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  • 1.
    Arheimer, Berit
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Lindström, Göran
    SMHI, Forskningsavdelningen, Hydrologi.
    Climate impact on floods: changes in high flows in Sweden in the past and the future (1911-2100)2015Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, nr 2, s. 771-784Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is an ongoing discussion whether floods occur more frequently today than in the past, and whether they will increase in number and magnitude in the future. To explore this issue in Sweden, we merged observed time series for the past century from 69 gauging sites throughout the country (450 000 km(2)) with high-resolution dynamic model projections of the upcoming century. The results show that the changes in annual maximum daily flows in Sweden oscillate between dry and wet periods but exhibit no significant trend over the past 100 years. Temperature was found to be the strongest climate driver of changes in river high flows, which are related primarily to snowmelt in Sweden. Annual daily high flows may decrease by on average -1% per decade in the future, mainly due to lower peaks from snowmelt in the spring (-2% per decade) as a result of higher temperatures and a shorter snow season. In contrast, autumn flows may increase by + 3% per decade due to more intense rainfall. This indicates a shift in floodgenerating processes in the future, with greater influence of rain-fed floods. Changes in climate may have a more significant impact on some specific rivers than on the average for the whole country. Our results suggest that the temporal pattern in future daily high flow in some catchments will shift in time, with spring floods in the northern-central part of Sweden occurring about 1 month earlier than today. High flows in the southern part of the country may become more frequent. Moreover, the current boundary between snow-driven floods in northern-central Sweden and rain-driven floods in the south may move toward higher latitudes due to less snow accumulation in the south and at low altitudes. The findings also indicate a tendency in observations toward the modeled projections for timing of daily high flows over the last 25 years. Uncertainties related to both the observed data and the complex model chain of climate impact assessments in hydrology are discussed.

  • 2.
    Berg, Peter
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Donnelly, Chantal
    SMHI, Forskningsavdelningen, Hydrologi.
    Gustafsson, David
    SMHI, Forskningsavdelningen, Hydrologi.
    Near-real-time adjusted reanalysis forcing data for hydrology2018Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 22, nr 2, s. 989-1000Artikel i tidskrift (Refereegranskat)
  • 3. Ceola, S.
    et al.
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Baratti, E.
    Bloeschl, G.
    Capell, Réne
    SMHI, Forskningsavdelningen, Hydrologi.
    Castellarin, A.
    Freer, J.
    Han, D.
    Hrachowitz, M.
    Hundecha, Yeshewatesfa
    SMHI, Forskningsavdelningen, Hydrologi.
    Hutton, C.
    Lindström, Göran
    SMHI, Forskningsavdelningen, Hydrologi.
    Montanari, A.
    Nijzink, R.
    Parajka, J.
    Toth, E.
    Viglione, A.
    Wagener, T.
    Virtual laboratories: new opportunities for collaborative water science2015Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, nr 4, s. 2101-2117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 4.
    Crochemore, Louise
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Ramos, Maria-Helena
    Pappenberger, Florian
    Bias correcting precipitation forecasts to improve the skill of seasonal streamflow forecasts2016Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 20, nr 9, s. 3601-3618Artikel i tidskrift (Refereegranskat)
  • 5.
    Crochemore, Louise
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Ramos, Maria-Helena
    Pappenberger, Florian
    Perrin, Charles
    Seasonal streamflow forecasting by conditioning climatology with precipitation indices2017Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 21, nr 3, s. 1573-1591Artikel i tidskrift (Refereegranskat)
  • 6. Dahl, M
    et al.
    Pers, Charlotta
    SMHI, Forskningsavdelningen, Hydrologi.
    Comparison of four models simulating phosphorus dynamics in Lake Vanern, Sweden2004Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 8, nr 6, s. 1153-1163Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 7.
    Foster, Kean
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Uvo, Cintia Bertacchi
    Olsson, Jonas
    SMHI, Forskningsavdelningen, Hydrologi.
    The development and evaluation of a hydrological seasonal forecast system prototype for predicting spring flood volumes in Swedish rivers2018Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 22, nr 5, s. 2953-2970Artikel i tidskrift (Refereegranskat)
  • 8.
    Graham, Phil
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Bergström, Sten
    SMHI, Forskningsavdelningen, Hydrologi.
    Land surface modelling in hydrology and meteorology - lessons learned from the Baltic Basin2000Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 4, nr 1, s. 13-22Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By both tradition and purpose, the land parameterization schemes of hydrological and meteorological models differ greatly. Meteorologists are concerned primarily with solving the energy balance, whereas hydrologists are most interested in the water balance. Meteorological climate models typically have multi-layered soil parameterisation that solves temperature fluxes numerically with diffusive equations. The same approach is carried over to a similar treatment of water transport. Hydrological models are not usually so interested in soil temperatures, but must provide a reasonable representation of soil moisture to get runoff right. To treat the heterogeneity of the soil, many hydrological models use only one laver with a statistical representation of soil variability. Such a hydrological model can be used on large scales while taking subgrid variability into account. Hydrological models also include lateral transport of water - an imperative if river discharge is to be estimated. The concept of a complexity chain for coupled modelling systems is introduced, together with considerations for mixing model components. Under BALTEX (Baltic Sea Experiment) and SWECLIM (Swedish Regional Climate Modelling Programme), a large-scale hydrological model of runoff in the Baltic Basin is used to review atmospheric climate model simulations. This incorporates both the runoff record and hydrological modelling experience into atmospheric model development. Results from two models are shown. A conclusion is that the key to improved models may be less complexity. Perhaps the meteorological models should keep their multi-layered approach for modelling soil temperature, bur add a simpler, yet physically consistent, hydrological approach for modelling snow processes and water transport in the soil.

  • 9. Hall, J.
    et al.
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Borga, M.
    Brazdil, R.
    Claps, P.
    Kiss, A.
    Kjeldsen, T. R.
    Kriauciuniene, J.
    Kundzewicz, Z. W.
    Lang, M.
    Llasat, M. C.
    Macdonald, N.
    McIntyre, N.
    Mediero, L.
    Merz, B.
    Merz, R.
    Molnar, P.
    Montanari, A.
    Neuhold, C.
    Parajka, J.
    Perdigao, R. A. P.
    Plavcova, L.
    Rogger, M.
    Salinas, J. L.
    Sauquet, E.
    Schaer, C.
    Szolgay, J.
    Viglione, A.
    Bloeschl, G.
    Understanding flood regime changes in Europe: a state-of-the-art assessment2014Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 18, nr 7, s. 2735-2772Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is growing concern that flooding is becoming more frequent and severe in Europe. A better understanding of flood regime changes and their drivers is therefore needed. The paper reviews the current knowledge on flood regime changes in European rivers that has traditionally been obtained through two alternative research approaches. The first approach is the data-based detection of changes in observed flood events. Current methods are reviewed together with their challenges and opportunities. For example, observation biases, the merging of different data sources and accounting for nonlinear drivers and responses. The second approach consists of modelled scenarios of future floods. Challenges and opportunities associated with flood change scenarios are discussed such as fully accounting for uncertainties in the modelling cascade and feedbacks. To make progress in flood change research, we suggest that a synthesis of these two approaches is needed. This can be achieved by focusing on long duration records and flood-rich and flood-poor periods rather than on short duration flood trends only, by formally attributing causes of observed flood changes, by validating scenarios against observed flood regime dynamics, and by developing low-dimensional models of flood changes and feedbacks. The paper finishes with a call for a joint European flood change research network.

  • 10. Iliopoulou, Theano
    et al.
    Aguilar, Cristina
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Bermudez, Maria
    Bezak, Nejc
    Ficchi, Andrea
    Koutsoyiannis, Demetris
    Parajka, Juraj
    Jose Polo, Maria
    Thirel, Guillaume
    Montanari, Alberto
    A large sample analysis of European rivers on seasonal river flow correlation and its physical drivers2019Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 23, nr 1, s. 73-91Artikel i tidskrift (Refereegranskat)
  • 11. Jaramillo, Fernando
    et al.
    Cory, Neil
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Laudon, Hjalmar
    van der Velde, Ype
    Hasper, Thomas B.
    Teutschbein, Claudia
    Uddling, Johan
    Dominant effect of increasing forest biomass on evapotranspiration: interpretations of movement in Budyko space2018Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 22, nr 1, s. 567-580Artikel i tidskrift (Refereegranskat)
  • 12.
    Kuentz, Anna
    et al.
    SMHI, Samhälle och säkerhet.
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Hundecha, Yeshewatesfa
    SMHI, Forskningsavdelningen, Hydrologi.
    Wagener, Thorsten
    Understanding hydrologic variability across Europe through catchment classification2017Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 21, nr 6, s. 2863-2879Artikel i tidskrift (Refereegranskat)
  • 13.
    Kuentz, Anna
    et al.
    SMHI, Samhälle och säkerhet.
    Mathevet, T.
    Gailhard, J.
    Hingray, B.
    Building long-term and high spatio-temporal resolution precipitation and air temperature reanalyses by mixing local observations and global atmospheric reanalyses: the ANATEM model2015Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, nr 6, s. 2717-2736Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Efforts to improve the understanding of past climatic or hydrologic variability have received a great deal of attention in various fields of geosciences such as glaciology, dendrochronology, sedimentology and hydrology. Based on different proxies, each research community produces different kinds of climatic or hydrologic reanalyses at different spatio-temporal scales and resolutions. When considering climate or hydrology, many studies have been devoted to characterising variability, trends or breaks using observed time series representing different regions or climates of the world. However, in hydrology, these studies have usually been limited to short temporal scales (mainly a few decades and more rarely a century) because they require observed time series (which suffer from a limited spatio-temporal density). This paper introduces ANATEM, a method that combines local observations and large-scale climatic information (such as the 20CR Reanalysis) to build long-term probabilistic air temperature and precipitation time series with a high spatio-temporal resolution (1 day and a few km(2)). ANATEM was tested on the reconstruction of air temperature and precipitation time series of 22 watersheds situated in the Durance River basin, in the French Alps. Based on a multi-criteria and multi-scale diagnosis, the results show that ANATEM improves the performance of classical statistical models - especially concerning spatial homogeneity - while providing an original representation of uncertainties which are conditioned by atmospheric circulation patterns. The ANATEM model has been also evaluated for the regional scale against independent long-term time series and was able to capture regional low-frequency variability over more than a century (1883-2010).

  • 14.
    Lidén, Rikard
    SMHI, Forskningsavdelningen, Hydrologi.
    A new approach for estimating suspended sediment yield1999Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 3, nr 2, s. 285-294Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A semi-distributed conceptual model, HBV-SED, for estimation of total suspended sediment concentration and yield at the outlet of a catchment was developed and tested through a case study. The base of the suspended sediment model is a dynamic hydrological model, which produces daily series of areal runoff and rainfall for each sub-basin as input to the sediment routine. A lumped measure of available sediment is accumulated continuously based on a linear relationship between log-transformed values of rainfall and erosion, while discharge of suspended sediment at the sub-basin outlet is dependent on runoff and amount of stored available sediment. Four model parameters are empirically determined through calibration against observed records of suspended sediment concentration. The model was applied to a 200 km(2) catchment with high altitude differences in the tropical parts of Bolivia, where recorded suspended sediment concentrations were available during a two-year period. 10,000 parameter sets were generated through a Monte Carlo procedure to evaluate the parameter sensitivity and interdependence. The predictability of the model was assessed through dividing the data record into a calibration and an independent period for which the model was validated and compared to the sediment rating curve technique. The results showed that the slope coefficients of the log-transformed model equations for accumulation and release were much stronger than the intercept coefficients. Despite an existing interdependence between the model parameters, the HBV-SED model gave clearly better results than the sediment rating curve technique for the validation period, indicating that the supply-based approach has a promising future as a tool for basic engineering applications.

  • 15. Nijzink, Remko
    et al.
    Hutton, Christopher
    Pechlivanidis, Ilias
    SMHI, Forskningsavdelningen, Hydrologi.
    Capell, Réne
    SMHI, Forskningsavdelningen, Hydrologi.
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Freer, Jim
    Han, Dawei
    Wagener, Thorsten
    McGuire, Kevin
    Savenije, Hubert
    Hrachowitz, Markus
    The evolution of root-zone moisture capacities after deforestation: a step towards hydrological predictions under change?2016Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 20, nr 12, s. 4775-4799Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The core component of many hydrological systems, the moisture storage capacity available to vegetation, is impossible to observe directly at the catchment scale and is typically treated as a calibration parameter or obtained from a priori available soil characteristics combined with estimates of rooting depth. Often this parameter is considered to remain constant in time. Using long-term data (30–40 years) from three experimental catchments that underwent significant land cover change, we tested the hypotheses that: (1) the root-zone storage capacity significantly changes after deforestation, (2) changes in the root-zone storage capacity can to a large extent explain post-treatment changes to the hydrological regimes and that (3) a time-dynamic formulation of the root-zone storage can improve the performance of a hydrological model.A recently introduced method to estimate catchment-scale root-zone storage capacities based on climate data (i.e. observed rainfall and an estimate of transpiration) was used to reproduce the temporal evolution of root-zone storage capacity under change. Briefly, the maximum deficit that arises from the difference between cumulative daily precipitation and transpiration can be considered as a proxy for root-zone storage capacity. This value was compared to the value obtained from four different conceptual hydrological models that were calibrated for consecutive 2-year windows.It was found that water-balance-derived root-zone storage capacities were similar to the values obtained from calibration of the hydrological models. A sharp decline in root-zone storage capacity was observed after deforestation, followed by a gradual recovery, for two of the three catchments. Trend analysis suggested hydrological recovery periods between 5 and 13 years after deforestation. In a proof-of-concept analysis, one of the hydrological models was adapted to allow dynamically changing root-zone storage capacities, following the observed changes due to deforestation. Although the overall performance of the modified model did not considerably change, in 51 % of all the evaluated hydrological signatures, considering all three catchments, improvements were observed when adding a time-variant representation of the root-zone storage to the model.In summary, it is shown that root-zone moisture storage capacities can be highly affected by deforestation and climatic influences and that a simple method exclusively based on climate data can not only provide robust, catchment-scale estimates of this critical parameter, but also reflect its time-dynamic behaviour after deforestation.

  • 16.
    Olsson, Jonas
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Uvo, C. B.
    Foster, Kean
    SMHI, Forskningsavdelningen, Hydrologi.
    Yang, Wei
    SMHI, Forskningsavdelningen, Hydrologi.
    Technical Note: Initial assessment of a multi-method approach to spring-flood forecasting in Sweden2016Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 20, nr 2, s. 659-667Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydropower is a major energy source in Sweden, and proper reservoir management prior to the spring-flood onset is crucial for optimal production. This requires accurate forecasts of the accumulated discharge in the spring-flood period (i.e. the spring-flood volume, SFV). Today's SFV forecasts are generated using a model-based climatological ensemble approach, where time series of precipitation and temperature from historical years are used to force a calibrated and initialized set-up of the HBV model. In this study, a number of new approaches to spring-flood forecasting that reflect the latest developments with respect to analysis and modelling on seasonal timescales are presented and evaluated. Three main approaches, represented by specific methods, are evaluated in SFV hindcasts for the Swedish river Vindelalven over a 10-year period with lead times between 0 and 4 months. In the first approach, historically analogue years with respect to the climate in the period preceding the spring flood are identified and used to compose a reduced ensemble. In the second, seasonal meteorological ensemble forecasts are used to drive the HBV model over the spring-flood period. In the third approach, statistical relationships between SFV and the large-sale atmospheric circulation are used to build forecast models. None of the new approaches consistently outperform the climatological ensemble approach, but for early forecasts improvements of up to 25% are found. This potential is reasonably well realized in a multi-method system, which over all forecast dates reduced the error in SFV by similar to 4 %. This improvement is limited but potentially significant for e.g. energy trading.

  • 17. Pappenberger, F.
    et al.
    Cloke, H. L.
    Persson, Anders
    SMHI, Forskningsavdelningen, Meteorologi.
    Demeritt, D.
    HESS Opinions "On forecast (in)consistency in a hydro-meteorological chain: curse or blessing?"2011Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 15, nr 7, s. 2391-2400Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Flood forecasting increasingly relies on numerical weather prediction forecasts to achieve longer lead times. One of the key difficulties that is emerging in constructing a decision framework for these flood forecasts is what to dowhen consecutive forecasts are so different that they lead to different conclusions regarding the issuing of warnings or triggering other action. In this opinion paper we explore some of the issues surrounding such forecast inconsistency (also known as "Jumpiness", "Turning points", "Continuity" or number of "Swings"). In thsi opinion paper we define forecast inconsistency; discuss the reasons why forecasts might be inconsistent; how we should analyse inconsistency; and what we should do about it; how we should communicate it and whether it is a totally undesirable property. The property of consistency is increasingly emerging as a hot topic in many forecasting environments.

  • 18.
    Pechlivanidis, Ilias
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Large-scale hydrological modelling by using modified PUB recommendations: the India-HYPE case2015Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, nr 11, s. 4559-4579Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The scientific initiative Prediction in Ungauged Basins (PUB) (2003-2012 by the IAHS) put considerable effort into improving the reliability of hydrological models to predict flow response in ungauged rivers. PUB's collective experience advanced hydrologic science and defined guidelines to make predictions in catchments without observed runoff data. At present, there is a raised interest in applying catchment models to large domains and large data samples in a multi-basin manner, to explore emerging spatial patterns or learn from comparative hydrology. However, such modelling involves additional sources of uncertainties caused by the inconsistency between input data sets, i.e. particularly regional and global databases. This may lead to inaccurate model parameterisation and erroneous process understanding. In order to bridge the gap between the best practices for flow predictions in single catchments and multi-basins at the large scale, we present a further developed and slightly modified version of the recommended best practices for PUB by Takeuchi et al. (2013). By using examples from a recent HYPE (Hydrological Predictions for the Environment) hydrological model set-up across 6000 subbasins for the Indian subcontinent, named India-HYPE v1.0, we explore the PUB recommendations, identify challenges and recommend ways to overcome them. We describe the work process related to (a) errors and inconsistencies in global databases, unknown human impacts, and poor data quality; (b) robust approaches to identify model parameters using a stepwise calibration approach, remote sensing data, expert knowledge, and catchment similarities; and (c) evaluation based on flow signatures and performance metrics, using both multiple criteria and multiple variables, and independent gauges for "blind tests". The results show that despite the strong physiographical gradient over the subcontinent, a single model can describe the spatial variability in dominant hydrological processes at the catchment scale. In addition, spatial model deficiencies are used to identify potential improvements of the model concept. Eventually, through simultaneous calibration using numerous gauges, the median Kling-Gupta efficiency for river flow increased from 0.14 to 0.64. We finally demonstrate the potential of multi-basin modelling for comparative hydrology using PUB, by grouping the 6000 subbasins based on similarities in flow signatures to gain insights into the spatial patterns of flow generating processes at the large scale.

  • 19.
    Pimentel, Rafael
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    Herrero, Javier
    Polo, Maria Jose
    Subgrid parameterization of snow distribution at a Mediterranean site using terrestrial photography2017Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 21, nr 2, s. 805-820Artikel i tidskrift (Refereegranskat)
  • 20. Pugliese, Alessio
    et al.
    Persiano, Simone
    Bagli, Stefano
    Mazzoli, Paolo
    Parajka, Juraj
    Arheimer, Berit
    SMHI, Forskningsavdelningen, Hydrologi.
    Capell, Réne
    SMHI, Forskningsavdelningen, Hydrologi.
    Montanari, Alberto
    Bloeschl, Guenter
    Castellarin, Attilio
    A geostatistical data-assimilation technique for enhancing macro-scale rainfall-runoff simulations2018Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 22, nr 9, s. 4633-4648Artikel i tidskrift (Refereegranskat)
  • 21.
    Sahlberg, Jörgen
    SMHI, Affärsverksamhet. SMHI, Forskningsavdelningen, Oceanografi.
    Physical modelling of the Akkajaure reservoir2003Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 7, nr 3, s. 268-282Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper describes the seasonal temperature development in the Akkajaure reservoir. one of the largest Swedish reservoirs. It lies in the headwaters of the river Lulealven in northern Sweden: it is 60 km long and 5 km wide with a maximum depth of 92 m. The maximum allowed variation in surface water level is 30 m. The temperature field in the reservoir is important for many biochemical processes. A one-dimensional lake model of the Akkajaure reservoir is developed from a lake model by Sahlberg (1983 and 1988). The dynamic eddy viscosity is calculated by a two equation turbulence model, a k-epsilon model and the hypolimnic eddy diffusivity formulation which is a function of the stability frequency (Hondzo et al., 1993). A comparison between calculated and measured temperature profiles showed a maximum discrepancy of 0.5-1.0degreesC over the period 1999-2002. Except for a few days in summer, the water temperature is vertically homogeneous. Over that period of years, a weak stratification of temperature occurred on only one to two weeks a year on different dates in July and August. This will have biological consequences.

  • 22.
    Sahlberg, Jörgen
    et al.
    SMHI, Affärsverksamhet. SMHI, Forskningsavdelningen, Oceanografi.
    Rahm, Lars
    SMHI, Forskningsavdelningen, Oceanografi.
    Light limitation of primary production in high latitude reservoirs2005Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 9, nr 6, s. 707-720Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To explore the effects of vertical mixing on the primary production in a northern reservoir, a Lagrangian particle dispersion model was coupled to a 1-D reservoir model where the vertical mixing was calculated using a k-epsilon model together with an empirically-based deep-water eddy viscosity. The primary production of each phytoplankton cell is assumed to be a function of the ambient light and not to be nutrient limited. The photoadaption follows first-order kinetics where the photoadaptive variables, alpha, beta, and P(m), describe the coefficients of the photosynthesis-irradiance curve. The model is applied to the northern reservoir Akkajaure, which is strongly regulated with a mean and maximum depth of 30 m and 100 m respectively. Based on the release of 1000 particles (plankton), the model calculated the mean primary production of each plankton, during four different growing seasons. Vertical mixing has a substantial effect on the vertical distribution of phytoplankton and, thus, on the primary production in a reservoir. It was found that primary production was greater in a cold summer with weak stratification than in a warm summer when the reservoir was more stratified.

  • 23. Steffens, K.
    et al.
    Larsbo, M.
    Moeys, J.
    Kjellstrom, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Jarvis, N.
    Lewan, E.
    Modelling pesticide leaching under climate change: parameter vs. climate input uncertainty2014Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 18, nr 2, s. 479-491Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Assessing climate change impacts on pesticide leaching requires careful consideration of different sources of uncertainty. We investigated the uncertainty related to climate scenario input and its importance relative to parameter uncertainty of the pesticide leaching model. The pesticide fate model MACRO was calibrated against a comprehensive one-year field data set for a well-structured clay soil in southwestern Sweden. We obtained an ensemble of 56 acceptable parameter sets that represented the parameter uncertainty. Nine different climate model projections of the regional climate model RCA3 were available as driven by different combinations of global climate models (GCM), greenhouse gas emission scenarios and initial states of the GCM. The future time series of weather data used to drive the MACRO model were generated by scaling a reference climate data set (1970-1999) for an important agricultural production area in south-western Sweden based on monthly change factors for 2070-2099. 30 yr simulations were performed for different combinations of pesticide properties and application seasons. Our analysis showed that both the magnitude and the direction of predicted change in pesticide leaching from present to future depended strongly on the particular climate scenario. The effect of parameter uncertainty was of major importance for simulating absolute pesticide losses, whereas the climate uncertainty was relatively more important for predictions of changes of pesticide losses from present to future. The climate uncertainty should be accounted for by applying an ensemble of different climate scenarios. The aggregated ensemble prediction based on both acceptable parameterizations and different climate scenarios has the potential to provide robust probabilistic estimates of future pesticide losses.

  • 24.
    Wetterhall, Fredrik
    et al.
    SMHI, Forskningsavdelningen, Hydrologi.
    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"2013Ingår i: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 17, nr 11, s. 4389-4399Artikel i tidskrift (Refereegranskat)
    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.

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