Change search
Refine search result
123 1 - 50 of 115
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Alexandersson, Hans
    et al.
    SMHI.
    Dahlström, Bengt
    SMHI, Core Services.
    Future climate in the Nordic region – survey and synthesis for the next century1992Report (Other academic)
    Abstract [en]

    The greenhouse gases carbon dioxide, methane, chlorfluorcarbons and nitrous  oxide are increasing due to man's activities. 0n physical grounds it is generally believed that this will influence the climate of the earth. Observational evidence, mainly global mean temperatures, indicate that the earth becomes warmer at present. It is, however, not possible to rule out that natura! factors have caused observed changes until now. Swedish data show small or no trends at present.

    The suggested scenarios for Sweden are given in interval form to express the large uncertainty. For temperature and precipitation in the years around 2030 we suggest the following changes compared with the levels around 1990.

                     Winter   Summer Winter     Summer.            

                     temp.    temp.     Prec.       Prec.

    Northern

    Sweden:    0.5-1.5  00-1.5     0-15 %   0-10 %

    Southern

    Sweden:    0.0-1.0  0.0-0.5    0-15 %   0-10 %

    Download full text (pdf)
    fulltext
  • 2.
    Alexandersson, Hans
    et al.
    SMHI.
    Eriksson, Bertil
    SMHI.
    Climate fluctuations in Sweden 1860–19871989Report (Other academic)
    Abstract [en]

    We are living in a time when there is a great concern and anxiety on climate changes, induced by man or natural. Figures showing trends or abrupt changes may not seldom be based on rather poor climate records. Thus we have started a climate project at SMHI where we have taken great care to avoid non- homogeneous records and where we have limited our aims to the period of instrumental records (mainly from 1860 in Sweden but a few stations have data from about 1750). Three elements have been studied extensively: temperature, precipitation and air pressure. Two main areas within Sweden were selected. In order to avoid non- homogeneous data the temporal analysis was preceded by a spatial homogeneity test which revealed several discontinuities and artificial trends. Long- term fluctuations were visualized by using a Gaussian low pass filter. One interesting feature is that the pressure difference northern to southern Sweden showed a decrease by about 10% around 1930. The corresponding decrease of the zonal wind may to some extent explain the quite large frequency of cold winters in later decades as high winter temperatures in Scandinavia is strongly connected with westerly and southwesterly inflow of mild and humid Atlantic air-masses. Another interesting but still somewhat questionable feature is the dry early decades.

    Download full text (pdf)
    fulltext
  • 3.
    Alexandersson, Hans
    et al.
    SMHI.
    Gollvik, Stefan
    Meterologi.
    Meuller, Lars
    SMHI.
    An energy balance model for prediction of surface temperatures1991Report (Other academic)
    Abstract [en]

    From the winter season 1988/89 and onwards an energy balance model has been used to estimate surface temperatures within a weather seivice system for the road authorities in "Östergötlands" and "Göteborg-Bohuslän" in Sweden. It is based on a simplified form of the energy balance equation at the surface and a numerical model with ten layers in the ground or road. In the road seivice system manually given forecasts of clouds and wind are used as input into the model. The initial values of surface temperatures are obtained on-line from the road stations involved. Forecasts of surface temperatures have been made for up to five hours and give significantly better results than e.g. perstistency or linear trend forecasts.

    The model has also been generalized to run directly on model output clouds an winds and to give forecasts for a large area. As starting values we then use screen temperatures analysed in a grid net with a resolution of about 20 km covering Scandinavia. Initial surface temperatures are obtained through extrapolation to the ground. Through a relaxation formula forecasted surface temperatures are then transformed back to screen level. The temperature forecasts obtained in this way seem to be much better than the LAM-model gives where the daily amplitude is too small.

    This latter model is henceforth called the objective system while the former is called the road seivice system. The two aystems have large parts in common. Differing parts are indicated in section headings ant text.

    Download full text (pdf)
    fulltext
  • 4.
    Andersson, Camilla
    et al.
    SMHI, Research Department, Air quality.
    Bergström, Robert
    SMHI, Research Department, Air quality.
    Bennet, Cecilia
    SMHI, Research Department, Air quality.
    Thomas, Manu
    SMHI, Research Department, Air quality.
    Robertson, Lennart
    SMHI, Research Department, Air quality.
    Kokkola, Harri
    FMI.
    Lehtinen, Kari
    FMI.
    MATCH-SALSA: Multi-scale Atmospheric Transport and CHemistry model coupled to the SALSA aerosol microphysics model2013Report (Other academic)
    Abstract [en]

    This report presents a new aerosol dynamics version of a European scale Eulerian CTM, MATCH. The new model is called MATCH-SALSA, and includes aerosol microphysics and several options for nucleation, wet scavenging and condensation. The report entails model description, evaluation and sensitivity tests.The new model reproduces observed higher particle number concentration (PNC) in central Europe and lower in remote regions. The model peak PNC occurs at the same particle size as the observed peak or at smaller sizes, which indicate missing growth. Total PNC is underestimated at some sites. The model performs well for particle mass, including SIA components. EC and OC are underestimated at many of the sites.The results are sensitive to the fraction of SOx emitted as H2SO4 and the optimum choice is site dependent. The model results are highly sensitive to whether organic nucleation is included or not. The model results are sensitive to amount of organic vapors in the condensation. The model can be used in applications knowing the restrictions of what the model manages well and what needs further improvements, which is detailed in the report.

    Download full text (pdf)
    FULLTEXT01
  • 5.
    Andersson, Tage
    SMHI, Research Department.
    Boundary clear air echos in southern Sweden2000Report (Other academic)
    Abstract [en]

    The C band weather radars of today are sensitive enough to record clear air echos from the boundary layer during the warmer seasons even in latitudes as high as Scandinavia. Such clear air echos have long been recognised in the US and a.o. used to retrieve the wind. Curiously enough, in Europe there has been, and perhaps still is, a wide spread belief among meteorologists that boundary layer clear air echos are absent there. The probable reason is that since European weather radars are almost only used to monitor precipitation, in most countries weak echos, supposed not to represent precipitation, are suppressed. This may be performed in many ways, for instance by using the STC (Sensitivity Time Control, also called Swept Gain) which suppresses echos close to the radar, or by thresholding weak echos in the radar images used. The threshold is usually about 10 dBz, and since most clear air echos are weaker, they do not appear in the images, though the radar rnight have recorded them.

    That these clear air echos actually are echos from the air, as from sharp refractive index gradients, insects or birds, is evident since Doppler radars show that they move, generally approximately with the winds recorded by other means. The exceptions are from targets heading towards a specific goal, as rnigrating birds, birds leaving a nocturnal roost and locust swarms.

    The concept 'clear air echos' refers to echos from a non-precipitating atmosphere. There is no commonly agreed stringent definition of clear air echos.

    Download full text (pdf)
    fulltext
  • 6.
    Andersson, Tage
    SMHI, Research Department.
    Using the Sun to check some weather radar parameters2000Report (Other academic)
    Abstract [en]

    Precipitation rnonitoring is a rnain task for weather radar applications. In quantitative applications, as estirnation of the rain rate, the fundamental quantity is the rneasurernent of the intensity of the retum signal strength, giving the so called reflectivity factor, or reflectivity, which is the rnain parameter for those estirnates. The calibration of weather radars for this purpose has been a rnain task in radar rneteorology since the first atternpts of estirnating rain rates in the early 1950ies. In spite of this there is still no intemational accepted procedure for this calibration and each rnanufacturer has his own calibration scherne.

    There is evidently a need fora target to calibrate against, which is cornrnon for all radars and easily accessible. This points towards astronornical targets. The rnoon is such a possible target, though the echo from it is too weak for routine calibrations. The sun ernits radiation in the radar frequencies. These signals are already widely used to deterrnine the orientation of the antenna (azirnuth and elevation angle ). The intensity of the radiation in these frequencies is not constant, but is rneasured by sorne observatories and rnay be used as a calibration source.

    The present work is an atternpt to design a calibration or checking procedure that can be used when the radar is working operatively.

    Download full text (pdf)
    fulltext
  • 7.
    Andersson, Tage
    et al.
    SMHI, Research Department.
    Mattisson, Ingemar
    SMHI.
    A field test of thermometer screens1991Report (Other academic)
    Abstract [en]

    For a period of nearly one year temperature readings from small sensors (high quality platinum resistance thermometers) in conventional screens (Stevensson type) and emaller screens (Lambrecht, Young and Vaisala) have been compared to those from a sensor of the same type in a ventilated screen (Teledyne). The test was financially supported by the Swedish Civil Board of Aviation and CDS Mätteknik, Skara. The reading from the Teledyne screen was used as reference and considered the 'true' air temperature. The deviations from the reference were mainly due to two factors:- the thermal inertia of the screens- radiation errors.The thermal inertia is largest for the larger screens. With rapid air temperature changes and calm winds the larger (Stevenson) screens lag behind much more than the smaller ones. Also the radiation errors are largest for calm winds. The extreme errors then occur during calm winds and clear sky. The errors found are larger than given in the literature. The largest error noted, +3. 6°C for one of the Stevenson screens, occurred a calm, clear evening. Generally the extreme errors occurred at sunset and sunrise, not in the a~ternoon when the irradiation has its maximum, because it then usually is windy. Generally the smaller screens followed the reference better than the Stevenson ones. However, with calm winds, clear sky and snow cover the small screens may rapidly get overheated. The averages for longer periods (months)

    Download full text (pdf)
    fulltext
  • 8.
    Bengtsson,, Lennart
    et al.
    SMHI.
    Gustafsson, Nils
    SMHI, Research Department, Meteorology.
    Döös, Bo
    SMHI.
    Söderman, Daniel
    Helsinki University in Finland.
    Moen, Lars
    SMHI, Research Department, Climate research - Rossby Centre.
    Thompson, Thomas
    SMHI.
    Jakobsson, Paul
    SMHI.
    Bleckert, Gunnar
    SMHI.
    Henriksson, Ann-Beate
    SMHI.
    Lindgren, Bo
    SMHI.
    Kållberg, Per
    SMHI, Research Department, Meteorology.
    The Meteorological Auto Code (MAC) and Numerical Weather Prediction (NWP) at SMHI2016Report (Other academic)
    Abstract [en]

    Sweden was a pioneering country in the development of NumericalWeather Prediction (NWP). The worlds first operational numerical forecast was produced already in 1954 by the International Meteorological Institute in Stockholm. SMHI started a bit later, but in 1961 a long term program for development of NWP was initiated. The activities grew gradually during the 1960’s and resulted in a core component for the SMHI forecast services. An early challenge was to overcome the limited computational resources with slow computational speed, small memory size and primitive software support. It was necessary to compensate for these limitations with dedicated work and creativity. A core component in this work was the software system MAC (Meteorological Auto Code) that was developed by the NWP group at SMHI. The MAC system is described in detail in this report and it included all computational software needed for the weather service, for example numerical models, objective analysis techniques, automatic data extraction, quality control of observations as well as forecast products in graphical or digital form.

    We hope that this report will provide the younger generation with some insight into the conditions for development of NWP during the 1960’s.

    Download full text (pdf)
    fulltext
  • 9.
    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.

    Download full text (pdf)
    fulltext
  • 10.
    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.

    Download full text (pdf)
    fulltext
  • 11.
    Bodin, Svante
    et al.
    SMHI, Research Department.
    Fredriksson, Ulf
    SMHI, Core Services.
    Uncertainty in wind forecasting for wind power networks1980Report (Other academic)
    Abstract [en]

    Accurate wind forecasts will be essential in the utilization of wind energy conversion systems (WECS). In order to assess the reliability at present forecast methods for wind speed forecast data from the USA and Sweden have been verified. Data represent different methods, numerical/statistical and subjective, different locations, seasons and heights. However, the data sets are too small to allow any definite conclusions. The results point to that none of the tested forecast methods meet the requirements on forecast error put forward by utilities. The best forecasts were obtained by subjective methods based on numerical prediction for projection times less than +18h. Beyond that time objective, numerical/statistical methods showed to be better. National weather services are recommended to improve forecast methods for shortrange forecasts, 0-12 hours ahead. To obtain sufficient forecast accuracy future WECS sites must also supply relevant observations of low level atmospheric structure.

    Download full text (pdf)
    fulltext
  • 12.
    Bringfelt, Bertil
    et al.
    SMHI, Research Department, Climate research - Rossby Centre.
    Räisänen, Jouni
    SMHI, Research Department, Climate research - Rossby Centre.
    Gollvik, Stefan
    Meterologi.
    Lindström, Göran
    SMHI, Research Department, Hydrology.
    Graham, Phil
    SMHI, Professional Services.
    Ullerstig, Anders
    SMHI, Research Department, Climate research - Rossby Centre.
    The land surface treatment for the Rossby Centre Regional Atmospheric Climate Model - version 2 (RCA2)2001Report (Other academic)
    Abstract [en]

    A new version of the land surface scheme has been completed and is now applied in comparative tests of version 2 of the Rossby Centre Regional Atmospheric Climate Model (RCA2) using analysed fields from the ECMWF reanalysis project (ERA). The scheme contains two soil layers and a vegetation layer. There are two prognostic temperatures, one covering the top soil layer plus vegetation and one for a second, deeper soil layer. There is also a third, bottom soil temperature relaxed to six-hourly ERA fields. For soil moisture there are two prognostic layers but no bottom relaxation is used. A hydrologically-based soil moisture model (beta model) is used to represent subgrid soil moisture variability. A hydrological snow model makes regard to subgrid temperature variability using a geographical database for variance of topography. There are equations for heat and moisture exchange between the two soil layers. Here the hydraulic and thermal properties depend on soil type and soil moisture. Transpiration flux transports moisture from both soil layers depending on a stomatal resistance of vegetation surfaces as function of daylight intensity, soil water deficit, fraction of frozen soil water, air temperature and water vapour pressure deficit in the air. A treatment of rainfall interception on vegetation is used, broadly following the ISBA model, with a vegetation layer storing intercepted water. Subgrid weighting of albedo, surface roughness and parameters for calculating surface resistance is made using a geographical database for area fraction of forest and open land. The leaf area index varies seasonally for short vegetation and for deciduous forest, but not for coniferous forest. A soil freezing/melting algorithm influencing soil temperature is used. Implicit methods are used for solving the equations of most surface variables. A summary of model results compared to observations, is given at the end of the report.

    Download full text (pdf)
    fulltext
  • 13.
    Bringfelt, Björn
    SMHI.
    A comparison of forest evapotranspiration determined by some independent methods1980Report (Other academic)
    Abstract [en]

    Two days of boundary layer measurements in Southern Sweden are presented .The field experiment was carried out in October 1977, as a pilot study. Mean quantities of wind, temperature and humidity were measured both in the surface and the Ekman layer. Radiation and soil temperature were also measured. The data suffer from some incompleteness anda certain amount of inaccuracy. Still you get a fairly good picture of the diurnal cycle of the atmospheric boundary layer under Nordic conditions.

    Download full text (pdf)
    fulltext
  • 14.
    Bringfelt, Björn
    SMHI.
    A forest evapotranspiration model using synoptic data1982Report (Other academic)
  • 15.
    Bringfelt, Björn
    SMHI.
    Test of a forest evapotranspiration model1986Report (Other academic)
    Abstract [en]

    The model computes daily forest evapotranspiration using routine weather observations. The model was developed from detailed meteorological and evapotranspiration measurements in a forest in the Velen hydrological research area in southern Sweden.The model was tested successfully against independent monthly evapotranspiration from the Velen area obtained by the water balance method. In this report the model is improved based on this comparison and the new model is tested against water balance data from two other hydrological research areas, Kassjöån and Lappträsket in middle and north Sweden.Model comparisons have been made for the Jädraås forest in middle Sweden where detailed meteorologicaI and evapotranspiration measurements have also been made. The model now has a parameter set for each of the forest stands in Velen and Jädraås.The model can interrelate various data such as routine weather data, hydrological data, rainfall interception and meteorological mast data. This may imply a better utilization of different data sets.It has been shown that knowledge of water losses from a forest can be used to estimate dry deposition of gaseous pollutants such as sulfur dioxide. In a new study the model will be used to estimate dry deposition of sulfur dioxide to the forests of Velen and Jädraås continuously during one year.

    Download full text (pdf)
    fulltext
  • 16.
    Bringfelt, Björn
    et al.
    SMHI.
    Backström, Hans
    SMHI, Professional Services.
    Kindell, Sven
    SMHI, Professional Services.
    Omstedt, Gunnar
    SMHI, Research Department, Air quality.
    Persson, Christer
    SMHI, Research Department, Air quality.
    Ullerstig, Anders
    SMHI, Research Department, Climate research - Rossby Centre.
    Calculations of PM-10 concentrations in Swedish cities - Modelling of inhalable particles1997Report (Other academic)
    Abstract [en]

    The project was initiated by the Swedish Environmental Protection Agency in order to improve the basis for making standards for PM-10 concentrations in urban air. Model development has been made for Norrköping and Gothenburg. Modelling has been necessary of both long-range and local contributions.

    The long-range dispersion has been simulated by the MATCH-Europe and MATCH-Sweden models, the former being a conventional dispersion model based on meteorology and emission data and the latter including also results from background air pollution measurements in Sweden and neighbouring countries.

    For the local scale, both car exhaust panicles and resuspended particles from a traffic source inventory are dispersed in the city using meteorological data and a Gaussian dispersion mode! and, if needed, a street canyon dispersion submodel. For panicle resuspension, a new model has been developed. The parameters of the resuspension model have been adjusted to two streets/measuring periods in Norrköping.

    At street level in Norrköping, the local model showed to contribute to a large part of the total concentration, especially in late winter and early spring due to resuspension. The MATCH mode! gives same underestimate due to the absence of organic compounds and simulation of PM-2.5 instead of PM-10. However, at some episodes in Norrköping and, in general, for a station at roof level in central Gothenburg and at the rural station Aspvreten, the model estimates of regional PM-2.5 concentrations constitute a larger part of the observed PM-10 concentrations. A good covariation in time with measured data occurs for both the MATCH model and the local model.

    Download full text (pdf)
    fulltext
  • 17.
    Carlund, Thomas
    SMHI, Core Services.
    Measurements of Solar Radiation in Sweden 1983-19982000Report (Other academic)
    Abstract [en]

    Since 1983 an automatic solar radiation network of 12 stations is operated by SMHI. At all 12 stations direct solar irradiance (Eppley NIP pyrheliometers) and global irradiance (Kipp & Zonen CMlO/CMl 1 pyranometers) are measured continuously. Together with general network information and uncertainty analyses, results of the radiation measurements during 1983 - 1998 are presented in this report.

    The resulting quality controlled database consists of yearly, monthly, daily and hourly values of direct (normal) solar and global radiation together with the diffuse sky radiation and sunshine duration, SD. Ed has been calculated from the hourly values of Eh and EK. Observed air temperature (2-m), relative humidity, wind direction and wind speed are available in the hourly radiation database, as well.

    Generally, the uncertainty of 6-minute and hourly values of direct and global radiation has been estimated to 3 % and 4 % (at 95 % confidence level), respectively. The precision of annual values has been estimated to 2 % for both quantities.

    The solar radiation climate in Sweden varies a lot, both in time and space. The dominating factors influencing the solar radiation climate are the latitudinal location and the prevailing cloud conditions.

    Download full text (pdf)
    fulltext
  • 18.
    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 .

    Download full text (pdf)
    fulltext
  • 19.
    Dahlström, Bengt
    SMHI, Core Services.
    Determination of areal precipitation for the Baltic Sea1986Report (Other academic)
    Abstract [en]

    The objective of this investigation has been to estimate areal precipitation for the Baltic Sea and its subbasins.The areal estimates have been computed by use of point precipitation data. These data have been submitted and corrected for the systematic deficits, inherent with precipitation measurement, by the respective Baltic bordering country.For the areal estimation of precipitation within the Baltic Sea and its subbasins the method of statistical interpolation has been applied on normalized precipitation fields. The normalized fields have been extrapolated from the available climatological point data.Areal estimates have been computed for individual months and years for theperiod 1951-70 and for the Pilot Study Year 1975/76. Estimates of areal mean precipitation are also presented for the climatological period 1931-60.The areal estimates indicate that the long-term average of the yearly recipitation amount for the whole of Baltic Sea, including the Danish Sounds and Kattegat, is between 590 mm and 660 mm, with a probable average of 625 mm. For the period 1951-70 the areal mean precipitation ranged from 479 mm to 726 mm.The computations of areal precipitation and its spatial and temporal istributions are illustrated in tables and on maps. The results are verified and previous investiqations are commented.

    Download full text (pdf)
    fulltext
  • 20.
    Engardt, Magnuz
    SMHI, Research Department, Air quality.
    Sulphur simulations for East Asia using the MATCH model with meteorological data from ECMWF2000Report (Other academic)
    Abstract [en]

    As part of a model intercomparison exercise, with participants from a number of Asian, European and American institutes, sulphur transport and conversion calculations were conducted over an East Asian domain for 2 different months in 1993. All participants used the same emission inventory and simulated concentration and deposition at a number of prescribed geographic locations. The participants were asked to run their respective model both with standard parameters, and with a set of given parameters, in order to exarnine the different behaviour of the models. The study included comparison with measured data and model-to-model intercomparisons, notably source-receptor relationships.

    We hereby describe the MATCH model, used in the study, and report some typical results. We find that although the standard and the prescribed set of model parameters differed significantly in terms of sulphur conversion and wet scavenging rate, the resulting change in atmospheric concentrations and surface depositions only change marginally. We show that it is often more critical to choose a representative gridbox value than selecting a parameter from the suite available.

    1. The modelled, near-surface, atmospheric concentration of sulphur in eastem China is typically 5-10 μg S m-3, with large areas exceeding 20 μg S m-3. In southem Japan the values range from 2-5 μg Sm-3. Atmospheric SO2  dominates over sulphate near the emission regions while sulphate concentrations are higher over e.g. the western Pacific. The sulphur deposition exceeds several g sulphur m-2 year-1 in large areas of China. Southem Japan receives 0.5-1 g S m-2 year-1. In January, the total wet deposition roughly equals the dry deposition, in May - when it rains more in the domain - total wet deposition is ca. 50% larger than total dry deposition.
    Download full text (pdf)
    fulltext
  • 21.
    Ericsson, Kjell
    SMHI.
    Atmospheric boundary layer field experiment in Sweden 1980, GOTEX II, part I1982Report (Other academic)
    Abstract [en]

    Data from a comprehensive atmospheric boundary layer experiment in southern Sweden are presented. The measurements were taken during some typical diurnal periods, featuring both convective, daytime regimes and nighttime stable conditions. The site is situated at Klockrike in southern Sweden. This is in an extremely flat district for being in Scandinavia, though the place must be considered as complex.

    Download full text (pdf)
    fulltext
  • 22.
    Ericsson, Kjell
    et al.
    SMHI.
    Hårsmar, Per-Olof
    SMHI, Core Services.
    Boundary layer measurements at Klockrike. Oct. 19771980Report (Other academic)
    Abstract [en]

    Two days of boundary layer measurements in Southern Sweden are presented .The field experiment was carried out in October 1977, as a pilot study. Mean quantities of wind, temperature and humidity were measured both in the surface and the Ekman layer. Radiation and soil temperature were also measured. The data suffer from some incompleteness anda certain amount of inaccuracy. Still you get a fairly good picture of the diurnal cycle of the atmospheric boundary layer under Nordic conditions.

    Download full text (pdf)
    fulltext
  • 23.
    Eriksson, Bertil
    SMHI.
    Data rörande Sveriges temperaturklimat1982Report (Other academic)
  • 24.
    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.

    Download full text (pdf)
    fulltext
  • 25.
    Eriksson, Bertil
    SMHI.
    Den "potentiella" evapotranspirationen i Sverige1981Report (Other academic)
    Abstract [en]

    In the introductory remarks some critical comments regardingthe concept of "potential" evapotranspiration are quoted. It has been proved repeatedly that the rate of evaporationin the biosphere isa function not only of meteorologicalfactors but also depends upon pedological and biophysiological factors.

    In spite of these objections field experiments have shown that it is possible to cornpute, with a certain degree of reliability, the total evaporation from rneteorological variables only: net radiation, wind velocity and saturation deficit. These tests refer to growing grass and certain crops. This is an indication that formulas containing only meteorological parameters do permit a realistic estimate of the largest possible actual evaporation from certain biotopes. Such cornputations, combined with a knowledge of the distribution of precipitation amounts, are useful rnainly because they maypoint to the need for irrigation.

    For 152 Swedish weather stations daily values (for the period1961-78) of potential evapotranspiration have been calculated according to two different formulas. The well-known formulaby Penman and another one by W Johansson have been used (Seeref 10). The rneteorological parameters available and necessary for the calculations are: daily means of air ternperature, windvelocity, cloud amount and water vapour pressure. In addition to these variables snow depth has been used. The cloud amount has served to provide an estimate of the total short wave radiation, using a regression equation. Daily values obtained in this way were tested against the result of direct measurements. The correlation coefficient was found to be 0.8. From the daily values of potential evapotranspiration accordingto Penman and Johansson monthly and annual values were computed as well as means and standard deviations for thewhole period.

    A comparison between monthly values from the two different equations shows the following. During the vegetation period the two methods give rather similar results. As the formula by Johansson is much easier to handle, it seems to be acceptableto use it for many purposes. During the winter half-year Johansson's formula gives higher values that Penman's. But, and this is important, neither was developed for winter conditions.

    The formula by Penman is sensitive to the values adopted fort he albedo. Two sets of values have been tried, 0.25 (0.75when the ground is covered by snow) and 0.12 (0.50). Using the lower figures for the albedo leads to an increase of the total evaporation values by as much as 20%, when compared with the values obtained by using the higer figures. The results presented in tables and charts refer to albedo values 0.12 (0.50).

    Download full text (pdf)
    fulltext
  • 26.
    Eriksson, Bertil
    SMHI.
    Graddagsstatistik för Sverige1980Report (Other academic)
    Abstract [sv]

    En statistisk bearbetning har utförts av rutinmässigt framräknade värden på antalet graddagar under eldningssäsongerna 1961/62 till 1978/79. Resultaten redovisas huvudsakligen i kartform.

    För 5 olika tidpunkter under säsongen ges medelantalet graddagar. Variabiliteten mellan olika säsonger belyses dels genom att standardavvikelsen för en full säsong kartlagts, dels ges kartor över de högsta och de lägsta värden som förekommit under den studerade perioden. En jämförelse med tidigare publicerad karta över medelantalet graddagar under ett år för perioden 1931-60 och den här publicerade kartan visar att den studerade perioden 61/62 - 78/79 har varit kallare än 30-årsperioden 31-60.

    Det är tydligt att antalet graddagar för en ort huvudsakligen är en funktion av ortens latitud, höjd över havet samt avstånd till större vattenyta. En regressionsanalys visar att 90-97% av variansen i rummet hos antalet graddagar i medeltal under en eldningssäsong kan förklaras med en lineär kombination av ovan nämnda tre variabler (deskpriptorer). En regressionsekvation för norra och en för södra Sverige presenteras för beräkning av antal graddagar för en ort vars årsmedeltemperatur ej är känd. Är årsmedeltemperaturen känd finns ett enkelt empiriskt samband mellan medelantal graddagar och årsmedeltemperaturen.

    Download full text (pdf)
    fulltext
  • 27.
    Eriksson, Bertil
    SMHI.
    Nederbörds- och humiditetsklimat i Sverige under vegetationsperioden1986Report (Other academic)
    Abstract [en]

    Precipitation amounts, corrected for measuring er rors, are presented on maps for different parts of the climatologically determined vegetation period. The variability and probability of summer precipitation amounts are analysed for stations having long records. The frequency of runs of different length for wet and dry summers is compared with random. Lowpass filter is used to smoth the time series.

    The difference between precipitation and evapotranspiration - here called humidity - is calculated and presented on maps for certain periods of the vegetation period.

    Download full text (pdf)
    fulltext
  • 28.
    Eriksson, Bertil
    SMHI.
    Snödjupsförhållanden i Sverige – Säsongerna 1950/51–1979/801989Report (Other academic)
    Abstract [en]

    Snow conditions during the 30 winter seasons 1950/51 - 79/80 have been studied. The snow depths at the middle and last day of the months concerned have been analyzed. The relative number of years with a snow cover reported at these dates was computed and is presented in tables and maps. The arithmetic mean values of snow depth were calculated for those years having a snow cover at the dates studied. These means are presented both in tables and on analyzed maps. Annual means of maximum snow depth were also computed, as well as the mean number of days with a snow cover. Median dates for the earliest and latest days with a snow cover is presented.

    A comparison ot the values for the period 50/51-79/80 with those for the period 1931-60 shows that the snow depths are in general higher during the later period. The mean winter temperatures were lower during the period 1951-80 than during the period 1931-60.

    Download full text (pdf)
    fulltext
  • 29.
    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.

    Download full text (pdf)
    fulltext
  • 30.
    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 .

    Download full text (pdf)
    fulltext
  • 31.
    Eriksson, Bertil
    SMHI.
    Statistisk analys av nederbördsdata: Del III. 200-åriga nederbördsserier1981Report (Other academic)
    Abstract [en]

    Long series of precipitation data exist from measurements made atthe old astronomical observatory in Stockholm. A rather completeseries from 1785 is available. In Uppsala rneasurements of precipitationamounts started as early as 1739 by Anders Celsius. Unfortunaletythis series hasa lot of interruptions so the values before1780 are not used in this sudy. It is easily found that themeasurements during certain early periods gave much toolow values.Correction factors are applied.-Themonthlyand annual values are treated by low-pass filters in order to eliminate the high frequencies. The filtered values are plotted and the curves show large ocillations from one period to another. But no constant periods or amplitudes are found. In a longtime perspective no secular trends of the precipitation climate are found in the series from the eastern parts of southern Sweden. The variability of the precipitation amounts is also studied. The results found are that the variability during the two centuries has been very constant.

    Download full text (pdf)
    fulltext
  • 32.
    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.

    Download full text (pdf)
    fulltext
  • 33.
    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

    Download full text (pdf)
    fulltext
  • 34.
    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.

    Download full text (pdf)
    fulltext
  • 35.
    Gollvik, Stefan
    Meterologi.
    Estimation of orographic precipitation by dynamical interpretation of synoptic model data1984Report (Other academic)
  • 36.
    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.

    Download full text (pdf)
    fulltext
  • 37.
    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.

    Download full text (pdf)
    fulltext
  • 38.
    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.

    Download full text (pdf)
    fulltext
  • 39.
    Häggmark, Lars
    et al.
    SMHI, Core Services.
    Ivarsson, Karl-Ivar
    SMHI, Core Services.
    Olofsson, Per-Olof
    Militära Vädertjänsten.
    MESAN Mesoskalig Analys1997Report (Other academic)
    Abstract [en]

    This report describes the work being done in developing the MESAN system for analyzing surface parameters and clouds. The following parameters are being analyzed:- 2 meter temperature,- precipitation in mm water for 1, 3, 12 and 12 hours accumulation time, and for new snow-cover in cm,- wind speed and direction and gust speed at 10 meter elevation,- visibility,- relative humidity,- total cloud cover,- amount and low clouds,- significant cloud base,- probability of observing significant cloud base,- higt of cloud top,- depth of snow cover, and- sea surface temperature.Hirlam data are normally used as first guess fields. Observatons are taken from synop, metar, Swedish climate stations, satellites, radars and automatic stations. Much work has been devoted to minimizing systematic errors in observations and investigating structure functions of first guess errors.The analys method used is optimal interpolation.

    Download full text (pdf)
    FULLTEXT01
  • 40.
    Jansson, Anna
    et al.
    SMHI, Core Services.
    Persson, Christer
    SMHI, Research Department, Air quality.
    Strandberg, Gustav
    SMHI, Research Department, Climate research - Rossby Centre.
    2D meso-scale re-analysis of precipitation, temperature and wind over Europe - ERAMESAN: Time period 1980-20042007Report (Other academic)
    Abstract [en]

    The need for long time series of gridded meteorological data with a fine spatial and temporal resolution has increased in recent years. The requirements for this type of gridded meteorological data fields arise from many different areas of the society, in connection to atmospheric environment studies of air quality and deposition and trends in these parameters, regional climate change, wind energy, hydrological studies etc. The aim of the present project is to investigate the possibility of producing historical, high quality and time consistent, meso-scale re analyses for the whole of Europe regarding precipitation, 2 m temperature and wind for at least 25 years back in time.The MESAN analysis system (Häggmark et al., 2000) at SMHI was chosen as a basis for the reanalysis and the system was adjusted to cover the whole of Europe. In order to find the most appropriate first guess fields to be used in the MESAN system, a pilot study was performed. ERA- 40 data from ECMWF was selected as best possible first guess fields for the re analysis. The performed re-analysis, which is denoted ERAMESAN, includes gridded data covering all Europe with a time resolution of 6 h and a spatial resolution of 0.1º (11 km) in a rotated latitude longitude coordinate system for the time-period 1980-2004. All analyses are archived in GRIB-format and stored on disc at SMHI. The dataset is also available within the EUMETNET optional programme Showcase EUROGRID.A partial validation for the years 1998-2000, using a cross validation procedure with independent observations (5.5% of the total amount of stations), shows an improvement in ERAMESAN compared to the ERA-40 data for all studied parameters with regard to root mean square deviation, mean absolute deviation and mean bias deviation for all seasons. The deviations are roughly of the order of 15% smaller compared to what is obtained from ERA-40. The frequency distribution of large precipitation amounts per day and high wind speeds are substantially better described in ERAMESAN compared to ERA-40. However, the tendency to underestimate the frequency of very large precipitation amounts or high wind speeds, compared to observations, can be seen also for ERAMESAN. It is important to be aware of this limitation when using ERAMESAN data for practical applications concerning evaluation of risks for extreme wind speeds or very large precipitation amounts or in e.g. wind energy studies.

    Download full text (pdf)
    FULLTEXT01
  • 41.
    Jansson, Dick
    SMHI.
    Studier av temperaturinversioner och vertikal vindskjuvning vid Sundsvall-Härnösands flygplats1980Report (Other academic)
    Abstract [en]

    Windshear is the local variation of the wind vector. Shear may be produced by different meteorological causes, such as fronts, low-level jets, mountain waves etc.Vertical windshear together with marked ground inversion may in unhappy situations be the determining factor to an aircraft accident.This paper is treating one method of measuring the shear and the temperature gradient by using data from a height, 350 feet above the aerodrome level.Some situations with SODAR-measurements are also discussed.The problems with shear in connection with aircraft take-off and landning are also treated in this report.

    Download full text (pdf)
    fulltext
  • 42.
    Josefsson, Weine
    SMHI, Research Department, Atmospheric remote sensing.
    Five years of solar UV-radiation monitoring in Sweden1996Report (Other academic)
    Abstract [en]

    A network of five stations measuring the solar UV-radiation has been operated for about five years. Data are presented as plotted time-series of monthly and yearly values for the sites. A general climatology can be deduced from these data. Daily and hourly maximum values are shown for each month as indicators of the potential extreme exposure levets. The !arge amma! variation at high  latitudes is easily seen in the data set. This illustrates the importance of rhe  solar  elevation  on  the leve! of the UV-irradiance. Influence of cloud variation and of larger changes in ozone is also detectable. A few examples of the daily variation also show the strong solar elevation dependence of  the  UV-irradiance.

    The quantity and unit of the  UV-radiation in this presentation  is CIE-weightecl  irradiance expressed  as MED (minimum erythemal dose), where one MED equals 210 Jm-2 values have been re- computed to refer to the international intercomparison of broad-band  meters  in Helsinki in 1995.  In the following named  WMO-STUK 1995 scale.

    As will be seen there are many sources of error and detailed studies are prevented by the !arge uncertainty connected with these data, Due to the short period of the record and the low accuracy no attempt  to study trends is done.

    Download full text (pdf)
    fulltext
  • 43.
    Josefsson, Weine
    SMHI, Research Department, Atmospheric remote sensing.
    Measurements of total ozone 1997 - 19992000Report (Other academic)
    Abstract [en]

    A summary of the quality control, quality assurance and measurements of total ozone at Norrköping and Vindeln during the period 1997-1999 is made. The Brewer #006 and Brewer #128 were compared to the travelling reference Brewer #017 at Vindeln in 1999. Major changes in the measurements and instruments are discussed. The reprocessing of all Brewer data since 1996 and the introduction of the new format recommended by WOUDC at the end of 1999 are documented.

    At the end of this three-year period the ozone layer has shown an increase after many years with several periods of considerable depletion. Therefore, the previous downward trend that was as large as -8% per decade has disappeared. The data set consists of 12 years of almost uninterrupted data at Norrköping. Most of the gaps have been possible to fill with satellite data to have monthly values based on a complete set of daily values. An intercomparison between ground based and TOMS Version 7 satellite based data shows an astonishing agreement in most cases.

    Data recorded at Abisko in 1926 and 1927 on the initiative of G.M.B. Dobson was found in the archive. They were recomputed to modem scales and the result shows that the thickness of the ozone layer at that time is similar to the present thickness. The long-term data sets now available from Vindeln and Norrköping give the opportunity to study the temporal and in some respect also the spatial characteristics of the total ozone. Both the spatial correlation and  he auto-correlation vary considerably over time.

    The Web-site for total ozone (under http://www.smhi.se) has made measurements available fora lot of people in almost real-time. Ozone data can be viewed as graphs or transferred by ftp. There are also some pages with general information as well as some links to related sites. In particular, this method for distribution of information has been found to be useful for the public, media and decision-makers.

    Download full text (pdf)
    fulltext
  • 44.
    Josefsson, Weine
    SMHI, Research Department, Atmospheric remote sensing.
    Solar ultraviolet radiation in Sweden1986Report (Other academic)
    Abstract [en]

    The ultraviolet radiation and the total ozone have been monitored in Norrköping, Sweden, since 1983. From these data it has been possible to develop a simple empirical model to compute the distibution of UV in Sweden. The result is presented as monthly maps.

    Samples of measured UV spectra are presented and their dependence on solar elevation and total ozone. Monthly values of UV-A, UV-B and weighted UV (DUV) is also given.

    The potential of measuring the sky UV radiance distribution is demonstrated as well as the capability of the Brewer to measure sulphur dioxide. A volcanic eruption on Iceland caused enhanced sulphur dioxide values in Sweden.

    Download full text (pdf)
    fulltext
  • 45.
    Josefsson, Weine
    SMHI, Research Department, Atmospheric remote sensing.
    Solar UV-radiation monitoring 19961996Report (Other academic)
    Abstract [en]

    Measurements of solar UV-racliation in a small Sweclish network are presented for 1996. this report can be regarded as a supplement to a previous report, Josefsson (l996) where the results of the previous five years were reported, and where details not presented in this small repor! can be found. The quantity ancl unit of the UV-radiation in this presentation is CIE-weighted irradiance expressed as MED (minimum erythemal dose), where one MED equals 210 Jm-2. The values have been recomputed to refer to the international intercomparison of broad-band meters at Helsinki in 1995. In the following referred to as the WMO-STUK 1995 scale.Although, the stratospheric ozone was severely depleted during the early parts of 1996, the yearly UV radiation recorded was slightly less than in previous years. This was mainly due to the very cloudy months of May, June and July.

    By combining the UV-record with concurrent records of the total ozone a small study of the anticorrelation of these two atmospheric parameters is illustrated. There are many sources of error and detailed studies are prevented by the !arge uncertainty connected with these data of UV-irradiance. Due to the short period of the record and the low accuracy no attempt to study trends is done.

    Download full text (pdf)
    fulltext
  • 46.
    Josefsson, Weine
    et al.
    SMHI, Research Department, Atmospheric remote sensing.
    Karlsson, Jan-Erik
    SMHI.
    Measurements of total ozone 1994-19961997Report (Other academic)
    Abstract [en]

    This report summarises the quality control, quality assurance and measurements of total ozone at Norrköping and Vindeln during the period 1994-1996. To ensure the quality and link the observations closely to the other ozone data participation in intercomparisons and intemational campaigns are noted. The Dobson #30 instrument was at Arosa in 1995 and showed good agreement with the reference Dobson instrument. The Brewer #006 was compared to the travelling reference Brewer #017 in 1996. Major changes in the measurements and instruments are discussed. In particular the introduction of the new instrument Brewer #128, which was compared to Brewer #017 twice in 1996. The first intercomparison pointed on the need of a change of the calibration whilst the second one was in agreement with the previous one. The new instrument seem to be more sensitive to the environment than the old one is. During the campaign at lzaifa it was noted that the photomultiplier of this instrument went saturated measuring in the UV- A. Fortunately, this will not affect the measurements of the total ozone.

    During these three years the ozone-layer has shown many periods of considerable depletion. Now the effects from the Pinatubo eruption has ceased and the sometimes thin layer of ozone can not be attributed to the eventual effects of the volcanic eruption. The extreme deficits of ozone in 1996 and also the down-ward trend, about -8% per decade, in the long-term data presentation are easily seen in the graphs. There will soon be 10 years of almost uninterrupted data available at Norrköping. During winter and spring the observations are delivered almost daily to a European centre in Thessaloniki, Greece, where data are collected. Daily maps are produced showing the total ozone for the northern hemisphere.

    The introduction of a Web-site for total ozone (under http://www.smhi.se) has made measurements almost real-time available for a lot of people. It can be viewed as graphs or transferred by ftp. There is also some pages with information as well as some links to related sites. In particular, this is useful for public, media and decision-makers.

    Download full text (pdf)
    fulltext
  • 47.
    Karlsson, Karl-Göran
    SMHI, Research Department, Atmospheric remote sensing.
    A NOAA AVHRR cloud climatology over Scandinavia covering the period 1991-20002001Report (Other academic)
    Abstract [en]

    A ten-year NOAA A VHRR cloud climatology with a horizontal resolution of four km has been compiled over the Scandinavian region based on results from near real-lime cloud classifications of the SMHl SCANDlA mode!. The frequency and geographic distribution ofthe cloud groups Low-, Medium- and High-level clouds, water and ice clouds and deep convective clouds have been studied in addition to the ten-ycar monthly means of total fractional cloud cover in the region. Furthennore, attempts to estimatc the diurnal cycle of cloudiness and typieal cloud patterns in various weather rcgimes (e.g., North Atlantic Oscillation phases) have been made.

    The cloud climate in the region was found ta be significantly affected by the distribution of land and sea. In particular. the Baltic Sea was shown to suppress summertime cloudiness substantially and this effect was shown to influence cloud conditions in major parts of the Scandinavian region. Huwever, interesting deviations from this cloudiness pattern were found in the Scandinavian mountain range, in the northern part af Scandinavia and over the Norwegian Sea.

    The quality af the satellite-based cloud information was examined by comparing with corresponding surface-observations given by SYNOP-based cloud climatologies for the same period. Results showed good agreement but specific problems were found in winter. In addition, some effects of the degradation of visible AVHRR channels were notieed. Comparisons have also been rnade with internationally used global cloud climate data sets, namely the  SYNOP-based CRU data set and the cloud climatologics from the ISCCP D2 series.

    Download full text (pdf)
    fulltext
  • 48.
    Karlsson, Karl-Göran
    SMHI, Research Department, Atmospheric remote sensing.
    Cloud classifications with the SCANDIA model1996Report (Other academic)
    Abstract [en]

    The cloud classification model SCANDIA (SMHI Cloud ANalysis model using DIgital AVHRR data) is described in this report. SCANDIA is based on multispectral processing of NOAA AVHRR imagery where cloud and surface analyses are produced in real-time for use in operational weather forecasting. Also other applications are described, e.g. compilation of cloud climatologies, estimation of snow area coverage and validation of cloud forecasts from numerical weather prediction models.

    Two different versions of the SCANDIA model are discussed. The first version was introduced in 1988 and the model structure is explained in detail. Model strengths and weaknesses are described by using comparisons with observed cloudiness from ordinary surface weather observations (SYNOP). Also the feedback response from operational weather forecasters is discussed. The second version was introduced in 1994, now operating on a larger area covering the major parts of northem Europe. Necessary modifications for operating on larger scales are described and new features for the identification and highlighting of situations with serious limitations of classification results are demonstrated.

    Download full text (pdf)
    fulltext
  • 49.
    Karlsson, Karl-Göran
    SMHI, Research Department, Atmospheric remote sensing.
    Satellite-estimated cloudiness from NOAA AVHRR data in the Nordic are during 19931994Report (Other academic)
    Abstract [en]

    A method to estimate monthly cloud conditions (total fractional cloud cover) from multispectral satellite data is described. The operational cloud classification scheme SCANDIA (the SMHI Cloud ANalysis model using DIgital AVHRR data), based on high resolution imagery from the polar orbiting NOAA satellites, is used to produce monthly cloud frequencies for all months of 1993. The annual mean is computed and the diurnal variation of cloudiness is investigated for June and December. Cloud analyses are made for an area covering the Nordic countries with a horizontal resolution of four km

    Comparisons with existing surface observations show very good agreement, especially in the summer half of the year. some problems are indicated in the winter season when a minor underestimation of cloudiness is noticed. The underestimation is mainly due to the non-separability of low-level water clouds from cloud-free areas at very low sun elevations. Despite these problems, general cloud patterns are well described also in cold winter situations. Improvements of the method are discussed and an enlargement of the analysis area is envisaged.

    The method is proposed as a valuable tool for local and regional monitoring of the cloud climatology. Comparisons with forecasted cloudiness from atmospheric models are suggested as well as special studies of cloud conditions in the Polar areas.

    Download full text (pdf)
    fulltext
  • 50. Kauker, Frank
    et al.
    Meier, Markus
    SMHI, Research Department, Oceanography.
    Reconstructing atmospheric surface data for the period 1902-1998 to force a coupled ocean-sea ice model of the Baltic Sea2002Report (Other academic)
123 1 - 50 of 115
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf