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  • Kratzer, Susanne
    et al.
    Kyryliuk, Dmytro
    Edman, Moa
    SMHI, Research Department, Oceanography.
    Philipson, Petra
    Lyon, Steve W.
    Synergy of Satellite, In Situ and Modelled Data for Addressing the Scarcity of Water Quality Information for Eutrophication Assessment and Monitoring of Swedish Coastal Waters2019In: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292, Vol. 11, no 17Article in journal (Refereed)
    Abstract [en]

    Monthly CHL-a and Secchi Depth (SD) data derived from the full mission data of the Medium Resolution Imaging Spectrometer (MERIS; 2002-2012) were analysed along a horizontal transect from the inner Braviken bay and out into the open sea. The CHL-a values were calibrated using an algorithm derived from Swedish lakes. Then, calibrated Chl-a and Secchi Depth (SD) estimates were extracted from MERIS data along the transect and compared to conventional monitoring data as well as to data from the Swedish Coastal zone Model (SCM), providing physico-biogeochemical parameters such as temperature, nutrients, Chlorophyll-a (CHL-a) and Secchi depth (SD). A high negative correlation was observed between satellite-derived CHL-a and SD (rho = -0.91), similar to the in situ relationship established for several coastal gradients in the Baltic proper. We also demonstrate that the validated MERIS-based estimates and data from the SCM showed strong correlations for the variables CHL-a, SD and total nitrogen (TOTN), which improved significantly when analysed on a monthly basis across basins. The relationship between satellite-derived CHL-a and modelled TOTN was also evaluated on a monthly basis using least-square linear regression models. The predictive power of the models was strong for the period May-November (R-2: 0.58-0.87), and the regression algorithm for summer was almost identical to the algorithm generated from in situ data in Himmerfjarden bay. The strong correlation between SD and modelled TOTN confirms that SD is a robust and reliable indicator to evaluate changes in eutrophication in the Baltic proper which can be assessed using remote sensing data. Amongst all three assessed methods, only MERIS CHL-a was able to correctly depict the pattern of phytoplankton phenology that is typical for the Baltic proper. The approach of combining satellite data and physio-biogeochemical models could serve as a powerful tool and value-adding complement to the scarcely available in situ data from national monitoring programs. In particular, satellite data will help to reduce uncertainties in long-term monitoring data due to its improved measurement frequency.

  • Hieronymus, Magnus
    et al.
    SMHI, Research Department, Oceanography.
    Hieronymus, Jenny
    SMHI, Research Department, Oceanography.
    Hieronymus, Fredrik
    On the Application of Machine Learning Techniques to Regression Problems in Sea Level Studies2019In: Journal of Atmospheric and Oceanic Technology, ISSN 0739-0572, E-ISSN 1520-0426, Vol. 36, no 9, p. 1889-1902Article in journal (Refereed)
    Abstract [en]

    Long sea level records with high temporal resolution are of paramount importance for future coastal protection and adaptation plans. Here we discuss the application of machine learning techniques to some regression problems commonly encountered when analyzing such time series. The performance of artificial neural networks is compared with that of multiple linear regression models on sea level data from the Swedish coast. The neural networks are found to be superior when local sea level forcing is used together with remote sea level forcing and meteorological forcing, whereas the linear models and the neural networks show similar performance when local sea level forcing is excluded. The overall performance of the machine learning algorithms is good, often surpassing that of the much more computationally costly numerical ocean models used at our institute.

  • Molinder, Jennie
    et al.
    Körnich, Heiner
    SMHI, Research Department, Meteorology.
    Olsson, Esbjörn
    SMHI, Research Department, Meteorology.
    Hessling, Peter
    The Use of Uncertainty Quantification for the Empirical Modeling of Wind Turbine Icing2019In: Journal of Applied Meteorology and Climatology, ISSN 1558-8424, E-ISSN 1558-8432, Vol. 58, no 9, p. 2019-2032Article in journal (Refereed)
    Abstract [en]

    A novel uncertainty quantification method is used to evaluate the impact of uncertainties of parameters within the icing model in the modeling chain for icing-related wind power production loss forecasts. As a first step, uncertain parameters in the icing model were identified from the literature and personal communications. These parameters are the median volume diameter of the hydrometeors, the sticking efficiency for snow and graupel, the Nusselt number, the shedding factor, and the wind erosion factor. The sensitivity of these parameters on icing-related wind power production losses is examined. An icing model ensemble representing the estimated parameter uncertainties is designed using so-called deterministic sampling and is run for two periods over a total of 29 weeks. Deterministic sampling allows an exact representation of the uncertainty and, in future applications, further calibration of these parameters. Also, the number of required ensemble members is reduced drastically relative to the commonly used random-sampling method, thus enabling faster delivery and a more flexible system. The results from random and deterministic sampling are compared and agree very well, confirming the usefulness of deterministic sampling. The ensemble mean of the nine-member icing model ensemble generated with deterministic sampling is shown to improve the forecast skill relative to one single forecast for the winter periods. In addition, the ensemble spread provides valuable information as compared with a single forecast in terms of forecasting uncertainty. However, addressing uncertainties in the icing model alone underestimates the forecast uncertainty, thus stressing the need for a fully probabilistic approach in the modeling chain for wind power forecasts in a cold climate.

  • Frogner, Inger-Lise
    et al.
    Singleton, Andrew T.
    Koltzow, Morten O.
    Andrae, Ulf
    SMHI, Research Department, Meteorology.
    Convection-permitting ensembles: Challenges related to their design and use2019In: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 145, p. 90-106Article in journal (Refereed)
    Abstract [en]

    Challenges related to the design and use of a convection-permitting ensemble (CPEPS) are discussed. In particular the scale-dependent predictability of precipitation and the use of a CPEPS as well as its potential added value over global ensemble prediction systems (EPS) are investigated. Forecasts of precipitation from the operational CPEPS in Finland, Norway and Sweden (MEPS) are used for the investigations. It is found that predictability for scales smaller than similar to 60 km is lost rapidly within the first 6 h of the forecast with the smallest predictable scale growing more slowly to similar to 100 km over the following 18-24 h. However, there is large case-to-case variability and the ensemble perturbations fail to become fully saturated, especially in winter, suggesting a weakness in the design of the ensemble. The added value of CPEPS over deterministic forecasts and coarser resolution EPSs is discussed with summary statistics and case-studies. It is shown that the added value varies between seasons and lead times. For precipitation there is an added value for both severe precipitation events and for precipitation/no precipitation decisions. The added value is higher in summer compared to winter and for shorter lead times compared to longer lead times.

  • Hankin, Barry
    et al.
    Strömqvist, Johan
    SMHI, Research Department, Hydrology.
    Burgess, Chris
    Pers, Charlotta
    SMHI, Research Department, Hydrology.
    Bielby, Sally
    Revilla-Romero, Beatriz
    Pope, Linda
    A New National Water Quality Model to Evaluate the Effectiveness of Catchment Management Measures in England2019In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 11, no 8, article id 1612Article in journal (Refereed)
    Abstract [en]

    This investigation reports on a new national model to evaluate the effectiveness of catchment sensitive farming in England, and how pollution mitigation measures have improved water quality between 2006 and 2016. An adapted HYPE (HYdrological Predictions for the Environment) model was written to use accurate farm emissions data so that the pathway impact could be accounted for in the land phase of transport. Farm emissions were apportioned into different runoff fractions simulated in surface and soil layers, and travel time and losses were taken into account. These were derived from the regulator's catchment change matrix' and converted to monthly load time series, combined with extensive point source load datasets. Very large flow and water quality monitoring datasets were used to calibrate the model nationally for flow, nitrogen, phosphorus, suspended sediments and faecal indicator organisms. The model was simulated with and without estimated changes to farm emissions resulting from catchment measures, and spatial and temporal changes to water quality concentrations were then assessed.

  • Stensen, Katarina
    et al.
    SMHI, Core Services.
    Matti, Bettina
    SMHI, Core Services.
    Rasmusson, Kristina
    SMHI, Research Department, Oceanography.
    Hjerdt, Niclas
    SMHI, Core Services.
    Modellstudie för att undersöka åtgärdersom påverkar lågflöden: – Delrapport 2 i regeringsuppdrag om åtgärder för att motverkavattenbrist i ytvattentäkter.2019Report (Other academic)
    Abstract [en]

    In 2018 the Swedish Meteorological and Hydrological Institute, SMHI was assigned toperform a study of measures to prevent water scarcity in surface water resources. Thework is ongoing and has been performed stepwise. This is the second report produced sofar. The report presents the results from a pre-study that was performed to evaluate theeffect of different measures on low flows and their potential to prevent water scarcity insurface water resources. The aim of the model study was to build a knowledge basis fordeveloping a tool that can be used to prevent water scarcity in surface water resources.Through the tool, municipalities and other actors in the water sector will be able tosimulate water availability in a catchment area independently.

    The weather has the largest impact on water availability, but there are different measuresthat can prevent water scarcity in surface water resources. The measures are mostlypreventative but some can be used in scarcity situations as well.

    The most effective measure is to use the water storage capacity in lakes and to regulatethem wisely. Obviously, this requires that there are lakes to regulate. In the southern partsof Sweden water availability is often good in wintertime while water scarcity occursduring summertime and at the beginning of fall. Through lake regulation, water can bestored in periods with significant water availability and used in periods when water isneeded. It is common to regulate lakes for hydropower production, but some lakes areregulated for water supply as well. SMHI regards this as an important aspect to considerin areas that are in risk for water scarcity since many permissions for water regulation aregoing to be reconsidered now.

    Measures on ditch, drainage and other watercourses can have a local effect, but it is notlarge enough to affect the low flows on a larger scale. Restoration of wetlands has as wellmostly a local effect since very large areas are required to impact on surface waterresources on a larger scale.

    In areas with significant water extractions, the low flow is affected if these are changed.Often, knowledge on water extraction still is inadequate and it is difficult to exactlycalculate the effect if water extractions are changed. It is also complicated to restrictwater extractions. Measures such as establishing water ponds for irrigation might havepotential provided they are filled during periods of good water availability. The effect ofextractions will then decrease during low flow periods.

    The ongoing work to prevent water scarcity in surface water resources will focus ondeveloping methods for sustainable water management. It is evident that the work withwater resources planning needs to be performed mutually between sectors in a catchmentarea. The tool that will be developed within this project will contribute to that this workcan be performed in a sustainable way.

  • Stensen, Katarina
    et al.
    SMHI, Core Services.
    Krunegård, Aino
    SMHI, Core Services.
    Rasmusson, Kristina
    SMHI, Research Department, Oceanography.
    Matti, Bettina
    SMHI, Core Services.
    Hjerdt, Niclas
    SMHI, Core Services.
    Sveriges vattentillgång utifrån perspektivet vattenbrist och torka: – Delrapport 1 i regeringsuppdrag om åtgärder för att motverka vattenbrist i ytvattentäkter.2019Report (Other academic)
    Abstract [en]

    In this report, the concept of drought in Sweden as well as the causes is discussed. Thereport also discusses the spatial variability of water resources in Sweden.

    Water shortage is when the demand for water surpasses the water available. It is thereforevery much dependent on the water usage.

    Climate change causes higher temperature and a warmer Sweden thus affecting wateravailability. In general both temperature and precipitation are expected to increase inwintertime leading to more water available during winters. However, higher temperaturesduring summers cause a higher evaporation which might lead to less water available insummertime, especially in the southern parts of Sweden. The climate change will increasethe number of extreme rainfall events. The amount of rain during such short-term extremerainfall events is usually much more than the soil´s infiltration capacity thus makingfloodings more common in future. Milder winters change the snow pattern, which inparticular affect rivers in the northern part of the country.

    During the summers 2016–2018, water shortages occurred in some parts of Sweden. Thecauses of water shortages were different for different parts and different years. Howeverit made Sweden to experience some of the impacts of climate change and a warmerclimate. It was an eye opener and showed us the importance of the adaptation to thesenew circumstances.

    Many factors are involved in the water availability. They can however be summarized in3 categories:

    • Climate – temperature and precipitation for example.
    • Storage capacity – how much water an area can store
    • Water usage

    As a country, Sweden has abundant water resources and available fresh water. But watershortage might still occur. Water availability and water usage can vary a lot locally whichmight lead to water shortage in some regions. To cope with water shortages priorities areneeded between different sectors and interests. Many stakeholders need to agree andcompromise on the usage of water.

  • Losjö, Katarina
    et al.
    SMHI, Professional Services.
    Södling, Johan
    SMHI, Professional Services.
    Wern, Lennart
    SMHI, Core Services.
    German, Jonas
    SMHI, Professional Services.
    Uppföljning av de svenska riktlinjerna för bestämning av dimensionerande flöden för dammanläggningar2019Report (Other academic)
    Abstract [en]

    Commissioned by Svenska kraftnät, the Swedish Meteorological and Hydrological Institute has carried out a follow-up study on the Swedish guidelines for determination of designs floods for dams. The main purpose was to investigate whether the Swedish meteorological and hydrological observation data show any signs of climatic change, which could affect the validity of the guidelines, formulated in 1990 (Flödeskommittén, 1990), later updated twice, in which the edition of 2015 (Svensk Energi et.al., 2015), emphasize the application also in a changing climate . The first follow-up study was performed in 2008 (Bergström m.fl., 2008), and the present study has used longer time series, both after 2008 and earlier than in the study of 2008.

    The guidelines prescribe that the calculation of design flood should be carried out using a hydrological model, and the following parameters are decided to be used in the simulations:

    • a snow cover with a statistical return period of 30 years
    • a 14-day precipitation sequence over 1000 km2
    • corrections of this sequence regarding the area of the catchment
    • corrections of the sequence regarding elevation above sea level and month of the year
    • extreme wind speed

    The present analyses have used long series of observation data from SMHI climatological and hydrological databases, mostly using the division of Sweden into five regions, described in the guidelines.

    • The analyses of the 14-day precipitation sequence has been made by analysing precipitation higher than 90 mm over 1000 km2 during 24 hours and 2 days during the period 1930-2018, as well as the 14-day precipitation sum 1961-2018. Also the highest point precipitation values have been analysed for the period 1945-2018.
    • It is not possible to find a trend in the data for neither of these analyses, in contrary to the findings in the previous follow-up, where an increase in the highest point precipitation was seen for the period 1961-2007.
    • Two adaptations of accumulated 14-day precipitation over three areas: 100, 100 and 10 000 km, to the areal correction curve in the guidelines show some discrepancies. However, the present analyses are made using another database than the basis of the original curve, and the results indicate that there is no immediate need for adjustment of the areal correction in the guidelines.
    • The distribution of high precipitation over the year has been studied, and it shows the same pattern as the monthly corrections of the sequence in the guidelines. The pattern is similar for the periods 1961-90 and 1991-2018.
    • The mean values of yearly largest snow cover have been analysed for the period 1904/05-2017/18. The results do not indicate any trend, only shorter time variations, neither for the whole period nor for the period 1961-2018. As the determination of snow cover with a return period of 30 years should be made using frequency analysis, the recommendations in the guidelines to use a long data period for the analyses are still valid.
    • An analysis of the daily highest flood peaks was made for data from 60 unregulated or very slightly regulated discharge stations. No long time trend that could reveal changes in flood risks can be seen in the results.
    • The geostrophic wind, an idealized average wind speed, computed from observations of air pressure, has been studied 1940-2017. For geostrophic wind of at least 25 m/s no signs of long term trend can be seen.
    • The analyses of the ratio between the design flood for flood design category I and the flood of a 100-year return period indicates increasing ratio with decreasing catchment area. This could

    The overall conclusion of the study is that there is presently no need for adjusting the parameters in the guidelines. The importance of using long time series for trend analyses is revealed.

  • Thomas, Manu
    et al.
    SMHI, Research Department, Air quality.
    Devasthale, Abhay
    SMHI, Research Department, Atmospheric remote sensing.
    L'Ecuyer, Tristan
    Wang, Shiyu
    SMHI, Research Department, Climate research - Rossby Centre.
    Koenigk, Torben
    SMHI, Research Department, Climate research - Rossby Centre.
    Wyser, Klaus
    SMHI, Research Department, Climate research - Rossby Centre.
    Snowfall distribution and its response to the Arctic Oscillation: an evaluation of HighResMIP models in the Arctic using CPR/CloudSat observations2019In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 12, no 8, p. 3759-3772Article in journal (Refereed)
  • Nilsson, E.
    et al.
    Li, K.
    Fridlund, J.
    Sulcius, S.
    Bunse, C.
    Karlsson, C. M. G.
    Lindh, Markus
    SMHI, Core Services.
    Lundin, D.
    Pinhassi, J.
    Holmfeldt, K.
    Genomic and Seasonal Variations among Aquatic Phages Infecting the Baltic Sea Gammaproteobacterium Rheinheimera sp. Strain BAL3412019In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 85, no 18, article id e01003-19Article in journal (Refereed)
  • Koenigk, Torben
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Fuentes Franco, Ramon
    SMHI, Research Department, Climate research - Rossby Centre.
    Towards normal Siberian winter temperatures?2019In: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 39, no 11, p. 4567-4574Article in journal (Refereed)
  • Mazur, Aleksandra K.
    et al.
    Wahlin, Anna K.
    Kalen, Ola
    SMHI, Core Services.
    The life cycle of small- to medium-sized icebergs in the Amundsen Sea Embayment2019In: Polar Research, ISSN 0800-0395, E-ISSN 1751-8369, Vol. 38, article id 3313Article in journal (Refereed)
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