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  • 181. Lyon, Steve W.
    et al.
    Nathanson, Marcus
    Spans, Andre
    Grabs, Thomas
    Laudon, Hjalmar
    Temnerud, Johan
    SMHI, Forskningsavdelningen, Hydrologi.
    Bishop, Kevin H.
    Seibert, Jan
    Specific discharge variability in a boreal landscape2012Ingår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 48, artikel-id W08506Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Specific discharge variations within a mesoscale catchment were studied on the basis of three synoptic sampling campaigns. These were conducted during stable flow conditions within the Krycklan catchment study area in northern Sweden. During each campaign, about 80 individual locations were measured for discharge draining from catchment areas ranging between 0.12 and 67 km(2). These discharge samplings allowed for the comparison between years within a given season (September 2005 versus September 2008) and between seasons within a given year (May 2008 versus September 2008) of specific discharge across this boreal landscape. There was considerable variability in specific discharge across this landscape. The ratio of the interquartile range (IQR) defined as the difference between the 75th and 25th percentiles of the specific discharges to the median of the specific discharges ranged from 37% to 43%. Factor analysis was used to explore potential relations between landscape characteristics and the specific discharge observed for 55 of the individual locations that were measured in all three synoptic sampling campaigns. Percentage wet area (i.e., wetlands, mires, and lakes) and elevation were found to be directly related to the specific discharge during the drier September 2008 sampling while potential annual evaporation was found to be inversely related. There was less of a relationship determined during the wetter post spring flood May 2008 sampling and the late summer rewetted September 2005 sampling. These results indicate the ability of forests to "dry out" parts of the catchment over the summer months while wetlands "keep wet" other parts. To demonstrate the biogeochemical implications of such spatiotemporal variations in specific discharge, we estimate dissolved organic carbon (DOC) exports with available data for the May 2008 and September 2008 samplings using both the spatially variable observed specific discharges and the spatially constant catchment average values. The average absolute difference in DOC export for the various subcatchments between using a variable and using a constant specific discharge was 28% for the May 2008 sampling and 20% for the September 2008 sampling.

  • 182.
    Strömqvist, Johan
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Dahne, Joel
    SMHI, Affärsverksamhet.
    Donnelly, Chantal
    SMHI, Forskningsavdelningen, Hydrologi.
    Lindström, Göran
    SMHI, Forskningsavdelningen, Hydrologi.
    Water and nutrient predictions in ungauged basins: set-up and evaluation of a model at the national scale2012Ingår i: Hydrological Sciences Journal, ISSN 0262-6667, E-ISSN 2150-3435, Vol. 57, nr 2, s. 229-247Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A dynamic water quality model, HYPE, was applied to a large, data-sparse region to study whether reliable information on water quantity and water quality could be obtained for both gauged and ungauged waterbodies. The model (called S-HYPE) was set up for all of Sweden (similar to 450 000 km(2)), divided into sub-basins with an average area of 28 km(2). Readily available national databases were used for physiographic data, emissions and agricultural practices, fixed values for representative years were used. Daily precipitation and temperature were used as the dynamic forcing of the model. Model evaluation was based on data from several hundred monitoring sites, of which approximately 90% had not been used in calibration on a daily scale. Results were evaluated using the Nash-Sutcliffe efficiency (NSE), correlation and relative errors: 92% of the spatial variation was explained for specific water discharge, and 88% and 59% for total nitrogen and total phosphorus concentrations, respectively. Day-to-day variations were modelled with satisfactory results for water discharge and the seasonal variation of nitrogen concentrations was also generally well captured. In 20 large, unregulated rivers the median NSE for water discharge was 0.84, and the corresponding number for 76 partly-regulated river basins was 0.52. In small basins, the NSE was typically above 0.6. These major achievements relative to previous similar experiments were ascribed to the step-wise calibration process using representative gauged basins and the use of amodelling concept, whereby coefficients are linked to physiographic variables rather than to specific sites.

  • 183.
    Arheimer, Berit
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Dahne, Joel
    SMHI, Affärsverksamhet.
    Donnelly, Chantal
    SMHI, Forskningsavdelningen, Hydrologi.
    Lindström, Göran
    SMHI, Forskningsavdelningen, Hydrologi.
    Strömqvist, Johan
    SMHI, Forskningsavdelningen, Hydrologi.
    Water and nutrient simulations using the HYPE model for Sweden vs. the Baltic Sea basin - influence of input-data quality and scale2012Ingår i: HYDROLOGY RESEARCH, ISSN 1998-9563, Vol. 43, nr 4, s. 315-329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Water resource management is often based on numerical models, and large-scale models are sometimes used for international strategic agreements. Sometimes the modelled area entails several political entities and river basins. To avoid methodological bias in results, methods and databases should be homogenous across political and geophysical boundaries, but this may involve fewer details and more assumptions. This paper quantifies the uncertainty when the same model code is applied using two different input datasets; a more detailed one for the country of Sweden (S-HYPE) and a more general one for the entire Baltic Sea basin (Balt-HYPE). Results from the two model applications were compared for the Swedish landmass and for two specific Swedish river basins. The results show that both model applications may be useful in providing spatial information of water and nutrients at various scales. For water discharge, most relative errors are <10% for S-HYPE and <25% for Balt-HYPE. Both applications reproduced the most mean concentration for nitrogen within 25% of the observed mean values, but phosphorus showed a larger scatter. Differences in model set-up were reflected in the simulation of both spatial and temporal dynamics. The most sensitive data were precipitation/temperature, agriculture and model parameter values.

  • 184. Olsson, Johanna Alkan
    et al.
    Jonsson, Anna C.
    Andersson, Lotta
    SMHI, Samhälle och säkerhet.
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    A model-supported participatory process for nutrient management: a socio-legal analysis of a bottom-up implementation of the EU Water Framework Directive2011Ingår i: International Journal of Agricultural Sustainability, ISSN 1473-5903, E-ISSN 1747-762X, Vol. 9, nr 2, s. 379-389Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A methodology for local stakeholders' involvement in water management using a catchment model as a platform for dialogue has been developed and tested in the Kaggebo Bay drainage area in the southeast of Sweden. The process involved farmers, rural households not connected to municipal wastewater treatment facilities, local and regional authorities as well as different water and agricultural experts. This paper aims to assess whether and how the methodology has succeeded in encouraging social learning and promoting action and which barriers can be identified. The assessment shows that the methodology is able to create confidence in the process and increase the willingness to act as the methodology was able to adapt the form and content of the dialogue to better fit the cognitive and relational needs of involved stakeholders. It is also shown that the process may lead to a probable improvement of the eutrophication situation. However, if these types of processes are to serve not only as a basis for social learning and action at the local level, but also as the basis for a broader process of societal learning, then a mechanism to confer local ideas to the regional and national levels has to be clarified.

  • 185.
    Arheimer, Berit
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Lindström, Göran
    SMHI, Forskningsavdelningen, Hydrologi.
    Olsson, Jonas
    SMHI, Forskningsavdelningen, Hydrologi.
    A systematic review of sensitivities in the Swedish flood-forecasting system2011Ingår i: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 100, nr 2-3, s. 275-284Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Since the early 1970s operational flood forecasts in Sweden have been based on the hydrological HBV model. However, the model is only one component in a chain of processes for production of hydrological forecasts. During the last 35 years there has been considerable work on improving different parts of the forecast procedure and results from specific studies have been reported frequently. Yet, the results have not been compared in any overall assessment of potential for improvements. Therefore we formulated and applied a method for translating results from different studies to a common criterion of error reduction. The aim was to quantify potential improvements in a systems perspective and to identify in which part of the production chain efforts would result in significantly better forecasts. The most sensitive (> 20% error reduction) components were identified for three different operational-forecast types. From the analyses of historical efforts to minimise the errors in the Swedish flood-forecasting system, it was concluded that 1) general runoff simulations and predictions could be significantly improved by model structure and calibration, model equations (e.g. evapotranspiration expression), and new precipitation input using radar data as a complement to station gauges; 2) annual spring-flood forecasts could be significantly improved by better seasonal meteorological forecast, fresh re-calibration of the hydrological model based on long time-series, and data assimilation of snow-pack measurements using georadar or gamma-ray technique; 3) short-term (2 days) forecasts could be significantly improved by up-dating using an auto-regressive method for discharge, and by ensembles of meteorological forecasts using the median at occasions when the deterministic forecast is out of the ensemble range. The study emphasises the importance of continuously evaluating the entire production chain to search for potential improvements of hydrological forecasts in the operational environment. (C) 2010 Elsevier B.V. All rights reserved.

  • 186.
    Andersson, Lotta
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Samuelsson, Patrick
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Assessment of climate change impact on water resources in the Pungwe river basin2011Ingår i: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 63, nr 1, s. 138-157Artikel i tidskrift (Refereegranskat)
  • 187. Reckermann, Marcus
    et al.
    Langner, Joakim
    SMHI, Forskningsavdelningen, Luftmiljö.
    Omstedt, Anders
    Göteborgs Universitet.
    von Storch, Hans
    Keevallik, Sirje
    Schneider, Bernd
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    Huenicke, Birgit
    BALTEX-an interdisciplinary research network for the Baltic Sea region2011Ingår i: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 6, nr 4, artikel-id 045205Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    BALTEX is an environmental research network dealing with the Earth system of the entire Baltic Sea drainage basin. Important elements include the water and energy cycle, climate variability and change, water management and extreme events, and related impacts on biogeochemical cycles. BALTEX was founded in 1993 as a GEWEX continental-scale experiment and is currently in its second 10 yr phase. Phase I (1993-2002) was primarily dedicated to hydrological, meteorological and oceanographic processes in the Baltic Sea drainage basin, hence mostly dealt with the physical aspects of the system. Scientific focus was on the hydrological cycle and the exchange of energy between the atmosphere, the Baltic Sea and the surface of its catchment. The BALTEX study area was hydrologically defined as the Baltic Sea drainage basin. The second 10 yr phase of BALTEX (Phase II: 2003-12) has strengthened regional climate research, water management issues, biogeochemical cycles and overarching efforts to reach out to stakeholders and decision makers, as well as to foster communication and education. Achievements of BALTEX Phase II have been the establishment of an assessment report of regional climate change and its impacts on the Baltic Sea basin (from hydrological to biological and socio-economic), the further development of regional physical climate models and the integration of biogeochemical and ecosystem models. BALTEX features a strong infrastructure, with an international secretariat and a publication series, and organizes various workshops and conferences. This article gives an overview of the BALTEX programme, with an emphasis on Phase II, with some examples from BALTEX-related research.

  • 188. Gleeson, Tom
    et al.
    Marklund, Lars
    SMHI, Forskningsavdelningen, Hydrologi.
    Smith, Leslie
    Manning, Andrew H.
    Classifying the water table at regional to continental scales2011Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 38, artikel-id L05401Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Water tables at regional to continental scales can be classified into two distinct types: recharge-controlled water tables that are largely disconnected from topography and topography-controlled water tables that are closely tied to topography. We use geomatic synthesis of hydrologic, geologic and topographic data sets to quantify and map water-table type over the contiguous United States using a dimensionless criterion introduced by Haitjema and Mitchell-Bruker (2005), called the water-table ratio, which differentiates water-table type. Our analysis indicates that specific regions of the United States have broadly contiguous and characteristic water-table types. Water-table ratio relates to water-table depth and the potential for regional groundwater flow. In regions with recharge-controlled water tables, for example the Southwest or Rocky Mountains, USA, water-tables depths are generally greater and more variable and regional groundwater flow is generally more important as a percentage of the watershed budget. Water-table depths are generally shallow and less variable, and regional groundwater flow is limited in areas with topography-controlled water tables such as the Northeast USA. The water-table ratio is a simple but powerful criterion for evaluating regional groundwater systems over broad areas. Citation: Gleeson, T., L. Marklund, L. Smith, and A. H. Manning (2011), Classifying the water table at regional to continental scales, Geophys. Res. Lett., 38, L05401, doi: 10.1029/2010GL046427.

  • 189.
    Olsson, Jonas
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Dahné, Joel
    SMHI, Affärsverksamhet.
    German, Jonas
    SMHI.
    Westergren, Bo
    Stockholm Vatten AB.
    von Scherling, Mathias
    Stockholm Vatten AB.
    Kjellson, Lena
    Stockholm Vatten AB.
    Olsson, Alf
    Sweco AB.
    En studie av framtida flödesbelastning på Stockholms huvudavloppssystem2011Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Denna studie utfördes inom SWEdish research programme on Climate, Impacts and Adaptation (SWECIA), finansierat av Stiftelsen för Miljöstratgisk Forskning (MISTRA), med delfinansiering från Stockholm Vatten AB.Studiens syfte var att bedöma flödesbelastningen på Stockholms huvudavloppssystem under resten av detta sekel mot bakgrund av både klimatförändring och befolkningsökning. Som underlag gjordes flödes-simuleringar med MIKE Urban. Referenssimuleringar för dagens klimat gjordes dels för ett representativt helår (1984), dels för c:a 200 utvalda regnhändelser mellan 1983 och 2007. I framtidssimuleringar beskrevs klimateffekten genom omskalning av indata (temperatur, nederbörd, avdunstning) i enlighet med klimatmodellscenarier och befolknings-effekten genom en ökning i enlighet med officiell bedömning.Resultaten indikerar framför allt att bräddade volymer till Mälaren och Saltsjön kommer att öka kraftigt, men även ett ökat inflöde till reningsverket, och därmed ökat behov av rening, samt en ökad översvämningsrisk.

  • 190. Teutschbein, Claudia
    et al.
    Wetterhall, Fredrik
    SMHI, Forskningsavdelningen, Hydrologi.
    Seibert, Jan
    Evaluation of different downscaling techniques for hydrological climate-change impact studies at the catchment scale2011Ingår i: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 37, nr 9-10, s. 2087-2105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydrological modeling for climate-change impact assessment implies using meteorological variables simulated by global climate models (GCMs). Due to mismatching scales, coarse-resolution GCM output cannot be used directly for hydrological impact studies but rather needs to be downscaled. In this study, we investigated the variability of seasonal streamflow and flood-peak projections caused by the use of three statistical approaches to downscale precipitation from two GCMs for a meso-scale catchment in southeastern Sweden: (1) an analog method (AM), (2) a multi-objective fuzzy-rule-based classification (MOFRBC) and (3) the Statistical DownScaling Model (SDSM). The obtained higher-resolution precipitation values were then used to simulate daily streamflow for a control period (1961-1990) and for two future emission scenarios (2071-2100) with the precipitation-streamflow model HBV. The choice of downscaled precipitation time series had a major impact on the streamflow simulations, which was directly related to the ability of the downscaling approaches to reproduce observed precipitation. Although SDSM was considered to be most suitable for downscaling precipitation in the studied river basin, we highlighted the importance of an ensemble approach. The climate and streamflow change signals indicated that the current flow regime with a snowmelt-driven spring flood in April will likely change to a flow regime that is rather dominated by large winter streamflows. Spring flood events are expected to decrease considerably and occur earlier, whereas autumn flood peaks are projected to increase slightly. The simulations demonstrated that projections of future streamflow regimes are highly variable and can even partly point towards different directions.

  • 191.
    Riml, Joakim
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Worman, Anders
    Response functions for in-stream solute transport in river networks2011Ingår i: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 47, artikel-id W06502Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper analyzes the effects of different hydrological mechanisms on the solute response in watershed stream networks. Important processes are due to the hydraulic and chemical retention of reactive solutes in transient storage zones and the cumulative consequences of these processes from a single transport pathway as well as from the network of transport pathways. Temporal moments are derived for a distributed stream network and for a compartment-in-series model. The temporal moments are evaluated and are utilized to derive formal expressions for translating the network parameters into compartmental model parameters. The analysis reveals that in addition to the hydraulic and chemical retention processes, the morphological and topological properties of a watershed have a distinct impact on the central temporal moments in terms of averaging of the solute load weighted distances as well as the transport parameters over the network. Kinetic (rate-limited) transient storage affects second-order and higher central temporal moments and thus has a secondary effect on the parameterization of compartmental models. Additional considerable contributions to all temporal moments are introduced when parameter variability along transport pathways is considered. The paper demonstrates an improved model outcome for phosphorus transport in a small Swedish watershed by accounting for the overall network effects when parameterizing a compartment-in-series model.

  • 192. Winterdahl, Mattias
    et al.
    Temnerud, Johan
    SMHI, Forskningsavdelningen, Hydrologi.
    Futter, Martyn N.
    Lofgren, Stefan
    Moldan, Filip
    Bishop, Kevin
    Riparian Zone Influence on Stream Water Dissolved Organic Carbon Concentrations at the Swedish Integrated Monitoring Sites2011Ingår i: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 40, nr 8, s. 920-930Artikel i tidskrift (Refereegranskat)
    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.

  • 193.
    Marklund, Lars
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Worman, Anders
    The use of spectral analysis-based exact solutions to characterize topography-controlled groundwater flow2011Ingår i: Hydrogeology Journal, ISSN 1431-2174, E-ISSN 1435-0157, Vol. 19, nr 8, s. 1531-1543Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Spectral analysis enhances the ability to analyze groundwater flow at a steady state by separating the top boundary condition into its periodic forms. Specifically, spectral analysis enables comparisons of the impact of individual spatial scales on the total flow field. New exact spectral solutions are presented for analyzing 3D groundwater flow with an arbitrarily shaped top boundary. These solutions account for depth-decaying, anisotropic and layered permeability while utilizing groundwater flux or the phreatic surface as a top boundary condition. Under certain conditions, groundwater flow is controlled by topography. In areas where the groundwater flow is controlled by the topography, the unknown water table is often approximated by the topography. This approximation induces a systematic error. Here, the optimal resolution of digital elevation models (DEMs) is assessed for use as a top boundary in groundwater flow models. According to the analysis, the water-table undulation is smoother than the topography; therefore, there is an upper limit to the resolution of DEMs that should be used to represent the groundwater surface. The ability to represent DEMs of various spectral solutions was compared and the results indicate that the fit is strongly dependent on the number of harmonics in the spectral solution.

  • 194.
    Wetterhall, Fredrik
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Graham, Phil
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Andreasson, Johan
    SMHI, Affärsverksamhet.
    Rosberg, Jörgen
    SMHI, Forskningsavdelningen, Hydrologi.
    Yang, Wei
    SMHI, Forskningsavdelningen, Hydrologi.
    Using ensemble climate projections to assess probabilistic hydrological change in the Nordic region2011Ingår i: Natural hazards and earth system sciences, ISSN 1561-8633, E-ISSN 1684-9981, Vol. 11, nr 8, s. 2295-2306Artikel i tidskrift (Refereegranskat)
    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.

  • 195.
    Graham, Phil
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Andersson, Lotta
    SMHI, Samhälle och säkerhet.
    Horan, Mark
    Kunz, Richard
    Lumsden, Trevor
    Schulze, Roland
    Warburton, Michele
    Wilk, Julie
    Yang, Wei
    SMHI, Forskningsavdelningen, Hydrologi.
    Using multiple climate projections for assessing hydrological response to climate change in the Thukela River Basin, South Africa2011Ingår i: Physics and Chemistry of the Earth, ISSN 1474-7065, E-ISSN 1873-5193, Vol. 36, nr 14-15, s. 727-735Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study used climate change projections from different regional approaches to assess hydrological effects on the Thukela River Basin in KwaZulu-Natal, South Africa. Projecting impacts of future climate change onto hydrological systems can be undertaken in different ways and a variety of effects can be expected. Although simulation results from global climate models (GCMs) are typically used to project future climate, different outcomes from these projections may be obtained depending on the GCMs themselves and how they are applied, including different ways of downscaling from global to regional scales. Projections of climate change from different downscaling methods, different global climate models and different future emissions scenarios were used as input to simulations in a hydrological model to assess climate change impacts on hydrology. A total of 10 hydrological change simulations were made, resulting in a matrix of hydrological response results. This matrix included results from dynamically downscaled climate change projections from the same regional climate model (RCM) using an ensemble of three GCMs and three global emissions scenarios, and from statistically downscaled projections using results from five GCMs with the same emissions scenario. Although the matrix of results does not provide complete and consistent coverage of potential uncertainties from the different methods, some robust results were identified. In some regards, the results were in agreement and consistent for the different simulations. For others, particularly rainfall, the simulations showed divergence. For example, all of the statistically downscaled simulations showed an annual increase in precipitation and corresponding increase in river runoff, while the RCM downscaled simulations showed both increases and decreases in runoff. According to the two projections that best represent runoff for the observed climate, increased runoff would generally be expected for this basin in the future. Dealing with such variability in results is not atypical for assessing climate change impacts in Africa and practitioners are faced with how to interpret them. This work highlights the need for additional, well-coordinated regional climate downscaling for the region to further define the range of uncertainties involved. (C) 2011 Elsevier Ltd. All rights reserved.

  • 196.
    Andersson, Helén
    et al.
    SMHI, Forskningsavdelningen, Oceanografi.
    Wallman, Patrik
    SMHI, Forskningsavdelningen, Hydrologi.
    Donnelly, Chantal
    SMHI, Forskningsavdelningen, Hydrologi.
    Visualization of hydrological, physical and biogeochemical modelling of the Baltic Sea using a GeoDomeTM2011Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    ECOSUPPORT-projektet syftar till att ta fram forskningsresultat om Östersjöns miljöstatus under olika scenarier av belastning av näringsämnen och fisketryck i ett framtida klimat. Resultaten kan ligga till grund som vägledning för beslutsfattare. För att forskningsresultaten skall kunna göras begripliga och tillgängliga har en ny form av vetenskapskommunikation prövats. Presentation av en stor mängd data samt beskrivning av fysiska och biogeokemiska processer på land och i havet gjordes med hjälp av en speciell visualiseringsplatform, Uniview, som visades på en kupolformad filmduk inuti en uppblåsbar domteater. Visualiseringen visades för olika typer av publik, t.ex. för beslutsfattare, politisk ledning, forskare och studenter. Överlag så har responsen varit mycket positiv och de flesta som tagit del av visningarna menar att den här formen av kommunikation gör det lättare att förstå och ta till sig komplexa data och sammanhang. Denna åsikt delades också av de vetenskapliga presentatörerna

  • 197.
    Temnerud, Johan
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Foelster, J.
    Buffam, I.
    Laudon, H.
    Erlandsson, M.
    Bishop, K.
    Can the distribution of headwater stream chemistry be predicted from downstream observations?2010Ingår i: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 24, nr 16, s. 2269-2276Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Small streams with catchment areas <2 km(2) make up the majority of all stream length and are of great ecological importance. Surveys of first and second order streams reveal great spatial and temporal variability in the water chemistry of these headwaters, but their assessment presents a serious challenge since systematic, representative data are usually only collected in larger streams and rivers. Using low flow synoptic survey data from seven mesoscale Swedish catchments, this study tests the hypothesis that downstream monitoring data can be used to predict key features of the distribution of chemistry in headwater streams [median and interquartile range (IQR)]. Three ecologically relevant analytes were tested: pH, acid neutralizing capacity (ANC) and total organic carbon (TOC). For all seven catchments, the outlets (36-127 km(2)) were considerably less acid with lower TOC than the median of the headwaters (<2 km(2), N = 19-45). Among catchments, headwater median and IQR were positively correlated with the value at the outlet, for all three analytes. A univariate general linear model (GLM) was used to predict the headwater chemistry distribution for each catchment from its outlet chemistry, using the relationship established with the other six catchments. Headwater median pH and IQR of ANC were well predicted by a single downstream sample [median adj. R(2) similar to 0.7, normalized root mean squared error (NRMSE) <0.7]. Other response variables were not as well predicted, with median adj. R(2) ranging from 0.08 to 0.48, and NRMSE up to 1.1. A minority of models were significant at alpha = 0.05, in part due to the limited availability of catchments with such extensive survey data. However, the clear trends observed suggest that with additional model development, downstream chemistry could ultimately provide a valuable tool for characterizing the range of chemistry in the contributing headwaters. Copyright (C) 2010 John Wiley & Sons, Ltd.

  • 198.
    Lindström, Göran
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Pers, Charlotta
    SMHI, Forskningsavdelningen, Hydrologi.
    Rosberg, Jörgen
    SMHI, Forskningsavdelningen, Hydrologi.
    Strömqvist, Johan
    SMHI, Forskningsavdelningen, Hydrologi.
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Development and testing of the HYPE (Hydrological Predictions for the Environment) water quality model for different spatial scales2010Ingår i: HYDROLOGY RESEARCH, ISSN 1998-9563, Vol. 41, nr 3-4, s. 295-319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The HYPE model is a hydrological model for small-scale and large-scale assessments of water resources and water quality, developed at the Swedish Meteorological and Hydrological Institute during 2005-2007. In the model, the landscape is divided into classes according to soil type, land use and altitude. In agricultural lands the soil is divided into three layers, each with individual computations of soil wetness and nutrient processes. The model simulates water flow and transport and turnover of nitrogen and phosphorus. Nutrients follow the same pathways as water in the model: surface runoff, macropore flow, tile drainage and outflow from individual soil layers. Rivers and lakes are described separately with routines for turnover of nutrients in each environment. Model parameters are global, or coupled to soil type or land use. The model was evaluated both by local calibrations to internal variables from different test basins and to data on discharge and nutrients from a large number of small basins. In addition, the estimated parameters were transferred to two larger basins in southern Sweden: River Ronnea and River Vindan. The resulting simulations were generally in good agreement with observations.

  • 199.
    Yang, Wei
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Andreasson, Johan
    SMHI, Affärsverksamhet.
    Graham, Phil
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Olsson, Jonas
    SMHI, Forskningsavdelningen, Hydrologi.
    Rosberg, Jörgen
    SMHI, Forskningsavdelningen, Hydrologi.
    Wetterhall, Fredrik
    SMHI, Forskningsavdelningen, Hydrologi.
    Distribution-based scaling to improve usability of regional climate model projections for hydrological climate change impacts studies2010Ingår i: HYDROLOGY RESEARCH, ISSN 1998-9563, Vol. 41, nr 3-4, s. 211-229Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As climate change could have considerable influence on hydrology and corresponding water management, appropriate climate change inputs should be used for assessing future impacts. Although the performance of regional climate models (RCMs) has improved over time, systematic model biases still constrain the direct use of RCM output for hydrological impact studies. To address this, a distribution-based scaling (DBS) approach was developed that adjusts precipitation and temperature from RCMs to better reflect observations. Statistical properties, such as daily mean, standard deviation, distribution and frequency of precipitation days, were much improved for control periods compared to direct RCM output. DBS-adjusted precipitation and temperature from two IPCC Special Report on Emissions Scenarios (SRESA1B) transient climate projections were used as inputs to the HBV hydrological model for several river basins in Sweden for the period 1961-2100. Hydrological results using DBS were compared to results with the widely-used delta change (DC) approach for impact studies. The general signal of a warmer and wetter climate was obtained using both approaches, but use of DBS identified differences between the two projections that were not seen with DC. The DBS approach is thought to better preserve the future variability produced by the RCM, improving usability for climate change impact studies.

  • 200.
    Yang, Wei
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Bardossy, Andras
    Caspary, Hans-Joachim
    Downscaling daily precipitation time series using a combined circulation- and regression-based approach2010Ingår i: Journal of Theoretical and Applied Climatology, ISSN 0177-798X, E-ISSN 1434-4483, Vol. 102, nr 3-4, s. 439-454Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this paper is to introduce a new conditional statistical model for generating daily precipitation time series. The generated daily precipitation can thus be used for climate change impact studies, e.g., crop production, rainfall-runoff, and other water-related processes. It is a stochastic model that links local rainfall events to a continuous atmospheric predictor, moisture flux, in addition to classified atmospheric circulation patterns. The coupled moisture flux is proved to be capable of capturing continuous property of climate system and providing extra information to determine rainfall probability and rainfall amount. The application was made to simultaneously downscale daily precipitation at multiple sites within the Rhine River basin. The results show that the model can well reproduce statistical properties of daily precipitation time series. Especially for extreme rainfall events, the model is thought to better reflect rainfall variability compared to the pure CP-based downscaling approach.

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