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  • 351. Rafael, S.
    et al.
    Martins, Helena
    SMHI, Research Department, Climate research - Rossby Centre.
    Marta-Almeida, M.
    Sa, E.
    Coelho, S.
    Rocha, A.
    Borrego, C.
    Lopes, M.
    Quantification and mapping of urban fluxes under climate change: Application of WRF-SUEWS model to Greater Porto area (Portugal)2017In: Environmental Research, ISSN 0013-9351, E-ISSN 1096-0953, Vol. 155, p. 321-334Article in journal (Refereed)
  • 352. Rafael, S.
    et al.
    Martins, Helena
    SMHI, Research Department, Climate research - Rossby Centre.
    Sa, E.
    Carvalho, D.
    Borrego, C.
    Lopes, M.
    Influence of urban resilience measures in the magnitude and behaviour of energy fluxes in the city of Porto (Portugal) under a climate change scenario2016In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 566, p. 1500-1510Article in journal (Refereed)
  • 353. Rammig, A.
    et al.
    Jonsson, A. M.
    Hickler, T.
    Smith, B.
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Sykes, M. T.
    Impacts of changing frost regimes on Swedish forests: Incorporating cold hardiness in a regional ecosystem model2010In: Ecological Modelling, ISSN 0304-3800, E-ISSN 1872-7026, Vol. 221, no 2, p. 303-313Article in journal (Refereed)
    Abstract [en]

    Understanding the effects of climate change on boreal forests which hold about 7% of the global terrestrial biomass carbon is a major issue. An important mechanism in boreal tree species is acclimatization to seasonal variations in temperature (cold hardiness) to withstand low temperatures during winter. Temperature drops below the hardiness level may cause frost damage. Increased climate variability under global and regional warming might lead to more severe frost damage events, with consequences for tree individuals, populations and ecosystems. We assessed the potential future impacts of changing frost regimes on Norway spruce (Picea abies L. Karst.) in Sweden. A cold hardiness and frost damage model were incorporated within a dynamic ecosystem model, LPJ-GUESS. The frost tolerance of Norway spruce was calculated based on daily mean temperature fluctuations, corresponding to time and temperature dependent chemical reactions and cellular adjustments. The severity of frost damage was calculated as a growth-reducing factor when the minimum temperature was below the frost tolerance. The hardiness model was linked to the ecosystem model by reducing needle biomass and thereby growth according to the calculated severity of frost damage. A sensitivity analysis of the hardiness model revealed that the severity of frost events was significantly altered by variations in the hardening rate and dehardening rate during current climate conditions. The modelled occurrence and intensity of frost events was related to observed crown defoliation, indicating that 6-12% of the needle loss could be attributed to frost damage. When driving the combined ecosystem-hardiness model with future climate from a regional climate model (RCM), the results suggest a decreasing number and strength of extreme frost events particularly in northern Sweden and strongly increasing productivity for Norway spruce by the end of the 21st century as a result of longer growing seasons and increasing atmospheric CO(2) concentrations. However, according to the model, frost damage might decrease the potential productivity by as much as 25% early in the century. (C) 2009 Elsevier B.V. All rights reserved.

  • 354. Raschke, E
    et al.
    Meywerk, J
    Warrach, K
    Andrae, Ulf
    SMHI, Research Department, Meteorology.
    Bergström, Sten
    SMHI, Research Department, Hydrology.
    Beyrich, F
    Bosveld, F
    Bumke, K
    Fortelius, C
    Graham, Phil
    SMHI, Research Department, Climate research - Rossby Centre.
    Gryning, S E
    Halldin, S
    Hasse, L
    Heikinheimo, M
    Isemer, H J
    Jacob, D
    SMHI.
    Jauja, I
    Karlsson, Karl-Göran
    SMHI, Research Department, Atmospheric remote sensing.
    Keevallik, S
    Koistinen, J
    van Lammeren, A
    Lass, U
    Launianen, J
    Lehmann, A
    Liljebladh, B
    Lobmeyr, M
    Matthaus, W
    Mengelkamp, T
    Michelson, Daniel
    SMHI, Core Services.
    Napiorkowski, J
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Piechura, J
    Rockel, B
    Rubel, F
    Ruprecht, E
    Smedman, A S
    Stigebrandt, A
    The Baltic Sea Experiment (BALTEX): A European contribution to the investigation of the energy and water cycle over a large drainage basin2001In: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 82, no 11, p. 2389-2413Article, review/survey (Refereed)
    Abstract [en]

    The Baltic Sea Experiment (BALTEX) is one of the five continental-scale experiments of the Global Energy and Water Cycle Experiment (GEWEX). More than 50 research groups from 14 European countries are participating in this project to measure and model the energy and water cycle over the large drainage basin of the Baltic Sea in northern Europe. BALTEX aims to provide a better understanding of the processes of the climate system and to improve and to validate the water cycle in regional numerical models for weather forecasting and climate studies. A major effort is undertaken to couple interactively the atmosphere with the vegetated continental surfaces and the Baltic Sea including its sea ice. The intensive observational and modeling phase BRIDGE, which is a contribution to the Coordinated Enhanced Observing Period of GEWEX, will provide enhanced datasets for the period October 1999-February 2002 to validate numerical models and satellite products. Major achievements have been obtained in an improved understanding of related exchange processes. For the first time an interactive atmosphere-ocean-land surface model for the Baltic Sea was tested. This paper reports on major activities and some results.

  • 355. Rasmus, S
    et al.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    Lehning, M
    Estimating snow conditions in Finland in the late 21st century using the SNOWPACK model with regional climate scenario data as input2004In: ANNALS OF GLACIOLOGY, VOL 38 2004, 2004, p. 238-244Conference paper (Refereed)
    Abstract [en]

    An assessment of possible snow changes in a changing climate for Finland is presented. The snowpack structure model SNOWPACK (developed at the Swiss Federal Institute for Snow and Avalanche Research) was used for calculating snow conditions at six different locations in Finland for the decades 1980-89 and 2080-89. Regional climate model (RCAO) data from the Rossby Centre, Sweden, were used as input to the SNOWPACK model. Ten years from the RCAO control run and scenario run Were chosen, and the snow conditions for different snow zones were calculated for these winters. The snow-cover depth and duration decreased at all locations in the scenario run cases, and the snow-cover quality also changed between the control and scenario runs: grains were bigger, snow was warmer and denser, and the fraction of faceted snow decreased while the fraction of icy or melting snow increased, even in mid-winter. Finally, the variability between different global climate predictions was analyzed. Significant differences were found between different climate-model outputs. The inter-model variable is comparable to the interannual variability of a single model. The qualitative Conclusions from the scenario run do not critically depend oil the climate-model variability.

  • 356. Refsgaard, J. C.
    et al.
    Madsen, H.
    Andreassian, V.
    Arnbjerg-Nielsen, K.
    Davidson, T. A.
    Drews, M.
    Hamilton, D. P.
    Jeppesen, E.
    Kjellstrom, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Olesen, J. E.
    Sonnenborg, T. O.
    Trolle, D.
    Willems, P.
    Christensen, J. H.
    A framework for testing the ability of models to project climate change and its impacts2014In: Climatic Change, ISSN 0165-0009, E-ISSN 1573-1480, Vol. 122, no 1-2, p. 271-282Article in journal (Refereed)
    Abstract [en]

    Models used for climate change impact projections are typically not tested for simulation beyond current climate conditions. Since we have no data truly reflecting future conditions, a key challenge in this respect is to rigorously test models using proxies of future conditions. This paper presents a validation framework and guiding principles applicable across earth science disciplines for testing the capability of models to project future climate change and its impacts. Model test schemes comprising split-sample tests, differential split-sample tests and proxy site tests are discussed in relation to their application for projections by use of single models, ensemble modelling and space-time-substitution and in relation to use of different data from historical time series, paleo data and controlled experiments. We recommend that differential-split sample tests should be performed with best available proxy data in order to build further confidence in model projections.

  • 357. Rex, M
    et al.
    von der Gathen, P
    Harris, N R P
    Lucic, D
    Knudsen, B M
    Braathen, G O
    Reid, S J
    De Backer, H
    Claude, H
    Fabian, R
    Fast, H
    Gil, M
    Kyro, E
    Mikkelsen, I S
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    Smit, H G
    Stahelin, J
    Varotsos, C
    Zaitcev, I
    In situ measurements of stratospheric ozone depletion rates in the Arctic winter 1991/1992: A Lagrangian approach1998In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 103, no D5, p. 5843-5853Article in journal (Refereed)
    Abstract [en]

    A Lagrangian approach has been used to assess the degree of chemically induced ozone loss in the Arctic lower stratosphere in winter 1991/1992. Trajectory calculations are used to identify air parcels probed by two ozonesondes at different points along the trajectories. A statistical analysis of the measured differences in ozone mixing ratio and the time the air parcel spent in sunlight between the measurements provides the chemical ozone loss. Initial results were first described by von der Gathen et al. [1995]. Here we present a more detailed description of the technique and a more comprehensive discussion of the results. Ozone loss rates of up to 10 ppbv per sunlit hour (or 54 ppbv per day) were found inside the polar vortex on the 475 K potential temperature surface (about 19.5 km in altitude) at the end of January. The period of rapid ozone loss coincides and slightly lags a period when temperatures were cold enough for type I polar stratospheric clouds to form. It is shown that the ozone loss occurs exclusively during the sunlit portions of the trajectories. The time evolution and vertical distribution of the ozone loss rates are discussed.

  • 358. Rodhe, H
    et al.
    Langner, Joakim
    SMHI, Research Department, Air quality.
    Gallardo, L
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Global scale transport of acidifying pollutants1995In: Water, Air and Soil Pollution, ISSN 0049-6979, E-ISSN 1573-2932, Vol. 85, no 1, p. 37-50Article in journal (Refereed)
    Abstract [en]

    During the past few years several attempts have been made to use three-dimensional tracer transport models to simulate the global distribution of sulfur and nitrogen compounds from both natural and anthropogenic sources. We review these studies and show examples of estimated distributions of the total deposition of sulfur, oxidized nitrogen and ammonium as well as the pH of precipitation. The simulated patterns are compared with observations. Weaknesses in these estimates resulting from lack of knowledge of emissions, chemical transformations and removal processes are emphasized and discussed. We also show examples of how the models can be used to estimate past and future deposition patterns. In particular, we use the IPCC scenario IS92a to estimate the possible sulfur deposition around the world in the year 2050. A comparison with critical load values for sulfur deposition indicates that substantial parts of South and East Asia are at risk for acidification problems in the future.

  • 359. Roth, Matthias
    et al.
    Jansson, Christer
    SMHI, Research Department, Climate research - Rossby Centre.
    Velasco, Erik
    Multi-year energy balance and carbon dioxide fluxes over a residential neighbourhood in a tropical city2017In: International Journal of Climatology, ISSN 0899-8418, E-ISSN 1097-0088, Vol. 37, no 5, p. 2679-2698Article in journal (Refereed)
  • 360. Ruete, Alejandro
    et al.
    Yang, Wei
    SMHI, Research Department, Hydrology.
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Stenseth, Nils Chr.
    Snall, Tord
    Disentangling effects of uncertainties on population projections: climate change impact on an epixylic bryophyte2012In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 279, no 1740, p. 3098-3105Article in journal (Refereed)
    Abstract [en]

    Assessment of future ecosystem risks should account for the relevant uncertainty sources. This means accounting for the joint effects of climate variables and using modelling techniques that allow proper treatment of uncertainties. We investigate the influence of three of the IPCC's scenarios of greenhouse gas emissions (special report on emission scenarios (SRES)) on projections of the future abundance of a bryophyte model species. We also compare the relative importance of uncertainty sources on the population projections. The whole chain global climate model (GCM)-regional climate model-population dynamics model is addressed. The uncertainty depends on both natural-and model-related sources, in particular on GCM uncertainty. Ignoring the uncertainties gives an unwarranted impression of confidence in the results. The most likely population development of the bryophyte Buxbaumia viridis towards the end of this century is negative: even with a low-emission scenario, there is more than a 65 per cent risk for the population to be halved. The conclusion of a population decline is valid for all SRES scenarios investigated. Uncertainties are no longer an obstacle, but a mandatory aspect to include in the viability analysis of populations.

  • 361.
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    Methods for statistical downscaling of GCM simulations1997Report (Other academic)
    Abstract [en]

    General Circulation Models (GCMs) are used to study the change of climate due to increases in greenhouse gases in the atmosphere. As GCMs operate on !arge spatial scales, and, furthermore, as the GCM-simulated temporal resolution corresponds to monthly averages at best, the usefulness of GCM data in impact studies and other applications is limited. The present-day free troposphere is modeled relatively well by the coarse GCMs, whereas local or even regional characteristics in surface or near-surface climate variables, their variability and the likelihood of extreme events cannot be obtained directly from GCMs. The same is likely true in the case of climate change experiments with GCMs. The results from GCMs can be superimposed on climatological local­ scale time series or interpreted in some other way in order to address the needs of impact studies. This is known as "downscaling" of GCM simulations. In this survey, five different downscaling methods are introduced. These are the conventional, the statistical, the stochastic, the dynamical and the composite methods. Only the statistical and, to a lesser extent, the stochastic approaches are discussed in detail. This survey is a planning document in the SWECLIM program.

  • 362.
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    On the Climate Change debate1999Report (Other academic)
  • 363.
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    Recent Development of a Regional Air/Land Surface/Sea/Ice Coupling Modeling System, “the RCAO Experience”2004In: Fourth Study Conference on BALTEX: Conference Proceedings / [ed] Hans-Jörg Isemer, 2004, p. 148-149Conference paper (Other academic)
  • 364.
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    Reflections on the uncertainty in climate scenarios.2005In: Uncertainty and Active Risk Management and Forestry / [ed] Kristina Blennow, Sveriges lantbruksuniversitet. Institutionen för sydsvensk skogsvetenskap , 2005, p. 22-24Conference paper (Other academic)
  • 365.
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    Växthuseffekten2005Report (Other academic)
    Abstract [sv]

    Växthuseffekten är en grundläggande egenskap hos jordens klimat. Växthuseffekten påverkar den globala strålningsbalansen, dvs. balansen mellan inkommande solstrålning och utgående värmestrålning. Därmed är växthuseffekten viktig för jordens energibalans och således vårt klimat. En naturlig växthuseffekt har så gott som alltid funnits på jorden, tack vare naturligt förekommande vattenånga och koldioxid i atmosfären. Den naturliga växthuseffekten har också varierat genom tiderna. Med den förstärkta växthuseffekten menas idag en ökning i växthuseffekten som är utöver naturliga variationer. Växthuseffektens förstärkning beror på utsläpp av koldioxid och andra växthusgaser som ger ändringar i atmosfärens sammansättning. De klimatförändringar som det resulterar i uppstår när klimatsystemet strävar efter att återskapa strålningsbalansen. Den kanske mest omtalade förändringen är att det blir varmare vid jordens yta. Klimatets förändring vid en förstärkt växthuseffekt är dock komplex och omfattar flera aspekter av klimatsystemet.Denna skrift behandlar växthuseffekten någorlunda grundligt. Den är avsedd för läsare utan fackkunskaper om klimatet. Klimatfrågan är mångfacetterad. Växthuseffekten ingår i dess naturvetenskapliga grund och insikt i växthuseffekten bör kunna bidra till debatten och arbetet med klimatfrågan.

  • 366.
    Rummukainen, Markku
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Bergström, Sten
    SMHI, Research Department, Hydrology.
    Källén, Erland
    Meterologi.
    Moen, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Rodhe, J.
    SMHI.
    Tjernström, M
    SWECLIM - The First Three Years2000Report (Other academic)
    Abstract [en]

    The Swedish Regional Clirnate Modeling Program (SWECLIM) is a 6-year national research effort with the airn of providing the Swedish society with more detailed regional climate scenarios than typically available from international global clirnate rnodel simulations. The background is the perceived further enhancernent of the greenhouse effect that is projected to lead to global warming and other changes m the clirnate systern. SWECLIM provides users within governmental organizations, businesses, political decision-rnaking, as well as media and the general public with expertise and synthesis of clirnate change issues, science, results and the detailed regional climate scenarios, to further the understanding of the future changes, to facilitate planning and realization of rnitigation and/or adaptation measures. This requires developrnent and use of regionalization techniques, regional rnodeling tools and other studies of the relevant regional processes and collected data. Apart from hydrological interpretation done of the clirnate scenarios, SWECLIM does not perfonn irnpact studies. Additional concretization of the clirnate scenarios by externa! groups, who possess branch-specific irnpact assessrnent expertise, is supported and encouraged by SWECLIM.

    This report describes the background of the SWECLIM-prograrn, the work undertaken during program phase 1,l asting from 1997 to June 2000. The model developrnent, the prepared regional climate and water resources scenarios, results from statistical downscaling and basic process studies and data analyses, as well as the interaction with users and media are covered. Finally, a brief introduction to the program phase 2 plans are provided.

  • 367.
    Rummukainen, Markku
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Bergström, Sten
    SMHI, Research Department, Hydrology.
    Persson, Gunn
    SMHI, Professional Services.
    Ressner, Elisabet
    SMHI.
    Anpassning till klimatförändringar: Kartläggning av arbete med sårbarhetsanalyser, anpassningsbehov och anpassningsåtgärder i Sverige till framtida klimatförändring2005Report (Other academic)
    Abstract [sv]

    Denna rapport är resultatet av ett uppdrag från Naturvårdsverket till SMHI (NV dnr 235-5045-04H k), som genomförts under hösten 2004. Syftet är att få en överblick över vilka aktörer som för närvarande är aktiva med att analysera eventuella effekter på samhället och att kartlägga anpassningsbehov. Avsikten är också att få en bild av planerade eller redan genomförda insatser och skyddsåtgärder på grund av en befarad klimatförändring. Kartläggningen omfattar ett flertal svenska myndigheter, företag samt ett antal relevanta bransch- och intresseorganisationer och forskningsfinansiärer.I rapporten redovisas även översiktligt de hinder i anpassningsarbetet som identifierats samt önskemål om förbättrat beslutsunderlag.Slutligen förs en översiktlig diskussion om tänkbara sektoriella effekter avav klimatförändringen, baserad på tidigare avnämarkontakter och forskningsinsatser inom området

  • 368.
    Rummukainen, Markku
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Bergström, Sten
    SMHI, Research Department, Hydrology.
    Persson, Gunn
    SMHI, Professional Services.
    Rodhe, J
    Tjernstrom, M
    The Swedish Regional Climate Modelling Programme, SWECLIM: A review2004In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 33, no 4-5, p. 176-182Article, review/survey (Refereed)
    Abstract [en]

    The Swedish Regional Climate Modelling Programme, SWECLIM, was a 6.5-year national research network for regional climate modeling, regional climate change projections and hydrological impact assessment and information to a wide range of stakeholders. Most of the program activities focussed on the regional climate system of Northern Europe. This led to the establishment of an advanced, coupled atmosphere-ocean-hydrology regional climate model system, a suite of regional climate change projections and progress on relevant data and process studies. These were, in turn, used for information and educational purposes, as a starting point for impact analyses on different societal sectors and provided contributions also to international climate research.

  • 369.
    Rummukainen, Markku
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Graham, Phil
    SMHI, Professional Services.
    Hansson, Ulf
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Ullerstig, Anders
    SMHI, Research Department, Climate research - Rossby Centre.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    PRUDENCE-related regional climate modeling at the SMHI/Rossby Centre2002In: PRUDENCE kick-off meeting / [ed] Jens Hesselbjerg Christensen, Danish Climate Centre DMI, Ministry of Transport , 2002, p. 40-41Conference paper (Other academic)
  • 370.
    Rummukainen, Markku
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Hewitt, Chris
    Jacob, Daniela
    The ENSEMBLES and the BALTEX Projects2007Conference paper (Other academic)
  • 371.
    Rummukainen, Markku
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Isaksen, I S A
    Rognerud, B
    Stordal, F
    A global model tool for three-dimensional multiyear stratospheric chemistry simulations: Model description and first results1999In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 104, no D21, p. 26437-26456Article in journal (Refereed)
    Abstract [en]

    The paper presents a new global modeling tool, Stratospheric Chemical Transport Model 2. It has been developed for effective three-dimensional multiyear stratospheric chemistry studies, featuring an extensive chemistry scheme, heterogeneous processing on sulfate aerosols, and some polar stratospheric cloud processes. The transport algorithm maintains sub-grid-scale distributions and connects vertically the stratospheric layers, even in a coarse vertical grid. The model has been integrated for 49 months, recycling 1 year of precalculated transport from a middle atmosphere general circulation model. One year of daily National Centers for Environmental Prediction global analyses are used as temperatures. Diurnal cycles of photolysis rates are recalculated every 7 days to give interaction with ozone changes. The model is able to describe most of the geographical and seasonal ozone variability and the meridional distributions of ozone, reactive nitrogen, chlorine, and bromine. Stratospheric diurnal cycles for nitrogen, hydrogen, chlorine, and bromine species are captured in detail. The upper stratosphere ozone deficiency, typical to models, is large. Its sensitivity to different ways of tuning are explored. Midlatitude, rather than polar, wintertime processes have so far been the focus in this model tool. The present transport and grid resolution are not suited for realistic simulations at high latitudes. As there is only a limited inclusion of polar stratospheric cloud (PSC) microphysics, chemical processing in the cold polar lower stratosphere also cannot be well simulated. For example, the Antarctic ozone hole is not simulated, but the modeled chemistry should be suitable for warm Arctic winters when type II PSCs and particle sedimentation do not occur.

  • 372.
    Rummukainen, Markku
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Johansson, Daniel J.A.
    Institutionen för energi och miljö, avdelningen för fysisk resursteori, Chalmers.
    Azar, Christian
    Institutionen för energi och miljö, avdelningen för fysisk resursteori, Chalmers.
    Langner, Joakim
    SMHI, Research Department, Air quality.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Smith, Henrik
    Centrum för miljö och klimatforskning, Lunds universitet.
    Uppdatering av den vetenskapliga grunden för klimatarbetet2011Report (Other academic)
    Abstract [sv]

    Det naturvetenskapliga kunskapsläget om klimatförändringarna förbättrats ständigt genom forskningen om klimatsystemet, klimatpåverkan, klimatets variationer och förändringar samt klimateffekter. Kunskapsläget är väletablerat när det gäller den grundläggande fysiken bakom växthuseffekten, liksom att genomsnittstemperaturen vid jordytan stigit de senaste femtio åren. Det är också mycket sannolikt att det mesta av den observerade uppvärmningen beror på mänsklig klimatpåverkan. Samtidigt finns det betydande osäkerheter när det gäller konsekvenserna av klimatförändringarna samt hur mycket utsläppen behöver minska för att man ska nå ett givet klimatmål. Värdet på klimatkänsligheten är den viktigaste faktorn för beräkningar av hur mycket växthusgaser vi kan släppa ut, givet ett visst temperaturmål. Forskningen visar att det behövs stora och snabba utsläppsminskningar för att uppnå tvågradersmålet. För att nå ett lägre temperaturmål, till exempel ett 1,5-gradersmål, är de nödvändiga utsläppsminskningarna än mer omfattande.  För att nå tvågradersmålet med en sannolikhet runt 70 % krävs uppskattningsvis att de globala växthusgasutsläppen minskar i storleksordningen 50‒60 % från år 2000 till 2050, och minskar med nära 100 % till 2100.  För att nå ett 1,5-gradersmål med en sannolikhet runt 70 % krävs globala nollutsläpp redan runt år 2050.  För att nå ett 1,5-gradersmål med en sannolikhet runt 50 % krävs uppskattningsvis att de globala växthusgasutsläppen minskar i storleksordningen 80 % från år 2000 till 2050, och med nära 100 % till 2100. Det är framför allt de kumulativa utsläppen av koldioxid och andra långlivade växthusgaser som räknas när det gäller hur stora klimatförändringarna blir bortom 2100. Ju senare de globala utsläppen kulminerar, och ju högre nivå de då är på, desto större blir utmaningen för att åstadkomma en tillräckligt snabb påföljande utsläppsminskningstakt. Reducerade utsläpp av kortlivade klimatpåverkande ämnen är viktigt främst i ett kortare perspektiv. Det finns olika modeller för hur de globala utsläppsminskningarna kan fördelas mellan olika regioner och länder. Dessa baseras inte på naturvetenskapliga principer utan är beroende av politiska och andra ställningstaganden. För en del länder skiljer sig resultaten mycket beroende på valet av fördelningsmodell. För de flesta industriländer är slutsatsen dock generellt sett densamma: jämfört med idag behöver deras utsläpp minska mycket kraftigt.  För att nå tvågradersmålet med i storleksordningen 70 % sannolikhet krävs, givet en globalt lika per capita fördelning av utsläppen från och med 2050, att utsläppen i Sverige minskar med cirka 70 % från år 2005 till 2050. Den motsvarande siffran för EU är cirka 80 %.  För att nå ett 1,5-gradersmål med i storleksordningen 70 % sannolikhet krävs, givet en globalt lika per capita fördelning av utsläppen från och med 2050, att utsläppen minskar från år 2005 till år 2050 med runt 100 % i Sverige och i EU, och i andra länder.  För att nå ett 1,5-gradersmål med i storleksordningen 50 % sannolikhet krävs, givet en globalt lika per capita fördelning av utsläppen från och med 2050, att utsläppen i Sverige och EU minskar med drygt 90 % från år 2005 till 2050. Nettoutsläpp av koldioxid från avskogning och utrikes luft- och sjöfart ingår inte i dessa uppskattningar. Generellt blir riskerna för allvarliga klimateffekter mindre ju mer ambitiöst temperaturmål som väljs, men riskerna försvinner inte med tvågradersmålet, och inte ens med ett 1,5-gradersmål. Jämfört med IPCC:s AR4 från 2007, har nya forskningsresultat publicerats om klimateffekter. I denna rapport har vi fokuserat på havsnivåhöjningen, havsförsurningen, den biologiska mångfalden samt klimateffekter i Arktis. Jämfört med genomgången av kunskapsläget i AR4 visar nya resultat att den framtida havsnivåhöjningen kan bli större, havsförsurningens effekter på marina ekosystem omfattande och även om en del arter kan vara anpassningsbara, kan världens ekosystem påverkas av skillnader i olika arters sårbarhet för klimatförändringarna. I Arktis sker snabba förändringar. Sammantaget ter sig riskerna för allvarliga klimateffekter större jämfört med AR4. Denna rapport utgår från naturvetenskaplig klimatforskning sedan 2007. Rapporten förordar inte något specifikt temperaturmål, någon specifik utsläppsbana eller specifika policybeslut. Dessa är föremål för politiska avgöranden.

  • 373.
    Rummukainen, Markku
    et al.
    SMHI, Core Services.
    Rockel, Burkhardt
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Christensen, Jens Hesselbjerg
    Reckermann, Marcus
    Twenty-First-Century Challenges in Regional Climate Modeling2015In: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 96, no 8, p. ES135-ES138Article in journal (Refereed)
  • 374.
    Rummukainen, Markku
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Ruosteenoja, K
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Impacts of Climate Change on Renewable Energy Sources: Their role in the Nordic energy system: A comprehensive report resulting from a Nordic Energy Research project2007Report (Other academic)
  • 375.
    Rummukainen, Markku
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    Bjorge, D
    Christensen, J H
    Christensen, O B
    Iversen, T
    Jylha, K
    Olafsson, H
    Tuomenvirta, H
    Regional climate scenarios for use in Nordic water resources studies2003In: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 34, no 5, p. 399-412Article in journal (Refereed)
    Abstract [en]

    According to global climate projections, a substantial global climate change will occur during the next decades, under the assumption of continuous anthropogenic climate forcing. Global models, although fundamental in simulating the response of the climate system to anthropogenic forcing are typically geographically too coarse to well represent many regional or local features. In the Nordic region, climate studies are conducted in each of the Nordic countries to prepare regional climate projections with more detail than in global ones. Results so far indicate larger temperature changes in the Nordic region than in the global mean, regional increases and decreases in net precipitation, longer growing season, shorter snow season etc. These in turn affect runoff, snowpack, groundwater, soil frost and moisture, and thus hydropower production potential, flooding risks etc. Regional climate models do not yet fully incorporate hydrology. Water resources studies are carried out off-line using hydrological models. This requires archived meteorological output from climate models. This paper discusses Nordic regional climate scenarios for use in regional water resources studies. Potential end-users of water resources scenarios are the hydropower industry, dam safety instances and planners of other lasting infrastructure exposed to precipitation, river flows and flooding.

  • 376.
    Rummukainen, Markku
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    Bringfelt, Björn
    SMHI, Research Department, Climate research - Rossby Centre.
    Ullerstig, Anders
    SMHI, Research Department, Climate research - Rossby Centre.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Willen, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    Hansson, Ulf
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    A regional climate model for northern Europe: model description and results from the downscaling of two GCM control simulations2001In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 17, no 5-6, p. 339-359Article in journal (Refereed)
    Abstract [en]

    This work presents a regional climate model, the Rossby Centre regional Atmospheric model(RCA1), recently developed from the High Resolution Limited Area Model (HIRLAM). The changes in the HIRLAM parametrizations, necessary for climate-length integrations, are described. A regional Baltic Sea ocean model and a modeling system for the Nordic inland lake systems have been coupled with RCA1. The coupled system has been used to downscale 10-year time slices from two different general circulation model (GCM) simulations to provide high-resolution regional interpretation of large-scale modeling. A selection of the results from the control runs, i.e. the present-day climate simulations, are presented: large-scale free atmospheric fields, the surface temperature and precipitation results and results for the on-line simulated regional ocean and lake surface climates. The regional model modifies the surface climate description compared to the GCM simulations, but it is also substantially affected by the biases in the GCM simulations. The regional model also improves the representation of the regional ocean and the inland lakes, compared to the GCM results.

  • 377.
    Rummukainen, Markku
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    Ullerstig, Anders
    SMHI, Research Department, Climate research - Rossby Centre.
    Bringfelt, Björn
    SMHI.
    Hansson, Ulf
    SMHI, Research Department, Climate research - Rossby Centre.
    Graham, Phil
    SMHI, Professional Services.
    RCA - Rossby Centre regional Atmospheric climate model: model description and results from the first multi-year simulation1997Report (Other academic)
  • 378.
    Rummukainen, Markku
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    SWECLIM participants, SWECLIM participants
    The Swedish regional climate modeling program 1996-2003: Final report2003Report (Other academic)
    Abstract [en]

    The Swedish Regional Climate Modeling Program (SWECLIM) was a 6.5-year national research effort with the aim of providing the Swedish society with more detailed regional climate scenarios than those available from international global climate mode! simulations. SWECLIM built up a new scientific niche in Sweden, namely that of climate modeling, provided users with regionally detailed climate scenarios, expert advice and synthesis of climate changescience. Regional climate modeling was a major activity, supported with studies of climate processes as well as on observed data on the Baltic Sea, regional hydrology and meteorology. The major impact study part was on hydrological modeling, to elaborate the potential impact of regional-scale climate change on hydropower, dam safety and water resources in general. Other types of impact studies were not performed by SWECLIM itself, but means were provided for outside experts to pursue such knowledge. This fmihered the general understanding of climate change and created new insights into planning processes, especially in Sweden, but also on theNordic, European and global arenas.Examples of practical users of the results were experts and decision-makers within national, regional and local administration, organizations, businesses, politicians, as well as media and the general public. These Swedish cfforts on climate science also contributed to international research and assessment networks, and to the quest for better knowledge base to act on in dealing with the climate problem.This repor! provides the final reporting of the SWECLIM-program, building on earlier reports and complements the results published in scientific journals, as reports, presented in meetings and provided to the general public. The focus here is on the work undertaken <luring program phase 2, lasting from July 2000 to June 2003.

  • 379.
    Rutgersson, Anna
    SMHI, Research Department, Climate research - Rossby Centre.
    A comparison between long term measured and modeled sensible heat and momentum fluxes using a High Resolution Limited Area Model (HIRLAM)2000In: Meteorologische Zeitschrift, ISSN 0941-2948, E-ISSN 1610-1227, Vol. 9, no 1, p. 31-39Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to study the surface fluxes obtained by a High Resolution Limited Area Model (HIRLAM), used for weather forecasts. The question arises whether the quality of the fluxes are high enough to make HIRLAM a proper tool for performing calculations of the water and energy budgets over the Baltic Sea, which is one of the aims of the BALTEX project. Turbulent fluxes modeled by HIRLAM are compared with direct flux measurements over sea for an extended time period. The model is shown to overestimate both sensible heat and momentum flux for the studied period. The sensible heat Aux for the studied period is overestimated by 8.1 W/m(2) and the momentum flux is systematically overestimated by 0.03 kg/ms(2) or 50 %. It is shown that the values of parameters in the surface parameterization scheme can be improved, for example will a lower value of the Charnock's coefficient agree better with the measurements. The sensitivity of the surface scheme to changes in mean parameters is studied. It is also shown that it is of great importance to have correct values of the near surface wind speed and the temperature difference between air and sea to obtain correct fluxes.

  • 380.
    Rutgersson, Anna
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Bumke, K
    Clemens, M
    Foltescu, Valentin
    SMHI.
    Lindau, R
    Michelson, Daniel
    SMHI, Core Services.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Precipitation estimates over the Baltic Sea: Present state of the art2001In: Nordic Hydrology, ISSN 0029-1277, E-ISSN 1996-9694, Vol. 32, no 4-5, p. 285-314Article in journal (Refereed)
    Abstract [en]

    Precipitation is one of the main components in the water balance, and probably the component determined with the greatest uncertainties. In the present paper we focus on precipitation (mainly rain) over the Baltic Sea as a part of the BAL-TEX project to examine the present state of the art concerning different precipitation estimates over that area. Several methods are used, with the focus on 1) interpolation of available synoptic stations; 2) a mesoscale analysis system including synoptic, automatic, and climate stations, as well as weather radar and an atmospheric model; and 3) measurements performed on ships. The investigated time scales are monthly and yearly and also some long-term considerations are discussed. The comparison shows that the differences between most of the estimates, when averaged over an extended period and a larger area, are in the order of 10-20%, which is in the same range as the correction of the synoptic gauge measurements due to wind and evaporation losses. In all data sets using gauge data it is important to include corrections for high winds. To improve the structure of precipitation over sea more focus is to be put on the use of radar data and combinations of radar data and other data. Interpolation methods that do not consider orographic effects must treat areas with large horizontal precipitation gradients with care. Due to the large variability in precipitation in time and space, it is important to use long time periods for climate estimates of precipitation. Ship measurements are a valuable contribution to precipitation information over sea, especially for seasonal and annual time scales.

  • 381.
    Rutgersson, Anna
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Jaagus, Jaak
    Schenk, Frederik
    Stendel, Martin
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Briede, Agrita
    Claremar, Bjorn
    Hanssen-Bauer, Inger
    Holopainen, Jari
    Moberg, Anders
    Nordli, Oyvind
    Rimkus, Egidijus
    Wibig, Joanna
    Recent Change-Atmosphere2015Chapter in book (Other academic)
    Abstract [en]

    This chapter describes observed changes in atmospheric conditions in the Baltic Sea drainage basin over the past 200-300 years. The Baltic Sea area is relatively unique with a dense observational network covering an extended time period. Data analysis covers an early period with sparse and relatively uncertain measurements, a period with well-developed synoptic stations, and a final period with 30+ years of satellite data and sounding systems. The atmospheric circulation in the European/Atlantic sector has an important role in the regional climate of the Baltic Sea basin, especially the North Atlantic Oscillation. Warming has been observed, particularly in spring, and has been stronger in the northern regions. There has been a northward shift in storm tracks, as well as increased cyclonic activity in recent decades and an increased persistence of weather types. There are no long-term trends in annual wind statistics since the nineteenth century, but much variation at the (multi-)decadal timescale. There are also no long-term trends in precipitation, but an indication of longer precipitation periods and possibly an increased risk of extreme precipitation events.

  • 382.
    Rutgersson, Anna
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    Net precipitation over the Baltic Sea during present and future climate conditions2002In: Climate Research (CR), ISSN 0936-577X, E-ISSN 1616-1572, Vol. 22, no 1, p. 27-39Article in journal (Refereed)
    Abstract [en]

    By using a process-oriented ocean model forced with data from a gridded synoptic database, net precipitation values (precipitation minus evaporation) over the Baltic Sea are obtained. For a range of realistic meteorological forcing the average annual value obtained from an 18 yr (1981-1998) simulation ranges between 1100 and 2500 m(3) s(-1). The monthly variations are significant with the highest values occurring in early summer and even negative values in late autumn. Ice is an important factor, and the net precipitation is close to zero in the southern basins with no ice. Calculated net precipitation for a 98 yr period (1901-1998) using river runoff and maximum ice extent indicates that the investigated 18 yr period was wetter than the almost 100 yr climate mean. A realistic climate estimate of net precipitation during the 20th century is estimated to be 1500 +/-1000 m(3) s(-1). The evaluation of 2 present day regional climate simulations indicated high precipitation, low evaporation, and thus excessive net precipitation compared to the climate estimate from this investigation. When simulating the effect of increased greenhouse gases, the change in net precipitation was positive but small due to the compensating effects of increased precipitation and increased evaporation associated with increased temperature and reduced ice.

  • 383.
    Rutgersson, Anna
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Smedman, A S
    Hogstrom, U
    Use of conventional stability parameters during swell2001In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 106, no C11, p. 27117-27134Article in journal (Refereed)
    Abstract [en]

    The situation with swell is of climatological importance over the Baltic Sea since swell is present during as much as 40% of the time. In this study, two periods with unstable and two periods with stable stratification and wind following swell are investigated. Data are taken at a small flat island in the Baltic Sea. During unstable stratification the turbulent structure shows great resemblance to the free convective boundary layer and scales with the boundary layer height. Since surface heat flux is too small to support the high levels of turbulence present, inactive turbulence is probably the dominating source. For the stably stratified layer, there are smaller differences between data with and without swell. The turbulence is mainly transported upward into the atmosphere with the aid of pressure fluctuations induced by the waves. For most of the data with swell the gradients are smaller than for growing sea. During unstable conditions the wind gradients are negative, indicating the presence of a wave-driven wind. The gradients increase with increasing height above the surface. The drag coefficient is smaller than is usually found for both stable and unstable stratification and varies very little with wind and stratification. There are only small variations in the heat transfer coefficients with changing stratification, but they are significantly different for stable and unstable stratification.

  • 384.
    Rutgersson, Anna
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Smedman, A S
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Measured and simulated latent and sensible heat fluxes at two marine sites in the Baltic Sea2001In: Boundary-layer Meteorology, ISSN 0006-8314, E-ISSN 1573-1472, Vol. 99, no 1, p. 53-84Article in journal (Refereed)
    Abstract [en]

    In this study, turbulent heat flux data from two sites within the Baltic Sea are compared with estimates from two models. The main focus is on the latent heat flux. The measuring sites are located on small islands close to the islands of Bornholm and Gotland. Both sites have a wide wind direction sector with undisturbed over-water fetch. Mean parameters and direct fluxes were measured on masts during May to December 1998. The two models used in this study are the regional-scale atmospheric model HIRLAM and the ocean model PROBE-Baltic. It is shown that both models overestimate the sensible and latent heat fluxes. The overestimation can, to a large extent, be explained by errors in the air-water temperature and humidity differences. From comparing observed and modelled data, the estimated 8-month mean errors in temperature and humidity are up to 1 degreesC and 1 g kg(-1),respectively. The mean errors in the sensible and latent heat fluxes for the same period are approximately 15 and 30 W m(-2), respectively. Bulk transfer coefficients used for calculating heat and humidity fluxes at the surface were shown to agree rather well with the measurements, at least for the unstable data. For stable stratification, the scatter in data is generally large, and it appears that the bulk formulation chosen overestimates turbulent heat fluxes.

  • 385. Rutter, Nick
    et al.
    Essery, Richard
    Pomeroy, John
    Altimir, Nuria
    Andreadis, Kostas
    Baker, Ian
    Barr, Alan
    Bartlett, Paul
    Boone, Aaron
    Deng, Huiping
    Douville, Herve
    Dutra, Emanuel
    Elder, Kelly
    Ellis, Chad
    Feng, Xia
    Gelfan, Alexander
    Goodbody, Angus
    Gusev, Yeugeniy
    Gustafsson, David
    Hellstroem, Rob
    Hirabayashi, Yukiko
    Hirota, Tomoyoshi
    Jonas, Tobias
    Koren, Victor
    Kuragina, Anna
    Lettenmaier, Dennis
    Li, Wei-Ping
    Luce, Charlie
    Martin, Eric
    Nasonova, Olga
    Pumpanen, Jukka
    Pyles, R. David
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Sandells, Melody
    Schaedler, Gerd
    Shmakin, Andrey
    Smirnova, Tatiana G.
    Staehli, Manfred
    Stoeckli, Reto
    Strasser, Ulrich
    Su, Hua
    Suzuki, Kazuyoshi
    Takata, Kumiko
    Tanaka, Kenji
    Thompson, Erin
    Vesala, Timo
    Viterbo, Pedro
    Wiltshire, Andrew
    Xia, Kun
    Xue, Yongkang
    Yamazaki, Takeshi
    Evaluation of forest snow processes models (SnowMIP2)2009In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 114, article id D06111Article, review/survey (Refereed)
    Abstract [en]

    Thirty-three snowpack models of varying complexity and purpose were evaluated across a wide range of hydrometeorological and forest canopy conditions at five Northern Hemisphere locations, for up to two winter snow seasons. Modeled estimates of snow water equivalent (SWE) or depth were compared to observations at forest and open sites at each location. Precipitation phase and duration of above-freezing air temperatures are shown to be major influences on divergence and convergence of modeled estimates of the subcanopy snowpack. When models are considered collectively at all locations, comparisons with observations show that it is harder to model SWE at forested sites than open sites. There is no universal "best'' model for all sites or locations, but comparison of the consistency of individual model performances relative to one another at different sites shows that there is less consistency at forest sites than open sites, and even less consistency between forest and open sites in the same year. A good performance by a model at a forest site is therefore unlikely to mean a good model performance by the same model at an open site (and vice versa). Calibration of models at forest sites provides lower errors than uncalibrated models at three out of four locations. However, benefits of calibration do not translate to subsequent years, and benefits gained by models calibrated for forest snow processes are not translated to open conditions.

  • 386.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    CO2- and aerosol-induced changes in vertically integrated zonal momentum budget in a GCM experiment1998In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 11, no 4, p. 625-639Article in journal (Refereed)
    Abstract [en]

    The German Climate Computing Center recently conducted a model experiment in which separate runs simulate the climatic response to increasing CO2 alone and to increasing CO2 together with direct radiative forcing by sulfate aerosols. One of the variables that shows interesting differences between the different runs is the nearsurface zonal-mean zonal wind. As compared with the control run, the midlatitude surface westerlies intensify and shift poleward in the CO2-only run in both hemispheres in both the northern winter (DJF) and summer (JJA). However, the aerosol forcing moderates these changes in general and, in particular, reverses the pattern of change in the Northern Hemisphere in JJA. Consistent differences between the various runs occur in the meridional distribution of sea level pressure. The origin of these simulated changes is studied by using the vertically integrated zonal-mean zonal momentum budget, utilizing the intimate linkage between the low-level wind and the surface stress and the close time-mean balance between the surface stress and the other terms in the budget. Regardless of the forcing used, momentum convergence in transient eddies is found to be the dominant agent of change in the extratropical Southern Hemisphere and in the Northern Hemisphere midlatitudes in JJA, In particular, the changes in the contribution of high-pass transients are relatively large and they seem to be qualitatively traceable to the changes in the tropospheric meridional temperature gradient. In the northern extratropics in DJE stationary eddies make an even larger contribution than the transients.

  • 387.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    CO2-induced changes in atmospheric angular momentum in CMIP2 experiments2003In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 16, no 1, p. 132-143Article in journal (Refereed)
    Abstract [en]

    The response of atmospheric angular momentum to a gradual doubling of CO2 is studied using 16 model experiments participating in the second phase of the Coupled Model Intercomparison Project (CMIP2). The relative angular momentum associated with atmospheric zonal winds increases in all but one of the models, although the magnitude of the change varies widely. About 90% of the 16-model mean increase comes from increasing westerly winds in the stratosphere and the uppermost low-latitude troposphere above 200 hPa. This increase in westerly winds reflects a steepening of the meridional temperature gradient near the tropopause and in the upper troposphere. The simulated temperature gradient at this height increases partly as an indirect consequence of the poleward decrease in the tropopause height, and partly because convection induces a maximum in warming in the tropical upper troposphere. The change in the omega angular momentum associated with the surface pressure distribution is in most models smaller than the change in the relative angular momentum, although its exact value is sensitive to the method of calculation.

  • 388.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    CO2-induced changes in interannual temperature and precipitation variability in 19 CMIP2 experiments2002In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 15, no 17, p. 2395-2411Article in journal (Refereed)
    Abstract [en]

    CO2-induced changes in the interannual variability of monthly surface air temperature and precipitation are studied using 19 model experiments participating in the second phase of the Coupled Model Intercomparison Project (CMIP2). The magnitude of variability in the control runs appears generally reasonable, but it varies a great deal between different models, almost all of which overestimate temperature variability on low-latitude land areas. In most models the gradual doubling of CO2 leads to a decrease in temperature variability in the winter half-year in the extratropical Northern Hemisphere and over the high-latitude Southern Ocean. Over land in low latitudes and in northern midlatitudes in summer, a slight tendency toward increased temperature variability occurs. The standard deviation of monthly precipitation increases, on average, where the mean precipitation increases but also does so in some areas where the mean precipitation decreases slightly. The coefficient of variation of precipitation (i.e., the ratio between the standard deviation and the mean) also tends to increase in most areas, especially where the mean precipitation decreases. However, the changes in variability are less similar between the 19 experiments than the changes in mean temperature and precipitation, at least partly because they have a much lower signal-to-noise ratio. In addition, the changes in the standard deviation of monthly temperature are generally much smaller than the time-mean warming, which suggests that future changes in the extremes of interannual temperature variability will be largely determined by the latter.

  • 389.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    CO2-induced climate change in CMIP2 experiments: Quantification of agreement and role of internal variability2001In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 14, no 9, p. 2088-2104Article in journal (Refereed)
    Abstract [en]

    CO2-induced changes in surface air temperature, precipitation, and sea level pressure are compared between model experiments participating in the second phase of the Coupled Model Intercomparison Project (CMIP2). A statistical formalism is applied, in which the average squared amplitude of the simulated climate changes is divided into a common signal and variances associated with internal variability and model differences. In the 20-yr period centered at the doubling of CO2 and for a set of 14-15 models, the dimensionless global relative agreement on gridbox-scale annual mean climate changes is 0.89 for surface air temperature but only 0.22 for precipitation and 0.46 for sea level pressure. A majority of the interexperiment differences are attributed to model differences; the contribution of internal variability to the differences in change is estimated as 16% for temperature, 34% for precipitation, and 32% for sea level pressure. For seasonal rather than annual climate changes, the agreement is lower and the contribution of internal variability to the interexperiment variance larger. Likewise, the relative agreement is worse and internal variability in relative terms more important earlier during the transient experiments than around the doubling of CO2. Conversely, when climate changes are averaged over larger areas than individual grid boxes, the relative agreement improves with increasing averaging domain (especially with precipitation and temperature) and the impact of internal variability decreases.

  • 390.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    CO2-induced climate change in northern Europé: comparison of 12 CMIP2 experiments.2000Report (Other academic)
  • 391.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    Internal variability as a cause of qualitative intermodel disagreement on anthropogenic climate changes1999In: Journal of Theoretical and Applied Climatology, ISSN 0177-798X, E-ISSN 1434-4483, Vol. 64, no 1-2, p. 1-13Article in journal (Refereed)
    Abstract [en]

    The qualitative agreement of two climate models, HADCM2 and ECHAM3, on the response of surface climate to anthropogenic climate forcing in the period 2020-2049 is studied. Special attention is paid to the role of internal climate variability as a source of intermodel disagreement. After illustrating the methods in an intermodel comparison of simulated changes in June-August mean precipitation, some global statistics are presented. Excluding surface air temperature, the four-season mean proportion of areas in which the two models agree on the sign of the climatic response is only 53-60% both for increases in CO2 alone and for increases in CO2 together with direct radiative forcing by sulphate aerosols, but somewhat larger, 59-70% for the separate aerosol effect. In areas where the response is strong (at least twice the standard error associated with internal variability) in both models, the agreement is better and the contrast between the different forcings becomes more marked. The proportion of agreement in such areas is 57-75% for the response to increases in CO2 alone, 64-84% for the response to combined CO2 and aerosol forcing, and as high as 88-94% for the separate aerosol effect. The relatively good intermodel agreement for aerosol-induced climate changes is suggested to be associated with the uneven horizontal distribution of aerosol forcing.

  • 392.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    Model-simulated CO2-induced changes in seasonal precipitation extremes2002In: INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE, 2002, p. 66-Conference paper (Other academic)
  • 393.
    Räisänen, Jouni
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Alexandersson, Hans
    SMHI.
    A probabilistic view on recent and near future climate change in Sweden2003In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 55, no 2, p. 113-125Article in journal (Refereed)
    Abstract [en]

    The decade 1991-2000 was warm and wet in Sweden, with 10-station mean temperature 0.8 degreesC above and 20-station mean precipitation 6% above the mean for 1961-1990. Here we study the question if such changes should be seen as a symptom of anthropogenic climate change or if they might be of purely natural origin. Using the control simulations of 19 atmosphere-ocean general circulation models and taking into account difference's between the simulated and observed interannual variability, we estimate that the recent increase in temperature and that in precipitation had both about a 6-7% chance to occur solely as a result of natural variability. Using the corresponding simulations with increasing CO2, we further estimate that the anthropogenic forcing raised the probability of the observed changes to occur to 23% for the increase in temperature and to 14% for the increase in precipitation. About half of the warming and about 30% of the increase in precipitation appear to be explained by anthropogenic forcing. The seasonal aspects of observed and simulated climate change are also discussed, with special emphasis on winter, when the observed warming has been much larger than expected from the model simulations. Finally, a probabilistic forecast for the Swedish climate in the first decade of the 21st century suggests a 95% (87%) possibility of warmer (wetter) annual mean conditions than in 1961-1990 on the average. One of the caveats in our analysis is that the model simulations exclude variations in solar and volcanic activity, the effects of which might not be fully covered by our resealing of interannual variability.

  • 394.
    Räisänen, Jouni
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Simulation of present-day climate in Northen Europé in the HadCM2 OAGCM1998Report (Other academic)
  • 395.
    Räisänen, Jouni
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Hansson, U
    Ullerstig, Anders
    SMHI, Research Department, Climate research - Rossby Centre.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Graham, Phil
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Willen, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    European climate in the late twenty-first century: regional simulations with two driving global models and two forcing scenarios2004In: Climate Dynamics, ISSN 0930-7575, E-ISSN 1432-0894, Vol. 22, no 1, p. 13-31Article in journal (Refereed)
    Abstract [en]

    A basic analysis is presented for a series of regional climate change simulations that were conducted by the Swedish Rossby Centre and contribute to the PRUDENCE (Prediction of Regional scenarios and Uncertainties for Defining EuropeaN Climate change risks and Effects) project. For each of the two driving global models HadAM3H and ECHAM4/OPYC3, a 30-year control run and two 30-year scenario runs (based on the SRES A2 and B2 emission scenarios) were made with the regional model. In this way, four realizations of climate change from 1961-1990 to 2071-2100 were obtained. The simulated changes are larger for the A2 than the B2 scenario (although with few qualitative differences) and in most cases in the ECHAM4/OPYC3-driven (RE) than in the HadAM3H-driven (RH) regional simulations. In all the scenario runs, the warming in northern Europe is largest in winter or late autumn. In central and southern Europe, the warming peaks in summer when it locally reaches 10 degreesC in the RE-A2 simulation and 6-7 degreesC in the RH-A2 and RE-B2 simulations. The four simulations agree on a general increase in precipitation in northern Europe especially in winter and on a general decrease in precipitation in southern and central Europe in summer, but the magnitude and the geographical patterns of the change differ markedly between RH and RE. This reflects very different changes in the atmospheric circulation during the winter half-year, which also lead to quite different simulated changes in windiness. All four simulations show a large increase in the lowest minimum temperatures in northern, central and eastern Europe, most likely due to reduced snow cover. Extreme daily precipitation increases even in most of those areas where the mean annual precipitation decreases.

  • 396.
    Räisänen, Jouni
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Hansson, Ulf
    SMHI, Research Department, Climate research - Rossby Centre.
    Ullerstig, Anders
    SMHI, Research Department, Climate research - Rossby Centre.
    Doescher, Ralf
    SMHI, Research Department, Climate research - Rossby Centre.
    Graham, Phil
    SMHI, Professional Services.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Samuelsson, Patrick
    SMHI, Research Department, Climate research - Rossby Centre.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    GCM driven simulations of recent and future climate with the Rossby Centre coupled atmosphere - Baltic Sea regional climate model RCAO2003Report (Other academic)
    Abstract [en]

    A series of six general circulation model (GCM) driven regional climate simulations made at the Rossby Centre, SMHI, during the year 2002 are documented. For both the two driving GCMs HadAM3H andECHAM4/OPYC3, a 30-year (1961-1990) control run and two 30-year (2071-2100) scenario runs have been made. The scenario runs are based on the IPCC SRES A2 and B2 forcing scenarios. These simulations were made at 49 km atmospheric resolution and they are part of the European PRUDENCE project.Many aspects of the simulated control climates compare favourably with observations, but some problems are also evident. For example, the simulated cloudiness and precipitation appear generally too abundant in northern Europe (although biases in precipitation measurements complicate the interpretation), whereas too clear and dry conditions prevail in southern Europe. There is a lot of similarity between the HadAM3Hdriven (RCAO-H) and ECHAM4/OPYC3-driven (RCAO-E) control simulations, although the problems associated with the hydrological cycle and cloudiness are somewhat larger in the latter.The simulated climate changes (2071-2100 minus 1961-1990) depend on both the forcing scenario (the changes are generally larger for A2 than B2) and the driving global model (the largest changes tend to occur in RCAO-E). In all the scenario simulations, the warming in northern Europe is largest in winter or autumn. In central and southern Europe, the warming peaks in summer and reaches in the RCAO-E A2 simulation locally 10°C. The four simulations agree on a general increase in precipitation in northern Europe especiallyin winter and on a general decrease in precipitation in southern and central Europe in summer, but the magnitude and the geographical patterns of the change differ a lot between RCAO-H and RCAO-E. Thisreflects very different changes in the atmospheric circulation during the winter half-year, which also have a large impact on the simulated changes in windiness. A very large increase in the lowest minimumtemperatures occurs in a large part of Europe, most probably due to reduced snow cover. Extreme daily precipitation increases even in most of those areas where the mean annual precipitation decreases.

  • 397.
    Räisänen, Jouni
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Joelsson, Rune
    SMHI, Research Department, Climate research - Rossby Centre.
    Changes in average and extreme precipitation in two regional climate model experiments2001In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 53, no 5, p. 547-566Article in journal (Refereed)
    Abstract [en]

    Two regional climate model experiments for northern and central Europe are studied focussing on greenhouse gas-induced changes in heavy precipitation. The average yearly maximum one-day precipitation P-max shows a general increase in the A hole model domain in both experiments, although the mean precipitation P-mcan decreases in the southern part of the area, especially in one of the experiments. The average yearly maximum six-hour precipitation increases even more than the one-day P-max suggesting a decrease in the timescale of heavy precipitation. The contrast between the P-max, and P-max changes in the southern part of the domain and the lack of such a contrast further north are affected by changes in wet-day frequency that stem, at least in part. from changes in atmospheric circulation. However, the yearly extremes of precipitation exhibit a larger percentage increase than the average wet-day precipitation. The signal-to-noise aspects of the model results are also studied in some detail. The 44 km grid-box-scaie changes in P-max are very heavily affected by inter-annual variability, with an estimated standard error ;of about 20% for the 10-year mean changes. However. the noise in P-max decreases sharply toward larger horizontal scales, and large-area mean changes in P-max can be estimated with similar accuracy to those in P-mcan Although a horizontal averaging of model results smooths out the small-scale details in the true climate change signal as well, this disadvantage is, in the case of P-max changes, much smaller than the advantage of reduced noise.

  • 398.
    Räisänen, Jouni
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Palmer, T N
    A probability and decision-model analysis of a multimodel ensemble of climate change simulations2001In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 14, no 15, p. 3212-3226Article in journal (Refereed)
    Abstract [en]

    Because of the inherent uncertainties in the computational representation of climate and because of unforced chaotic climate variability, it is argued that climate change projections should be expressed in probabilistic form. In this paper, 17 Coupled Model Intercomparison Project second-phase experiments sharing the same gradual increase in atmospheric CO2 are treated as a probabilistic multimodel ensemble projection of future climate. Tools commonly used for evaluation of probabilistic weather and seasonal forecasts are applied to this climate change ensemble. The probabilities of some temperature- and precipitation-related events defined for 20-yr seasonal means of climate are first studied. A cross-verification exercise is then used to obtain an upper estimate of the quality of these probability forecasts in terms of Brier skill scores, reliability diagrams, and potential economic value. Skill and value estimates are consistently higher for temperature- related events (e.g., will the 20-yr period around the doubling of CO2 be at least 1 degreesC warmer than the present?) than for precipitation-related events (e.g., will the mean precipitation decrease by 10% or more?). For large enough CO2 forcing, however, probabilistic projections of precipitation-related events also exhibit substantial potential economic value for a range of cost-loss ratios. The treatment of climate change information in a probabilistic rather than deterministic manner (e.g., using the ensemble consensus forecast) can greatly enhance its potential value.

  • 399.
    Räisänen, Jouni
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    Ullerstig, Anders
    SMHI, Research Department, Climate research - Rossby Centre.
    Downscaling of greenhouse gas induced climate change in two GCMs with the Rossby Centre regional climate model for northern Europe2001In: Tellus. Series A, Dynamic meteorology and oceanography, ISSN 0280-6495, E-ISSN 1600-0870, Vol. 53, no 2, p. 168-191Article in journal (Refereed)
    Abstract [en]

    Two 2 x 10-year climate change experiments made with the Rossby Centre regional Atmospheric climate model(RCA) are reported. These two experiments are driven by boundary data from two global climate change simulations, one made with HadCM2 and the other with ECKAM4/OPYC3, in which the global mean warming is virtually the same, 2.6 degreesC. The changes in mean temperature and precipitation show similarities (including broadly the same increase in temperature and in northern Europe a general increase in annual precipitation) as well as differences between the two RCA experiments. These changes are strongly governed by the driving GCM simulations. Even on the RCA grid box scale, the differences in change between RCA and the driving GCM are generally smaller than the differences between the two GCMs. Typically about a half of the local differences between the two RCA simulations are attributed to noise generated by internal variability, which also seems to explain a substantial part of the RCA-GCM differences particularly for precipitation change. RCA includes interactive model components for the Baltic Sea and inland lakes of northern Europe. The simulated changes in these water bodies are discussed with emphasis on the wintertime ice conditions. Comparison with an earlier RCA experiment indicates that a physically consistent treatment of these water bodies is also of importance for the simulated atmospheric climate change.

  • 400.
    Räisänen, Jouni
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    Ullerstig, Anders
    SMHI, Research Department, Climate research - Rossby Centre.
    Bringfelt, Björn
    SMHI.
    Hansson, Ulf
    SMHI, Research Department, Climate research - Rossby Centre.
    Willén, Ulrika
    SMHI, Research Department, Climate research - Rossby Centre.
    The First Rossby Centre Regional Climate Scenario - Dynamical Downscaling of CO2-induced Climate Change in the HadCM2 GCM1999Report (Other academic)
5678910 351 - 400 of 493
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