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  • 651.
    Funquist, Lennart
    SMHI, Research Department, Oceanography.
    En hydrodynamisk modell för spridnings- och cirkulationsberäkningar i Östersjön: Slutrapport1985Report (Other academic)
  • 652.
    Persson, Christer
    et al.
    SMHI, Research Department, Air quality.
    Wern, Lennart
    SMHI, Core Services.
    Luftvårdsstudie avseende industrikombinatet i Nynäshamn - depositionsberäkningar av koldamm1985Report (Other academic)
  • 653.
    Karlsson, Karl-Göran
    SMHI, Research Department, Atmospheric remote sensing.
    Information från Meteosat - forskningsrön och operationell tillämpning1985Report (Other academic)
  • 654.
    Fredriksson, Ulf
    SMHI, Core Services.
    Spridningsberäkningar för AB Åkerlund & Rausings fabrik i Lund1985Report (Other academic)
  • 655.
    Persson, Christer
    et al.
    SMHI, Research Department, Air quality.
    Wern, Lennart
    SMHI, Core Services.
    Spridnings- och depositionsberäkningar för avfallsförbränningsanläggning i Sofielund1985Report (Other academic)
  • 656.
    Persson, Christer
    et al.
    SMHI, Research Department, Air quality.
    Wern, Lennart
    SMHI, Core Services.
    Spridnings- och depositionsberäkningar för avfalls- förbränningsanläggningar i Sofielund och Högdalen1985Report (Other academic)
  • 657.
    Persson, Christer
    et al.
    SMHI, Research Department, Air quality.
    Funquist, Lennart
    SMHI, Research Department, Oceanography.
    Local scale plume model for nitrogen oxides: Model description1984Report (Other academic)
  • 658.
    Omstedt, Gunnar
    SMHI, Research Department, Air quality.
    An operational air pollution model using routine meteorological data1984Report (Other academic)
  • 659.
    Gollvik, Stefan
    Meterologi.
    Estimation of orographic precipitation by dynamical interpretation of synoptic model data1984Report (Other academic)
  • 660.
    Laurin, Sten
    SMHI.
    Population exposure to SO2 and NOx from different sources in Stockholm1984Report (Other academic)
  • 661.
    Lönnqvist., Olov
    SMHI.
    Congression – A fast regression technique with a great number of functions of all predictors1984Report (Other academic)
  • 662.
    Eriksson, Bertil
    SMHI.
    Data rörande Sveriges temperaturklimat1982Report (Other academic)
  • 663.
    Ericsson, Kjell
    SMHI.
    Atmospheric boundary layer field experiment in Sweden 1980, GOTEX II, part I1982Report (Other academic)
  • 664.
    Schoeffler, Pierre
    SMHI.
    Dissipation, dispersion and stability of numerical schemes for advection and diffusion1982Report (Other academic)
  • 665.
    Bringfelt, Björn
    SMHI.
    A forest evapotranspiration model using synoptic data1982Report (Other academic)
  • 666.
    Törnevik, Håkan
    SMHI.
    An aerobiological model for operational forecasts of pollen concentration in the air1982Report (Other academic)
  • 667.
    Omstedt, Gunnar
    SMHI, Research Department, Air quality.
    Spridning av luftförorening från skorsten i konvektiva gränsskikt1982Report (Other academic)
  • 668.
    Undén, Per
    Meterologi.
    The Swedish Limited Area Model: Part A. Formulation1982Report (Other academic)
  • 669.
    Pershagen, H.
    SMHI.
    Maximisnödjup i Sverige (perioden 1905–70)1981Report (Other academic)
    Abstract [en]

    Data have been obtained from 40 selected meteorological stations.The following monthly tables have been prepared:

    A Various statistical information in cm.B The five highest and lowest values with year of occurrence.C Relative frequency.D Classification of the depth of snow.E The five mast and least severe snow-seasons for each station.F The five mast and least severe snow-seasons in certain regions.G The five mast and least severe snow-conditions divided inta regions and months with indication of year.H Maximum depth of snow at each station and <luring each of the 72 years  with indication of month.I  Various stalistical information derived from the values of table H.K Highest and lowest yearly maximum and difference in cm.L Extreme values of the depth of snow.

  • 670.
    Lönnqvist., Olov
    SMHI.
    Nederbördsstatistik med praktiska tillämpningar: Precipitation statistics with practical applications1981Report (Other academic)
    Abstract [en]

    Precipitation statistics for Sweden are presented in a very special way in order to serve as a planning tool in the Weather Service. Empirical Orthogonal Functions for the precipitation based on monthly normals for 643 stations, 1931-1960, are applied to two practical design problems, viz. geographical areas for weather forecasting and the network of synoptic stations. The paper also deals with maritime and continental areas of Sweden. The representativity of results obtained is judged by a sample af precipitation data for the last 100 years.A discussion is given as to the usefulness of the climatological method for the actual aoplication purposes as compared with correlation af time-series of precipiation and other weather parameters.

  • 671.
    Liljas, Erik
    SMHI, Core Services.
    Analys av moln och nederbörd genom automatisk klassning av AVHRR-data1981Report (Other academic)
  • 672.
    Melgarejo, José
    SMHI.
    Similarity theory and resistance laws for the atmospheric boundary layer1981Report (Other academic)
  • 673.
    Eriksson, Bertil
    SMHI.
    Den "potentiella" evapotranspirationen i Sverige1981Report (Other academic)
  • 674.
    Eriksson, Bertil
    SMHI.
    Statistisk analys av nederbördsdata: Del III. 200-åriga nederbördsserier1981Report (Other academic)
  • 675.
    Omstedt, Anders
    SMHI, Research Department, Oceanography.
    A sensitivity analysis of steady, free floating ice1980Report (Other academic)
    Abstract [en]

    The equation for steady, free floating ice is derived and analysed for a shallow sea. The analysis treats how accurate the free ice drift can be computed when variations in the ingoing parameters are introduced. Besides errors due to  unperfect winds, areas with large currents cause bad accuracy. If further more the bottom depth is neglected in these areas the accuracy become worse. Variable ice roughness and variable friction velocity introduce errors which are less important but still noticable in the computed ice drift.

  • 676.
    Persson, Christer
    et al.
    SMHI, Research Department, Air quality.
    Omstedt, Gunnar
    SMHI, Research Department, Air quality.
    En modell för beräkning av luftföroreningars spridning och deposition på mesoskala1980Report (Other academic)
    Abstract [sv]

    Mängden föroreningar, som förs till atmosfären, har under de senaste trettio åren kraftigt ökats. Deposition av dessa till marken leder till en rad biologiska effekter. Risker för skador på olika ekosystem genom deposition av tex tungmetaller och syra har därför alltmer börjat diskuteras som viktiga lokaliseringskriterier för fossileldade kraftverk och vissa större industrier. Depositionen av bly i omedelbar närhet av livligt trafikerade motorleder är ett annat exempel där negativa miljöeffekter befaras.

    Uppställandet av effektrelaterade utsläppskriterier medför ett behov av redskap för att kunna göra kvantitativa uppskattningar av förväntade depositioner i omgivningen av en källa. För kraftverk kan behovet av information om depositionsfördelningen, som underlag för lokaliseringsbeslut, röra ett område med flera hundra kilometers utsträckning.

    Vid studier av den lokala spridningen runt en punktkälla har under lång tid den gaussiska plymmodellen varit allmänt använd. Den utgör ett enkelt och i många fall mycket bra hjälpmedel, men har avsevärda begränsningar i de fall då depositionsprocesser och kemiska omvandlingar måste inkluderas i beräkningarna. I modeller baserade på diffusionsekvationen, där vissa antaganden om den turbulenta diffusiviteten görs (sk K-teori), finns möjlighet att på ett väsentligt mer realistiskt sätt inkludera processer som rör deposition och kemiska omvandlingar. Nackdelen är dock att den matematiska behandlingen blir mer komplicerad.

    Numeriska lösningar av diffusionsekvationen har använts av tex Bo in & Persson (1975) och Omstedt & Rodhe (1977). I båda fallen gällde tillämpningarna föroreningsspridning på storregional skala. Maul (1977) har presenterat en analytisk lösning, som tillämpats på föroreningsspridning på mesoskala. Svårigheterna vid tillämpningen av K-teorin är framförallt att bestämma riktiga värden på de ingångsparametrar som fordras. För analytiska lösningar finns dessutom matematiska hinder för godtyckliga vind- och diffusivitetsprofiler. Detta har resulterat i att beräkningar med K-modeller hittills huvudsakligen utförts för några enkla medelprofiler.

    Avsikten med föreliggande projekt har varit att utveckla en för praktiskt brukanvändbar spridningsmodell för studier av torr- och våtdepositionen av föroreningar på lokal- och mesoskala, där godtyckliga vind- och diffusivitetsprofiler kan användas. Dessa genereras med hjälp av en gränsskiktsmodell för olika vädersituationer.

  • 677.
    Eriksson, Bertil
    SMHI.
    Sveriges Vattenbalans. Årsmedelvärden (1931–60) av nederbörd, avdunstning och avrinning1980Report (Other academic)
    Abstract [en]

    The correction factors, which were proposed in an earlier report RMK 17 (1980) to be applied to measured precipitation amounts, have been used on the normal annual values for the period 1931-60. A map is presented, where corrected values from about 260 stations have been used for the analysis. To get the normal annual evaporation values the normal runoff values have been subtracted from the corrected precipitation annual sums. A map is drawn showing the pattern of the normal evaporation in Sweden. The map and the values show good agreement in those points, where reliable evaporation values are available. The conclusion is drawn that the corrections of the precipitation data have the correct order of magnitude. However, there are of course great uncertainties in the details of the map of the normal evaporation in southern Sweden in some areas values above 500 mm per year appear. In order to verify these results, another independent method must be used. It  seems appropriate to establish regression equations between evaporation and the summer mean temperature and maybe even other variables like wind velocity, cloudiness, vapour pressure deficit.

    Area mean values of runoff, precipitation and evapotranspiration amounts have been calculated from the maps by integration. The mean annual precipitation amount for the whole of Sweden was found to be 745 mm. This value is 28% higher than the value computed from uncorrected data. 18% units are due to corrections for losses due to wind, evaporation and adhesion, when measuring the precipitation amounts. The rest, 10% units, is an effect of the fact that the precipitation stations are too few in higher regions. For the country as a whole is found that somewhat less than 50% of the precipitation evaporates as water vapour into the atrnosphere. In mountanious regions, where the largest precipitation amounts fall, only about 15% dissapear into the air.

  • 678.
    Eriksson, Bertil
    SMHI.
    Statistisk analys av nederbördsdata: Del II. Frekvensanalys av månadsnederbörd1980Report (Other academic)
    Abstract [en]

    The frequency distributions of monthly precipitation amounts have been investigated. Data from the period 1931-78 for 262 Swedish and 26 Norwegian stations have been used. The statistical analysis consists of determining the capacity of well-known frequency distribution functions to match the empirical distributions. The following functions were tested: gamma distributions with 2 or 3 parameters, log-normaldistributions with 2 or 3 parameters and the Weibull distribution with 3 parameters. The methods used to determine theparameters of the above-mentioned functions were either the momentum or the maximum- likelihood method. About 3500 distributions were studied. The results of the different tests gave a statistically significant answer to the question: Which of the investigated functions is superior to the other functions best in describing the observed distributions? The gamma distribution was found to have the highest score. In 86% of all case s there was no significant difference, at the 90% confidence level, between observed and computed frequencies. The log-normal distribution hasa much lower capacity to describe the empirical distributions studied.

    From the gamma distribution with the obtained values of its shape and scale parameters certain percentile values were computed, namely: P01, P05, P10, P25, P50, P75, P95, and P99. The results are presented in the form of charts. The charts showing monthly isohyets for different percentile values are briefly cornrnented.

    Maps of the variability of monthly precipitation amounts are also presented. The variability is expressed by means to the coefficient of variation. This variability parameter shows small differences between different regions in Sweden.

    The measuring errors of precipitation observations are discussed. Corrections of measured amounts ought to be applied for the three most important errors viz, the aerodynamic, evaporation and adhesion losses. The most important losses and at the same time those which are most difficult to estimate are due to the wind effects around the orifice of the precipitation gauge. The corrections ought to be determined individually for each station and month with regard to the wind regime and the exposure of the gauge for the station concerned. With these factors in mind and knowing the proportions between snow and rain precipitation corrections have been proposed for the monthly values. On an average for all Swedish stations used in this investigation the mean annual amounts of precipitation for the period 1931-78 should be increased by 18%. In the water balance equation the values thus increased seem to agree reasonably well with generally accepted values for evaporation and run-off .

  • 679.
    Bringfelt, Björn
    SMHI.
    A comparison of forest evapotranspiration determined by some independent methods1980Report (Other academic)
  • 680.
    Ericsson, Kjell
    et al.
    SMHI.
    Hårsmar, Per-Olof
    SMHI, Core Services.
    Boundary layer measurements at Klockrike. Oct. 19771980Report (Other academic)
  • 681.
    Jansson, Dick
    SMHI.
    Studier av temperaturinversioner och vertikal vindskjuvning vid Sundsvall-Härnösands flygplats1980Report (Other academic)
  • 682.
    Eriksson, Bertil
    SMHI.
    Graddagsstatistik för Sverige1980Report (Other academic)
  • 683.
    Bodin, Svante
    et al.
    SMHI, Research Department.
    Fredriksson, Ulf
    SMHI, Core Services.
    Uncertainty in wind forecasting for wind power networks1980Report (Other academic)
  • 684.
    Sahlberg, Jörgen
    et al.
    SMHI, Professional Services.
    Törnevik, Håkan
    SMHI.
    A study of large scale cooling in the Bay of Bothnia1980Report (Other academic)
  • 685.
    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.

  • 686.
    Eriksson, Bertil
    SMHI.
    Statistisk analys av nederbördsdata: Del I. Arealnederbörd1979Report (Other academic)
    Abstract [en]

    Precipitation data on mean values for large areas have been analysed from two points of view. In the first section of this report the data have been looked upon as time series. In the second section they have been regarded as samples from a population.

    The reliability of the data is discussed. It is stated that the values are underestimated. The correction factor may be as high as 30%. Half of this correction is related to the representativity of the precipitation network and is mainly due to the fact that the proportion of stations at high levels is too low. The other half is related to measurement errors, mainly losses due to wind, turbulence and evaporation.

    The time series analysis consists of three parts. In the first one a ' so-called run-test is used to investigate the stationarity of the series. There seemst o be no reason to reject the hypothesis that the series are stationary. After that the frequencies of long runs are X2 -tested against a random model and against models with very low autocorrelation lag- one coefficients. The best fit is found for the model without autocorrelation. In the third part some of the series are filtered with low-pass filters. The results are in accordance with the run-test viz that there are no detectable trends neither linear nor cyclic.

    In the second section seven different distribution functions are tested. The following ones are used: Normal, log-normal (both two and three parameters), gamma (two and three parameters), Weibull and FisherTippett type I. The parameters of these functions are estimated with the maximum-likelihood method or the momentum method. The x2 -test gave no definit answer to the question which one is the mast suitable function. It was possible to reject the lagnormal distribution with three parameters, and the threeparameter r-distribution had no advantage compared with the two-parameter version.

    By studying the outermost values of the distributions it was evident that neither the normal nor the lognormal distribution were able to fit the observed data satisfactory. It was not possible to say which of the two distributions, r or Weibull, is the best one. For very low and even very high values the Weibull distribution seems to be able to describe the observedvalues somewhat better than the gamma distribution can do. Arguments can be delivered both in the favour of rand of Weibull.

    The percentiles, according to the gamma distribution, P01, P05, P10, P25, P50, P75, P90, P95 and P99 are presented . Even P01, P05, P95 and P99 calculated from Weibull distribution are given.

    Those monthly values laying outside P01 and P99 as well as those outside P05 and P95 are listed both according to gamma and Weibull distributions.

    A proposal to a climatological terminologi is presented. The range of a climatological variable is divided into 7 classes. These classes contains 1, 4, 20, 50, 20, 4 respectively 1% of the events. The values belonging to the outmost classes are called extreme values, those in the middle class should be called normal values.

    At the end of the report a list is given of the 10 events, which, according to gamma distributions, have the lowest climatological probability. Some cases have extremely low probabilities.

  • 687.
    Eriksson, Bertil
    SMHI.
    Temperaturfluktuationer under senaste 100 åren1979Report (Other academic)
    Abstract [en]

    In order to investigate, if it is possible to trace anytendencies to increasing variability of the climate<luring the last decades, series of temperature datahave been treated. Five-day means of temperature havebeen analysed from two aspects. The mean conditions<luring running ten-year-periods have been studied aswell as the fluctuations of the variability (expressedwith the aid of standard deviation). Results in theform of diagrams are presented and cornrnented shortly

  • 688.
    Bodin, Svante
    SMHI, Research Department.
    En numerisk prognosmodell för det atmosfäriska gränsskiktet, grundad på den turbulenta energiekvationen1979Report (Other academic)
    Abstract [en]

    The inter est in numerical modeling of the atmosphericboundary layer has grown considerably over the lastdecade. At SMHI and el s ewhere boundary layer modelsfind app l i c a ti on s in local forecasting , especially atairports, i n a i r pollution diffusion and disper s ions t udi e s and i n wind energy programmes .In this report an one - dimensio nal nume r ical boundarylayer model is der iv e d a nd numeri cal simulatio ns ofboundary layer data f r om Australia and Finla nd arepresented and d is cussed. The model, which is the f i rststep towards a three-dimens ional model, is based onthe so-called Gutman a pproach and incorporates theturbulent energy e quation f or turb ulence closure . Ascale analysis is performed , that shows that unless agrid distance of 20 km or less can be use d i n a threedimensionalmodel it is more profitable t o use an onedimensionalone with more sophisticated physical parameterizations.The model also includ e s condensat i on, i e fog andclouds, and complete radiat i on computations. A predictiveequation for surface temperature is used inconjunction with a simple soil moisture model.The numerical solution employs a variety of the CrankNicolsonscheme called Laasonen's scheme. The verticalcoordinate is transformed log-linearly into a new heightcoordinate to allow better resolution close to theground. 35 grid points are used to describe the boundarylayer up to 2000 m. A time step of 4 minutes has beenused in the simulations.Two versions of the model, the Gutman version andausual "Ekman" version, have been tested on day 33 and34 of the Wangara data. The two versions have been comparedand the Ekman version has also been compared withthe simulations of Yamada & Mellor (1975).The results show that the Ekman version is superiorwhen simulating the wind of the Wangara data. The thermalboundary layer development is very well predictedby both versions. Comparisons with Yamada & Mellorspeak in favour of the present model.Conclusions are drawn and some future work is outlined .The model is intended to undergo operational tests atArlanda airport in the near future.

  • 689.
    Haag, Tomas
    SMHI.
    Byggnadsindustrins väderberoende: Seminarieuppsats i företagsekonomi, B-nivå1978Report (Other academic)
    Abstract [sv]

    Redan 1969 visade en undersökning vid Svenska Byggnadsentreprenörsförbundet att byggnadsindustrin var intresserad av en branschanpassad väderprognos. Följande arbete syftar till att sondera byggnadsindustrins väderberoende samt hur en för branschen ändamålsenlig väderprognos bör se ut och distribueras.

    Byggnadsindustrin är som näringsgren mycket betydande för samhällsekonomin. Den svarar för ca 8% av BNP och sysselsätter ca 200 000 årsarbetare. Under senaste 10-årsperioden har det lagts ner mycket arbete föratt nå en rationellare byggnadsproduktion. Detta främst genom utarbetandet av den så kallade systematiska arbetsberedningen. Den syftar till att förebygga störningar och minska konsekvenserna av dessa. Då skall speciellt intresse ägnas åt de mest störningskänsliga punkterna och här måste vädrets inverkan på vissa arbetsoperationer beaktas. Gör man klart för sig vilka arbetsoperationer som är beroende av de olika väderelementen samt ritar in försvarsåtgärder och skyddade reservarbeten i planerna kan man, med hjälp av en ändamålsenlig väderprognos, fatta säkrare beslut om vilka åtgärder som skall utföras.

    Genom att utnyttja denna "byggprognos" kan arbetsledningen två ggr/dag fatta beslut över arbete vid väderberoende arbetsoperationer med hjälp av färska prognoser. Detta medför att försvarsåtgärder används endast då de behövs men då i god tid. Samt att det vid mycket dåliga förhållanden finns reservarbeten planerade som kan påbörjas utan dyrbara uppehåll, dessutom slipper man dyrbara överraskningar vid väderomslag.

    Med ändamålsenlig väderinformation menas en regional prognos med de väderelement som är av vikt för byggnadsindustrin samt att denna byggprognos distribueras på ett lämpligt sätt. Regionernas storlek kommer att variera så att man får så stora regioner som möjligt med "samma" väder. Statens Vägverk har delat in landet i 24 olika regioner vid beställning av sina "vägprognoser". Det är en beprövad indelning som anses vara användbar.

  • 690.
    Eriksson, Bertil
    SMHI.
    Vegetationsperioden i Sverige beräknad från temperaturobservationer1978Report (Other academic)
    Abstract [en]

    The starting and ending date of the vegetationen period hasbeen calculated from the Swedish temperature observationnetwork for the period 1961-74. The dates have been determinedfor individual years. The criterium used for the determinationof the dates is daily mean temperature 6° during at least fourday s. Maps showing the mean starting and ending date of thevegetation period as well as the length of period have been drawn.A table is presented giving those years with the earliest andlatest dates of the arrival and end of the vegetation period.

  • 691.
    Omstedt, Anders
    et al.
    SMHI, Research Department, Oceanography.
    Sahlberg, Jörgen
    SMHI, Professional Services.
    Some results from a joint Swedish-Finnish sea ice experiment, March, 19771978Report (Other academic)
    Abstract [en]

    A joint Swedish-Finnish sea-ice experiment was performed during March 1977. Measurements in the atmosphere, ice and sea were made during six days onboard the Finnish Research vessel Aranda stationed in the ice field in the Bay of Bothnia. During two days measurements were also carried out from thetwo Swedish icebreakers Atle and Tor. This report presents the data and some results from the Swedish group.

  • 692.
    Holmström, Ingemar
    et al.
    SMHI.
    Stokes, John
    SMHI.
    Statistical forecasting of sea level changes in the Baltic1978Report (Other academic)
    Abstract [en]

    By expanding sea level data from 6 Swedish observation stations inte empirical orthogonal functions a very simple picture of the response of the Baltic to atmospheric forcing is obtained. It is found that not less than 65.5 per cent of the total variance is due to a general rise or lowering of the whole surface.The time scale corresponds to the time scale of large scale atmospheric disturbances. This inderdependence has been used in order to establish a regression equation between surface pressure fields and sea level variations which is used for prediction. In the statistical treatment extensive use is made of the empirical orthogonal function technique.

  • 693.
    Eriksson, Bertil
    SMHI.
    Den dagliga och årliga variationen av temperatur, fuktighet och vindhastighet vid några orter i Sverige1977Report (Other academic)
    Abstract [en]

    Hourly observations from aerodroms have been used to calcul atehourly means of the most important climatological variables.For those varibles showing a marked daily and annual variationisopleth diagrams have been analys ed for air temperature, humidi tyand wind velocity. The results are given for 11 places. Theperiod used i s in general the years 1955-1975. In the text shor tcomments are given to the different diagrams. Some differencesand similarities between stations have been pointed out.

  • 694.
    Lundqvist, Jan-Eric
    et al.
    SMHI.
    Udin, Ingemar
    SMHI, Core Services.
    Ice accretion on ships with special emphasis on Baltic conditions1977Report (Other academic)
    Abstract [en]

    Since the middle of the 1960-ties, ice accretion reports have been collected from ships travelling in the Baltic. The data from these reports have been processed and the relation between ice accretion and meteorological and oceanographic parameters have been studied. The investigation comprises merchant vessels of a size typical for the Baltic. This report presents the results from the icing campaign. It contains a general description, including factors causing icing, the freezing process etc. Results from other investigations have been studied and comparisons made. Forecasting of ice accretion is discussed and the method now used at SMHI is described. Finally some comments are given on how to avoid or decrease the ice accretion.

  • 695.
    Collins, William.G.
    SMHI.
    A parameterization model for calculation of vertical fluxes of momentum due to terrain induced gravity waves1976Report (Other academic)
    Abstract [en]

    Various sources of informatio n indicate vertic al fluxes of mountain induced wave momentum to be on the order of several tenths of a Pascal over mountaineous terrain . The implied wind tendencies in layers of wave absorption in typical situations are several meters per second per day . On the basis of the size of this probable effect , a parameterization model has been developed to calculate t h e momentum fluxes within the framework of a large- scale numerical weather prediction model. The calculation model assumes a continuous linear wind profile as well as constant stability within each layer . The hydrostatic assumption is made for the total motion . The vertical velocities and resultant vertical momenturn fluxes are caused by the air being forced over the topography . For this mode l , the individual spectral elements of the terrain height are not important . Rather , an integral ov er the elements is used as the forcing function which determines the momen - turn flux magnitude . This forcing function must be determine-d as a function of horizontal direction for each largescale grid box . Sample calculations are given which illustrate the results possible from the parameterization model .

  • 696.
    Nyberg, Anders
    SMHI.
    On transport of sulphur over the North Atlantic1976Report (Other academic)
    Abstract [en]

    The sulphur content in the precipitation collected 1 on ocean weather ships in the North Atlantic has been analysed . From these data and from results of trajectory computations it is concluded that considerable amounts of anthropogenic sulphur are transported from North America towards Europe. The dry deposition of sulphur over the Atlantic , except close to the emitting sources, must be very small. The amount of sulphur in the precipitation from air coming from the high pressure area near the Azores is very small and thus one can say that the normal value of natural sulphur in precipitation cannot be much larger than 0.1 mg/1.

  • 697.
    Holmström, Ingemar
    SMHI.
    Optimization of atmospheric models1976Report (Other academic)
    Abstract [en]

    Applying variational methods toa mathematical model of the atmosphere an entirely new type of equations for forecasting atmospheric parameters is derived. The method also defines vertical eigenfunctions to the model. In a simplified case some of the eigenfunctions are compared with empirically obtained data and conclusions are drawn regarding the validity of some of the approximations in the mathematical model.

  • 698.
    Moen, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    A multi-level quasi-geostrophic model for short range weather predictions1975Report (Other academic)
    Abstract [en]

    A quite generally formulated multilevel quasi-geostrophic medel with possibilities to include second order terms in the vorticity equation is derived. The model includes friction, topography, latent heat and sensible heat. The treatment of the variable boundary conditions, smoothing and ellipticity control is described.

  • 699.
    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.

  • 700.
    Bodin, Svante
    SMHI, Research Department.
    Development on an unsteady atmospheric boundary layer model1974Report (Other academic)
    Abstract [en]

    To serve as an aid in preparing lecal ferecasts as well as landing ferecasts at airports, a develepment ef an atmospheric boundary layer model has been started at SMHI. The model is going to use large scale wind, temperature and moisture predictions from a numerical weather prediction model as variable boundary conditions. Instead ef using the ordinary Ekman boundary layer equations an approach due te L N Gutman (1969) has been used in deriving a set of one-dimensional boundary layer equations. It is shown that this formulation filters out inertial- diffusive oscillations, which are present in an Ekman boundary layer due to time variation in the geostrephic wind.

    Experiments with variable large scale winds have been done, using a simple dry medel with prescribed variations in the boundary values for wind and temperature. A turbulent exchange coefficient formulation has been used, which is based on Monin & Obukhov´s similarity theory and which uses a mixing length formulation due to Blackadar. For the numerical solution a Crank-Nicolson scheme has been used. The computations show large differences between the steady state and the unsteady state solutions.This is shown in wind hodegraphs as well as in time functions of friction velocity,u* and cross isobar angle. Finally, from two different analytical solutions as well as a finite difference solution of the heat conduction equation, heat fluxes at the earth's surface due to heat conduction in the soil have been computed. These analytical solutions have been compared in terms of accuracy and efficiency.

11121314 651 - 700 of 700
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