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  • 2151. White, Christopher J.
    et al.
    Carlsen, Henrik
    Robertson, Andrew W.
    Klein, Richard J. T.
    Lazo, Jeffrey K.
    Kumar, Arun
    Vitart, Frederic
    de Perez, Erin Coughlan
    Ray, Andrea J.
    Murray, Virginia
    Bharwani, Sukaina
    MacLeod, Dave
    James, Rachel
    Fleming, Lora
    Morse, Andrew P.
    Eggen, Bernd
    Graham, Richard
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Becker, Emily
    Pegion, Kathleen V.
    Holbrook, Neil J.
    McEvoy, Darryn
    Depledge, Michael
    Perkins-Kirkpatrick, Sarah
    Brown, Timothy J.
    Street, Roger
    Jones, Lindsey
    Remenyi, Tomas A.
    Hodgson-Johnston, Indi
    Buontempo, Carlo
    Lamb, Rob
    Meinke, Holger
    Arheimer, Berit
    SMHI, Research Department, Hydrology.
    Zebiak, Stephen E.
    Potential applications of subseasonal-to-seasonal (S2S) predictions2017In: Meteorological Applications, ISSN 1350-4827, E-ISSN 1469-8080, Vol. 24, no 3, p. 315-325Article in journal (Refereed)
  • 2152. Wibig, Joanna
    et al.
    Maraun, Douglas
    Benestad, Rasmus
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Lorenz, Philip
    Christensen, Ole Bossing
    Projected Change-Models and Methodology2015Chapter in book (Other academic)
    Abstract [en]

    General (global) circulation models (GCMs) are a useful tool for studying how climate may change in the future. Although GCMs have high temporal resolution, their spatial resolution is low. To simulate the future climate of the Baltic Sea region, it is necessary to downscale GCM data. This chapter describes the two conceptually different ways of downscaling: regional climate models (RCMs) nested in GCMs and using empirical and/or statistical relations between large-scale variables from GCMs and small-scale variables. There are many uncertainties in climate models, including uncertainty related to future land use and atmospheric greenhouse gas concentrations, limits on the amount of input data and their accuracy, and the chaotic nature of weather. The skill of methods for describing regional climate futures is also limited by natural climate variability. For the Baltic Sea area, the lack of an oceanic component in RCMs and poor representation of forcing by aerosols and changes in land use are major limitations.

  • 2153.
    Wickström, Kjell
    SMHI.
    Bedömning av kylvattenrecipienten för ett kolkraftverk vid Oskarshamnsverket1987Report (Other academic)
    Abstract [sv]

    Utsläppet av 18 m3 /s kylvatten från det planerade kolkraftverket ger en ca 20 procentig förstoring av det nu kylvattenpåverkade området.

    Vid utsläpp från Stora Båden kommer området norrut längs Ävrö att påverkas av något högre övertemperaturer, både i ytan och på djupare nivåer, se fig. 3 och 4, än om det släpps ut via Hamnefjärden. Ett utsläpp i Hamnefjärden integrerat med utsläppen från kärnkraftverket ger samma spridningssätt och spridningsväg som tidigare kartläggningar visat.

    Vid utsläpp av kylvatten i Borholmsfjärden ger ett utsläpp på 4.5 m3 Is en påverkan på hela fjärden. Isotermen för övertemperaturen 1 °c täcker en yta av 50-75% av fjärden.

    Vintertid blir ytvattenplymerna större. Då ligger även stora delar av Norre fjärd inom området för 1 °c övertemperatur.

    SMHI föreslår att utsläpp av kylvatten sker enligt alternativ 1. När det gäller reservutsläpp i Borholmsfjärden bör inte mer än 4.5 m3 /s släppas där. Detta om man vill begränsa avkylningsområdet till Borholmsfjärden och Norre fjärd.

  • 2154.
    Wickström, Kjell
    SMHI.
    Oskarshamnsverket - kylvattenutsläpp i havet: Slutrapport1990Report (Other academic)
  • 2155.
    Wickström, Kjell
    SMHI.
    Vågdata från svenska kustvatten 19861988Report (Other academic)
    Abstract [sv]

    Under hösten 1978 startade SMHI med medel från Nämnden för Energiproduktionsforskning registrering av vindgenererade vågor i svenska kustvatten. SMHI har tidigar presenterat vågdata från åren 1978 - 1985. Denna rapport redovisar vågklimatdata för år 1986. Registreringarna görs med två typer av instrument. I närheten av fasta kassunfyrar används bottenfasta ekolod, som flera gånger per sekund mäter avståndet botten - vattenytan. Via kabel går data till en microprocessor (automatstation) i kassunfyren, där viss bearbetning av våguppgifter sker. Vågdata går därefter på telefonlinje till SMHls dator i Norrköping, där nya våguppgifter varje timma kan avläsas på en bildskärm.

    På platser, där kabelförbindelse till en automatstation skulle bli alltför lång, mäts vågorna med en accelerometerboj (wave rider) på ytan. Bojen sänder på radio in våguppgifter till en närbelägen automatstation.

    Fasta stationer med ekolod finns nu på fyrarna Almagrundet, Gustav Dalen Ölands Södra Grund och Trubaduren Svenska Björn är en kassunfyr där ett svensk finskt sammarbete har resulterat i en lång mätserie med en finsk accelerometerboj och mottagningsstation i en av SMHl:s automatstationer. Accelerometerboj har också använts under perioder, 6-12 månader långa, vid Väderöarna, Hoburgen och i Laholmsbukten. Under 1986 har accelerometerbojar använts vid östergarn och Väderöarna.

    Energiforskningsnämnden och SMHI har gemensamt finansierat vågmätningar och bearbetning.

  • 2156.
    Wickström, Kjell
    et al.
    SMHI.
    Hillgren, Robert
    SMHI, Core Services.
    Spridningsberäkningar för EKA-NOBELs fabrik i Stockviksverken1990Report (Other academic)
    Abstract [sv]

    SMHI har på uppdrag av Casco Nobel AB utfört spridningsundersökningar i Sundsvallsbukten för att klarlägga spridningen av natriumklarat från EKA Nobels fabrik i Stockviksverken.

    Vi har valt att kombinera resultaten från strömmätningar och en tredimensionell numerisk modell för att beskriva några typiska strömningsmönster för utsläppsområdet.

    De olika spridningssituationerna som förekommer vid nordlig och sydlig vind samt under islagd tid beskriver cirka 90 procent av alla möjliga situationer.

    För att verifiera modell- och beräkningsresultaten har spårämnesundersökningar genomförts under två dagar. Samtidigt har ström- och skiktningsförhållanden kontrollerats.

    Av resultaten framgår att spridningen av avloppsvattnet sker till övervägande del i ytvattnet och är koncentrerat till området innanför linjen. Essvikslandets norra udde och Alnöns sydvästra hörn. Avloppsvattnet når framförallt strandzonen kring Essvikslandets norra del. Utspädningen av avloppsvattnet ger dock förhållandevis låga koncentrationer (cirka 0,01 ug/1).

  • 2157. Widmann, Martin
    et al.
    Bedia, Joaquin
    Gutierrez, Jose M.
    Bosshard, Thomas
    SMHI, Research Department, Hydrology.
    Hertig, Elke
    Maraun, Douglas
    Casado, Maria J.
    Ramos, Petra
    Cardoso, Rita M.
    Soares, Pedro M. M.
    Ribalaygua, Jamie
    Page, Christian
    Fischer, Andreas M.
    Herrera, Sixto
    Huth, Radan
    Validation of spatial variability in downscaling results from the VALUE perfect predictor experiment2019In: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 39, no 9, p. 3819-3845Article in journal (Refereed)
  • 2158.
    Wilcke, Renate
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Selecting regional climate scenarios for impact modelling studies2016In: Environmental Modelling & Software, ISSN 1364-8152, E-ISSN 1873-6726, Vol. 78, p. 191-201Article in journal (Refereed)
    Abstract [en]

    In climate change research ensembles of climate simulations are produced in an attempt to cover the uncertainty in future projections. Many climate change impact studies face difficulties using the full number of simulations available, and therefore often only subsets are used. Until now such subsets were chosen based on their representation of temperature change or by accessibility of the simulations. By using more specific information about the needs of the impact study as guidance for the clustering of simulations, the subset fits the purpose of climate change impact research more appropriately. Here, the sensitivity of such a procedure is explored, particularly with regard to the use of different climate variables, seasons, and regions in Europe. While temperature dominates the clustering, the resulting selection is influenced by all variables, leading to the conclusion that different subsets fit different impact studies best. (C) 2016 The Authors. Published by Elsevier Ltd.

  • 2159. Wilk, J.
    et al.
    Andersson, Lotta
    SMHI, Core Services. SMHI, Research Department, Hydrology.
    Graham, Phil
    SMHI, Professional Services.
    Wikner, J. J.
    Mokwatlo, S.
    Petja, B.
    From forecasts to action - What is needed to make seasonal forecasts useful for South African smallholder farmers?2017In: International Journal of Disaster Risk Reduction, E-ISSN 2212-4209, Vol. 25, p. 202-211Article in journal (Refereed)
  • 2160.
    Wilk, Julie
    et al.
    SMHI, Research Department, Hydrology.
    Andersson, Lotta
    SMHI, Core Services.
    Warburton, Michele
    Adaptation to climate change and other stressors among commercial and small-scale South African farmers2013In: Regional Environmental Change, ISSN 1436-3798, E-ISSN 1436-378X, Vol. 13, no 2, p. 273-286Article in journal (Refereed)
    Abstract [en]

    Commercial and small-scale farmers in South Africa are exposed to many challenges. Interviews with 44 farmers in the upper Thukela basin, KwaZulu-Natal, were conducted to identify common and specific challenges for the two groups and adaptive strategies for dealing with the effects of climate and other stressors. This work was conducted as part of a larger participatory project with local stakeholders to develop a local adaptation plan for coping with climate variability and change. Although many challenges related to exposure to climate variability and change, weak agricultural policies, limited governmental support, and theft were common to both farming communities, their adaptive capacities were vastly different. Small-scale farmers were more vulnerable due to difficulties to finance the high input costs of improved seed varieties and implements, limited access to knowledge and agricultural techniques for water and soil conservation and limited customs of long-term planning. In addition to temperature and drought-related challenges, small-scale farmers were concerned about soil erosion, water logging and livestock diseases, challenges for which the commercial farmers already had efficient adaptation strategies in place. The major obstacle hindering commercial farmers with future planning was the lack of clear directives from the government, for example, with regard to issuing of water licences and land reform. Enabling agricultural communities to procure sustainable livelihoods requires implementation of strategies that address the common and specific challenges and strengthen the adaptive capacity of both commercial and small-scale farmers. Identified ways forward include knowledge transfer within and across farming communities, clear governmental directives and targeted locally adapted finance programmes.

  • 2161. Wilk, Julie
    et al.
    Hjerpe, Mattias
    Yang, Wei
    SMHI, Research Department, Hydrology.
    Fan, Hua
    Farm-scale adaptation under extreme climate and rapid economic transition2015In: Environment, Development and Sustainability, ISSN 1387-585X, E-ISSN 1573-2975, Vol. 17, no 3, p. 393-407Article in journal (Refereed)
    Abstract [en]

    This paper aims to analyse what shapes farmers' vulnerability and adaptation strategies in the context of rapid change. Xinjiang is semi-arid, with extremes of temperature, growing seasons and winds. Favourable socioeconomic conditions have boosted the wellbeing of farmers in the past decades. Interviews with forty-seven farmers led to the categorization of five groups according to the predominant type of farming activity: animal farmers, government farmers (leasing land from the Xinjiang Production and Construction Group), crop farmers, agri-tourism operators and entrepreneurs. High government support has aided farmers to deal with climate challenges, through advanced technology, subsidies and loans. Farmers, however, greatly contribute to their own high adaptive capacity through inventiveness, flexibility and a high knowledge base. Although the future climate will entail hotter temperatures, farmers can be seen as generally well equipped to deal with these challenges because of the high adaptive capacity they currently have and utilize. Those that are most vulnerable are those that have difficulty to access credit e.g. animal farmers and those that do not want to change their agricultural systems e.g. from pastoral lifestyles to include tourism-based operations.

  • 2162.
    Wilk, Julie
    et al.
    SMHI, Research Department, Hydrology.
    Jonsson, Anna
    SMHI, Core Services.
    Rydhagen, Birgitta
    Rani, Ashu
    Kumar, Arun
    The perspectives of the urban poor in climate vulnerability assessments - The case of Kota, India2018In: Urban Climate, ISSN 2212-0955, E-ISSN 2212-0955, Vol. 24, p. 633-642Article in journal (Refereed)
  • 2163. Wilk, Julie
    et al.
    Kniveton, Dominic
    Andersson, Lotta
    SMHI, Core Services.
    Layberry, Russell
    Todd, Martin C.
    Hughes, Denis
    Ringrose, Susan
    Vanderpost, Cornelis
    Estimating rainfall and water balance over the Okavango River Basin for hydrological applications2006In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 331, no 1-2, p. 18-29Article in journal (Refereed)
    Abstract [en]

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

  • 2164. Willems, P.
    et al.
    Arnbjerg-Nielsen, K.
    Olsson, Jonas
    SMHI, Research Department, Hydrology.
    Nguyen, V. T. V.
    Climate change impact assessment on urban rainfall extremes and urban drainage: Methods and shortcomings2012In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 103, p. 106-118Article in journal (Refereed)
    Abstract [en]

    Cities are becoming increasingly vulnerable to flooding because of rapid urbanization, installation of complex infrastructure, and changes in the precipitation patterns caused by anthropogenic climate change. The present paper provides a critical review of the current state-of-the-art methods for assessing the impacts of climate change on precipitation at the urban catchment scale. Downscaling of results from global circulation models or regional climate models to urban catchment scales are needed because these models are not able to describe accurately the rainfall process at suitable high temporal and spatial resolution for urban drainage studies. The downscaled rainfall results are however highly uncertain, depending on the models and downscaling methods considered. This uncertainty becomes more challenging for rainfall extremes since the properties of these extremes do not automatically reflect those of average precipitation. In this paper, following an overview of some recent advances in the development of innovative methods for assessing the impacts of climate change on urban rainfall extremes as well as on urban hydrology and hydraulics, several existing difficulties and remaining challenges in dealing with this assessment are discussed and further research needs are described. (C) 2011 Elsevier B.V. All rights reserved.

  • 2165. Willers, Saskia M.
    et al.
    Eriksson, Charlotta
    Gidhagen, Lars
    SMHI, Research Department, Air quality.
    Nilsson, Mats E.
    Pershagen, Goran
    Bellander, Tom
    Fine and coarse particulate air pollution in relation to respiratory health in Sweden2013In: European Respiratory Journal, ISSN 0903-1936, E-ISSN 1399-3003, Vol. 42, no 4, p. 924-934Article in journal (Refereed)
    Abstract [en]

    Health effects have repeatedly been associated with residential levels of air pollution. However, it is difficult to disentangle effects of long-term exposure to locally generated and long-range transported pollutants, as well as to exhaust emissions and wear particles from road traffic. We aimed to investigate effects of exposure to particulate matter fractions on respiratory health in the Swedish adult population, using an integrated assessment of sources at different geographical scales. The study was based on a nationwide environmental health survey performed in 2007, including 25 851 adults aged 18-80 years. Individual exposure to particulate matter at residential addresses was estimated by dispersion modelling of regional, urban and local sources. Associations between different size fractions or source categories and respiratory outcomes were analysed using multiple logistic regression, adjusting for individual and contextual confounding. Exposure to locally generated wear particles showed associations for blocked nose or hay fever, chest tightness or cough, and restricted activity days with odds ratios of 1.5-2 per 10-mu g.m(-3) increase. Associations were also seen for locally generated combustion particles, which disappeared following adjustment for exposure to wear particles. In conclusion, our data indicate that long-term exposure to locally generated road wear particles increases the risk of respiratory symptoms in adults.

  • 2166. Willers, Saskia M.
    et al.
    Eriksson, Charlotta
    Gidhagen, Lars
    SMHI, Research Department, Air quality.
    Nilsson, Mats E.
    Pershagen, Goran
    Bellander, Tom
    Traffic Related Air Pollution and Respiratory Health in Sweden: The Roadside Study2009In: EPIDEMIOLOGY, ISSN 1044-3983, Vol. 20, no 6, p. S29-S30Article in journal (Other academic)
  • 2167.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Comparison of Model and Cloud Radar Derived Cloud Vertical Structure and Overlap for the BALTEX BRIDGE Campaign.2004In: Fourth Study Conference on BALTEX: Conference Proceedings / [ed] Hans-Jörg Isemer, 2004, p. 18-Conference paper (Other academic)
  • 2168.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Comparison of modeled and radar measured cloud fraction and overlap2005In: Extended abstracts of a WMO/WCRP-sponsored Regional-Scale Climate Modelling Workshop [Elektronisk resurs] : high-resolution climate modelling : assessment, added value and applications, Lund, Sweden, 29 March-2 April 2004 / [ed] Lars Bärring & René Laprise, Lund: Department of Physical Geography & Ecosystems Analysis, Lund University , 2005, p. 128-Conference paper (Other academic)
  • 2169.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Preliminary use of CM-SAF cloud and radiation products for evaluation of regional climate simulations: Visiting Scientist Report Climate Monitoring SAF (CM-SAF)2008Report (Other academic)
    Abstract [en]

    We have compared monthly mean cloud and radiation fields from the EUMETSAT Climate Monitoring SAF (CM-SAF, http://www.cmsaf.eu) data base with the clouds and radiation simulated by the Rossby Centre regional climate model (RCA) and by the European Centre Medium range Weather Forecast model (ECMWF) over Europe and North Africa for the time period January 2005 to December 2006.ECMWF and RCA overestimate the cloud fraction by 20% over snow covered regions in the north east of Europe and overestimate the surface downwelling longwave radiation (SDL) by 20-40W/m2 and surface outgoing longwave radiation by 10-30W/m2. The RCA-simulated clouds have too much cloud water in northern Europe in summer and in autumn and they therefore reflect too much shortwave radiation at the TOA (TRS) and this also leads to an underestimation of the incoming shortwave radiation (SIS) at the surface. Over most of Europe and over sea ECMWF (all year) and RCA (in winter-spring) underestimate the cloud fraction which could explain a corresponding underestimate of TRS, overestimate of SIS and underestimate of SDL. The satellites overestimate cloud cover over sea due to problems in the treatment of sub-pixel cloudiness and therefore the models underestimates are larger over sea. Mainly RCA but also ECMWF overestimate cloud fraction on top of mountains and underestimate it along mountain ranges and have corresponding differences in the TOA and surface radiation fluxes compared to the CM-SAF data.Over North Africa RCA underestimates TRS by -11W/m2 and overestimates the TOA emitted thermal radiation (TET) by 8W/m2. ECMWF underestimates TRS by -28W/m2 and overestimates TET by 14W/m2. These errors are similar to what has been found for many other global models and are attributed to clear sky errors either due to too high surface temperatures, errors in emissivity, albedo or lack of aerosols. Adding clear and cloudy skies radiation fluxes to the CM-SAF data base would help us to understand the reasons for ECMWF and RCA errors. The polar orbiting satellite retrieval for 2005-2006 erroneously overestimated cloud fraction over North Africa, which also affects the CM-SAF derived surface radiation fluxes.

  • 2170.
    Willén, Ulrika
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Crewell, S.
    Comparison of model and cloud radar derived cloud vertical structure and overlap.2004In: 14th International Conference on Clouds and Precipitation(ICCP), 2004, p. 1434-1437Conference paper (Other academic)
  • 2171.
    Willén, Ulrika
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Crewell, S
    Baltink, H K
    Sievers, O
    Assessing model predicted vertical cloud structure and cloud overlap with radar and lidar ceilometer observations for the Baltex Bridge Campaign of CLIWA-NET2005In: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 75, no 3, p. 227-255Article in journal (Refereed)
    Abstract [en]

    The cloud vertical distribution and overlap of four large-scale models operating at different horizontal and vertical resolutions have been assessed using radar and lidar observations from the Baltex Bridge Campaign of CLIWA-NET. The models range from the global European Centre for Medium range Weather Forecast (ECMWF) model, to the Regional Atmospheric Climate Model (RACMO) and the Rossby Centre Atmospheric (RCA) regional climate model, to the non-hydrostatic meso-scale Lokal Model (LM). Different time averaging periods for the radar data were used to estimate the uncertainty of the point-to-space transformations of the observations. Relative to the observations, all models underestimated the height of the lowest cloud base. Clouds occurred more frequently in the models but with smaller cloud fractions below 7 km. The findings confirm previous cloud radar studies which found that models overestimate cloud fractions above 7 km. Radar-observed clouds were often thinner than the model vertical resolutions, which can have serious implications on model cloud overlap and radiation fluxes. The radar-derived cloud overlap matrix, which takes into account the overlap of all vertical layers, was found to be close to maximum-random overlap. Using random overlap for vertically continuous clouds with vertical gradients in cloud fraction larger than 40-50% per kilometre gave the best fit to the data. The gradient approach could be improved by making it resolution- and cloud system-dependent. Previous cloud radar overlap studies have considered the overlap of two cloud layers as a function of maximum and random overlap. Here, it was found that the two-layer overlap could be modelled by a mixture of maximum and minimum overlap. (c) 2005 Elsevier B.V. All rights reserved.

  • 2172.
    Willén, Ulrika
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Baltink, Henk Klein
    Quante, Markus
    COMPARISON OF MODEL AND CLOUD RADAR DERIVED CLOUD OVERLAP2002Conference paper (Other academic)
  • 2173. Winsor, P
    et al.
    Rodhe, J
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Baltic Sea ocean climate: an analysis of 100 yr of hydrographic data with focus on the freshwater budget2001In: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 18, no 1-2, p. 5-15Article in journal (Refereed)
    Abstract [en]

    The Baltic Sea climate is analysed based upon long-term oceanographic measurements. The objective of the work is to study the natural variability of present day climate with focus on the freshwater budget. The results are designed to be used for validation of climate models and for discrimination of the significance of modelled climate change scenarios. Almost 100 yr of observations are used in the study, including data for river runoff, water exchange through the Danish Straits (as calculated from river runoff and from sea level data from the Kattegat), salinity data from the Baltic Sea and the Kattegat, and oxygen content in the deep Baltic Sea. The analyses illustrate that freshwater supply to the Baltic shows large variations on time scales up to several decades. The long-term variations in freshwater storage are closely correlated to accumulated changes in river runoff. This indicates strong positive feedback between the amount of outflowing surface water from the Baltic Sea and the salinity of the inflowing Kattegat water. One implication of the study is that climate control simulations must cover several decades, probably up to 100 yr in order to capture the natural variability of present day climate. Also, models designed to study climate change for the Baltic Sea probably need to start integrating from the present day.

  • 2174. Winterdahl, Mattias
    et al.
    Laudon, Hjalmar
    Lyon, Steve W.
    Pers, Charlotta
    SMHI, Research Department, Hydrology.
    Bishop, Kevin
    Sensitivity of stream dissolved organic carbon to temperature and discharge: Implications of future climates2016In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, no 1, p. 126-144Article in journal (Refereed)
    Abstract [en]

    Dissolved organic carbon (DOC) is a significant constituent in aquatic ecosystems with concentrations in streams influenced by both temperature and water flow pathway dynamics associated with changes in discharge (streamflow). We investigated the sensitivity of DOC concentrations in 12 high-latitude headwater streams to changes in temperature and discharge using a mathematical model. The implications of differences in sensitivities were explored by using downscaled projections of air temperature and discharge to simulate possible trajectories of DOC concentrations in a changing climate. We found two distinct responses: (i) catchments where stream DOC sensitivity was high to temperature but low to discharge and (ii) catchments where stream DOC sensitivity was low to temperature but high to discharge. Streams with strong seasonal DOC dynamics were more sensitive to temperature changes than nonseasonal systems. In addition, stream DOC sensitivity to discharge was strongly correlated with vertical soil water DOC differences in the near-stream zone. Simulations of possible future changes in DOC concentrations indicated median increases of about 4-24% compared to current levels when using projections of air temperature and discharge but even larger increases were observed for base flow concentrations (13-42%). Streams with high-temperature sensitivity showed the largest increases in DOC concentrations. Our results suggest that future climatic changes could bring significant increases in surface water DOC concentrations in boreal and hemiboreal areas but that the response ultimately is dependent on vertical soil solution DOC differences and soil organic carbon distribution.

  • 2175. Winterdahl, Mattias
    et al.
    Temnerud, Johan
    SMHI, Research Department, Hydrology.
    Futter, Martyn N.
    Lofgren, Stefan
    Moldan, Filip
    Bishop, Kevin
    Riparian Zone Influence on Stream Water Dissolved Organic Carbon Concentrations at the Swedish Integrated Monitoring Sites2011In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 40, no 8, p. 920-930Article in journal (Refereed)
    Abstract [en]

    Short-term variability in stream water dissolved organic carbon (DOC) concentrations is controlled by hydrology, climate and atmospheric deposition. Using the Riparian flow-concentration Integration Model (RIM), we evaluated factors controlling stream water DOC in the Swedish Integrated Monitoring (IM) catchments by separating out hydrological effects on stream DOC dynamics. Model residuals were correlated with climate and deposition-related drivers. DOC was most strongly correlated to water flow in the northern catchment (Gammtratten). The southern Aneboda and Kindla catchments had pronounced seasonal DOC signals, which correlated weakly to flow. DOC concentrations at GAyenrdsjon increased, potentially in response to declining acid deposition. Soil temperature correlated strongly with model residuals at all sites. Incorporating soil temperature in RIM improved model performance substantially (20-62% lower median absolute error). According to the simulations, the RIM conceptualization of riparian processes explains between 36% (Kindla) and 61% (Aneboda) of the DOC dynamics at the IM sites.

  • 2176.
    Wittgren, Hans B.
    et al.
    SMHI.
    Maehlum, T
    Wastewater treatment wetlands in cold climates1997In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 35, no 5, p. 45-53Article in journal (Refereed)
    Abstract [en]

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

  • 2177.
    Wittgren, Hans Bertil
    SMHI, Research Department.
    Kvävetransport till Slätbaken från Söderköpingsåns avrinningsområde1995Report (Other academic)
  • 2178.
    Wittgren, Hans Bertil
    et al.
    SMHI, Research Department.
    Arheimer, Berit
    SMHI, Research Department, Hydrology.
    Source apportionment of riverine nitrogen transport based on catchment modelling1996In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 33, no 4-5, p. 109-115Article in journal (Refereed)
    Abstract [en]

    Source apportionment of river substance transport, i.e. estimation of how much each source in each subbasin contributes to the river-mouth transport is a vital step in achieving the most efficient management practices to reduce pollutant loads to the sea. In this study, the spatially lumped (at sub-catchment level), semiempirical PULSE hydrological model, with a nitrogen routine coupled to if was used to perform source apportionment of nitrogen transport in the Soderkopingsan river basin (882 km(2)) in south-eastern Sweden, for the period 1991-93. The river basin was divided into 28 subbasins and the following sources were considered: land leakage from the categories forest arable and ley/pasture; point sources, and; atmospheric deposition on lake surfaces. The calibrated model yielded an explained variance of 60%, based on comparison of measured and modelled river nitrogen (Total N) concentrations. Eight subbasins, with net contributions to the river-mouth transport exceeding 3 kg ha(-1) yr(-1), were identified as the most promising candidates for cost efficient nitrogen management. The other 20 subbasins all had net contributions below 3 kg ha(-1) yr(-1). Arable land contributed 63% of the nitrogen transport at the river mouth and would thus be in focus for management measures. However, point sources (18% contribution to net transport) should also be considered due to their relatively high accessibility for removal measures (high concentrations). E.g., the most downstream subbasin, with the largest wastewater treatment plant in the whole river basin, had a net contribution of 16 kg ha(-1) yr(-1). This method for source apportionment may provide authorities with quantitative information about where in a river basin, and at which sources, they should focus their attention. However, once this is done, an analysis with higher resolution has to be performed in each of the interesting subbasins, before decisions on actual management measures can be taken. Copyright (C) 1996 IAWQ.

  • 2179.
    Wittgren, Hans Bertil
    et al.
    SMHI, Research Department.
    Tobiason, S
    Nitrogen removal from pretreated wastewater in surface flow wetlands1995In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 32, no 3, p. 69-78Article in journal (Refereed)
    Abstract [en]

    The wastewater treatment plant in the town of Oxelosund (12,500 inhabitants), Sweden, has mechanical and chemical treatment for removal of BOD and phosphorus. With the aim to achieve 50% nitrogen removal, a surface flow wetland system of 21 ha was created as a final step during 1993. It consists of 5 cells, where 2+2 are operated in parallel with a final common cell, This allows intermittent filling and emptying, the goal of which is to promote both nitrification and denitrification for a design flow of 6000 m(3) day(-1). During the first year of operation, August 1993 to July 1994, the wetland removed 720 kg ha(-1) of total nitrogen from the load of 1810 kg ha(-1). Ammonium-N was the dominant fraction at the inlet as well as at the outlet, 79% and 90% of total nitrogen, respectively. The large fraction of NH4+ at the outlet showed that nitrification was the limiting step. An intensive monitoring effort in May 1994 indicated that neither wastewater toxicity nor oxygen deficiency were likely to limit nitrification. Instead, sub-optimal hydraulic loading conditions; a lack of suitable surfaces for ion exchange of NH4+ as well as for attachment of nitrifiers; and phosphorus deficiency, were considered potentially important factors in limiting nitrification. In addition to nitrogen removal, the wetland system reduced total phosphorus, BOD7 and E. coli (44 degrees C) to very low levels at the outlet.

  • 2180. Woick, H
    et al.
    Dewitte, S
    Feijt, A
    Gratzki, A
    Hechler, P
    Hollmann, R
    Karlsson, Karl-Göran
    SMHI, Research Department, Atmospheric remote sensing.
    Laine, V
    Lowe, P
    Nitsche, H
    Werscheck, M
    Wollenweber, G
    The satellite application facility on climate monitoring2002In: EARTH'S ATMOSPHERE, OCEAN AND SURFACE STUDIES, 2002, no 11, p. 2405-2410Conference paper (Refereed)
    Abstract [en]

    The Satellite Application Facility on Climate Monitoring is a joint project of the National Meteorological Services and other institutes from Belgium, Finland, Germany, Sweden and The Netherlands. The objective of the project is to set up a system to provide atmospheric and oceanographic data sets from (primarily) operational geostationary and polar orbiting meteorological satellites for climate monitoring, research and applications at regional European scale, for some products on a global scale. Initial operational SAF products are related to clouds, radiation budget, ocean status and water vapour content in the atmosphere. SAF operations are foreseen to start in 2004. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

  • 2181. Wolski, Tomasz
    et al.
    Wisniewski, Bernard
    Giza, Andrzej
    Kowalewska-Kalkowska, Halina
    Boman, Hanna
    Grabbi-Kaiv, Silve
    Hammarklint, Thomas
    SMHI, Core Services.
    Holfort, Juergen
    Lydeikaite, Zydrune
    Extreme sea levels at selected stations on the Baltic Sea coast2014In: Oceanologia, ISSN 0078-3234, Vol. 56, no 2, p. 259-290Article in journal (Refereed)
    Abstract [en]

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

  • 2182. Wolters, L
    et al.
    Cats, G
    Gustafsson, Nils
    SMHI, Research Department, Meteorology.
    Wilhelmsson, T
    Data-parallel numerical methods in a weather forecast model1995In: Applied Numerical Mathematics, ISSN 0168-9274, E-ISSN 1873-5460, Vol. 19, no 1-2, p. 159-171Article in journal (Refereed)
    Abstract [en]

    The results presented in this paper are part of a research project to investigate the possibilities to apply massively parallel architectures for numerical weather forecasting. Within numerical weather forecasting several numerical techniques are used to solve the model equations. This paper compares the performance of implementations on a MasPar system of two techniques, finite difference and spectral, that are adopted in the numerical weather forecasting model HIRLAM. The operational HIRLAM model is based on finite difference methods, while the spectral model is still in a research phase. Also the differences in relative performance of these methods on the MasPar and vector architectures will be discussed.

  • 2183. Worman, A.
    et al.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    Riml, Joakim
    SMHI, Research Department, Hydrology.
    The power of runoff2017In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 548, p. 784-793Article in journal (Refereed)
  • 2184. Worman, Anders
    et al.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    Akesson, Anna
    Riml, Joakim
    SMHI, Research Department, Hydrology.
    Drifting runoff periodicity during the 20th century due to changing surface water volume2010In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 24, no 26, p. 3772-3784Article in journal (Refereed)
    Abstract [en]

    Fourier and wavelet analyses were used to reveal the dominant trends and coherence of a more than one-century-long time series of precipitation and discharge in several watersheds in Sweden, two of which were subjected to hydropower and intensive agriculture. During the 20th century, there was a gradual, significant drift of the dominant discharge periodicity in agricultural watersheds. This study shows that the steepness of the Fourier spectrum of runoff from the May to October period each year increased gradually during the century, which suggests a more predictable intra-annual runoff pattern (more apart from white-noise). In the agricultural watershed, the coherence spectrum of precipitation and runoff is generally high with a consistent white-noise relationship for precipitation during the 20th century, indicating that precipitation is not controlling the drift of the discharge spectrum. In the hydropower regulated watershed, there was a sudden decrease of the discharge spectrum slope when regulation commenced in the 1920s. This study develops a new theory in which the runoff spectrum is related to the hydraulic and hydro-morphological characteristics of the watershed. Using this theory, we explain the changes in runoff spectra in the two watersheds by the anthropogenic change in surface water volume and, hence, changes in kinematic wave celerity and water transit times. The reduced water volume in the agricultural watershed would also contribute to decreasing evaporation, which could explain a slightly increasing mean discharge during the 20th century despite the fact that precipitation was statistically constant in the area. Copyright (C) 2010 John Wiley & Sons, Ltd.

  • 2185. Wormbs, N.
    et al.
    Nilsson, A.E.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Sörlin, S.
    The History of Emerging Arctic Climate Modelling, poster presented at the IPY final conference in Oslo2010Conference paper (Other academic)
  • 2186. Wramneby, Anna
    et al.
    Smith, Benjamin
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Hot spots of vegetation-climate feedbacks under future greenhouse forcing in Europe2010In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 115, article id D21119Article in journal (Refereed)
    Abstract [en]

    We performed simulations of future biophysical vegetation-climate feedbacks with a regional Earth System Model, RCA-GUESS, interactively coupling a regional climate model and a process-based model of vegetation dynamics and biogeochemistry. Simulated variations in leaf area index and in the relative coverage of evergreen forest, deciduous forest, and open land vegetation in response to simulated climate influence atmospheric state via variations in albedo, surface roughness, and the partitioning of the land-atmosphere heat flux into latent and sensible components. The model was applied on a similar to 50 x 50 km grid over Europe under a future climate scenario. Three potential "hot spots" of vegetation-climate feedbacks could be identified. In the Scandinavian Mountains, reduced albedo resulting from the snow-masking effect of forest expansion enhanced the winter warming trend. In central Europe, the stimulation of photosynthesis and plant growth by "CO2 fertilization" mitigated warming, through a negative evapotranspiration feedback associated with increased vegetation cover and leaf area index. In southern Europe, increased summer dryness restricted plant growth and survival, causing a positive warming feedback through reduced evapotranspiration. Our results suggest that vegetation-climate feedbacks over the European study area will be rather modest compared to the radiative forcing of increased global CO2 concentrations but may modify warming projections locally, regionally, and seasonally, compared with results from traditional "off-line" regional climate models lacking a representation of the relevant feedback mechanisms.

  • 2187. Wu, Dong L.
    et al.
    Baum, Bryan A.
    Choi, Yong-Sang
    Foster, Michael J.
    Karlsson, Karl-Göran
    SMHI, Research Department, Atmospheric remote sensing.
    Heidinger, Andrew
    Poulslsen, Caroline
    Pavolonis, Michael
    Riedi, Jerome
    Roebeling, Robert
    Sherwood, Steven
    Thoss, Anke
    SMHI, Research Department, Atmospheric remote sensing.
    Watts, Philip
    TOWARD GLOBAL HARMONIZATION OF DERIVED CLOUD PRODUCTS2017In: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 98, no 2, p. ES49-ES52Article in journal (Refereed)
  • 2188. Wu, Minchao
    et al.
    Schurgers, Guy
    Rummukainen, Markku
    SMHI, Core Services.
    Smith, Benjamin
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Jansson, Christer
    Siltberg, Joe
    May, Wilhelm
    Vegetation-climate feedbacks modulate rainfall patterns in Africa under future climate change2016In: Earth System Dynamics, ISSN 2190-4979, E-ISSN 2190-4987, Vol. 7, no 3, p. 627-647Article in journal (Refereed)
  • 2189. Wulff, A.
    et al.
    Karlberg, M.
    Olofsson, M.
    Torstensson, A.
    Riemann, L.
    Steinhoff, F. S.
    Chierici, M.
    Mohlin, Malin
    SMHI.
    Ekstrand, N.
    THE FUTURE FOR BALTIC CYANOBACTERIA?2017In: Phycologia, ISSN 0031-8884, E-ISSN 2330-2968, Vol. 56, no 4, p. 199-200Article in journal (Refereed)
  • 2190. Wulff, Angela
    et al.
    Karlberg, Maria
    Olofsson, Malin
    Torstensson, Anders
    Riemann, Lasse
    Steinhoff, Franciska S.
    Mohlin, Malin
    SMHI.
    Ekstrand, Nina
    Chierici, Melissa
    Ocean acidification and desalination: climate-driven change in a Baltic Sea summer microplanktonic community2018In: Marine Biology, ISSN 0025-3162, E-ISSN 1432-1793, Vol. 165, no 4, article id 63Article in journal (Refereed)
  • 2191. WULFF, F
    et al.
    Rahm, Lars
    SMHI, Research Department, Oceanography.
    LONG-TERM, SEASONAL AND SPATIAL VARIATIONS OF NITROGEN, PHOSPHORUS AND SILICATE IN THE BALTIC - AN OVERVIEW1988In: Marine Environmental Research, ISSN 0141-1136, E-ISSN 1879-0291, Vol. 26, no 1, p. 19-37Article in journal (Refereed)
  • 2192. WULFF, F
    et al.
    STIGEBRANDT, A
    Rahm, Lars
    SMHI, Research Department, Oceanography.
    NUTRIENT DYNAMICS OF THE BALTIC SEA1990In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 19, no 3, p. 126-133Article in journal (Refereed)
  • 2193.
    Wyser, Klaus
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Modeled and observed clouds during Surface Heat Budget of the Arctic Ocean (SHEBA)2005In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 110, no D9, article id D09207Article in journal (Refereed)
    Abstract [en]

    [1] Observed monthly mean cloud cover from the SHEBA site is found to differ by a substantial amount during winter depending on cloud observing instrument. This makes it difficult for climate modelers to evaluate modeled clouds and improve parameterizations. Many instruments and human observers cannot properly detect the thinnest clouds and count them as clear sky instead, resulting in too low cloud cover. To study the impact from the difficulties in the detection of thin clouds, we compute cloud cover in our model with a filter that removes the thinnest clouds. Optical thickness is used as a proxy to identify thin clouds as we are mainly interested in the impact of clouds on radiation. With the results from a regional climate model simulation of the Arctic, we can reproduce the large variability in wintertime cloud cover between instruments when assuming different cloud detection thresholds. During winter a large fraction of all clouds are optically thin, which causes the large sensitivity to filtering by optical thickness. During summer, most clouds are far above the optical thickness threshold and filtering has no effect. A fair comparison between observed and modeled cloud cover should account for thin clouds that may be present in models but absent in the observational data set. Difficulties with the proper identification of clouds and clear sky also has an effect on cloud radiative forcing. The derived clear-sky longwave flux at the surface can vary by some W m(-2) depending on the lower limit for the optical thickness of clouds. This impacts on the "observed'' LW cloud radiative forcing and suggests great care is needed in using satellite-derived cloud radiative forcing for model development.

  • 2194.
    Wyser, Klaus
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Du, P.
    Girard, E.
    Willen, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Cassano, J.
    Christensen, J. H.
    Curry, J. A.
    Dethloff, K.
    Haugen, J. -E
    Jacob, D.
    Koltzow, M.
    Laprise, R.
    Lynch, A.
    Pfeifer, S.
    Rinke, A.
    Serreze, M.
    Shaw, M. J.
    Tjernstrom, M.
    Zagar, M.
    An evaluation of Arctic cloud and radiation processes during the SHEBA year: simulation results from eight Arctic regional climate models2008In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 30, no 2-3, p. 203-223Article in journal (Refereed)
    Abstract [en]

    Eight atmospheric regional climate models (RCMs) were run for the period September 1997 to October 1998 over the western Arctic Ocean. This period was coincident with the observational campaign of the Surface Heat Budget of the Arctic Ocean (SHEBA) project. The RCMs shared common domains, centred on the SHEBA observation camp, along with a common model horizontal resolution, but differed in their vertical structure and physical parameterizations. All RCMs used the same lateral and surface boundary conditions. Surface downwelling solar and terrestrial radiation, surface albedo, vertically integrated water vapour, liquid water path and cloud cover from each model are evaluated against the SHEBA observation data. Downwelling surface radiation, vertically integrated water vapour and liquid water path are reasonably well simulated at monthly and daily timescales in the model ensemble mean, but with considerable differences among individual models. Simulated surface albedos are relatively accurate in the winter season, but become increasingly inaccurate and variable in the melt season, thereby compromising the net surface radiation budget. Simulated cloud cover is more or less uncorrelated with observed values at the daily timescale. Even for monthly averages, many models do not reproduce the annual cycle correctly. The inter-model spread of simulated cloud-cover is very large, with no model appearing systematically superior. Analysis of the co-variability of terms controlling the surface radiation budget reveal some of the key processes requiring improved treatment in Arctic RCMs. Improvements in the parameterization of cloud amounts and surface albedo are most urgently needed to improve the overall performance of RCMs in the Arctic.

  • 2195.
    Wyser, Klaus
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Modelling clouds and radiation in the Arctic2005In: Extended abstracts of a WMO/WCRP-sponsored Regional-Scale Climate Modelling Workshop [Elektronisk resurs] : high-resolution climate modelling : assessment, added value and applications / [ed] Lars Bärring & René Laprise, Lund: Department of Physical Geography & Ecosystems Analysis, Lund University , 2005, p. 128-Conference paper (Other academic)
  • 2196.
    Wyser, Klaus
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Modelling clouds and radiation in the ARctic.2004In: 14th International conference on clouds and precipitation, 2004, p. 1442-1445Conference paper (Other academic)
  • 2197.
    Wyser, Klaus
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    Strandberg, Gustav
    SMHI, Research Department, Climate research - Rossby Centre.
    Nordic regionalisation of a greenhouse-gas stabilisation scenario2006Report (Other academic)
    Abstract [en]

    The impact of a CO2 stabilisation on the Swedish climate is investigated with the regional climate model RCA3 driven by boundary conditions obtained from a global coupled climate system model (CCSM3). The global model has been forced with observed greenhouse gas concentrations from pre-industrial conditions until today’s, and with an idealised further increase until the stabilisation level is reached. After stabilisation the model integration continues for another 150+ years in order to follow the delayed response of the climate system over a period of time.Results from the global and regional climate model are compared against observations and ECMWF reanalysis for 1961-1990. For this period, the global model is found to be too cold over Europe and with a zonal flow from the North Atlantic towards Europe that is too strong. The climate of the driving global model controls the climate of the regional model and the same deviations from one are thus inherited by the other. We therefore analyse the relative climate changes differences, or ratios, of climate variables between future's and today's climate.Compared to pre-industrial conditions, the global mean temperature changes by about 1.5oC as a result of the stabilisation at 450 ppmv equivalent CO2. Averaged over Europe, the temperature change is slightly larger, and it is even larger for Sweden and Northern Europe. Annual mean precipitation for Europe is unaffected, but Sweden receives more precipitation under higher CO2 levels. The inter-annual and decadal variability of annual mean temperature and precipitation does not change with any significant degree.The changes in temperature and precipitation are not evenly distributed with the season: the largest warming and increased precipitation in Northern Europe occurs during winter months while the summer climate remains more or less unchanged. The opposite is true for the Mediterranean region where the precipitation decreases mostly during summer. This also implies higher summer temperatures, but changes in winter are smaller. No substantial change in the wind climate over Europe is found.

  • 2198.
    Wåhlstrom, Irene
    et al.
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    A model sensitivity study for the sea-air exchange of methane in the Laptev Sea, Arctic Ocean2014In: Tellus. Series B, Chemical and physical meteorology, ISSN 0280-6509, E-ISSN 1600-0889, Vol. 66, article id 24174Article in journal (Refereed)
    Abstract [en]

    The ocean's sinks and sources determine the concentration of methane in the water column and by that regulating the emission of methane to the atmosphere. In this study, we investigate how sensitive the sea-air exchange of methane is to increasing/decreasing sinks and sources as well as changes of different drivers with a time-dependent biogeochemical budget model for one of the shallow shelf sea in the Siberian Arctic, the Laptev Sea. The applied changes are: increased air temperature, river discharge, wind, atmospheric methane, concentration of nutrients in the river runoff or flux of methane from the sediment. Furthermore, simulations are performed to examine how the large range in observations for methane concentration in the Lena River as well as the rate of oxidation affects the net sea-air exchange. In addition, a simulation with five of these changes applied together was carried out to simulate expected climate change at the end of this century. The result indicates that none of the simulations changed the seawater to becoming a net sink for atmospheric methane and all simulations except three increased the outgassing to the atmosphere. The three exceptions were: doubling the atmospheric methane, decreasing the rivers' concentration of methane and increasing the oxidation rate where the latter is one of the key mechanisms controlling emission of methane to the atmosphere.

  • 2199.
    Wåhlström, Irene
    et al.
    SMHI, Research Department, Oceanography.
    Dieterich, Christian
    SMHI, Research Department, Oceanography.
    Pemberton, Per
    SMHI, Research Department, Oceanography.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Impact of increasing inflow of warm Atlantic water on the sea-air exchange of carbon dioxide and methane in the Laptev Sea2016In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, no 7, p. 1867-1883Article in journal (Refereed)
  • 2200.
    Wåhlström, Irene
    et al.
    SMHI, Research Department, Oceanography.
    Eilola, Kari
    SMHI, Research Department, Oceanography.
    Edman, Moa
    SMHI, Research Department, Oceanography.
    Almroth-Rosell, Elin
    SMHI, Research Department, Oceanography.
    Evaluation of open sea boundary conditions for the coastal zone. A model study in the northern part of the Baltic Proper.2017Report (Other academic)
    Abstract [en]

    The environmental conditions in the coastal zone are strongly connected with the conditions in the open sea as the transports across the boundaries are extensive. Therefore, it is of critical importance that coastal zone models have lateral boundary forcing of high quality and required parameters with good coverage in space and time.

    The Swedish Coastal zone Model (SCM) is developed at SMHI to calculate water quality in the coastal zone. This model is currently forced by the outcome from a one-dimensional model, assimilated to observations along the coast. However, these observations are scarce both in space, time and do usually not include all required parameters. In addition, the variability closer to the coast may be underestimated by the open sea monitoring stations used for the data assimilation. These problems are partly overcome by utilize the one-dimensional model that resolves all the variables used in the SCM. However, the method is not applicable for examine either the past period or future scenario where the latter analyze how climate change might affect the coastal zone. In the present study, we therefore evaluate the possibility to use results from a three-dimensional coupled physical and biogeochemical model of the Baltic Sea as open sea boundary conditions for the coastal zone, primarily to investigate the two periods mentioned above.

    Seven sensitivity experiments have been carried out in a pilot area of the coastal zone, the northern part of the Baltic proper, including the Stockholm Archipelago. The sensitivity tests were performed in order to explore methods to extract the outcome from the three-dimensional model, RCO-SCOBI, and apply as lateral boundary forcing for the SCM. RCO-SCOBI is a model for the open Baltic Sea with high horizontal and vertical resolution of the required variables. The results from the different tests were examined and evaluated against observations in the coastal zone. This was executed for both the physical and the biogeochemical variables utilizing a statistical method.

    The results from this study concluded that the outcome from the RCO-SCOBI is applicable as forcing files for the SCM. The best results in the tests was obtained with a method extracting depth profiles for the required variables from the RCO-SCOBI at a position 10 nautical miles to the east and 10 nautical miles to the south in the Baltic proper or north in the Gulf of Bothnia outside each of the outer basins.

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