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  • 2101.
    Wesslander, Karin
    SMHI, Core Services.
    Coastal eutrophication status assessment using HEAT 1.0 (WFD methodology) versus HEAT 3.0 (MSFD methodology) and  Development of an oxygen consumption  indicator2017Report (Other academic)
    Abstract [en]

    This report contains two parts which are self standing reports and a contribution to the HELCOM project EUTRO-OPER. The work has been funded and commissioned by SwAM (Swedish agency for marine and water management) 2014-2015.

    • Coastal eutrophication status assessment using HEAT 1.0 (WFD methodology) versus HEAT 3.0 (MSFD methodology)

    Eutrophication status is assessed nationally in coastal waters within the Water Framework Directive (WFD) and in open sea areas within the Marine Strategy Framework Directive (MSFD). Both WFD and MSFD consider eutrophication but with different approaches and it is therefore a need for harmonisation in the assessment process.   The Excel based tool HEAT (HELCOM Eutrophication Assessment Tool) has been used in previous assessments in the HELCOM region. There are two versions of the tool; HEAT 1.0 and HEAT 3.0, the first is based on the WFD methodology and the second is based on the MSFD methodology. The main difference between HEAT 1.0 and HEAT 3.0 is how the indicators are grouped. Here we assess the eutrophication status in coastal waters by applying HEAT and compare the results with the national WFD assessments. The present test includes data on 33 selected coastal water bodies in five countries: Estonia, Finland, Latvia, Poland and Sweden. Data on reference condition, acceptable deviation, status and class boundaries of all indicators used in WFD for reporting ecological status (biological and physical-chemical) have been provided for each tested water body. The data has been inserted in the HEAT 1.0 and HEAT 3.0 tools and been compared with the national WFD assessments.   Both HEAT versions gave lower status in more than 50 % of the cases. For some tests the status changed to sub-GES from GES when HEAT is applied. The good/moderate boundary is the same in both HEAT and the WFD while the lower class boundaries in general are stricter in HEAT, which explains the lower status. In national WFD assessments expert judgment is used when there is little, no or very uncertain in situ data. The status in HEAT is given by the one-out-all-out principle but it is still possible to include expert judgment through the weighting factors.

    • Development of an oxygen consumption indicator

    It was investigated if the oxygen consumption can be used as an oxygen indicator for the Baltic Sea. The method is based on the idea of calculating the oxygen consumption in a stabile layer below the productive zone during summer and relating this to nutrient concentrations. With more nutrients available there is an increased biological production. By estimating how much oxygen is needed to mineralise the biological material it may be possible to link the oxygen consumption to eutrophication.

    The oxygen consumption was calculated for the BY15-Gotland Deep in the Eastern Gotland Basin. We identified a stabile layer between 30 and 50 m and a large change in both oxygen and nutrients from June to August. However, the oxygen consumption had a very high inter-annual variation and there were no significant correlation with the winter mean of nutrient concentrations. It was not possible to calculate the diffusion between the layers because of too sparse measurements at the stratification which limits the method. The calculation of the diffusion is however possible to improve with a model. Further on, the depth of the stabile layer is varying between areas and also between years.   We realised that the method has too many restrictions to be a functional indicator. A functional indicator shall not be dependent on heavy modelling or demand too much on expert judgement. We also investigated if a possible candidate to use as a more simple oxygen consumption indicator could be the use of oxygen saturation at a specific depth. If we assume that the temperature has not changed much since the establishment of stratification we may expect that changes in oxygen saturation observed in August at this depth would be caused by the biological oxygen consumption occurring during late spring and summer. The correlation with winter mean nutrients slightly improved in this case.

  • 2102.
    Wesslander, Karin
    SMHI, Core Services.
    Coastal eutrophication status assessment using HEAT 1.0 (WFD methodology) versus HEAT 3.0 (MSFD methodology) and Development of an oxygen consumption indicator2017Report (Other academic)
    Abstract [en]

    This report contains two parts which are self standing reports and a contribution to the HELCOM project EUTRO-OPER. The work has been funded and commissioned by SwAM (Swedish agency for marine and water management) 2014-2015.

    • Coastal eutrophication status assessment using HEAT 1.0 (WFD methodology) versus HEAT 3.0 (MSFD methodology)

    Eutrophication status is assessed nationally in coastal waters within the Water Framework Directive (WFD) and in open sea areas within the Marine Strategy Framework Directive (MSFD). Both WFD and MSFD consider eutrophication but with different approaches and it is therefore a need for harmonisation in the assessment process.  The Excel based tool HEAT (HELCOM Eutrophication Assessment Tool) has been used in previous assessments in the HELCOM region. There are two versions of the tool; HEAT 1.0 and HEAT 3.0, the first is based on the WFD methodology and the second is based on the MSFD methodology. The main difference between HEAT 1.0 and HEAT 3.0 is how the indicators are grouped. Here we assess the eutrophication status in coastal waters by applying HEAT and compare the results with the national WFD assessments. The present test includes data on 33 selected coastal water bodies in five countries: Estonia, Finland, Latvia, Poland and Sweden. Data on reference condition, acceptable deviation, status and class boundaries of all indicators used in WFD for reporting ecological status (biological and physical-chemical) have been provided for each tested water body. The data has been inserted in the HEAT 1.0 and HEAT 3.0 tools and been compared with the national WFD assessments.  Both HEAT versions gave lower status in more than 50 % of the cases. For some tests the status changed to sub-GES from GES when HEAT is applied. The good/moderate boundary is the same in both HEAT and the WFD while the lower class boundaries in general are stricter in HEAT, which explains the lower status. In national WFD assessments expert judgment is used when there is little, no or very uncertain in situ data. The status in HEAT is given by the one-out-all-out principle but it is still possible to include expert judgment through the weighting factors.

    • Development of an oxygen consumption indicator

    t was investigated if the oxygen consumption can be used as an oxygen indicator for the Baltic Sea. The method is based on the idea of calculating the oxygen consumption in a stabile layer below the productive zone during summer and relating this to nutrient concentrations. With more nutrients available there is an increased biological production. By estimating how much oxygen is needed to mineralise the biological material it may be possible to link the oxygen consumption to eutrophication. The oxygen consumption was calculated for the BY15-Gotland Deep in the Eastern Gotland Basin. We identified a stabile layer between 30 and 50 m and a large change in both oxygen and nutrients from June to August. However, the oxygen consumption had a very high inter-annual variation and there were no significant correlation with the winter mean of nutrient concentrations. It was not possible to calculate the diffusion between the layers because of too sparse measurements at the stratification which limits the method. The calculation of the diffusion is however possible to improve with a model. Further on, the depth of the stabile layer is varying between areas and also between years.  We realised that the method has too many restrictions to be a functional indicator. A functional indicator shall not be dependent on heavy modelling or demand too much on expert judgement. 

    We also investigated if a possible candidate to use as a more simple oxygen consumption indicator could be the use of oxygen saturation at a specific depth. If we assume that the temperature has not changed much since the establishment of stratification we may expect that changes in oxygen saturation observed in August at this depth would be caused by the biological oxygen consumption occurring during late spring and summer. The correlation with winter mean nutrients slightly improved in this case.

  • 2103.
    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. 

  • 2104.
    Wesslander, Karin
    et al.
    SMHI, Core Services.
    Viktorsson, Lena
    SMHI, Core Services.
    Summary of the Swedish National Marine Monitoring 2016 - Hydrography, nutrients and phytoplankton2017Report (Other academic)
    Abstract [en]

    Results from the Swedish national marine monitoring in the pelagic during 2016 are presented. The institutes who conduct the national monitoring are SMHI (Swedish meteorological and hydrological institute), SU (Stockholm University) and UMF (Umeå marine sciences centre). The presented parameters in this report are; salinity, temperature, oxygen, dissolved inorganic phosphorous, total phosphorous, dissolved inorganic nitrogen, total nitrogen, dissolved silica, chlorophyll and phytoplankton. Secchi depth, zooplankton, humus, primary production, pH and alkalinity are also measured but not presented. Seasonal plots for surface waters are presented in Appendix I.  Time series for surface waters (0-10 m) and bottom waters are presented in Appendix II. The amount of nutrients in the sub-basins of the Baltic Sea is presented per season and year in Appendix III.Exceptional events 2016 

    • A warm September due to several high pressure systems, with temperatures more than one standard deviation above mean in almost all stations from Skagerrak, Kattegat and the Baltic Proper.
    • Low oxygen in Kattegat bottom water during autumn as can be seen in the seasonal plots for both Anholt E and Fladen.
    • Improved oxygen condition in the East Gotland Basin, due to an increased frequency of deep water inflows in comparison to the period 1983 until the large inflow in December 2014. The inflow of 30 km3 in the beginning of the year could be tracked in the deep water in the Eastern Gotland Basin in June.
    •  Elevated levels of silicate have been observed in the Baltic Sea since 2014 and the silicate levels were also elevated this year but mainly in the central and the northern parts of the Baltic Proper.
    • In July there were high cell numbers of the dinoflagellate Dinophysis acuminata, which caused high levels of toxins in blue mussels. During this period it was forbidden to harvest blue mussels along the Bohus coast.
    • Unusual long period of cyanobacteria bloom in the Baltic Sea.
  • 2105.
    Wesslander, Karin
    et al.
    SMHI, Core Services.
    Viktorsson, Lena
    SMHI, Core Services.
    Fölster, Jens
    Drakare, Stina
    Sonesten, Lars
    Förslag till plan för revidering av fysikalisk-kemiska bedömningsgrunder för ekologisk status i sjöar, vattendrag och kustvatten Del A: SJÖAR OCH VATTENDRAG (SLU) Del B: KUSTVATTEN (SMHI)2017Report (Other academic)
  • 2106.
    Wesslander, Karin
    et al.
    SMHI, Core Services.
    Viktorsson, Lena
    SMHI, Core Services.
    Skjevik, Ann-Turi
    SMHI, Core Services.
    The Swedish National Marine Monitoring Programme 2018. Hydrography Nutrients Phytoplankton2019Report (Other academic)
    Abstract [en]

    This report presents the main results of the Swedish national marine monitoring programme of thepelagic during 2018. The monitoring data of hydrography, nutrients and phytoplankton are analysedfor the seas surrounding Sweden: the Skagerrak, the Kattegat, the Sound, the Baltic Proper, theBothnian Sea and the Bothnian Bay.The national environmental monitoring of the pelagic is carried out by SMHI (SwedishMeteorological and Hydrological Institute), Stockholm University and UMF (Umeå Marine SciencesCentre). Data is collected, analysed and reported with support from Swedish environmentalmonitoring and on behalf of by SwAM (Swedish Agency for Marine and Water Management). TheSMHI monitoring is made in cooperation between the national environmental monitoring of thepelagic and the SMHI oceanographic sampling programme for the seas surrounding Sweden and is cofinancedby SwAM and SMHI. This annual summary of the national monitoring is made by SMHI andis financed by the contract between SwAM and SMHI.The weather in 2018 was characterized by high air temperatures and a few storms that impliedconsequences for the state in the sea. The spring arrived quickly and the sea surface temperatureincreased rapidly from April to May. In August and September two storms, named Johanne and Knud,passed the region and the surface layer was well-mixed at several stations. At the East coast upwellingevents were noted in both the Baltic Proper and the Bothnian Sea.During the year there were two small deep water inflows to the Baltic Proper that temporarilyimproved the oxygen condition in the southern parts. No improvements of the oxygen condition wereseen in the Eastern and Western Gotland Basins, instead the amount of hydrogen sulphide increased inthese basins during the year.The spring bloom had arrived in the Skagerrak and the Kattegat in March and concentrations ofdissolved inorganic phosphorus (DIP) and dissolved inorganic nitrogen (DIN) were close to or at thedetection limit from April to September. In the Skagerrak and the Kattegat the spring bloom wasdominated by the diatom Skeletonema marinoi. In the Baltic Proper the spring bloom was observed amonth later, in April. The extensive cyanobacteria bloom in the Baltic Proper started already in Mayand during the late September cruise cyanobacteria were still abundant. The dinoflagellateProrocentrum compressum was found in high cell numbers during the autumn at all stations on theWest coast. This flagellate has rarely been observed previously and although it is not harmful it isinteresting when species suddenly occur and stay for a longer period. The potentially harmful diatomgenus Pseudo-nitzschia bloomed in the beginning of December.Surface concentrations of DIP and DIN were mainly normal except from in the Skagerrak and theKattegat where concentrations were lower than usual in December. Concentrations of silicate wereabove normal levels before the spring bloom at most of the stations and in the Baltic Proper silicatewas also high in the autumn.In 2018 there were some difficulties with available research vessels for the planned cruises and somecruises needed to be cancelled with short notice. Many planned observations were therefore missed, inparticular during the summer period.

  • 2107.
    Wesslander, Karin
    et al.
    SMHI, Core Services.
    Viktorsson, Lena
    SMHI, Core Services.
    Skjevik, Ann-Turi
    SMHI, Core Services.
    The SwedishNational MarineMonitoringProgramme 2017: HydrographyNutrientsPhytoplankton2018Report (Other academic)
    Abstract [en]

    This report presents the main results of the Swedish national marine monitoring programme of the pelagic during 2017. The monitoring data of hydrography, nutrients and phytoplankton are analysed for the seas surrounding Sweden: Skagerrak, Kattegat, The Sound, Baltic Proper, Bothnian Sea and Bothnian Bay. The monitoring is carried out by SMHI (Swedish Meteorological and Hydrological Institute), SU (Stockholm University) and UMF (Umeå Marine Sciences Centre) and the monitoring programme is co-funded by SwAM (Swedish Agency for Marine and Water Management), SMHI, SU and UMF. Data is collected, analysed and reported with support from Swedish environmental monitoring and commissioned by SwaM.

    The Baltic current along the Swedish west coast implies large variations in surface salinity and the unusually large outflow of brackish water from the Baltic Sea in 2017 was reflected as low surface salinity in Skagerrak and Kattegat in the beginning of the year. There were no major deep water inflows to the Baltic Sea during 2017 but a few inflows of minor magnitude. These minor inflows only temporarily improved the oxygen condition in the Bornholm Basin and in the southern part of the Eastern Gotland Basin.

    The salinity below the halocline was above normal in the Gotland Basins and in the Northern Baltic Proper, and also in the surface layer in the Eastern Gotland Basin for almost the whole year.

    In Skagerrak and Kattegat, surface concentrations of phosphate and dissolved inorganic nitrogen were normal while dissolved silica concentrations were elevated especially in spring. In the Baltic Sea, the concentration of silicate in the surface water was elevated in all basins. According to the estimated total content of silicate there has been an increase in silica content in the Baltic Sea since the early 1990’s. Surface concentrations of phosphate were above normal in the Gotland basins and the Northern Baltic Proper while inorganic nitrogen content was above normal in parts of the Arkona and Bornholm basins. During spring and summer, the inorganic nitrogen was consumed at greater depths than usual in the Baltic Proper. In particular concentrations of phosphate and dissolved silica were generally lower than normal in the bottom layer.

    Instead of diatoms, the flagellate genus Pseudochattonella, which is potentially toxic to fish, bloomed in the Kattegat and Skagerrak areas in February – April. During autumn there was a prolonged diatom bloom though. In the Baltic Sea spring bloom occurred in April. The cyanobacteria bloom began in May already with Aphanizomenon flos-aquae. During June and July all three of the filamentous cyanobacteria, A. flos-aquae, Dolichospermum lemmermannii and the potentially harmful Nodularia spumigena were found in the phytoplankton samples in various amounts.

    In the Bothnian Sea, the sea surface temperature during summer was lower than normal and the oxygen conditions in the bottom layer was not critical but still below normal levels.

  • 2108. 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.

  • 2109.
    Westring, Gustaf
    SMHI.
    Brofjordens kraftstation: Kompletterande simulering och analys av kylvattenspridning i Trommekilen1991Report (Other academic)
  • 2110.
    Westring, Gustaf
    SMHI.
    Isförhållanden utmed Sveriges kust: Isstatistik från svenska farleder och farvatten under normalperioderna 1931-60 och 1961-901995Report (Other academic)
  • 2111.
    Westring, Gustaf
    SMHI.
    Isförhållandena i svenska farvatten under normalperioden 1961-902009Report (Other academic)
  • 2112.
    Westring, Gustaf
    SMHI.
    Vågmätningar utanför Kristianopel: Slutrapport1991Report (Other academic)
  • 2113.
    Westring, Gustaf
    et al.
    SMHI.
    Andersson, Jan
    SMHI, Core Services.
    Lindh, Henrik
    SMHI, Core Services.
    Axelsson, Robert
    SMHI.
    Forsmark - en temperaturstudie: Slutrapport1993Report (Other academic)
  • 2114.
    Westring, Gustaf
    et al.
    SMHI.
    Wickström, Kjell
    SMHI.
    Spridningsberäkningar för Höganäs kommun1990Report (Other academic)
  • 2115.
    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.

  • 2116.
    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.

  • 2117.
    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.

  • 2118.
    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.

  • 2119. 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.

  • 2120. 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)
  • 2121. 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.

  • 2122.
    Wickström, Kjell
    SMHI.
    Bedömning av kylvattenrecipienten för ett kolkraftverk vid Oskarshamnsverket1987Report (Other academic)
  • 2123.
    Wickström, Kjell
    SMHI.
    Oskarshamnsverket - kylvattenutsläpp i havet: Slutrapport1990Report (Other academic)
  • 2124.
    Wickström, Kjell
    SMHI.
    Vågdata från svenska kustvatten 19861988Report (Other academic)
  • 2125.
    Wickström, Kjell
    et al.
    SMHI.
    Hillgren, Robert
    SMHI, Core Services.
    Spridningsberäkningar för EKA-NOBELs fabrik i Stockviksverken1990Report (Other academic)
  • 2126. 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)
  • 2127.
    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.

  • 2128. 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)
  • 2129.
    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.

  • 2130. 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.

  • 2131.
    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)
  • 2132. Wilk, Julie
    et al.
    Kniveton, Dominic
    Andersson, Lotta
    SMHI, Core Services.
    Layberry, Russell
    Todd, Martin C.
    Hughes, Denis
    Ringrose, Susan
    Vanderpost, Cornelis
    Estimating rainfall and water balance over the Okavango River Basin for hydrological applications2006In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 331, no 1-2, p. 18-29Article in journal (Refereed)
    Abstract [en]

    A historical database for use in rainfall-runoff modeling of the Okavango River Basin in Southwest Africa is presented. The work has relevance for similar data-sparse regions. The parameters of main concern are rainfall and catchment water balance, which are key variables for subsequent studies of the hydrological impacts of development and climate change. Rainfall estimates are based on a combination of in situ gauges and satellite sources. Rain gauge measurements are most extensive from 1955 to 1972, after which they are drastically reduced due to the Angolan civil war. The sensitivity of the rainfall fields to spatial interpolation techniques and the density of gauges were evaluated. Satellite based rainfall estimates for the basin are developed for the period from 1991 onwards, based on the Tropical Rainfall Measuring Mission (TRMM) and Special Sensor Microwave Imager (SSM/I) datasets. The consistency between the gauges and satellite estimates was considered. A methodology was developed to allow calibration of the rainfall-runoff hydrological model against rain gauge data from 1960 to 1972, with the prerequisite that the model should be driven by satellite derived rainfall products from ` 1990 onwards. With the rain gauge data, addition of a single rainfall station (Longa) in regions where stations earlier were lacking was more important than the chosen interpolation method. Comparison of satellite and gauge rainfall outside the basin indicated that the satellite overestimates rainfall by 20%. A non-linear correction was derived by fitting the rainfall frequency characteristics to those of the historical rainfall data. This satellite rainfall dataset was found satisfactory when using the Pitman rainfall-runoff model (Hughes, D., Andersson, L., Wilk, J., Savenije, H.H.G., this issue. Regional calibration of the Pitman model for the Okavango River. Journal of Hydrology). Intensive monitoring in the region is recommended to increase accuracy of the comprehensive satellite rainfall estimate calibration procedure. (c) 2006 Elsevier B.V. All rights reserved.

  • 2133. 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.

  • 2134. 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.

  • 2135. 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)
  • 2136.
    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)
  • 2137.
    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)
  • 2138.
    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.

  • 2139.
    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)
  • 2140.
    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.

  • 2141.
    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)
  • 2142. 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.

  • 2143. 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.

  • 2144. 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.

  • 2145.
    Wittgren, Hans B.
    et al.
    SMHI.
    Maehlum, T
    Wastewater treatment wetlands in cold climates1997In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 35, no 5, p. 45-53Article in journal (Refereed)
    Abstract [en]

    The best prospects for successful wetland treatment should be in the warmer regions of the world, but studies in North America and Scandinavia show that wetland treatment may be feasible also in cooler regions. A review shows that the number of wetlands of different types (free water surface, FWS; horizontal and vertical subsurface flow, SSF), treating different kinds of wastewater, is steadily increasing in most parts of the cold temperate regions of the world. The major wetland engineering concerns in cold climates, which are discussed in this paper, are related to: (1) ice formation, and its implications for hydraulic performance; (2) hydrology and hydraulic issues besides ice formation; and (3) the thermal consequences for biologically or microbiologically mediated treatment processes. Energy- and water-balance calculations, as well as thermal modeling, are useful tools for successful design and operation of treatment wetlands, but the shortage of data makes it necessary to adopt a conservative approach. The treatment processes often appear less temperature sensitive in full-scale wetlands as compared to laboratory incubations. Several possible explanations are discussed in the paper: (1) sedimentation playing a significant role, (2) overdimensioning in relation to some constituents, (3) seasonal adsorption (cation exchange) of ammonium, and (4) temperature adaptation of the microbial community. Experience shows that cold climate wetlands can meet effluent criteria for the most important treatment parameters. To gain wide acceptance, however, we need to become more specific about design and construction, and also about operation, maintenance and cost-effectiveness. These goals require detailed knowledge about processes in full-scale wetlands, including long-term changes and response to maintenance. (C) 1997 IAWQ.

  • 2146.
    Wittgren, Hans Bertil
    SMHI, Research Department.
    Kvävetransport till Slätbaken från Söderköpingsåns avrinningsområde1995Report (Other academic)
  • 2147.
    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.

  • 2148.
    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.

  • 2149. 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.

  • 2150. Wolski, Tomasz
    et al.
    Wisniewski, Bernard
    Giza, Andrzej
    Kowalewska-Kalkowska, Halina
    Boman, Hanna
    Grabbi-Kaiv, Silve
    Hammarklint, Thomas
    SMHI, Core Services.
    Holfort, Juergen
    Lydeikaite, Zydrune
    Extreme sea levels at selected stations on the Baltic Sea coast2014In: Oceanologia, ISSN 0078-3234, Vol. 56, no 2, p. 259-290Article in journal (Refereed)
    Abstract [en]

    The purpose of this article is to analyse and describe the extreme characteristics of the water levels and illustrate them as the topography of the sea surface along the whole Baltic Sea coast. The general pattern is to show the maxima and minima of Baltic Sea water levels and the extent of their variations in the period from 1960 to 2010. A probability analysis is carried out on the annual sea level maxima and minima for 31 water level gauges in order to define the probability of occurrence of theoretical sea levels once in a specific number of years. The spatial distribution of sea levels for hundred-year maximum and minimum water levels is illustrated. Then, the number of storm surges for the accepted criteria are presented: these numbers increased in the 50-year period analysed. The final part of the work analyses some extreme storm events and calculates the static value and dynamic deformation of the sea surface by mesoscale, deep low-pressure systems.

4041424344 2101 - 2150 of 2198
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