Change search
Refine search result
1234567 151 - 200 of 2198
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 151.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Brandt, Maja
    SMHI, Core Services.
    Grahn, Gun
    SMHI.
    Roos, Elisabet
    SMHI.
    Sjöö, Allan
    SMHI.
    Modellerad kvävetransport, retention och källfördelning för södra Sverige1997Report (Other academic)
  • 152.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Dahne, Joel
    SMHI, Professional Services.
    Donnelly, Chantal
    SMHI, Research Department, Hydrology.
    Climate Change Impact on Riverine Nutrient Load and Land-Based Remedial Measures of the Baltic Sea Action Plan2012In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 41, no 6, p. 600-612Article in journal (Refereed)
    Abstract [en]

    To reduce eutrophication of the Baltic Sea, all nine surrounding countries have agreed upon reduction targets in the HELCOM Baltic Sea Action Plan (BSAP). Yet, monitoring sites and model concepts for decision support are few. To provide one more tool for analysis of water and nutrient fluxes in the Baltic Sea basin, the HYPE model has been applied to the region (called Balt-HYPE). It was used here for experimenting with land-based remedial measures and future climate projections to quantify the impacts of these on water and nutrient loads to the sea. The results suggest that there is a possibility to reach the BSAP nutrient reduction targets by 2100, and that climate change may both aggravate and help in some aspects. Uncertainties in the model results are large, mainly due to the spread of the climate model projections, but also due to the hydrological model.

  • 153.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Dahne, Joel
    SMHI, Professional Services.
    Donnelly, Chantal
    SMHI, Research Department, Hydrology.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    Strömqvist, Johan
    SMHI, Research Department, Hydrology.
    Water and nutrient simulations using the HYPE model for Sweden vs. the Baltic Sea basin - influence of input-data quality and scale2012In: HYDROLOGY RESEARCH, ISSN 1998-9563, Vol. 43, no 4, p. 315-329Article in journal (Refereed)
    Abstract [en]

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

  • 154.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Donnelly, Chantal
    SMHI, Research Department, Hydrology.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    Regulation of snow-fed rivers affects flow regimes more than climate change2017In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, article id 62Article in journal (Refereed)
  • 155.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Hjerdt, Niclas
    SMHI, Core Services.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    Artificially Induced Floods to Manage Forest Habitats Under Climate Change2018In: FRONTIERS IN ENVIRONMENTAL SCIENCE, ISSN 2296-665X, Vol. 6, article id 102Article in journal (Refereed)
  • 156.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Lidén, R.
    SMHI.
    Nitrogen and phosphorus concentrations from agricultural catchments - influence of spatial and temporal variables2000In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 227, no 1-4, p. 140-159Article in journal (Refereed)
    Abstract [en]

    The eutrophication problem has drawn attention to nutrient leaching from arable land in southern Sweden, and further understanding of spatial and temporal variability is needed in order to develop decision-making tools. Thus, the influence of spatial and temporal variables was analysed statistically using empirical time series of different nutrient species from 35 well-documented catchments (2-35 km(2)), which have been monitored for an average of 5 years. In the spatial analysis several significant correlations between winter median concentrations and catchment characteristics were found. The strongest correlation was found between inorganic nitrogen and land use, while concentrations of different phosphorus species were highly correlated to soil texture. Multiple linear regression models gave satisfactory results for prediction of median winter concentrations in unmeasured catchments, especially for inorganic nitrogen and phosphate. In the analysis of temporal variability within catchments, internal variables from a dynamic hydrological model (HBV) were linked to concentration fluxes. It was found that phosphorus and inorganic nitrogen concentrations were elevated during flow increase at low-Bow conditions, while they were diluted as the wetness in the catchment increased. During unmonitored periods regression models were successful in predicting temporal variability of total phosphorus, phosphate and inorganic nitrogen, while organic nitrogen and particulate phosphorus could not be predicted with this approach. Dividing the data into different flow categories did not improve the prediction of nutrient concentration dynamics. The results and literature review presented, confirm parts of the present HBV-W model approach and will be useful for further development of nutrient routines linked to dynamic hydrological models. (C) 2000 Elsevier Science B.V. All rights reserved.

  • 157.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    Climate impact on floods: changes in high flows in Sweden in the past and the future (1911-2100)2015In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, no 2, p. 771-784Article in journal (Refereed)
    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.

  • 158.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    A systematic review of sensitivities in the Swedish flood-forecasting system2011In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 100, no 2-3, p. 275-284Article, review/survey (Refereed)
    Abstract [en]

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

  • 159.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Lowgren, M
    Pers, Charlotta
    SMHI, Research Department, Hydrology.
    Rosberg, Jörgen
    SMHI, Research Department, Hydrology.
    Integrated catchment modeling for nutrient reduction: Scenarios showing impacts, potential, and cost of measures2005In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 34, no 7, p. 513-520Article in journal (Refereed)
    Abstract [en]

    A hydrological-based model (HBV-NP) was applied to a catchment (1900 km(2)) in the southern part of Sweden. Careful characterization of the present load situation and the potential for improved treatment or reduced soil leaching were analyzed. Several scenarios were modeled to find strategies to reach the Swedish environmental goals of reducing anthropogenic nitrogen load by 30% and phosphorus load by 20%. It was stated that the goals could be reached by different approaches that would affect different polluters and social sectors. However, no single measure was enough by itself. Instead, a combination of measures was necessary to achieve the goals. The nitrogen goal was the most difficult to attain. In order to be cost-effective, these measures should be applied to areas contributing the most to the net loading of the sea. This strategy could reduce the costs by 70%-80% when compared with implementing the measures in the entire catchment. Integrated catchment models may thus be helpful tools for reducing costs in environmental control programs.

  • 160.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Nilsson, Johanna
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    Experimenting with Coupled Hydro-Ecological Models to Explore Measure Plans and Water Quality Goals in a Semi-Enclosed Swedish Bay2015In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 7, no 7, p. 3906-3924Article in journal (Refereed)
    Abstract [en]

    Measure plans are currently being developed for the Water Framework Directive (WFD) by European water authorities. In Sweden, such plans include measures for good ecological status in the coastal ecosystem. However, the effect of suggested measures is not yet known. We therefore experimented with different nutrient reduction measures on land and in the sea, using a model system of two coupled dynamic models for a semi-enclosed bay and its catchment. The science question was whether it is worthwhile to implement measures in the local catchment area to reach local environmental goals, or if the status of the Bay is more governed by the water exchange with the Sea. The results indicate that by combining several measures in the catchment, the nutrient load can be reduced by 15%-20%. To reach the same effect on nutrient concentrations in the Bay, the concentrations of the sea must be reduced by 80%. Hence, in this case, local measures have a stronger impact on coastal water quality. The experiment also show that the present targets for good ecological status set up by the Swedish water authorities may be unrealistic for this Bay. Finally, we discuss when and how to use hydro-ecological models for societal needs.

  • 161.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Pers, Charlotta
    SMHI, Research Department, Hydrology.
    Kväveretention i svenska sjöar och vattendrag – betydelse för utsläpp från reningsverk2007Report (Other academic)
    Abstract [en]

    This report has been compiled on request of the Swedish Environmental Protection Agency to facilitate the discussion with the EU Commission. The EU Commission has announced that it will take Sweden to the European Court of Justice for failing to ensure proper treatment of urban waste water according to the Urban Waste Water Treatment Directive (Directive 91/271/EEC). In Sweden natural nitrogen removal (retention) in waterbodies is considered as part of the treatment of emissions, when transported to the sea. Nitrogen retention is a well-known phenomenon that includes several natural biogeochemical processes, which permanently remove nitrogen from the water. The effect may be considerable in areas with many lakes. Sweden has 92 000 lakes larger than 1 hectare. It is rather normal with 30-70% nitrogen retention in Swedish lakes and rivers. The main process for natural nitrogen retention is denitrification, which is the same process that is applied for biological treatment in waste water plants. Natural retention is hard to measure, however, and has to be estimated based on several assumptions like so many other fluxes in nature. In Sweden a model system has been developed for large-scale calculation of nutrient transport, including retention, from land to the sea, with relatively high geographic resolution. The system couples field-scale models with catchment models and is scientifically documented and reviewed. It has been applied since 1997 for international reporting to HELCOM. The catchment model (HBVNP) is tuned and evaluated against monitored time-series of measurements where such are available. The nitrogen retention that is calculated with HBV-NP is composed of nitrogen that is permanently transferred to the atmosphere and sediment, and which therefore will not further contribute to the eutrophication of water systems.

  • 162.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Pers, Charlotta
    SMHI, Research Department, Hydrology.
    Lessons learned? Effects of nutrient reductions from constructing wetlands in 1996–2006 across Sweden2016In: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992, p. 1-11Article in journal (Refereed)
  • 163.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Torstensson, G
    Wittgren, Hans Bertil
    SMHI, Research Department.
    Landscape planning to reduce coastal eutrophication: agricultural practices and constructed wetlands2004In: Landscape and Urban Planning, ISSN 0169-2046, E-ISSN 1872-6062, Vol. 67, no 1-4, p. 205-215Article in journal (Refereed)
    Abstract [en]

    Southern Sweden suffers from coastal eutrophication and one reason is the high nitrogen load through rivers. The major part of this load originates from diffuse land-based sources, e.g. arable soil leaching. Effective reduction of load from such sources demand careful landscape analysis, combined with changed behaviour of the stakeholders. This study describes a chain of methods to achieve trustworthy management plans that are based on numerical modelling and stakeholders participation and acceptance. The effect of some measures was unexpected when modelling their impact on the catchment scale. Management scenarios to reduce riverine nitrogen load were constructed in an actor game (i.e. role-play) for the Genevadsan catchment in southern Sweden. The game included stakeholders for implementation of a loading standard for maximum nitrogen transport at the river mouth. Scenarios were defined after negotiation among involved actors and included changes in agricultural practices, improved wastewater treatment, and establishment of wetlands. Numerical models were used to calculate the nitrogen reduction for different measures in each scenario. An index model (STANK) calculated the root zone leaching of nitrogen from crops at four type farms. This generated input to a catchment scale model (HBV-N) and farm economics. The economic impact of different sets of remedial measures was evaluated for each type farm and then extrapolated to the catchment. The results from scenario modelling show that possible changes in agricultural practices (such as tuning, timing of fertilisation and ploughing, changed crop cultivation) could reduce the nitrogen load to the sea by some 30%, while wetland construction only reduced the original load by some 5%. In the most cost-effective scenario agricultural practices could reduce the riverine load by 86 t per year at a cost of 1.0 million SEK, while constructed wetlands only reduced the load by 14 t per year at a cost of 1.7 million SEK. Thus, changed agricultural practices can be the most effective and less expensive way to reduce nitrogen transport from land to the sea, while constructed wetlands with realistic allocations and sizes may only have small impact on riverine nitrogen transport from land to sea. The overall experience is that actor games and numerical modelling are useful tools in landscape planning for analysing stakeholders' behaviour and the impact of measures to reduce coastal eutrophication. (C) 2003 Elsevier Science B.V. All rights reserved.

  • 164.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Wittgren, H B
    Modelling nitrogen removal in potential wetlands at the catchment scale2002In: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992, Vol. 19, no 1, p. 63-80Article in journal (Refereed)
    Abstract [en]

    The reduction of nitrogen fluxes from land to sea is an important task in areas with estuarine or marine eutrophication. Wetland creation has been proposed as one method to reduce nitrogen from streams draining agricultural areas. In this study, a scenario of nitrogen removal in created wetlands was evaluated by mathematical modelling of nitrogen fluxes in a catchment (224 km(2)) in southern Sweden. The scenario was based on topographically realistic siting of 40 potential wetlands with a total area of 0.92 km(2) (0.4% of the catchment area). Nitrogen removal in the wetlands was described with a simple and robust first-order model, which was modified and evaluated against data from eight monitored surface-flow wetlands. However, the modifications gave no substantial support for changing the basic model. For catchment-scale modelling this wetland model was incorporated into a dynamic process-based catchment model (HBV-N). The catchment was then divided to several coupled subbasins, so that the wetland influence on nitrogen load could be estimated separately for each potential wetland. The modelling showed that the 40 potential wetlands would reduce the nitrogen transport to the coast with approximately 6%. Specific removal rates ranged between 57 and 466 kg ha(-1) yr(-1) for the different wetlands, depending on residence time (size and hydraulic loading) and nitrogen concentration in inflow. Due to temperature dependence and seasonal variation in water discharge, significant decrease in nitrogen concentrations mainly occurred during summer periods with low loading. The study illustrates that catchment modelling is a useful method for analysing wetland creation plans, and that wetland creation must cover fairly large areas and be combined with other measures in order to achieve substantial reduction of nitrogen fluxes to coastal waters. Further monitoring of existing wetlands will improve the removal expression and decrease uncertainty. For instance, at present it could not be deducted whether wetlands with low average residence times ( < 2 days) have net removal or net resuspension on an annual basis. (C) 2002 Elsevier Science B.V. All rights reserved.

  • 165.
    Arheimer, Berit
    et al.
    SMHI, Research Department, Hydrology.
    Wittgren, Hans Bertil
    SMHI, Research Department.
    MODELING THE EFFECTS OF WETLANDS ON REGIONAL NITROGEN TRANSPORT1994In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 23, no 6, p. 378-386Article in journal (Refereed)
    Abstract [en]

    Created wetlands have been suggested as a method to reduce nitrogen transport to the Baltic Sea. This paper presents a dynamic conceptual model for simulation of the hypothetical effect of wetlands on nitrogen export to the coastal zone. The study was performed in the Soder-kopingsan drainage basin (882 km(2)) in southeastern Sweden, discharging into the Baltic Sea. An empirically based routine for wetland retention was calibrated separately and incorporated in the model. Scenarios with different location and size of wetlands were analyzed. It was estimated that conversion of 1% (8.8 km(2)) of this basin into wetlands would reduce the nitrogen transport by 10-16% and that more than 5% (45 km(2)) conversion to wetlands is required to reduce the transport by 50%. It was concluded that creation of wetlands should be considered, primarily, downstream from major lakes, in coastal areas, and where the summer load is a significant portion of the annual load. Some further conclusions from the study were that: i) the net reduction of nitrogen transport per unit area of wetland decreases with increasing total area of wetlands in a drainage basin; ii) the wetland retention efficiency obtained in studies of individual wetlands can not be extrapolated in a linear fashion to estimate the net reduction of nitrogen transport at the mouth of a whole drainage basin; iii) the seasonal hydrological and hydrochemical dynamics are of fundamental importance for wetland retention efficiency, which complicates comparison and extrapolation of results from one region to another.

  • 166. Arnbjerg-Nielsen, K.
    et al.
    Willems, P.
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    Beecham, S.
    Pathirana, A.
    Gregersen, I. Bulow
    Madsen, H.
    Nguyen, V. -T-V
    Impacts of climate change on rainfall extremes and urban drainage systems: a review2013In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 68, no 1, p. 16-28Article, review/survey (Refereed)
    Abstract [en]

    A review is made of current methods for assessing future changes in urban rainfall extremes and their effects on urban drainage systems, due to anthropogenic-induced climate change. The review concludes that in spite of significant advances there are still many limitations in our understanding of how to describe precipitation patterns in a changing climate in order to design and operate urban drainage infrastructure. Climate change may well be the driver that ensures that changes in urban drainage paradigms are identified and suitable solutions implemented. Design and optimization of urban drainage infrastructure considering climate change impacts and co-optimizing these with other objectives will become ever more important to keep our cities habitable into the future.

  • 167.
    Arneborg, Lars
    et al.
    SMHI, Research Department, Oceanography.
    Höglund, Anders
    SMHI, Research Department, Oceanography.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Lensu, Mikko
    Ljungman, Olof
    Mattsson, Johan
    Oil drift modeling in pack ice - Sensitivity to oil-in-ice parameters2017In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 144, p. 340-350Article in journal (Refereed)
  • 168.
    Arneborg, Lars
    et al.
    SMHI, Research Department, Oceanography.
    Jansson, Par
    Staalstrom, Andre
    Broström, Göran
    Tidal Energy Loss, Internal Tide Radiation, and Local Dissipation for Two-Layer Tidal Flow over a Sill2017In: Journal of Physical Oceanography, ISSN 0022-3670, E-ISSN 1520-0485, Vol. 47, no 7, p. 1521-1538Article in journal (Refereed)
  • 169. Arnold, S. R.
    et al.
    Emmons, L. K.
    Monks, S. A.
    Law, K. S.
    Ridley, D. A.
    Turquety, S.
    Tilmes, S.
    Thomas, J. L.
    Bouarar, I.
    Flemming, J.
    Huijnen, V.
    Mao, J.
    Duncan, B. N.
    Steenrod, S.
    Yoshida, Y.
    Langner, Joakim
    SMHI, Research Department, Air quality.
    Long, Y.
    Biomass burning influence on high-latitude tropospheric ozone and reactive nitrogen in summer 2008: a multi-model analysis based on POLMIP simulations2015In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, no 11, p. 6047-6068Article in journal (Refereed)
    Abstract [en]

    We have evaluated tropospheric ozone enhancement in air dominated by biomass burning emissions at high latitudes (>50 degrees N) in July 2008, using 10 global chemical transport model simulations from the POLMIP multimodel comparison exercise. In model air masses dominated by fire emissions, Delta O-3/Delta CO values ranged between 0.039 and 0.196 ppbv ppbv(-1) (mean: 0.113 ppbv ppbv(-1)) in freshly fire-influenced air, and between 0.140 and 0.261 ppbv ppb(-1) (mean: 0.193 ppbv) in more aged fire-influenced air. These values are in broad agreement with the range of observational estimates from the literature. Model Delta PAN/Delta CO enhancement ratios show distinct groupings according to the meteorological data used to drive the models. ECMWF-forced models produce larger Delta PAN/Delta CO values (4.47 to 7.00 pptv ppbv(-1)) than GEOS5-forced models (1.87 to 3.28 pptv ppbv(-1)), which we show is likely linked to differences in efficiency of vertical transport during poleward export from mid-latitude source regions. Simulations of a large plume of biomass burning and anthropogenic emissions exported from towards the Arctic using a Lagrangian chemical transport model show that 4-day net ozone change in the plume is sensitive to differences in plume chemical composition and plume vertical position among the POLMIP models. In particular, Arctic ozone evolution in the plume is highly sensitive to initial concentrations of PAN, as well as oxygenated VOCs (acetone, acetaldehyde), due to their role in producing the peroxyacetyl radical PAN precursor. Vertical displacement is also important due to its effects on the stability of PAN, and subsequent effect on NOx abundance. In plumes where net ozone production is limited, we find that the lifetime of ozone in the plume is sensitive to hydrogen peroxide loading, due to the production of HOx from peroxide photolysis, and the key role of HO2 + O-3 in controlling ozone loss. Overall, our results suggest that emissions from biomass burning lead to large-scale photochemical enhancement in high-latitude tropospheric ozone during summer.

  • 170.
    Arnér, Erik
    SMHI.
    Simulering av vårflöden med HBV-modellen1991Report (Other academic)
    Abstract [en]

    In order to improve the HBV-models ability to forecast the start of the spring flood, a degree-day model which uses the daily extreme temperatures to calculate snow accumulation and snowmelt was tested. The temperatures each day were assumed to vary linearly between the daily maximum and the daily minimum temperatu.re. Precipitation was distributed within each timestep as rain and snow according to the time the temperature had been on either side of a threshold temperature. Snow accumulation and snowmelt were calculated seperately du.ring timesteps where the extreme temperatures enclosed the threshold temperature. The simulation results were compared to those obtained by the original HBV-model, which uses the daily mean temperatu.res only. Six Swedish basins with different size and climate were selected, and totally 88 years were simulated and analyzed. The results showed that the new model improved the predictions of the start of the spring flood a bit, hut on the other hand it yielded lower values of the efficiency criterion, the R2-value. The results varied between the examined basins, hut altogether the performance of the new model was as good as the performance of the original HB Vmodel, and the models were considered equivalent. A test of the influence of the refreezing parameter in the new mode! was done in two small basins. The refreezing parameter was changed in steps from 0.00 to 0.21, and at each step the other snow parameters were recalibrated. It was found that the value of the refreezing parameter can have some influence, but the most important is that it exists so the snow is dry then the melting starts in spring. The amount of refreezing water can to some extent be controlled by other parameters in the model. In one of the basins the effect of the quality of used temperature data in the models was tested. This was done by running the models with data from one station at a time. Temperature data from three stations were used, and for every new station the snow parameters were recalibrated. It was noted that the simulation results were changed as much when the used temperature station was changed as when the model was changed. The results indicated that the new model was more dependant on accurate temperature data than the original HB V -model. The POC automatic calibration method (Har lin, 1991) has been used in this project, and almost 50 calibrations have been macie. The experience of this new method was good. The report includes a description of the HBV-model anda literature review on modeling snowmelt-runoff.

  • 171. Arritt, Raymond W.
    et al.
    Rummukainen, Markku
    SMHI, Core Services.
    CHALLENGES IN REGIONAL-SCALE CLIMATE MODELING2011In: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 92, no 3, p. 365-368Article in journal (Other academic)
  • 172. Ashcroft, Linden
    et al.
    Coll, Joan Ramon
    Gilabert, Alba
    Domonkos, Peter
    Brunet, Manola
    Aguilar, Enric
    Castella, Merce
    Sigro, Javier
    Harris, Ian
    Undén, Per
    SMHI, Research Department, Meteorology.
    Jones, Phil
    A rescued dataset of sub-daily meteorological observations for Europe and the southern Mediterranean region, 1877-20122018In: Earth System Science Data, ISSN 1866-3508, E-ISSN 1866-3516, Vol. 10, no 3, p. 1613-1635Article in journal (Refereed)
  • 173. ASKNE, J
    et al.
    LEPPARANTA, M
    Thompson, Thomas
    SMHI.
    THE BOTHNIAN EXPERIMENT IN PREPARATION FOR ERS-1, 1988 (BEPERS-88) - AN OVERVIEW1992In: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 13, no 13, p. 2377-2398Article in journal (Refereed)
    Abstract [en]

    BEPERS-88 was an extensive field campaign on the use of Synthetic Aperture Radar (SAR) in sea ice remote sensing in the Baltic Sea. This experiment was performed in order to study the possibilities of using the ERS-1 satellite SAR (and radar altimeter) in connection with the brackish ice in the Baltic Sea. The Canada Centre for Remote Sensing CV-580 C/X-band SAR was flown and an extensive validation programme was carried out. The data have been used for SAR image analysis, backscatter investigations, geophysical validation of SAR over sea ice, and evaluation of the potentials of SAR in operational ice information services. The results indicate that SAR can be used to discriminate between ice and open water, classify ice types into three categories, quantify ice ridging intensity, and determine the ice drift. As an operational tool SAR is expected to be an excellent complement to NOAA imagery and ground truth.

  • 174.
    Asp, Magnus
    et al.
    SMHI, Professional Services.
    Berggreen-Clausen, Steve
    SMHI, Professional Services.
    Berglöv, Gitte
    SMHI, Professional Services.
    Björck, Emil
    SMHI, Professional Services.
    Johnell, Anna
    SMHI, Professional Services.
    Axén Mårtensson, Jenny
    SMHI, Core Services.
    Ohlsson, Alexandra
    SMHI, Professional Services.
    Persson, Håkan
    SMHI, Professional Services.
    Sjökvist, Elin
    SMHI, Professional Services.
    Framtidsklimat i Stockholms län - enligt RCP-scenarier2015Report (Other academic)
    Abstract [en]

    The report describes todays and future climate in Stockholm County based on observations and climate modelling. Regional modelled RCP4.5 and RCP8.5 scenarios have been further downscaled to 4×4 km2 resolution. The results are presented as meteorological and hydrological indices based on statistically processed model data.

  • 175.
    Asp, Magnus
    et al.
    SMHI, Professional Services.
    Berggreen-Clausen, Steve
    SMHI, Professional Services.
    Berglöv, Gitte
    SMHI, Professional Services.
    Björck, Emil
    SMHI, Professional Services.
    Johnell, Anna
    SMHI, Professional Services.
    Axén Mårtensson, Jenny
    SMHI, Core Services.
    Ohlsson, Alexandra
    SMHI, Professional Services.
    Persson, Håkan
    SMHI, Professional Services.
    Sjökvist, Elin
    SMHI, Professional Services.
    Framtidsklimat i Södermanlands län - enligt RCP-scenarier2015Report (Other academic)
    Abstract [en]

    The report describes todays and future climate in Södermanland County based on observations and climate modelling. Regional modelled RCP4.5 and RCP8.5 scenarios have been further downscaled to 4×4 km2 resolution. The results are presented as meteorological and hydrological indices based on statistically processed model data.

  • 176.
    Asp, Magnus
    et al.
    SMHI, Professional Services.
    Berggreen-Clausen, Steve
    SMHI, Professional Services.
    Berglöv, Gitte
    SMHI, Professional Services.
    Björck, Emil
    SMHI, Professional Services.
    Johnell, Anna
    SMHI, Professional Services.
    Axén Mårtensson, Jenny
    SMHI, Core Services.
    Ohlsson, Alexandra
    SMHI, Professional Services.
    Persson, Håkan
    SMHI, Professional Services.
    Sjökvist, Elin
    SMHI, Professional Services.
    Framtidsklimat i Östergötlands län - enligt RCP-scenarier2015Report (Other academic)
    Abstract [en]

    The report describes todays and future climate in Östergötland County based on observations and climate modelling. Regional modelled RCP4.5 and RCP8.5 scenarios have been further downscaled to 4×4 km2 resolution. The results are presented as meteorological and hydrological indices based on statistically processed model data.

  • 177. Astrom, Christofer
    et al.
    Astrom, Daniel Oudin
    Andersson, Camilla
    SMHI, Research Department, Air quality.
    Ebi, Kristie L.
    Forsberg, Bertil
    Vulnerability Reduction Needed to Maintain Current Burdens of Heat-Related Mortality in a Changing Climate-Magnitude and Determinants2017In: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 14, no 7, article id 741Article in journal (Refereed)
  • 178. Astrom, Christofer
    et al.
    Ebi, Kristie L.
    Langner, Joakim
    SMHI, Research Department, Air quality.
    Forsberg, Bertil
    Developing a Heatwave Early Warning System for Sweden: Evaluating Sensitivity of Different Epidemiological Modelling Approaches to Forecast Temperatures2015In: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 12, no 1, p. 254-267Article in journal (Refereed)
    Abstract [en]

    Over the last two decades a number of heatwaves have brought the need for heatwave early warning systems (HEWS) to the attention of many European governments. The HEWS in Europe are operating under the assumption that there is a high correlation between observed and forecasted temperatures. We investigated the sensitivity of different temperature mortality relationships when using forecast temperatures. We modelled mortality in Stockholm using observed temperatures and made predictions using forecast temperatures from the European Centre for Medium-range Weather Forecasts to assess the sensitivity. We found that the forecast will alter the expected future risk differently for different temperature mortality relationships. The more complex models seemed more sensitive to inaccurate forecasts. Despite the difference between models, there was a high agreement between models when identifying risk-days. We find that considerations of the accuracy in temperature forecasts should be part of the design of a HEWS. Currently operating HEWS do evaluate their predictive performance; this information should also be part of the evaluation of the epidemiological models that are the foundation in the HEWS. The most accurate description of the relationship between high temperature and mortality might not be the most suitable or practical when incorporated into a HEWS.

  • 179. Astrom, Christofer
    et al.
    Orru, Hans
    Rocklov, Joacim
    Strandberg, Gustav
    SMHI, Research Department, Climate research - Rossby Centre.
    Ebi, Kristie L.
    Forsberg, Bertil
    Heat-related respiratory hospital admissions in Europe in a changing climate: a health impact assessment2013In: BMJ Open, ISSN 2044-6055, E-ISSN 2044-6055, Vol. 3, no 1, article id e001842Article in journal (Refereed)
    Abstract [en]

    Objectives: Respiratory diseases are ranked second in Europe in terms of mortality, prevalence and costs. Studies have shown that extreme heat has a large impact on mortality and morbidity, with a large relative increase for respiratory diseases. Expected increases in mean temperature and the number of extreme heat events over the coming decades due to climate change raise questions about the possible health impacts. We assess the number of heat-related respiratory hospital admissions in a future with a different climate. Design: A Europe-wide health impact assessment. Setting: An assessment for each of the EU27 countries. Methods: Heat-related hospital admissions under a changing climate are projected using multicity epidemiological exposure-response relationships applied to gridded population data and country-specific baseline respiratory hospital admission rates. Times-series of temperatures are simulated with a regional climate model based on four global climate models, under two greenhouse gas emission scenarios. Results: Between a reference period (1981-2010) and a future period (2021-2050), the total number of respiratory hospital admissions attributed to heat is projected to be larger in southern Europe, with three times more heat attributed respiratory hospital admissions in the future period. The smallest change was estimated in Eastern Europe with about a twofold increase. For all of Europe, the number of heat-related respiratory hospital admissions is projected to be 26 000 annually in the future period compared with 11 000 in the reference period. Conclusions: The results suggest that the projected effects of climate change on temperature and the number of extreme heat events could substantially influence respiratory morbidity across Europe.

  • 180.
    Axe, Philip
    SMHI, Research Department, Oceanography.
    Oceanographic applications of coastal radar2013Report (Other academic)
    Abstract [en]

    This report documents the 2010 Coastal Radar Workshop organised by the Swedish Meteorological and Hydrological Institute with support from the Swedish Environmental Protection Agency. The aim of the report is to provide background information on coastal oceanographic radar for a wider professional audience and to provide a basis for further Nordic cooperation in the field of oceanographic (coastal) radar with the ultimate aim of establishing a Nordic network covering (initially) the shared waters of the Skagerrak and Kattegat.Information on currents in near real time is seldom available when needed by many day to day applications and services. Data are needed for safe and efficient ship routing in narrow areas of hightraffic such as in the northern Kattegat, Danish Straits, Bornholm Strait and the Gulf of Finland. At the entrances of major ports and where [environmentally] dangerous cargos are carried currentinformation can be of crucial importance. For this reason the Swedish Maritime Administration maintains current observations in critical areas. However, these are point measurements and in the waters mentioned above topography may alter currents both in strength and direction in nearby areas. Hence, complementary spatial information on the behaviour of currents is preferable.Access to high quality, spatially resolved current information is critical both for effective oil spill containment and greatly increases the chances for successful outcomes of search and rescue operations. Combining data from models and observations will reduce the search area in rescue operations and make planning and combat of oil spill operations more efficient. In addition, areal near real time current observations are likely to promote research and development related to fish larvae transports, the spread of alien species, improve oceanographic models and lead to the better understanding of ocean and coastal sea processes.The present workshop highlights and extends the knowledge base on European and US experiences, user needs and available technical systems for areal current observations. Taking into account thatNordic views are usually coherent, opportunities to coordinate and cooperate in establishing and running an operational pilot system at a Nordic level seem realistic. The workshop intends to lay the foundation for carrying this work further.

  • 181.
    Axe, Philip
    SMHI, Research Department, Oceanography.
    Temporal and spatial monitoring of eutrophication variables in CEMP2008Report (Other academic)
    Abstract [en]

    The OSPAR Revised Eutrophication Monitoring Programme (ETG 05/3/Info.1-E) requests that nutrient "monitoring should include sufficient samples to confirm that the maximum winter nutrient concentration has been determined", while para. 7 of the Terms of Reference for the preparation of guidance on the spatial and temporal resolution of monitoring for nutrients and eutrophication effects (ICG 003) states that "there are at least nine different water types covered by the OSPAR Maritime Area"..."guidance must, therefore, be at least complex enough to cover each type with sufficient clarity to guide contracting parties in their evaluation of the temporal and spatial coverage required to adequately assess the relevant water body".This document summarises the national reports submitted to the OSPAR Intersessional Correspondence Group on Eutrophication Monitoring, and highlights common problems faced in the monitoring of (primarily) inorganic nutrients and chlorophyll. In addition, it presents tests of different approaches to solving the spatial and temporal sampling problems associated with delivering marine eutrophication data.Based on tests of model data, monthly sampling appears adequate to give a good estimate of annual mean concentrations. Buoy data suggests that this would not be sufficient where there is tidal variability. It was not possible to determine maximum concentrations through a practical ship sampling scheme, or by using extreme value statistics.The optimum sampling programme to observe rapid events is likely to be a combination of ferrybox systems, which appear to be reliable and give both good spatial and temporal coverage, combined with buoy observations. To ensure data of sufficient quality, these must be controlled against conventional research vessel observations. Research vessels still have a role in seasonal mapping, and in providing data of sufficient quality for trend analysis from a large area. This is likely to remain so, at leastuntil technologies such as gliders and optical nutrient sensors become widely available and capable of delivering reliable, high quality data.

  • 182.
    Axe, Philip
    et al.
    SMHI, Research Department, Oceanography.
    Hansson, Martin
    SMHI, Core Services.
    Håkansson, Bertil
    SMHI, Research Department, Oceanography.
    The National Monitoring Programme in the Kattegat and Skagerrak2004Report (Other academic)
    Abstract [en]

    To facilitate the development of the OSPAR eutrophication monitoring programme, this report presents the statistical strength of trends reported in the 2002 Common Procedure Report1. After correcting nutrient records to a reference salinity of 30 psu (to compensate for the effects of dilution), ortho-phosphate concentration exhibits a significant negative trend in the inshore Kattegat and Skagerrak. Significant decreases in silicate were observed in all areas. These changes caused changes in Redfield and other nutrient ratios. Indirect indicators of eutrophication (autumn, bottom oxygen concentration; growing-season chlorophyll-a concentration) exhibited significant trends. Chlorophyll-a concentration increased in the Skagerrak, while oxygen concentration decreased in all areas, apart from the inshore Kattegat.Spatial characteristics of the study area were tested using probability mapping. The Kattegat was found to be well represented by 8 divisions, while 4 areas were suitable Skagerrak.Changes in the current monitoring programme were not recommended. Increasing sampling frequency could interfere with the statistical independence of measurements – an assumption for the validity of trend calculations. Filling gaps in the existing time series improves the statistical significance of observed trends. This requires effective data exchange between monitoring institutions, and possibly data archaeology.

  • 183.
    Axe, Philip
    et al.
    SMHI, Research Department, Oceanography.
    Lindow, Helma
    SMHI, Core Services.
    Hydrographic Conditions Around Offshore Banks2005Report (Other academic)
    Abstract [en]

    This report details the results of an investigation into hydrographic and hydrochemical conditions over ten offshore banks around the coast of south Sweden. Four of these banks are situated in the Kattegat. The remainder lie in the southern and western Baltic Proper. The investigation included field sampling, where each bank was visited on one occasion, and the temperature and salinity structure mapped while the concentrations of nutrients were measured. These data were analysed, and results compared and complemented with predictions from operational numerical models (for currents and waves). The banks are areas with strong horizontal gradients in temperature and salinity. They influence the large scale circulation, steering mean currents through the deeper water, resulting in the mean currents over the banks being weak. The influence of short term wind events are significant however, with intense, short-lived currents occurring over the banks. Nutrient concentrations in the waters above the banks were very similar to those in the adjacent basins. Immediately over the bottom however, silicate concentrations were often higher than at similar depths away from the banks. Similarly, oxygen saturation immediately above the bottom was frequently lower than in mid-water at the same depth. In the Kattegat, large areas are at risk from seasonal oxygen deficiency. The shallow nature of the banks however often means that they escape the worst impacts.

  • 184.
    Axe, Philip
    et al.
    SMHI, Research Department, Oceanography.
    Wesslander, Karin
    SMHI, Core Services.
    Kronsell, Johan
    SMHI, Core Services.
    Confidence rating for OSPAR COMP2012Report (Other academic)
    Abstract [en]

    With the adoption of the Marine Strategy Framework Directive and the Water Framework Directive, EU Member States are obliged to achieve “Good” or “Good Environmental” Status within a certain time frame, or be obliged to take remedial action. There is therefore a need to quantify the quality of the monitoring programmes on which such status assessments are based, as a part of assessing the confidence in the status assessment. Within the framework of the OSPAR Convention on the Protection of the North East Atlantic, Germany and the Netherlands presented a suggestion for how such an assessment could be made. This report documents the application of this methodology to stations in the Swedish National Monitoring Programme within the OSPAR area, and also within the Sound, which may in future be included in the Greater North Sea region under the Marine Strategy Directive. The variability of eutrophication parameters with salinity was examined. In the Kattegat, inorganic nutrient variability was least at the highest salinities, suggesting that a reliable status assessment could be made more easily with data from this region, for example, rather than in the dynamic near coast region. Assessing the coverage of the existing monitoring programme, it was found that horizontal gradients in assessment parameters (generally seasonal averages) varied by less than about 30% between stations, which suggests that the programme has reasonable spatial coverage, though additional stations would improve matters. Looking at each station individually, the current vertical sampling resolution appears adequate for most parameters, apart from chlorophyll a and inorganic nutrients during the growing season. Temporal coverage is adequate for the total nutrient concentrations, but is insufficient for the inorganic nutrients and chlorophyll a, as well as for the deep water oxygen concentration in the Sound. The poor temporal coverage of chlorophyll a and inorganic nutrients could be relatively easily improved by the addition of a two channel (nitrate + nitrite, and orthophosphate) autoanalyser onto the existing ferrybox platforms in use in these waters. Addressing these problems using traditional measuring platforms and buoys would be more costly. The poor temporal coverage of chlorophyll a and inorganic nutrients could be relatively easily improved by the addition of a two channel (nitrate + nitrite, and orthophosphate) autoanalyser onto the existing ferrybox platforms in use in these waters. Addressing these problems using traditional measuring platforms and buoys would be more costly.

  • 185.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    BSRA-15: A Baltic Sea Reanalysis 1990–20042013Report (Other academic)
    Abstract [en]

    Oceanographic observations are often of high quality but are available only with low resolution in time and space. On the other hand, model fields have high resolution in time and space but are not necessarily in agreement with observations. To bridge the gap between these very different kinds of data sets, a reanalysis can be made, which means that fixed versions of the numerical model and the data assimilation system are used to analyse a period of several years. This report describes an oceanographic reanalysis covering the period 1990 to 2004 (15 whole years). The horizontal resolution is 3 nautical miles in the Baltic Sea and 12 nautical miles in the North Sea, and the vertical resolution varies between 4 meters near the surface to 60 meters in the deepest part (up to 24 vertical layers). The time resolution of the reanalysis product is 6 hours. The numerical ocean model used is HIROMB (High-Resolution Operational Model for the Baltic), version 3.0. The data assimilation method used in this reanalysis is the Successive Corrections Method (SCM) for salinity and temperature, whereas ice observations in terms of ice charts were simply interpolated. The result looks good in terms of sea levels, ice fields, and salinity and temperature structure, whereas currents have not been validated. This oceanographic reanalysis was probably the first one ever for the Baltic Sea (when it was done in 2005) and may serve as a starting point before longer, more advanced reanalyses are produced.

  • 186.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    On the variability of Baltic Sea deepwater mixing1998In: JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS, Vol. 103, no C10, p. 21667-21682Article in journal (Refereed)
    Abstract [en]

    Historical oceanographic data from the period 1964-1997 from two deep subbasins (the Gotland Deep and the Landsort Deep) in the Baltic Sea have been analyzed, by using a budget method on stagnant periods, with respect to vertical diffusion and vertical energy flux density in the deep water. It was found that the rate of deepwater mixing varied with the seasons, with higher rates in fall and winter compared to spring and summer. Further, according to the analyzed data, the downward flux density of energy available for vertical diffusion decreased with increasing depth in the Gotland Deep. In the Landsort Deep, however, the flux density increased somewhat, probably because of topographic concentration of the energy, before decreasing toward the bottom. Moreover, the vertical energy flux densities were compared with the expected flux density from the local wind. It is proposed that in the Gotland Deep, which is outside the coastal boundary layer, the observed deepwater mixing is dominated by the energy input from the wind via inertial currents and internal waves. In the Landsort Deep, however, which is within the coastal boundary layer, the expected flux density of energy from the local wind cannot explain the observed rate of work against the buoyancy forces. It is proposed that the active coastal boundary layer plays a central role in the transfer of energy to mixing processes in the deep water.

  • 187.
    Axell, Lars
    SMHI, Research Department, Oceanography.
    Wind-driven internal waves and Langmuir circulations in a numerical ocean model of the southern Baltic Sea2002In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 107, no C11, article id 3204Article in journal (Refereed)
    Abstract [en]

    [1] A one-dimensional numerical ocean model of the southern Baltic Sea is used to investigate suitable parameterizations of unresolved turbulence and compare with available observations. The turbulence model is a k-epsilon model that includes extra source terms P-IW and P-LC of turbulent kinetic energy (TKE) due to unresolved, breaking internal waves and Langmuir circulations, respectively. As tides are negligible in the Baltic Sea, topographic generation of internal wave energy (IWE) is neglected. Instead, the energy for deepwater mixing in the Baltic Sea is provided by the wind. At each level the source term P-IW is assumed to be related to a vertically integrated pool of IWE, E-0, and the buoyancy frequency N at the same level, according to P-IW (z) proportional to E0Ndelta (z). This results in vertical profiles of epsilon (the dissipation rate of TKE) and K-h (the eddy diffusivity) according to epsilon proportional to N-delta and K-h proportional to Ndelta-2 below the main pycnocline. Earlier observations are inconclusive as to the proper value of delta, and here a range of values of delta is tested in hundreds of 10-year simulations of the southern Baltic Sea. It is concluded that delta = 1.0 +/- 0.3 and that a mean energy flux density to the internal wave field of about (0.9 +/- 0.3) x 10(-3) W m(-2) is needed to explain the observed salinity field. In addition, a simple wind-dependent formulation of the energy flux to the internal wave field is tested, which has some success in describing the short- and long-term variability of the deepwater turbulence. The model suggests that similar to16% of the energy supplied to the surface layer by the wind is used for deepwater mixing. Finally, it is also shown that Langmuir circulations are important to include when modeling the oceanic boundary layer. A simple parameterization of Langmuir circulations is tuned against large-eddy simulation data and verified for the Baltic Sea.

  • 188.
    Axell, Lars
    et al.
    SMHI, Research Department, Oceanography.
    Liu, Ye
    SMHI, Research Department, Oceanography.
    Application of 3-D ensemble variational data assimilation to a Baltic Sea reanalysis 1989-20132016In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 68, article id 24220Article in journal (Refereed)
    Abstract [en]

    A 3-D ensemble variational (3DEnVar) data assimilation method has been implemented and tested for oceanographic data assimilation of sea surface temperature (SST), sea surface salinity (SSS), sea ice concentration (SIC), and salinity and temperature profiles. To damp spurious long-range correlations in the ensemble statistics, horizontal and vertical localisation was implemented using empirical orthogonal functions. The results show that the 3DEnVar method is indeed possible to use in oceanographic data assimilation. So far, only a seasonally dependent ensemble has been used, based on historical model simulations. Near-surface experiments showed that the ensemble statistics gave inhomogeneous and anisotropic horizontal structure functions, and assimilation of real SST and SIC fields gave smooth, realistic increment fields. The implementation was multivariate, and results showed that the cross-correlations between variables work in an intuitive way, for example, decreasing SST where SIC was increased and vice versa. The profile data assimilation also gave good results. The results from a 25-year reanalysis showed that the vertical salinity and temperature structure were significantly improved, compared to both dependent and independent data.

  • 189.
    Axell, Lars
    et al.
    SMHI, Research Department, Oceanography.
    Ljungman, Olof
    SMHI, Research Department, Oceanography.
    A One-Equation Turbulence Model for Geophysical Applications: Comparison with Data and the k - epsilon Model2001In: Environmental Fluid Mechanics, ISSN 1567-7419, E-ISSN 1573-1510, Vol. 1, no 1, p. 71-106Article in journal (Refereed)
    Abstract [en]

    A one-equation turbulence model is presented, in which the turbulent kinetic energy k is calculated with a transport equation whereas the turbulent length scale l is calculated with an algebraic expression. The value of l depends on the local stratification and reduces to the classical kappa vertical bar z vertical bar scaling for unstratified flows near a wall, where vertical bar z vertical bar is the distance to the wall. The length scale decreases during stable stratification, and increases for unstable stratification compared to the neutral case. In the limit of strong stable stratification, the so-called buoyancy length scale proportional to k(1/2)N(-1) is obtained, where N is the buoyancy frequency. The length scale formulation introduces a single model parameter which is calibrated against experimental data. The model is verified extensively against laboratory measurements and oceanic data, and comparisons are made with the two-equation k-epsilon model. It is shown that the performance of the proposed k model is almost identical to that of the k-epsilon model. In addition, the stability functions of Launder are revisited and adjusted to obtain better agreement with recent data.

  • 190.
    Axelsson, G.
    et al.
    SMHI.
    Eklind, R.
    SMHI.
    Ovädret på Östersjön 23 juli 19851985Report (Other academic)
  • 191. Bailey, Helen
    et al.
    Fossette, Sabrina
    Bograd, Steven J.
    Shillinger, George L.
    Swithenbank, Alan M.
    Georges, Jean-Yves
    Gaspar, Philippe
    Strömberg, Patrik
    SMHI, Core Services.
    Paladino, Frank V.
    Spotila, James R.
    Block, Barbara A.
    Hays, Graeme C.
    Movement Patterns for a Critically Endangered Species, the Leatherback Turtle (Dermochelys coriacea), Linked to Foraging Success and Population Status2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 5, article id e36401Article in journal (Refereed)
    Abstract [en]

    Foraging success for pelagic vertebrates may be revealed by horizontal and vertical movement patterns. We show markedly different patterns for leatherback turtles in the North Atlantic versus Eastern Pacific, which feed on gelatinous zooplankton that are only occasionally found in high densities. In the Atlantic, travel speed was characterized by two modes, indicative of high foraging success at low speeds (<15 km d(-1)) and transit at high speeds (20-45 km d(-1)). Only a single mode was evident in the Pacific, which occurred at speeds of 21 km d(-1) indicative of transit. The mean dive depth was more variable in relation to latitude but closer to the mean annual depth of the thermocline and nutricline for North Atlantic than Eastern Pacific turtles. The most parsimonious explanation for these findings is that Eastern Pacific turtles rarely achieve high foraging success. This is the first support for foraging behaviour differences between populations of this critically endangered species and suggests that longer periods searching for prey may be hindering population recovery in the Pacific while aiding population maintenance in the Atlantic.

  • 192. Bais, A F
    et al.
    Gardiner, B G
    Slaper, H
    Blumthaler, M
    Bernhard, G
    McKenzie, R
    Webb, A R
    Seckmeyer, G
    Kjeldstad, B
    Koskela, T
    Kirsch, P J
    Grobner, J
    Kerr, J B
    Kazadzis, S
    Leszczynski, K
    Wardle, D
    Josefsson, Weine
    SMHI, Research Department, Atmospheric remote sensing.
    Brogniez, C
    Gillotay, D
    Reinen, H
    Weihs, P
    Svenoe, T
    Eriksen, P
    Kuik, F
    Redondas, A
    SUSPEN intercomparison of ultraviolet spectroradiometers2001In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 106, no D12, p. 12509-12525Article in journal (Refereed)
    Abstract [en]

    Results from an intercomparison campaign of ultraviolet spectroradiometers that was organized at Nea Michaniona, Greece July, 1-13 1997, are presented. Nineteen instrument systems from 15 different countries took part and provided spectra of global solar UV irradiance for two consecutive days from sunrise to sunset every half hour. No data exchange was allowed between participants in order to achieve absolutely independent results among the instruments. The data analysis procedure included the determination of wavelength shifts and the application of suitable corrections to the measured spectra, their standardization to common spectral resolution of 1 nm full width at half maximum and the application of cosine corrections. Reference spectra were calculated for each observational time, derived for a set of instruments which were objectively selected and used as comparison norms for the assessment of the relative agreement among the various instruments. With regard to the absolute irradiance measurements, the range of the deviations from the reference for all spectra was within +/- 20%. About half of the instruments agreed to within +/-5%, while only three fell outside the +/- 10% agreement limit. As for the accuracy of the wavelength registration of the recorded spectra, for most of the spectroradiometers (14) the calculated wavelength shifts were smaller than 0.2 nm. The overall outcome of the campaign was very encouraging, as it was proven that the agreement among the majority of the instruments was good and comparable to the commonly accepted uncertainties of spectral UV measurements. In addition, many of the instruments provided consistent results relative to at least the previous two intercomparison campaigns, held in 1995 in Ispra, Italy and in 1993 in Garmisch-Partenkirchen, Germany. As a result of this series of intercomparison campaigns, several of the currently operating spectroradiometers operating may be regarded as a core group Of instruments, which with the employment of proper operational procedures are capable of providing quality spectral solar UV measurements.

  • 193. Bal, S.
    et al.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Spangehl, T.
    Cubasch, U.
    On the robustness of the solar cycle signal in the Pacific region2011In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 38, article id L14809Article in journal (Refereed)
    Abstract [en]

    The potential role of the stratosphere for the 11-year solar cycle signal in the Pacific region is investigated by idealized simulations using a coupled atmosphere-ocean general circulation model. The model includes a detailed representation of the stratosphere and accounts for changes in stratospheric heating rates from prescribed time dependent variations of ozone and spectrally high resolved solar irradiance. Three transient simulations are performed spanning 21 solar cycles each. The simulations use slightly different ozone perturbations representing uncertainties of solar induced ozone variations. The model reproduces the main features of the 20th century observed solar response. A persistent mean sea level pressure response to solar forcing is found for the eastern North Pacific extending over North America. Moreover, there is evidence for a La Nina-like response assigned to solar maximum conditions with below normal SSTs in the equatorial eastern Pacific, reduced equatorial precipitation, enhanced off-equatorial precipitation and an El Nino-like response a couple of years later, thus confirming the response to solar forcing at the surface seen in earlier studies. The amplitude of the solar signal in the Pacific region depends to a great extent on the choice of the centennial period averaged. Citation: Bal, S., S. Schimanke, T. Spangehl, and U. Cubasch (2011), On the robustness of the solar cycle signal in the Pacific region, Geophys. Res. Lett., 38, L14809, doi:10.1029/2011GL047964.

  • 194. Bal, Sourabh
    et al.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Spangehl, Thomas
    Cubasch, Ulrich
    Enhanced residual mean circulation during the evolution of split type sudden stratospheric warming in observations and model simulations2018In: Proceedings of the Indian Academy of Sciences, Earth and Planetary Sciences, ISSN 0253-4126, E-ISSN 0973-774X, Vol. 127, no 5, article id 68Article in journal (Refereed)
  • 195. Bal, Sourabh
    et al.
    Schimanke, Semjon
    SMHI, Research Department, Oceanography.
    Spangehl, Thomas
    Cubasch, Ulrich
    Variable influence on the equatorial troposphere associated with SSW using ERA-Interim2017In: Proceedings of the Indian Academy of Sciences, Earth and Planetary Sciences, ISSN 0253-4126, E-ISSN 0973-774X, Vol. 126, no 2, article id UNSP 19Article in journal (Refereed)
  • 196. Balaji, Venkatramani
    et al.
    Maisonnave, Eric
    Zadeh, Niki
    Lawrence, Bryan N.
    Biercamp, Joachim
    Fladrich, Uwe
    SMHI, Research Department, Climate research - Rossby Centre.
    Aloisio, Giovanni
    Benson, Rusty
    Caubel, Arnaud
    Durachta, Jeffrey
    Foujols, Marie-Alice
    Lister, Grenville
    Mocavero, Silvia
    Underwood, Seth
    Wright, Garrett
    CPMIP: measurements of real computational performance of Earth system models in CMIP62017In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 10, no 1, p. 19-34Article in journal (Refereed)
  • 197. Baldacchini, Chiara
    et al.
    Castanheiro, Ana
    Maghakyan, Nairuhi
    Sgrigna, Gregorio
    Verhelst, Jolien
    Alonso, Rocio
    Amorim, Jorge Humberto
    SMHI, Research Department, Air quality.
    Bellan, Patrick
    Bojovic, Danijela Dunisijevic
    Breuste, Juergen
    Buhler, Oliver
    Cantar, Ilie C.
    Carinanos, Paloma
    Carriero, Giulia
    Churkina, Galina
    Dinca, Lucian
    Esposito, Raffaela
    Gawronski, Stanislaw W.
    Kern, Maren
    Le Thiec, Didier
    Moretti, Marco
    Ningal, Tine
    Rantzoudi, Eleni C.
    Sinjur, Iztok
    Stojanova, Biljana
    Urosevic, Mira Anicic
    Velikova, Violeta
    Zivojinovic, Ivana
    Sahakyan, Lilit
    Calfapietra, Carlo
    Samson, Roeland
    How Does the Amount and Composition of PM Deposited on Platanus acerifolia Leaves Change Across Different Cities in Europe?2017In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 51, no 3, p. 1147-1156Article in journal (Refereed)
  • 198. Baranizadeh, Elham
    et al.
    Murphy, Benjamin N.
    Julin, Jan
    Falahat, Saeed
    SMHI, Core Services.
    Reddington, Carly L.
    Arola, Antti
    Ahlm, Lars
    Mikkonen, Santtu
    Fountoukis, Christos
    Patoulias, David
    Minikin, Andreas
    Hamburger, Thomas
    Laaksonen, Ari
    Pandis, Spyros N.
    Vehkamaki, Hanna
    Lehtinen, Kari E. J.
    Riipinen, Ilona
    Implementation of state-of-the-art ternary new-particle formation scheme to the regional chemical transport model PMCAMx-UF in Europe2016In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 9, no 8, p. 2741-2754Article in journal (Refereed)
  • 199. Baron, P.
    et al.
    Murtagh, D. P.
    Urban, J.
    Sagawa, H.
    Ochiai, S.
    Kasai, Y.
    Kikuchi, K.
    Khosrawi, F.
    Körnich, Heiner
    SMHI, Research Department, Meteorology.
    Mizobuchi, S.
    Sagi, K.
    Yasui, M.
    Observation of horizontal winds in the middle-atmosphere between 30 degrees S and 55 degrees N during the northern winter 2009-20102013In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 13, no 12, p. 6049-6064Article in journal (Refereed)
    Abstract [en]

    Although the links between stratospheric dynamics, climate and weather have been demonstrated, direct observations of stratospheric winds are lacking, in particular at altitudes above 30 km. We report observations of winds between 8 and 0.01 hPa (similar to 35-80 km) from October 2009 to April 2010 by the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station. The altitude range covers the region between 35-60 km where previous space-borne wind instruments show a lack of sensitivity. Both zonal and meridional wind components were obtained, though not simultaneously, in the latitude range from 30 degrees S to 55 degrees N and with a single profile precision of 7-9 ms(-1) between 8 and 0.6 hPa and better than 20 ms(-1) at altitudes above. The vertical resolution is 5-7 km except in the upper part of the retrieval range (10 km at 0.01 hPa). In the region between 1-0.05 hPa, an absolute value of the mean difference <2 ms(-1) is found between SMILES profiles retrieved from different spectroscopic lines and instrumental settings. Good agreement (absolute value of the mean difference of similar to 2 ms(-1)) is also found with the European Centre for Medium-Range Weather Forecasts (ECMWF) analysis in most of the stratosphere except for the zonal winds over the equator (difference >5 ms(-1)). In the mesosphere, SMILES and ECMWF zonal winds exhibit large differences (>20 ms(-1)), especially in the tropics. We illustrate our results by showing daily and monthly zonal wind variations, namely the semi-annual oscillation in the tropics and reversals of the flow direction between 50-55 degrees N during sudden stratospheric warmings. The daily comparison with ECMWF winds reveals that in the beginning of February, a significantly stronger zonal westward flow is measured in the tropics at 2 hPa compared to the flow computed in the analysis (difference of similar to 20 ms(-1)). The results show that the comparison between SMILES and ECMWF winds is not only relevant for the quality assessment of the new SMILES winds, but it also provides insights on the quality of the ECMWF winds themselves. Although the instrument was not specifically designed for measuring winds, the results demonstrate that space-borne sub-mm wave radiometers have the potential to provide good quality data for improving the stratospheric winds in atmospheric models.

  • 200. Barreiro, Marcelo
    et al.
    Sitz, Lina
    de Mello, Santiago
    Fuentes Franco, Ramon
    SMHI, Research Department, Climate research - Rossby Centre.
    Renom, Madeleine
    Farneti, Riccardo
    Modelling the role of Atlantic air-sea interaction in the impact of Madden-Julian Oscillation on South American climate2019In: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 39, no 2, p. 1104-1116Article in journal (Refereed)
1234567 151 - 200 of 2198
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
v. 2.35.7
|