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  • 101.
    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)
    Abstract [en]

    Results of the first 10-year climate change experiment made with the Rossby Centre regional climate model (RCA) are described. The boundary data for this experiment were derived from two simulations with the .global HadCM2 ocean-atmosphere GCM, a control run anda scenario run with 150% higher equivalent CO2 and 2.6°C higher global mean surface air temperature.

    Some of the climate changes (scenario run - control run) simulated by RCA are substantial. The annual mean temperature in the Nordic region increases by roughly 4°C, with largest warming in winter. Annual absolute minimum temperatures increase even more than the winter mean temperature, presumably due to greatly reduced snow and ice cover. Precipitation is also simulated to increase in northern Europe, locally by 40% in the annual mean in Swedish Lappland. The larger time mean precipitation is accompanied by a marked increase in the number of days with heavy precipitation.

    The large-scale temperature and precipitation changes simulated by RCA are similar to those in HadCM2. Unlike HadCM2, however, RCA simulates a strong local maximum of wintertime warming over the northern parts of the Baltic Sea. This is caused by radically reduced ice cover, but the crude treatment of the Baltic Sea and its ice even in RCA complicates the interpretation. Large differences between the models occur in the simulated changes of winter mean total cloudiness and near-surface wind speed, demonstrating the sensitivity of these to differences in resolution and/or physical parameterizations.

    The significance of the simulated climate changes against interannual variability depends on the parameter considered. Of highest statistical significance are changes in surface air temperature and strongly temperature-related variables such as snow and ice cover. In general, changes in annual means are more commonly significant than those in seasonal means. The impact of the limited averaging period is also studied by comparing the 10-year mean climate changes simulated by the driving HadCM2 mode! with climate changes inferred from much longer HadCM2 integrations.

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  • 102.
    Sahlberg, Jörgen
    et al.
    SMHI, Professional Services.
    Törnevik, Håkan
    SMHI.
    A study of large scale cooling in the Bay of Bothnia1980Report (Other academic)
    Abstract [en]

    This report treats the large scale cooling in the Bay ofBothnia . From the heat conduction equation an expressionis derived describing the changes in water temperaturea s a function of net longwave radiation, sensible heatflux and latent heat flux. The water temperature is definedas the mean water temperature in the central basin. Themeteorological and water temperature data, needed for theheat flux calculations , have been extracted from analysedweather maps a nd analysed water temperature maps. Twocooling periods have been investigated. The first 1972/ 73had a slow decrease in the water temperature while in thesecond , 1973/74 , the cooling was rapid . The result showsa good agreement between calculated and analysed watertemperature .

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  • 103.
    Schoeffler, Pierre
    SMHI.
    Dissipation, dispersion and stability of numerical schemes for advection and diffusion1982Report (Other academic)
    Abstract [en]

    Advection and diffusion are fundamental processes in the atmosphere. They express the permanent balance between inertial and viscous forces. Some numerical treatments the equations, describing these processes, are presented. Three spatial discretization techniques, second order finite differences, linear finite element and pseudospectral, are tested in connection with a finite difference time integration. Dissipation, dispersion and stability of the numerical schemes for the linearized equations are investigated both theoretically and with the help of numerical simulations. Results with non-linear equations are also shown.

    In conclusion there is a presentation of the less conventional Monte Carlo method for diffusion.

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  • 104.
    Segersson, David
    SMHI, Research Department, Air quality.
    Numerical Quantification of Driving Rain on Buildings2003Report (Other academic)
    Abstract [en]

    Rain, which is given a horizontal velocity component by the influence of wind, is termed winddriven or driving rain. Driving rain is one of the main sources to the amount of moisture a building is exposed to, and thereby contributes to the processes deteriorating the building envelope. Examples of damages to the building envelope that the onslaught of driving rain directly or indirectly can contribute to are: cracks caused by the freezing of water absorbed in the facade, mould or rot, corrosion of concrete reinforcements and soiling patterns. Knowledge about the exposure of a building to driving rain is needed in order to minimise the deteriorating processes, and thus contributes to ensure a satisfactory performance of the building design.

    This work is meant as an introduction to the field of numerical quantification of driving rain on buildings. Focus is set on three-dimensional simulation of the wind flow and raindrop trajectories using CFD (Computational Fluid Dynamics). lnterest is also paid to some specific properties of rainfall, such as drop size distributions and drag forces on raindrops. The study includes a detailed description of a method to calculate the driving rain distribution on a building, as well as application of the method to a rectangular facade. A qualitative evaluation of the results indicates that the method can be used to calculate the mean distribution of driving rain on simple geometries with sufficient accuracy.

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  • 105.
    Strandberg, Gustav
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Bärring, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Hansson, Ulf
    SMHI, Research Department, Climate research - Rossby Centre.
    Jansson, Christer
    SMHI, Research Department, Climate research - Rossby Centre.
    Jones, Colin
    SMHI, Research Department, Climate research - Rossby Centre.
    Kjellström, Erik
    SMHI, Research Department, Climate research - Rossby Centre.
    Kupiainen, Marco
    SMHI, Research Department, Climate research - Rossby Centre.
    Nikulin, Grigory
    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.
    CORDEX scenarios for Europe from the Rossby Centre regional climate model RCA42015Report (Other academic)
    Abstract [en]

    This report documents Coordinated Regional Downscaling Experiment (CORDEX) climate model simulations at 50 km horizontal resolution over Europe with the Rossby Centre regional atmospheric model (RCA4) for i) a ERA-Interim-driven (ERAINT) simulation used to evaluate model performance in the recent past climate, ii) historical simulations of the recent decades with forcing from nine different global climate models (GCMs) and iii) future scenarios RCP 4.5 and RCP 8.5 forced by the same nine different GCMs. Those simulations represent a subset of all CORDEX simulations produced at the Rossby Centre and a general conclusion drawn at the Rossby Centre is that such large ensembles could not have been produced without the establishment of an efficient production chain as outlined here. The first part of this report documents RCA4 and its performance in a perfect boundary simulation where ERAINT was downscaled. RCA4 is to a large extent replicating the large-scale circulation in ERAINT, but some local biases in mean sea level pressure appear. In general the seasonal cycles of temperature and precipitation are simulated in relatively close agreement to observations. Some biases occur, such as too much precipitation in northern Europe and too little in the south. In winter, there is also too much precipitation in eastern Europe. Temperatures are generally biased low in northern Europe and in the Mediterranean region in winter while overestimated temperatures are seen in southeastern Europe in winter and in the Mediterranean area in summer. RCA4 performs generally well when simulating the recent past climate taking boundary conditions from the GCMs. A large part of the RCA4 simulated climate is attributed to the driving GCMs, but RCA4 creates its own climate inside the model domain and adds details due to higher resolution. All nine downscaled GCMs share problems in their representation of the large-scale circulation in winter. This feature is inherited in RCA4. The biases in large-scale circulation induce some biases in temperature and precipitation in RCA4. The climate change signal in the RCP 4.5 and RCP 8.5 ensembles simulated by RCA4 is very similar to what has been presented previously. Both scenarios RCP 4.5 and RCP 8.5 project Europe to be warmer in the future. In winter the warming is largest in northern Europe and in summer in southern Europe. The summer maximum daily temperature increases in a way similar to summer temperature, but somewhat more in southern Europe. The winter minimum daily temperature in northern Europe is the temperature that changes the most. Precipitation is projected to increase in all seasons in northern Europe and decrease in southern Europe. The largest amount of rainfall per day (and per seven day period) is projected to increase in almost all of Europe and in all seasons. At the same time the longest period without precipitation is projected to be longer in southern Europe. Small changes in mean wind speed are generally projected. There are, however, regions with significant changes in wind. The ensemble approach is a way to describe the uncertainties in the scenarios, but there are other possible ensembles using other models which would give other results. Still, the ensemble used here is found to be similar enough to these other possible ensembles to be representative of the whole set of GCMs. Dynamical downscaling using RCA4 changes the climate change signal, and the ensemble spread is sometimes reduced, but the ensemble of nine RCA4 simulations, using different GCMs, is considered to be representative of the full ensemble. All scenarios agree on a climate change pattern; the amplitude of the change is determined by the choice of scenario. The relative importance of the chosen scenario increases with time.

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  • 106.
    Svensson, Jan
    SMHI.
    Remote sensing of atmospheric temperature profiles by TIROS Operational Vertical Sounder1985Report (Other academic)
    Abstract [en]

    A new inversion method for temperature retrievals from satellite soundings isdescribed. The basis of the inversion method is the radiative transfer equation.Surface observations of temperature, humidity and pressure are alsoincluded. Basis splines have been used to represent the temperature and humidityprofiles. Some physical constraints are also included. This leads toalinear least-squares problem with linear inequality constraints. The extensiontoa nonlinear least-squares problem is discussed.

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  • 107.
    Taesler, Roger
    SMHI, Research Department.
    Köldperioden av olika längd och förekomst1986Report (Other academic)
  • 108.
    Thompson, Thomas
    et al.
    SMHI.
    Udin, Ingemar
    SMHI, Core Services.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    Sea surface temperatures in waters surrounding Sweden1974Report (Other academic)
    Abstract [en]

    One of the sub-projects within the sea ice research programme carried out at SMHI deals with the thermodynamics of the sea and the ice. In these studies the sea surface temperature plays a fundamental r ole. During the latest years considerable efforts have been made in order to obtain more temperature observations, in particular from the open sea. Various vessels have been equipped with new instruments, the collection of observations improved, the sea surface temperature distribution analyzed every second day and all information stored in digital form.

    The instruments are discribed and their specifications given in the report. Various observational methods are compared and examples of sea surface temperature analyses for the period July 1973 - July 1974  illustrating yearly variations, tendency to circulation patterns, coastal effects, up-welling etc. are given.

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  • 109. Tjernström, M
    et al.
    Rummukainen, Markku
    SMHI, Research Department, Climate research - Rossby Centre.
    Bergström, Sten
    SMHI, Research Department, Hydrology.
    Rodhe, J.
    SMHI.
    Persson, Gunn
    SMHI, Professional Services.
    Klimatmodellering och klimatscenarier ur SWECLIMs perspektiv2003Report (Other academic)
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  • 110.
    Törnevik, Håkan
    SMHI.
    An aerobiological model for operational forecasts of pollen concentration in the air1982Report (Other academic)
    Abstract [en]

    Roughly 10-15% of the population in Sweden suffers from allergic reactions from airborne pollen. One of the most common allergene pollen is the one from birch (Betula verrucosa and Betula pubescens). The pollen season is limited to a period of 3-4 weeks in spring. However, the start of the season varies at most ±2 weeks from year to year . The variation of pollen dispersion during the season also varies substantially between different years. Hypothesizing that these variations are related to exogenous processes, especially climatic influence, a simplified prediction model that simulates the aerobiological process has been developed. The model has been proven to give satisfactory results and was operationally tested for the Stockholm area during springtime 1981 and 1982.

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  • 111.
    Udin, Ingemar
    et al.
    SMHI, Core Services.
    Mattisson, Ingemar
    SMHI.
    Havsis- och snöinformation ur datorbearbetade satellitdata – en modellstudie1979Report (Other academic)
    Abstract [en]

    Computer programs have been developed for handling of NOAA VHRR digital data. The programs include geometric corrections, presentation of calibration data, derivation of data, variation of grey scales, different presentation forms etc. A SAAB D23 computer has been used for the computations. Line printer has mostly been used for presentation of data, but also electrostatic plotter and ink jet plotter have been used. The analogue VHRR data was digitized at the Swedish Defense Rese·arch Board. The soft ware has mainly been applied to sea ice and snow studies but also in a less degree to studies of sea surface temperature and examination of data, which was supposed to be the oil spill at platform Bravo ·in the Ekofisk area. Digital processed satellite data are more useful than photographic pictures both for sea ice and snow mapping. Quantification of snow cover and sorne ice parameters is possible, but for many purposes a multispectral data analysis is necessary in order to avoid false information. A short sea ice study with computer processed LANDSAT data has also been carried out. The soft ware used was developed at the Swedish Defense Research Board.

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  • 112.
    Undén, Per
    Meterologi.
    The Swedish Limited Area Model: Part A. Formulation1982Report (Other academic)
    Abstract [en]

    This report is a description of the Swedish limited area model, at present (June 1982) tested operationally with encouraging results. The models is based on the ECMWF-model, although some simplifications have been done in the physic package. The major differences are that this model uses a simpler radiation scheme although a diurnal cycle is included, and for the convection scheme a simple adjustment is used.

    To avoid problems with the poles the grid has been trans formed, and a fictious north-pole is placed at 180° longitude and 30° latitude. A relaxation zone (Kållberg, 1977) is used with a width of 8 points, where the solution of the model and the boundaries are weighted together.

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  • 113.
    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.

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  • 114.
    Zengmao, Wu
    SMHI.
    Numerical analysis of initialization procedure in a two-dimensional lake breeze model1986Report (Other academic)
    Abstract [en]

    This paper describes the dynamic initialization procedures of a two-dimensional lake breeze model, based on radiosonde data at one site. Three approaches of initialization have been tested. The results prove that dynamical balance between mass and momentum fields can be obtained from unbalanced, inexact first guesses, but there is an obvious difference between resufts calculated with each initialization procedure. In comparison, we found that the approach, onedimensional dynamic initialization with nudging, probably is preferable to the others.

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  • 115.
    Zengmao, Wu
    SMHI.
    Numerical study of lake-land breeze over Lake Vättern, Sweden1986Report (Other academic)
    Abstract [en]

    This paper describes a two- dimensional lake breeze model With turbulent energy closure. The simulated results show that (1) the front of the lake breeze progresses inland faster in the late afternoon than at the fully developed stage;(2) the lake breeze and land breeze have larger extension offshore than inland. The acceleration of the front in the declining phase of the lake breeze is explained in terms of the decreased turbulent friction acting on the head of the lake breeze. The larger extension offshore, probably, is attributed to the smaller roughness of water surface and to the offshore synoptic wind.

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