRBC), were used. Temporal and spatial properties of the predictors were carefully evaluated to derive the optimum setting for each method, and MOFRBC and SDSM were implemented in two modes, with and without humidity as predictor. The results showed that ( 1) precipitation was most successfully downscaled in the southern and eastern catchments located close to the coast, ( 2) winter properties were generally better downscaled, ( 3) MOFRBC and SDSM performed overall better than the analogue methods, ( 4) the modeled interannual variation in precipitation was improved when humidity was added to the predictor set, and ( 5), the annual precipitation cycle was well captured with all methods.

  • 1617.
    Wetterhall, Fredrik
    et al.
    SMHI, Research Department, Hydrology.
    Bardossy, Andras
    Chen, Deliang
    Halldin, Sven
    Xu, Chong-yu
    Statistical downscaling of daily precipitation over Sweden using GCM output2009In: Journal of Theoretical and Applied Climatology, ISSN 0177-798X, E-ISSN 1434-4483, Vol. 96, no 1-2, p. 95-103Article in journal (Refereed)
    Abstract [en]

    A classification of Swedish weather patterns (SWP) was developed by applying a multi-objective fuzzy-rule-based classification method (MOFRBC) to large-scale-circulation predictors in the context of statistical downscaling of daily precipitation at the station level. The predictor data was mean sea level pressure (MSLP) and geopotential heights at 850 (H850) and 700 hPa (H700) from the NCEP/NCAR reanalysis and from the HadAM3 GCM. The MOFRBC was used to evaluate effects of two future climate scenarios (A2 and B2) on precipitation patterns on two regions in south-central and northern Sweden. The precipitation series were generated with a stochastic, autoregressive model conditioned on SWP. H850 was found to be the optimum predictor for SWP, and SWP could be used instead of local classifications with little information lost. The results in the climate projection indicated an increase in maximum 5-day precipitation and precipitation amount on a wet day for the scenarios A2 and B2 for the period 2070-2100 compared to 1961-1990. The relative increase was largest in the northern region and could be attributed to an increase in the specific humidity rather than to changes in the circulation patterns.

  • 1618.
    Wetterhall, Fredrik
    et al.
    SMHI, Research Department, Hydrology.
    Graham, Phil
    SMHI, Research Department, Climate research - Rossby Centre.
    Andreasson, Johan
    SMHI, Professional Services.
    Rosberg, Jörgen
    SMHI, Research Department, Hydrology.
    Yang, Wei
    SMHI, Research Department, Hydrology.
    Using ensemble climate projections to assess probabilistic hydrological change in the Nordic region2011In: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 11, no 8, p. 2295-2306Article in journal (Refereed)
    Abstract [en]

    Assessing hydrological effects of global climate change at local scales is important for evaluating future hazards to society. However, applying climate model projections to local impact models can be difficult as outcomes can vary considerably between different climate models, and including results from many models is demanding. This study combines multiple climate model outputs with hydrological impact modelling through the use of response surfaces. Response surfaces represent the sensitivity of the impact model to incremental changes in climate variables and show probabilies for reaching a priori determined thresholds. Response surfaces were calculated using the HBV hydrological model for three basins in Sweden. An ensemble of future climate projections was then superimposed onto each response surface, producing a probability estimate for exceeding the threshold being evaluated. Site specific impacts thresholds were used where applicable. Probabilistic trends for future change in hazards or potential can be shown and evaluated. It is particularly useful for visualising the range of probable outcomes from climate models and can easily be updated with new results as they are made available.

  • 1619.
    Wetterhall, Fredrik
    et al.
    SMHI, Research Department, Hydrology.
    Pappenberger, F.
    Alfieri, L.
    Cloke, H. L.
    Thielen-del Pozo, J.
    Balabanova, S.
    Danhelka, J.
    Vogelbacher, A.
    Salamon, P.
    Carrasco, I.
    Cabrera-Tordera, A. J.
    Corzo-Toscano, M.
    Garcia-Padilla, M.
    Garcia-Sanchez, R. J.
    Ardilouze, C.
    Jurela, S.
    Terek, B.
    Csik, A.
    Casey, J.
    Stankunavicius, G.
    Ceres, V.
    Sprokkereef, E.
    Stam, J.
    Anghel, E.
    Vladikovic, D.
    Eklund, C. Alionte
    Hjerdt, N.
    Djerv, H.
    Holmberg, F.
    Nilsson, J.
    Nystrom, K.
    Susnik, M.
    Hazlinger, M.
    Holubecka, M.
    HESS Opinions "Forecaster priorities for improving probabilistic flood forecasts"2013In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 17, no 11, p. 4389-4399Article in journal (Refereed)
    Abstract [en]

    Hydrological ensemble prediction systems (HEPS) have in recent years been increasingly used for the operational forecasting of floods by European hydrometeorological agencies. The most obvious advantage of HEPS is that more of the uncertainty in the modelling system can be assessed. In addition, ensemble prediction systems generally have better skill than deterministic systems both in the terms of the mean forecast performance and the potential forecasting of extreme events. Research efforts have so far mostly been devoted to the improvement of the physical and technical aspects of the model systems, such as increased resolution in time and space and better description of physical processes. Developments like these are certainly needed; however, in this paper we argue that there are other areas of HEPS that need urgent attention. This was also the result from a group exercise and a survey conducted to operational forecasters within the European Flood Awareness System (EFAS) to identify the top priorities of improvement regarding their own system. They turned out to span a range of areas, the most popular being to include verification of an assessment of past forecast performance, a multi-model approach for hydrological modelling, to increase the forecast skill on the medium range (> 3 days) and more focus on education and training on the interpretation of forecasts. In light of limited resources, we suggest a simple model to classify the identified priorities in terms of their cost and complexity to decide in which order to tackle them. This model is then used to create an action plan of short-, medium-and long-term research priorities with the ultimate goal of an optimal improvement of EFAS in particular and to spur the development of operational HEPS in general.

  • 1620. Weyhenmeyer, Gesa A.
    et al.
    Froberg, Mats
    Karltun, Erik
    Khalili, Maria
    Kothawala, Dolly
    Temnerud, Johan
    SMHI, Research Department, Hydrology.
    Tranvik, Lars J.
    Selective decay of terrestrial organic carbon during transport from land to sea2012In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 18, no 1, p. 349-355Article in journal (Refereed)
    Abstract [en]

    Numerous studies have estimated carbon exchanges at the landatmosphere interface, more recently also including estimates at the freshwateratmosphere interface. Less attention has been paid to lateral carbon fluxes, in particular to the fate of terrestrial carbon during transport from soils via surface waters to the sea. Using extensive datasets on soil, lake and river mouth chemistry of the boreal/hemiboreal region we determined organic carbon (OC) stocks of the O horizon from catchment soils, annual OC transports through more than 700 lakes (OClakeflux) and the total annual OC transport at Sweden's 53 river mouths (OCseaflux). We show here that a minimum of 0.030.87% yr(-1) of the OC soil stocks need to be exported to lakes in order to sustain the annual OClakeflux. Across Sweden we estimated a total OClakeflux of similar to 2.9 Mtonne yr(-1), which corresponds to similar to 10% of Sweden's total terrestrial net ecosystem production, and it is over 50% higher than the total OCseaflux. The OC loss during transport to the sea follows a simple exponential decay with an OC half-life of similar to 12 years. Water colour, a proxy often used for dissolved humic matter, is similarly lost exponentially but about twice as fast as OC. Thus, we found a selective loss of the coloured portion of soil-derived OC during its transport through inland waters, prior to being discharged into the sea. The selective loss is water residence time dependent, resulting in that the faster the water flows through the landscape the less OC and colour is lost. We conclude that increases in runoff will result in less efficient losses of OC, and particularly of colour, if the time for OC transformations in the landscape shortens. Consequently, OC reaching the sea is likely to become more coloured, and less processed, which can have far-reaching effects on biogeochemical cycles.

  • 1621. White, Christopher J.
    et al.
    Carlsen, Henrik
    Robertson, Andrew W.
    Klein, Richard J. T.
    Lazo, Jeffrey K.
    Kumar, Arun
    Vitart, Frederic
    de Perez, Erin Coughlan
    Ray, Andrea J.
    Murray, Virginia
    Bharwani, Sukaina
    MacLeod, Dave
    James, Rachel
    Fleming, Lora
    Morse, Andrew P.
    Eggen, Bernd
    Graham, Richard
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Becker, Emily
    Pegion, Kathleen V.
    Holbrook, Neil J.
    McEvoy, Darryn
    Depledge, Michael
    Perkins-Kirkpatrick, Sarah
    Brown, Timothy J.
    Street, Roger
    Jones, Lindsey
    Remenyi, Tomas A.
    Hodgson-Johnston, Indi
    Buontempo, Carlo
    Lamb, Rob
    Meinke, Holger
    Arheimer, Berit
    SMHI, Research Department, Hydrology.
    Zebiak, Stephen E.
    Potential applications of subseasonal-to-seasonal (S2S) predictions2017In: Meteorological Applications, ISSN 1350-4827, E-ISSN 1469-8080, Vol. 24, no 3, p. 315-325Article in journal (Refereed)
  • 1622. Wibig, Joanna
    et al.
    Maraun, Douglas
    Benestad, Rasmus
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Lorenz, Philip
    Christensen, Ole Bossing
    Projected Change-Models and Methodology2015Chapter in book (Other academic)
    Abstract [en]

    General (global) circulation models (GCMs) are a useful tool for studying how climate may change in the future. Although GCMs have high temporal resolution, their spatial resolution is low. To simulate the future climate of the Baltic Sea region, it is necessary to downscale GCM data. This chapter describes the two conceptually different ways of downscaling: regional climate models (RCMs) nested in GCMs and using empirical and/or statistical relations between large-scale variables from GCMs and small-scale variables. There are many uncertainties in climate models, including uncertainty related to future land use and atmospheric greenhouse gas concentrations, limits on the amount of input data and their accuracy, and the chaotic nature of weather. The skill of methods for describing regional climate futures is also limited by natural climate variability. For the Baltic Sea area, the lack of an oceanic component in RCMs and poor representation of forcing by aerosols and changes in land use are major limitations.

  • 1623. Widmann, Martin
    et al.
    Bedia, Joaquin
    Gutierrez, Jose M.
    Bosshard, Thomas
    SMHI, Research Department, Hydrology.
    Hertig, Elke
    Maraun, Douglas
    Casado, Maria J.
    Ramos, Petra
    Cardoso, Rita M.
    Soares, Pedro M. M.
    Ribalaygua, Jamie
    Page, Christian
    Fischer, Andreas M.
    Herrera, Sixto
    Huth, Radan
    Validation of spatial variability in downscaling results from the VALUE perfect predictor experiment2019In: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 39, no 9, p. 3819-3845Article in journal (Refereed)
  • 1624.
    Wilcke, Renate
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Selecting regional climate scenarios for impact modelling studies2016In: Environmental Modelling & Software, ISSN 1364-8152, E-ISSN 1873-6726, Vol. 78, p. 191-201Article in journal (Refereed)
    Abstract [en]

    In climate change research ensembles of climate simulations are produced in an attempt to cover the uncertainty in future projections. Many climate change impact studies face difficulties using the full number of simulations available, and therefore often only subsets are used. Until now such subsets were chosen based on their representation of temperature change or by accessibility of the simulations. By using more specific information about the needs of the impact study as guidance for the clustering of simulations, the subset fits the purpose of climate change impact research more appropriately. Here, the sensitivity of such a procedure is explored, particularly with regard to the use of different climate variables, seasons, and regions in Europe. While temperature dominates the clustering, the resulting selection is influenced by all variables, leading to the conclusion that different subsets fit different impact studies best. (C) 2016 The Authors. Published by Elsevier Ltd.

  • 1625. Wilk, J.
    et al.
    Andersson, Lotta
    SMHI, Core Services. SMHI, Research Department, Hydrology.
    Graham, Phil
    SMHI, Professional Services.
    Wikner, J. J.
    Mokwatlo, S.
    Petja, B.
    From forecasts to action - What is needed to make seasonal forecasts useful for South African smallholder farmers?2017In: International Journal of Disaster Risk Reduction, E-ISSN 2212-4209, Vol. 25, p. 202-211Article in journal (Refereed)
  • 1626.
    Wilk, Julie
    et al.
    SMHI, Research Department, Hydrology.
    Andersson, Lotta
    SMHI, Core Services.
    Warburton, Michele
    Adaptation to climate change and other stressors among commercial and small-scale South African farmers2013In: Regional Environmental Change, ISSN 1436-3798, E-ISSN 1436-378X, Vol. 13, no 2, p. 273-286Article in journal (Refereed)
    Abstract [en]

    Commercial and small-scale farmers in South Africa are exposed to many challenges. Interviews with 44 farmers in the upper Thukela basin, KwaZulu-Natal, were conducted to identify common and specific challenges for the two groups and adaptive strategies for dealing with the effects of climate and other stressors. This work was conducted as part of a larger participatory project with local stakeholders to develop a local adaptation plan for coping with climate variability and change. Although many challenges related to exposure to climate variability and change, weak agricultural policies, limited governmental support, and theft were common to both farming communities, their adaptive capacities were vastly different. Small-scale farmers were more vulnerable due to difficulties to finance the high input costs of improved seed varieties and implements, limited access to knowledge and agricultural techniques for water and soil conservation and limited customs of long-term planning. In addition to temperature and drought-related challenges, small-scale farmers were concerned about soil erosion, water logging and livestock diseases, challenges for which the commercial farmers already had efficient adaptation strategies in place. The major obstacle hindering commercial farmers with future planning was the lack of clear directives from the government, for example, with regard to issuing of water licences and land reform. Enabling agricultural communities to procure sustainable livelihoods requires implementation of strategies that address the common and specific challenges and strengthen the adaptive capacity of both commercial and small-scale farmers. Identified ways forward include knowledge transfer within and across farming communities, clear governmental directives and targeted locally adapted finance programmes.

  • 1627. Wilk, Julie
    et al.
    Hjerpe, Mattias
    Yang, Wei
    SMHI, Research Department, Hydrology.
    Fan, Hua
    Farm-scale adaptation under extreme climate and rapid economic transition2015In: Environment, Development and Sustainability, ISSN 1387-585X, E-ISSN 1573-2975, Vol. 17, no 3, p. 393-407Article in journal (Refereed)
    Abstract [en]

    This paper aims to analyse what shapes farmers' vulnerability and adaptation strategies in the context of rapid change. Xinjiang is semi-arid, with extremes of temperature, growing seasons and winds. Favourable socioeconomic conditions have boosted the wellbeing of farmers in the past decades. Interviews with forty-seven farmers led to the categorization of five groups according to the predominant type of farming activity: animal farmers, government farmers (leasing land from the Xinjiang Production and Construction Group), crop farmers, agri-tourism operators and entrepreneurs. High government support has aided farmers to deal with climate challenges, through advanced technology, subsidies and loans. Farmers, however, greatly contribute to their own high adaptive capacity through inventiveness, flexibility and a high knowledge base. Although the future climate will entail hotter temperatures, farmers can be seen as generally well equipped to deal with these challenges because of the high adaptive capacity they currently have and utilize. Those that are most vulnerable are those that have difficulty to access credit e.g. animal farmers and those that do not want to change their agricultural systems e.g. from pastoral lifestyles to include tourism-based operations.

  • 1628.
    Wilk, Julie
    et al.
    SMHI, Research Department, Hydrology.
    Jonsson, Anna
    SMHI, Core Services.
    Rydhagen, Birgitta
    Rani, Ashu
    Kumar, Arun
    The perspectives of the urban poor in climate vulnerability assessments - The case of Kota, India2018In: Urban Climate, ISSN 2212-0955, E-ISSN 2212-0955, Vol. 24, p. 633-642Article in journal (Refereed)
  • 1629. Willems, P.
    et al.
    Arnbjerg-Nielsen, K.
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    Nguyen, V. T. V.
    Climate change impact assessment on urban rainfall extremes and urban drainage: Methods and shortcomings2012In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 103, p. 106-118Article in journal (Refereed)
    Abstract [en]

    Cities are becoming increasingly vulnerable to flooding because of rapid urbanization, installation of complex infrastructure, and changes in the precipitation patterns caused by anthropogenic climate change. The present paper provides a critical review of the current state-of-the-art methods for assessing the impacts of climate change on precipitation at the urban catchment scale. Downscaling of results from global circulation models or regional climate models to urban catchment scales are needed because these models are not able to describe accurately the rainfall process at suitable high temporal and spatial resolution for urban drainage studies. The downscaled rainfall results are however highly uncertain, depending on the models and downscaling methods considered. This uncertainty becomes more challenging for rainfall extremes since the properties of these extremes do not automatically reflect those of average precipitation. In this paper, following an overview of some recent advances in the development of innovative methods for assessing the impacts of climate change on urban rainfall extremes as well as on urban hydrology and hydraulics, several existing difficulties and remaining challenges in dealing with this assessment are discussed and further research needs are described. (C) 2011 Elsevier B.V. All rights reserved.

  • 1630. Willers, Saskia M.
    et al.
    Eriksson, Charlotta
    Gidhagen, Lars
    SMHI, Research Department, Air quality.
    Nilsson, Mats E.
    Pershagen, Goran
    Bellander, Tom
    Fine and coarse particulate air pollution in relation to respiratory health in Sweden2013In: European Respiratory Journal, ISSN 0903-1936, E-ISSN 1399-3003, Vol. 42, no 4, p. 924-934Article in journal (Refereed)
    Abstract [en]

    Health effects have repeatedly been associated with residential levels of air pollution. However, it is difficult to disentangle effects of long-term exposure to locally generated and long-range transported pollutants, as well as to exhaust emissions and wear particles from road traffic. We aimed to investigate effects of exposure to particulate matter fractions on respiratory health in the Swedish adult population, using an integrated assessment of sources at different geographical scales. The study was based on a nationwide environmental health survey performed in 2007, including 25 851 adults aged 18-80 years. Individual exposure to particulate matter at residential addresses was estimated by dispersion modelling of regional, urban and local sources. Associations between different size fractions or source categories and respiratory outcomes were analysed using multiple logistic regression, adjusting for individual and contextual confounding. Exposure to locally generated wear particles showed associations for blocked nose or hay fever, chest tightness or cough, and restricted activity days with odds ratios of 1.5-2 per 10-mu g.m(-3) increase. Associations were also seen for locally generated combustion particles, which disappeared following adjustment for exposure to wear particles. In conclusion, our data indicate that long-term exposure to locally generated road wear particles increases the risk of respiratory symptoms in adults.

  • 1631. Willers, Saskia M.
    et al.
    Eriksson, Charlotta
    Gidhagen, Lars
    SMHI, Research Department, Air quality.
    Nilsson, Mats E.
    Pershagen, Goran
    Bellander, Tom
    Traffic Related Air Pollution and Respiratory Health in Sweden: The Roadside Study2009In: EPIDEMIOLOGY, ISSN 1044-3983, Vol. 20, no 6, p. S29-S30Article in journal (Other academic)
  • 1632.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Comparison of Model and Cloud Radar Derived Cloud Vertical Structure and Overlap for the BALTEX BRIDGE Campaign.2004In: Fourth Study Conference on BALTEX: Conference Proceedings / [ed] Hans-Jörg Isemer, 2004, p. 18-Conference paper (Other academic)
  • 1633.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Comparison of modeled and radar measured cloud fraction and overlap2005In: Extended abstracts of a WMO/WCRP-sponsored Regional-Scale Climate Modelling Workshop [Elektronisk resurs] : high-resolution climate modelling : assessment, added value and applications, Lund, Sweden, 29 March-2 April 2004 / [ed] Lars Bärring & René Laprise, Lund: Department of Physical Geography & Ecosystems Analysis, Lund University , 2005, p. 128-Conference paper (Other academic)
  • 1634.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Preliminary use of CM-SAF cloud and radiation products for evaluation of regional climate simulations: Visiting Scientist Report Climate Monitoring SAF (CM-SAF)2008Report (Other academic)
    Abstract [en]

    We have compared monthly mean cloud and radiation fields from the EUMETSAT Climate Monitoring SAF (CM-SAF, http://www.cmsaf.eu) data base with the clouds and radiation simulated by the Rossby Centre regional climate model (RCA) and by the European Centre Medium range Weather Forecast model (ECMWF) over Europe and North Africa for the time period January 2005 to December 2006.ECMWF and RCA overestimate the cloud fraction by 20% over snow covered regions in the north east of Europe and overestimate the surface downwelling longwave radiation (SDL) by 20-40W/m2 and surface outgoing longwave radiation by 10-30W/m2. The RCA-simulated clouds have too much cloud water in northern Europe in summer and in autumn and they therefore reflect too much shortwave radiation at the TOA (TRS) and this also leads to an underestimation of the incoming shortwave radiation (SIS) at the surface. Over most of Europe and over sea ECMWF (all year) and RCA (in winter-spring) underestimate the cloud fraction which could explain a corresponding underestimate of TRS, overestimate of SIS and underestimate of SDL. The satellites overestimate cloud cover over sea due to problems in the treatment of sub-pixel cloudiness and therefore the models underestimates are larger over sea. Mainly RCA but also ECMWF overestimate cloud fraction on top of mountains and underestimate it along mountain ranges and have corresponding differences in the TOA and surface radiation fluxes compared to the CM-SAF data.Over North Africa RCA underestimates TRS by -11W/m2 and overestimates the TOA emitted thermal radiation (TET) by 8W/m2. ECMWF underestimates TRS by -28W/m2 and overestimates TET by 14W/m2. These errors are similar to what has been found for many other global models and are attributed to clear sky errors either due to too high surface temperatures, errors in emissivity, albedo or lack of aerosols. Adding clear and cloudy skies radiation fluxes to the CM-SAF data base would help us to understand the reasons for ECMWF and RCA errors. The polar orbiting satellite retrieval for 2005-2006 erroneously overestimated cloud fraction over North Africa, which also affects the CM-SAF derived surface radiation fluxes.

  • 1635.
    Willén, Ulrika
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Crewell, S.
    Comparison of model and cloud radar derived cloud vertical structure and overlap.2004In: 14th International Conference on Clouds and Precipitation(ICCP), 2004, p. 1434-1437Conference paper (Other academic)
  • 1636.
    Willén, Ulrika
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Crewell, S
    Baltink, H K
    Sievers, O
    Assessing model predicted vertical cloud structure and cloud overlap with radar and lidar ceilometer observations for the Baltex Bridge Campaign of CLIWA-NET2005In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 75, no 3, p. 227-255Article in journal (Refereed)
    Abstract [en]

    The cloud vertical distribution and overlap of four large-scale models operating at different horizontal and vertical resolutions have been assessed using radar and lidar observations from the Baltex Bridge Campaign of CLIWA-NET. The models range from the global European Centre for Medium range Weather Forecast (ECMWF) model, to the Regional Atmospheric Climate Model (RACMO) and the Rossby Centre Atmospheric (RCA) regional climate model, to the non-hydrostatic meso-scale Lokal Model (LM). Different time averaging periods for the radar data were used to estimate the uncertainty of the point-to-space transformations of the observations. Relative to the observations, all models underestimated the height of the lowest cloud base. Clouds occurred more frequently in the models but with smaller cloud fractions below 7 km. The findings confirm previous cloud radar studies which found that models overestimate cloud fractions above 7 km. Radar-observed clouds were often thinner than the model vertical resolutions, which can have serious implications on model cloud overlap and radiation fluxes. The radar-derived cloud overlap matrix, which takes into account the overlap of all vertical layers, was found to be close to maximum-random overlap. Using random overlap for vertically continuous clouds with vertical gradients in cloud fraction larger than 40-50% per kilometre gave the best fit to the data. The gradient approach could be improved by making it resolution- and cloud system-dependent. Previous cloud radar overlap studies have considered the overlap of two cloud layers as a function of maximum and random overlap. Here, it was found that the two-layer overlap could be modelled by a mixture of maximum and minimum overlap. (c) 2005 Elsevier B.V. All rights reserved.

  • 1637.
    Willén, Ulrika
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Baltink, Henk Klein
    Quante, Markus
    COMPARISON OF MODEL AND CLOUD RADAR DERIVED CLOUD OVERLAP2002Conference paper (Other academic)
  • 1638. Winsor, P
    et al.
    Rodhe, J
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Baltic Sea ocean climate: an analysis of 100 yr of hydrographic data with focus on the freshwater budget2001In: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 18, no 1-2, p. 5-15Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea climate is analysed based upon long-term oceanographic measurements. The objective of the work is to study the natural variability of present day climate with focus on the freshwater budget. The results are designed to be used for validation of climate models and for discrimination of the significance of modelled climate change scenarios. Almost 100 yr of observations are used in the study, including data for river runoff, water exchange through the Danish Straits (as calculated from river runoff and from sea level data from the Kattegat), salinity data from the Baltic Sea and the Kattegat, and oxygen content in the deep Baltic Sea. The analyses illustrate that freshwater supply to the Baltic shows large variations on time scales up to several decades. The long-term variations in freshwater storage are closely correlated to accumulated changes in river runoff. This indicates strong positive feedback between the amount of outflowing surface water from the Baltic Sea and the salinity of the inflowing Kattegat water. One implication of the study is that climate control simulations must cover several decades, probably up to 100 yr in order to capture the natural variability of present day climate. Also, models designed to study climate change for the Baltic Sea probably need to start integrating from the present day.

  • 1639. Winterdahl, Mattias
    et al.
    Laudon, Hjalmar
    Lyon, Steve W.
    Pers, Charlotta
    SMHI, Research Department, Hydrology.
    Bishop, Kevin
    Sensitivity of stream dissolved organic carbon to temperature and discharge: Implications of future climates2016In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, no 1, p. 126-144Article in journal (Refereed)
    Abstract [en]

    Dissolved organic carbon (DOC) is a significant constituent in aquatic ecosystems with concentrations in streams influenced by both temperature and water flow pathway dynamics associated with changes in discharge (streamflow). We investigated the sensitivity of DOC concentrations in 12 high-latitude headwater streams to changes in temperature and discharge using a mathematical model. The implications of differences in sensitivities were explored by using downscaled projections of air temperature and discharge to simulate possible trajectories of DOC concentrations in a changing climate. We found two distinct responses: (i) catchments where stream DOC sensitivity was high to temperature but low to discharge and (ii) catchments where stream DOC sensitivity was low to temperature but high to discharge. Streams with strong seasonal DOC dynamics were more sensitive to temperature changes than nonseasonal systems. In addition, stream DOC sensitivity to discharge was strongly correlated with vertical soil water DOC differences in the near-stream zone. Simulations of possible future changes in DOC concentrations indicated median increases of about 4-24% compared to current levels when using projections of air temperature and discharge but even larger increases were observed for base flow concentrations (13-42%). Streams with high-temperature sensitivity showed the largest increases in DOC concentrations. Our results suggest that future climatic changes could bring significant increases in surface water DOC concentrations in boreal and hemiboreal areas but that the response ultimately is dependent on vertical soil solution DOC differences and soil organic carbon distribution.

  • 1640. Winterdahl, Mattias
    et al.
    Temnerud, Johan
    SMHI, Research Department, Hydrology.
    Futter, Martyn N.
    Lofgren, Stefan
    Moldan, Filip
    Bishop, Kevin
    Riparian Zone Influence on Stream Water Dissolved Organic Carbon Concentrations at the Swedish Integrated Monitoring Sites2011In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 40, no 8, p. 920-930Article in journal (Refereed)
    Abstract [en]

    Short-term variability in stream water dissolved organic carbon (DOC) concentrations is controlled by hydrology, climate and atmospheric deposition. Using the Riparian flow-concentration Integration Model (RIM), we evaluated factors controlling stream water DOC in the Swedish Integrated Monitoring (IM) catchments by separating out hydrological effects on stream DOC dynamics. Model residuals were correlated with climate and deposition-related drivers. DOC was most strongly correlated to water flow in the northern catchment (Gammtratten). The southern Aneboda and Kindla catchments had pronounced seasonal DOC signals, which correlated weakly to flow. DOC concentrations at GAyenrdsjon increased, potentially in response to declining acid deposition. Soil temperature correlated strongly with model residuals at all sites. Incorporating soil temperature in RIM improved model performance substantially (20-62% lower median absolute error). According to the simulations, the RIM conceptualization of riparian processes explains between 36% (Kindla) and 61% (Aneboda) of the DOC dynamics at the IM sites.

  • 1641.
    Wittgren, Hans Bertil
    SMHI, Research Department.
    Kvävetransport till Slätbaken från Söderköpingsåns avrinningsområde1995Report (Other academic)
  • 1642.
    Wittgren, Hans Bertil
    et al.
    SMHI, Research Department.
    Arheimer, Berit
    SMHI, Research Department, Hydrology.
    Source apportionment of riverine nitrogen transport based on catchment modelling1996In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 33, no 4-5, p. 109-115Article in journal (Refereed)
    Abstract [en]

    Source apportionment of river substance transport, i.e. estimation of how much each source in each subbasin contributes to the river-mouth transport is a vital step in achieving the most efficient management practices to reduce pollutant loads to the sea. In this study, the spatially lumped (at sub-catchment level), semiempirical PULSE hydrological model, with a nitrogen routine coupled to if was used to perform source apportionment of nitrogen transport in the Soderkopingsan river basin (882 km(2)) in south-eastern Sweden, for the period 1991-93. The river basin was divided into 28 subbasins and the following sources were considered: land leakage from the categories forest arable and ley/pasture; point sources, and; atmospheric deposition on lake surfaces. The calibrated model yielded an explained variance of 60%, based on comparison of measured and modelled river nitrogen (Total N) concentrations. Eight subbasins, with net contributions to the river-mouth transport exceeding 3 kg ha(-1) yr(-1), were identified as the most promising candidates for cost efficient nitrogen management. The other 20 subbasins all had net contributions below 3 kg ha(-1) yr(-1). Arable land contributed 63% of the nitrogen transport at the river mouth and would thus be in focus for management measures. However, point sources (18% contribution to net transport) should also be considered due to their relatively high accessibility for removal measures (high concentrations). E.g., the most downstream subbasin, with the largest wastewater treatment plant in the whole river basin, had a net contribution of 16 kg ha(-1) yr(-1). This method for source apportionment may provide authorities with quantitative information about where in a river basin, and at which sources, they should focus their attention. However, once this is done, an analysis with higher resolution has to be performed in each of the interesting subbasins, before decisions on actual management measures can be taken. Copyright (C) 1996 IAWQ.

  • 1643.
    Wittgren, Hans Bertil
    et al.
    SMHI, Research Department.
    Tobiason, S
    Nitrogen removal from pretreated wastewater in surface flow wetlands1995In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 32, no 3, p. 69-78Article in journal (Refereed)
    Abstract [en]

    The wastewater treatment plant in the town of Oxelosund (12,500 inhabitants), Sweden, has mechanical and chemical treatment for removal of BOD and phosphorus. With the aim to achieve 50% nitrogen removal, a surface flow wetland system of 21 ha was created as a final step during 1993. It consists of 5 cells, where 2+2 are operated in parallel with a final common cell, This allows intermittent filling and emptying, the goal of which is to promote both nitrification and denitrification for a design flow of 6000 m(3) day(-1). During the first year of operation, August 1993 to July 1994, the wetland removed 720 kg ha(-1) of total nitrogen from the load of 1810 kg ha(-1). Ammonium-N was the dominant fraction at the inlet as well as at the outlet, 79% and 90% of total nitrogen, respectively. The large fraction of NH4+ at the outlet showed that nitrification was the limiting step. An intensive monitoring effort in May 1994 indicated that neither wastewater toxicity nor oxygen deficiency were likely to limit nitrification. Instead, sub-optimal hydraulic loading conditions; a lack of suitable surfaces for ion exchange of NH4+ as well as for attachment of nitrifiers; and phosphorus deficiency, were considered potentially important factors in limiting nitrification. In addition to nitrogen removal, the wetland system reduced total phosphorus, BOD7 and E. coli (44 degrees C) to very low levels at the outlet.

  • 1644. Woick, H
    et al.
    Dewitte, S
    Feijt, A
    Gratzki, A
    Hechler, P
    Hollmann, R
    Karlsson, Karl-Göran
    SMHI, Research Department, Atmospheric remote sensing.
    Laine, V
    Lowe, P
    Nitsche, H
    Werscheck, M
    Wollenweber, G
    The satellite application facility on climate monitoring2002In: EARTH'S ATMOSPHERE, OCEAN AND SURFACE STUDIES, 2002, no 11, p. 2405-2410Conference paper (Refereed)
    Abstract [en]

    The Satellite Application Facility on Climate Monitoring is a joint project of the National Meteorological Services and other institutes from Belgium, Finland, Germany, Sweden and The Netherlands. The objective of the project is to set up a system to provide atmospheric and oceanographic data sets from (primarily) operational geostationary and polar orbiting meteorological satellites for climate monitoring, research and applications at regional European scale, for some products on a global scale. Initial operational SAF products are related to clouds, radiation budget, ocean status and water vapour content in the atmosphere. SAF operations are foreseen to start in 2004. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

  • 1645. Wolters, L
    et al.
    Cats, G
    Gustafsson, Nils
    SMHI, Research Department, Meteorology.
    Wilhelmsson, T
    Data-parallel numerical methods in a weather forecast model1995In: Applied Numerical Mathematics, ISSN 0168-9274, E-ISSN 1873-5460, Vol. 19, no 1-2, p. 159-171Article in journal (Refereed)
    Abstract [en]

    The results presented in this paper are part of a research project to investigate the possibilities to apply massively parallel architectures for numerical weather forecasting. Within numerical weather forecasting several numerical techniques are used to solve the model equations. This paper compares the performance of implementations on a MasPar system of two techniques, finite difference and spectral, that are adopted in the numerical weather forecasting model HIRLAM. The operational HIRLAM model is based on finite difference methods, while the spectral model is still in a research phase. Also the differences in relative performance of these methods on the MasPar and vector architectures will be discussed.

  • 1646. Worman, A.
    et al.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    Riml, Joakim
    SMHI, Research Department, Hydrology.
    The power of runoff2017In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 548, p. 784-793Article in journal (Refereed)
  • 1647. Worman, Anders
    et al.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    Akesson, Anna
    Riml, Joakim
    SMHI, Research Department, Hydrology.
    Drifting runoff periodicity during the 20th century due to changing surface water volume2010In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 24, no 26, p. 3772-3784Article in journal (Refereed)
    Abstract [en]

    Fourier and wavelet analyses were used to reveal the dominant trends and coherence of a more than one-century-long time series of precipitation and discharge in several watersheds in Sweden, two of which were subjected to hydropower and intensive agriculture. During the 20th century, there was a gradual, significant drift of the dominant discharge periodicity in agricultural watersheds. This study shows that the steepness of the Fourier spectrum of runoff from the May to October period each year increased gradually during the century, which suggests a more predictable intra-annual runoff pattern (more apart from white-noise). In the agricultural watershed, the coherence spectrum of precipitation and runoff is generally high with a consistent white-noise relationship for precipitation during the 20th century, indicating that precipitation is not controlling the drift of the discharge spectrum. In the hydropower regulated watershed, there was a sudden decrease of the discharge spectrum slope when regulation commenced in the 1920s. This study develops a new theory in which the runoff spectrum is related to the hydraulic and hydro-morphological characteristics of the watershed. Using this theory, we explain the changes in runoff spectra in the two watersheds by the anthropogenic change in surface water volume and, hence, changes in kinematic wave celerity and water transit times. The reduced water volume in the agricultural watershed would also contribute to decreasing evaporation, which could explain a slightly increasing mean discharge during the 20th century despite the fact that precipitation was statistically constant in the area. Copyright (C) 2010 John Wiley & Sons, Ltd.

  • 1648. Wormbs, N.
    et al.
    Nilsson, A.E.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Sörlin, S.
    The History of Emerging Arctic Climate Modelling, poster presented at the IPY final conference in Oslo2010Conference paper (Other academic)
  • 1649. Wramneby, Anna
    et al.
    Smith, Benjamin
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Hot spots of vegetation-climate feedbacks under future greenhouse forcing in Europe2010In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 115, article id D21119Article in journal (Refereed)
    Abstract [en]

    We performed simulations of future biophysical vegetation-climate feedbacks with a regional Earth System Model, RCA-GUESS, interactively coupling a regional climate model and a process-based model of vegetation dynamics and biogeochemistry. Simulated variations in leaf area index and in the relative coverage of evergreen forest, deciduous forest, and open land vegetation in response to simulated climate influence atmospheric state via variations in albedo, surface roughness, and the partitioning of the land-atmosphere heat flux into latent and sensible components. The model was applied on a similar to 50 x 50 km grid over Europe under a future climate scenario. Three potential "hot spots" of vegetation-climate feedbacks could be identified. In the Scandinavian Mountains, reduced albedo resulting from the snow-masking effect of forest expansion enhanced the winter warming trend. In central Europe, the stimulation of photosynthesis and plant growth by "CO2 fertilization" mitigated warming, through a negative evapotranspiration feedback associated with increased vegetation cover and leaf area index. In southern Europe, increased summer dryness restricted plant growth and survival, causing a positive warming feedback through reduced evapotranspiration. Our results suggest that vegetation-climate feedbacks over the European study area will be rather modest compared to the radiative forcing of increased global CO2 concentrations but may modify warming projections locally, regionally, and seasonally, compared with results from traditional "off-line" regional climate models lacking a representation of the relevant feedback mechanisms.

  • 1650. Wu, Dong L.
    et al.
    Baum, Bryan A.
    Choi, Yong-Sang
    Foster, Michael J.
    Karlsson, Karl-Göran
    SMHI, Research Department, Atmospheric remote sensing.
    Heidinger, Andrew
    Poulslsen, Caroline
    Pavolonis, Michael
    Riedi, Jerome
    Roebeling, Robert
    Sherwood, Steven
    Thoss, Anke
    SMHI, Research Department, Atmospheric remote sensing.
    Watts, Philip
    TOWARD GLOBAL HARMONIZATION OF DERIVED CLOUD PRODUCTS2017In: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 98, no 2, p. ES49-ES52Article in journal (Refereed)
3031323334 1601 - 1650 of 1683
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