<p>Utanför Östergarnsholm, öster om Gotland, har mätningar utförts sedan våren 1995. Mätningarna är gjorda med instrument monterade på en 30 m hög mast samt med hjälp av vågbojar. Mätstationerna är placerade så att vid vind från Gotland blir vågorna begränsade av avståndet från mätstation till land (kallat fetch). Då vinden kommer norr och söder om Gotland, kan vågorna antas komma från öppet hav. Denna klara uppdelning på fetch är både till för- och nackdel för studien. En modell gjord och beskriven av Khama (1986), bygger i stora drag på integrering av vågspektrum. Modellen beskriver den signifikanta våghöjdens beroende av vind, varaktighet (den tid det blåst med konstant hastighet över ett område) och fetch. Modellen är indelad i två delar, där den ena är beroende av vind och fetch och den andra enbart av vind, därför att fetchen är så lång att den förlorar signifikans. Storleken på den dimensionslösa fetchen, x, bestämmer gränsen när vågorna beror på fetch och när de kommer från öppet hav. I modellen är denna gräns satt till 22 000, men borde enligt denna studie ligga betydligt lägre. Modellens resultat och mätningar stämmer förhållandevis bra överens vid fetchberoende förhållanden. Dock så underskattar modellen våghöjden en aning, vilket ökar för ökande våghöjd. Vid stor skillnad mellan våg- och vindriktning är det ökad risk för stora skillnader mellan modell och mätningar. Modellen överskattar signifikanta våghöjden 2-3 gånger för öppet hav, eftersom modellen antar att vågor hela tiden kommer från samma håll och inte tar hänsyn till synoptiska förändringar under transporttiden. Modellens funktion för varaktighet ger en större ökning av våghöjd än vad den faktiska ökningen är. Funktionen för varaktighen har därför om, men visar sig endast gälla för ung sjö, med definitionen C_p/U<0.9. Vid dyning då C_p/U>1.2, ökar våghöjden med tiden betydligt mindre än vid ung sjö. Stabilitet har också viss påverkan på våghöjden, dock har inga särskilda skillnader mellan modell och mätningar iakttagits beroende på stabilitet.</p><p> </p><p> </p><p> </p> / <p>By the coast of Östergarnsholm, on the east side of Gotland, measurements have been carried out since spring 1995. The measurements are performed by using instruments on a 30 meter  high tower, but also by means of wave buoys. The measuring stations are placed in such a way that in case of wind from Gotland the waves are limited by the distance from the measuring station to the shore (called fetch). However, when the wind is not by the coast of Gotland, the waves could be considered to originate from the open sea. This obvious division of fetch is both limiting and beneficial for the study. A model created and described by Khama (1986), is more or less based on the integration of wave spectrum. The model illustrates how the significant wave height depends on wind, duration (the amount of time it has been blowing with constant velocity within an area) and fetch. The model is divided into two parts, whereas one is dependent on wind and fetch and the other one is solely dependent on wind, since the fetch is long enough to lose significance. The size of the dimensionless fetch, x, decides the barrier when the waves are dependent on fetch and when they originate from the open sea. In the model this barrier is set at 22 000, but should according to this study be set considerably lower. The measurements and result of the model coincides relatively well in case of fetch-dependency. However, the model is slightly underestimating the wave height, which increases in line with increasing wave height. In case of great difference between wave- and wind direction there is a bigger risk of great differences between the model and the measurements. The model is overestimating the significant wave height 2-3 times for the open sea, since the model suggests that waves always originate from the same direction. Instead of just studying waves from the open sea, that solely are wind-dependent, consideration to duration should also be made. The models function for duration suggests a greater rise in wave height than it actually is. The function for duration is therefore revised, but appears only to be valid for young sea, defined as follows C_p/U<0.9. By swell whenC_p/U>1.2, the wave height is increasing less with time than during young sea. Stability has also appeared to have some effect on the wave height, thus no particular differences between the model and the measurements have been observed depending on stability.</p><p> </p>

<p>An important factor in forecast models today is cirrus clouds, but not much are known about their dynamics which makes them hard to parameterize. In this study a new theory was derived to enable a more correct way to describe the interplay between radiative heating and dynamical motions in these clouds. This hypothesis was tested by performing three dimensional simulations of cirrus clouds, using the University of Utah Large Eddy Simulator (UULES). Eleven clouds of varying initial radius and ice water mixing ratio were examined, with the aim of finding a pattern in their dynamical features. The model was set up without short wave radiation from the sun, and without any precipitation affecting the clouds, leaving only terrestrial heating and atmospheric cooling to create motions in the clouds. Two categories of initial dynamics could be seen:</p><p>• Isentropic adjustment: The isentropes within the cloud are adjusting to the environment due to rising of the cloud. Causes horizontal spreading through continuity.</p><p>• Density current: A dominating initial feature is spreading in small mixed layers at the cloud top and bottom. Caused by the density difference between the cloud and its environment.</p><p>An interesting phenomenon showing up in the simulations was mammatus clouds, which were visible in two of the cases. The only instability available to create these clouds was the radiative heating difference, which does not agree with present theories for how they form.</p><p>Two dimensionless numbers S and C were derived to describe the nature of the spreading motions and convection in the cloud. Both these numbers agreed with results.</p> / <p>Cirrusmoln har en viktig roll i dagens prognosmodeller, men är svåra att parametrisera på ett bra sätt eftersom man inte har tillräcklig kunskap om deras dynamik och utveckling. I denna studie togs en ny teori fram för att göra det möjligt att på ett mer korrekt sätt beskriva samspelet mellan strålningsuppvärmning och dynamiska rörelser i dessa moln. Hypotesen testades sedan genom att utföra tredimensionella simuleringar av cirrus moln med hjälp av University of Utah Large Eddy Simulator (UULES). Elva moln med varierande initiella radier och isvatteninnehåll undersöktes, med målet att finna ett mönster i dynamik och utveckling. UULES ställdes in så att miljön där molnen simulerades varken innehöll kortvågsstrålning från solen eller nederbörd. Således fanns det bara en resterande faktor för att skapa rörelser i molnen; skillnaden i den infraröda strålningsuppvärmningen mellan molntopp och molnbas. Två kategorier av initiella rörelser uppstod i molnen:</p><p>• Justering av isotroper: Molnen stiger i höjd vilket gör att isotroperna inuti dem justeras till omgivningen. Detta orsakar horisontell spridning genom kontinuitet.</p><p>• Densitets ström: Horisontell spridning av molnen koncentrerad till mixade skikt i de övre och undre delarna. Orsakas av skillnad i densitet mellan moln och omgivning.</p><p>Ett intressant fenomen som visade sig i två av simuleringarna var mammatusmoln. Den enda instabiliteten tillgänglig för att skapa dessa moln var skillnaden i strålningsuppvärmning mellan molntopp och -bas. Detta stämmer inte överrens med nuvarande teorier för hur dessa moln skapas.</p><p>Två dimensionslösa tal, S och C togs fram för att indikera vilken av de initiella rörelserna som dominerar i molnet, samt vilken typ av konvektion som dominerar. Båda dessa tal stämde väl överrens med resultat.</p>

Two types of mesoscale wind-speed jet and their effects on boundary-layer structure were studied. The first is a coastal jet off the northern California coast, and the second is a katabatic jet over Vatnajökull, Iceland. Coastal regions are highly populated, and studies of coastal meteorology are of general interest for environmental protection, fishing industry, and for air and sea transportation. Not so many people live in direct contact with glaciers but properties of katabatic flows are important for understanding glacier response to climatic changes. Hence, the two jets can potentially influence a vast number of people. Flow response to terrain forcing, transient behavior in time and space, and adherence to simplified theoretical models were examined. The turbulence structure in these stably stratified boundary layers was also investigated. Numerical modeling is the main tool in this thesis; observations are used primarily to ensure a realistic model behavior. Simple shallow-water theory provides a useful framework for analyzing high-velocity flows along mountainous coastlines, but for an unexpected reason. Waves are trapped in the inversion by the curvature of the wind-speed profile, rather than by an infinite stability in the inversion separating two neutral layers, as assumed in the theory. In the absence of blocking terrain, observations of steady-state supercritical flows are not likely, due to the diurnal variation of flow criticality. In many simplified models, non-local processes are neglected. In the flows studied here, we showed that this is not always a valid approximation. Discrepancies between simulated katabatic flow and that predicted by an analytical model are hypothesized to be due to non-local effects, such as surface inhomogeneity and slope geometry, neglected in the theory. On a different scale, a reason for variations in the shape of local similarity scaling functions between studies is suggested to be differences in non-local contributions to the velocity variance budgets.

A faithful depiction of the tropical atmosphere requires three-dimensional sets of observations. Despite the increasing amount of observations presently available, these will hardly ever encompass the entire atmosphere and, in addition, observations have errors. Additional (background) information will always be required to complete the picture. Valuable added information comes from the physical laws governing the flow, usually mediated via a numerical weather prediction (NWP) model. These models are, however, never going to be error-free, why a reliable estimate of their errors poses a real challenge since the whole truth will never be within our grasp. The present thesis addresses the question of improving the analysis procedures for NWP in the tropics. Improvements are sought by addressing the following issues: - the efficiency of the internal model adjustment, - the potential of the reliable background-error information, as compared to observations, - the impact of a new, space-borne line-of-sight wind measurements, and - the usefulness of multivariate relationships for data assimilation in the tropics. Most NWP assimilation schemes are effectively univariate near the equator. In this thesis, a multivariate formulation of the variational data assimilation in the tropics has been developed. The proposed background-error model supports the mass-wind coupling based on convectively-coupled equatorial waves. The resulting assimilation model produces balanced analysis increments and hereby increases the efficiency of all types of observations. Idealized adjustment and multivariate analysis experiments highlight the importance of direct wind measurements in the tropics. In particular, the presented results confirm the superiority of wind observations compared to mass data, in spite of the exact multivariate relationships available from the background information. The internal model adjustment is also more efficient for wind observations than for mass data. In accordance with these findings, new satellite wind observations are expected to contribute towards the improvement of NWP and climate modeling in the tropics. Although incomplete, the new wind-field information has the potential to reduce uncertainties in the tropical dynamical fields, if used together with the existing satellite mass-field measurements. The results obtained by applying the new background-error representation to the tropical short-range forecast errors of a state-of-art NWP model suggest that achieving useful tropical multivariate relationships may be feasible within an operational NWP environment.

The present thesis deals with the ocean circulation from two viewpoints: Pro primo, the dependence of the global thermohaline ocean circulation (THC) on the parameterization of the small-scale vertical mixing processes in the interior of the ocean, and, pro secundo, the dynamics of the circulation in the Nordic Seas. The THC is found be crucially dependent on the parameterization of the small-scale vertical mixing, two types of which have been compared: The commonly used constant diffusivity and a, physically more plausible, stability-dependent parameterization. For constant diffusivity the circulation weakens when the equator-to-pole surface density difference is decreased, consonant with commonly held prejudices. However, for stability-dependent diffusivity the circulation is enhanced. This conclusion has been reached using two investigative techniques, viz. a scale analysis as well as a numerical zonally-averaged and equatorially symmetric THC model. However, if asymmetric flows are considered, the dynamics become more complex to interpret. It has, nevertheless, been concluded that when the degree of asymmetry of the surface-density distribution is taken to be fixed, the response of the circulation to changes of the surface-density distribution corresponds to that from the symmetric investigation. The studies of the Nordic Seas are mainly based on satellite-altimetric data providing Sea-Level Anomalies (SLAs). These are utilized to estimate the seasonal cycle as well as the inter-annual variability of the depth-integrated flows. The seasonal cycle is examined using the winter-to-summer difference of the barotropic flow, with focus on the entire region as well as on two sections extending from a common point in the central Norwegian Sea to Svinøy on the Norwegian coast and to the Faroe Islands, respectively. The total barotropic transport is estimated to be around 10 Sv larger during winter than in summer, of which 8 Sv are associated with the barotropic re-circulation gyre in the interior of the Norwegian Sea, the remainder being linked to the Atlantic inflow across the Iceland-Scotland Ridge. The inter-annual variability of the circulation in the Nordic Seas is investigated on the basis of a theoretical analysis permitting independent calculation of the barotropic flow along closed isobaths using SLA data as well as wind data. The barotropic flow based on SLA data is found to co-vary with the flow estimated using wind data.

Utanför Östergarnsholm, öster om Gotland, har mätningar utförts sedan våren 1995. Mätningarna är gjorda med instrument monterade på en 30 m hög mast samt med hjälp av vågbojar. Mätstationerna är placerade så att vid vind från Gotland blir vågorna begränsade av avståndet från mätstation till land (kallat fetch). Då vinden kommer norr och söder om Gotland, kan vågorna antas komma från öppet hav. Denna klara uppdelning på fetch är både till för- och nackdel för studien. En modell gjord och beskriven av Khama (1986), bygger i stora drag på integrering av vågspektrum. Modellen beskriver den signifikanta våghöjdens beroende av vind, varaktighet (den tid det blåst med konstant hastighet över ett område) och fetch. Modellen är indelad i två delar, där den ena är beroende av vind och fetch och den andra enbart av vind, därför att fetchen är så lång att den förlorar signifikans. Storleken på den dimensionslösa fetchen, x, bestämmer gränsen när vågorna beror på fetch och när de kommer från öppet hav. I modellen är denna gräns satt till 22 000, men borde enligt denna studie ligga betydligt lägre. Modellens resultat och mätningar stämmer förhållandevis bra överens vid fetchberoende förhållanden. Dock så underskattar modellen våghöjden en aning, vilket ökar för ökande våghöjd. Vid stor skillnad mellan våg- och vindriktning är det ökad risk för stora skillnader mellan modell och mätningar. Modellen överskattar signifikanta våghöjden 2-3 gånger för öppet hav, eftersom modellen antar att vågor hela tiden kommer från samma håll och inte tar hänsyn till synoptiska förändringar under transporttiden. Modellens funktion för varaktighet ger en större ökning av våghöjd än vad den faktiska ökningen är. Funktionen för varaktighen har därför om, men visar sig endast gälla för ung sjö, med definitionen Cp/U&lt;0.9. Vid dyning då Cp/U&gt;1.2, ökar våghöjden med tiden betydligt mindre än vid ung sjö. Stabilitet har också viss påverkan på våghöjden, dock har inga särskilda skillnader mellan modell och mätningar iakttagits beroende på stabilitet. / By the coast of Östergarnsholm, on the east side of Gotland, measurements have been carried out since spring 1995. The measurements are performed by using instruments on a 30 meter  high tower, but also by means of wave buoys. The measuring stations are placed in such a way that in case of wind from Gotland the waves are limited by the distance from the measuring station to the shore (called fetch). However, when the wind is not by the coast of Gotland, the waves could be considered to originate from the open sea. This obvious division of fetch is both limiting and beneficial for the study. A model created and described by Khama (1986), is more or less based on the integration of wave spectrum. The model illustrates how the significant wave height depends on wind, duration (the amount of time it has been blowing with constant velocity within an area) and fetch. The model is divided into two parts, whereas one is dependent on wind and fetch and the other one is solely dependent on wind, since the fetch is long enough to lose significance. The size of the dimensionless fetch, x, decides the barrier when the waves are dependent on fetch and when they originate from the open sea. In the model this barrier is set at 22 000, but should according to this study be set considerably lower. The measurements and result of the model coincides relatively well in case of fetch-dependency. However, the model is slightly underestimating the wave height, which increases in line with increasing wave height. In case of great difference between wave- and wind direction there is a bigger risk of great differences between the model and the measurements. The model is overestimating the significant wave height 2-3 times for the open sea, since the model suggests that waves always originate from the same direction. Instead of just studying waves from the open sea, that solely are wind-dependent, consideration to duration should also be made. The models function for duration suggests a greater rise in wave height than it actually is. The function for duration is therefore revised, but appears only to be valid for young sea, defined as follows Cp/U&lt;0.9. By swell whenCp/U&gt;1.2, the wave height is increasing less with time than during young sea. Stability has also appeared to have some effect on the wave height, thus no particular differences between the model and the measurements have been observed depending on stability.

Wind farms are nowadays more often constructed in alpine terrain than earlier due to theprofitable wind resource as well as, often, less conflicting interests than in more denselypopulated areas. The cold climate poses a relatively new challenge to the wind power industrysince icing of the wind turbine blades and sensors may induce losses in production, increasethe wear and tear of the components, leading to a shortening of structural life time as well as itdecreases the availability and hence reducing the economical profitability for the owner.This study focuses on modelling of ice accretion on a vertically mounted cylinder,dimensioned to correspond to an IceMonitor, and comparing the results with measured iceload on a similar instrument during the winter of 2009/2010. The modelling is carried outwith both a statistical approach using multiple linear regression and a physical approach usingmodel for ice accretion. Ice load was also modelled for the period 1989-2009 using the ERAinterimre-analysis data set in order to compare the winter 09/10 with a longer referenceseries. Modelled ice loads for four winters between 2005 and 2009 were compared withproduction data to investigate a possible connection between ice load and production losses.The results showed that the statistical approach was unable in its current form toreproduce and predict measured ice loads and the method was deemed unsuitable. Thephysical model shows more promising results, although with problems in modelling rapid iceaccretion and ice shedding events.No clear connection between measured production losses and modelled ice loads wasfound when analyzing available data. Uncertainties in input data correction as well asimportance of ice density are possible sources of error.Due to confidentiality of some of the data, the measurement sites used in this thesis aredenoted site A, site B and site C.

An important factor in forecast models today is cirrus clouds, but not much are known about their dynamics which makes them hard to parameterize. In this study a new theory was derived to enable a more correct way to describe the interplay between radiative heating and dynamical motions in these clouds. This hypothesis was tested by performing three dimensional simulations of cirrus clouds, using the University of Utah Large Eddy Simulator (UULES). Eleven clouds of varying initial radius and ice water mixing ratio were examined, with the aim of finding a pattern in their dynamical features. The model was set up without short wave radiation from the sun, and without any precipitation affecting the clouds, leaving only terrestrial heating and atmospheric cooling to create motions in the clouds. Two categories of initial dynamics could be seen: • Isentropic adjustment: The isentropes within the cloud are adjusting to the environment due to rising of the cloud. Causes horizontal spreading through continuity. • Density current: A dominating initial feature is spreading in small mixed layers at the cloud top and bottom. Caused by the density difference between the cloud and its environment. An interesting phenomenon showing up in the simulations was mammatus clouds, which were visible in two of the cases. The only instability available to create these clouds was the radiative heating difference, which does not agree with present theories for how they form. Two dimensionless numbers S and C were derived to describe the nature of the spreading motions and convection in the cloud. Both these numbers agreed with results. / Cirrusmoln har en viktig roll i dagens prognosmodeller, men är svåra att parametrisera på ett bra sätt eftersom man inte har tillräcklig kunskap om deras dynamik och utveckling. I denna studie togs en ny teori fram för att göra det möjligt att på ett mer korrekt sätt beskriva samspelet mellan strålningsuppvärmning och dynamiska rörelser i dessa moln. Hypotesen testades sedan genom att utföra tredimensionella simuleringar av cirrus moln med hjälp av University of Utah Large Eddy Simulator (UULES). Elva moln med varierande initiella radier och isvatteninnehåll undersöktes, med målet att finna ett mönster i dynamik och utveckling. UULES ställdes in så att miljön där molnen simulerades varken innehöll kortvågsstrålning från solen eller nederbörd. Således fanns det bara en resterande faktor för att skapa rörelser i molnen; skillnaden i den infraröda strålningsuppvärmningen mellan molntopp och molnbas. Två kategorier av initiella rörelser uppstod i molnen: • Justering av isotroper: Molnen stiger i höjd vilket gör att isotroperna inuti dem justeras till omgivningen. Detta orsakar horisontell spridning genom kontinuitet. • Densitets ström: Horisontell spridning av molnen koncentrerad till mixade skikt i de övre och undre delarna. Orsakas av skillnad i densitet mellan moln och omgivning. Ett intressant fenomen som visade sig i två av simuleringarna var mammatusmoln. Den enda instabiliteten tillgänglig för att skapa dessa moln var skillnaden i strålningsuppvärmning mellan molntopp och -bas. Detta stämmer inte överrens med nuvarande teorier för hur dessa moln skapas. Två dimensionslösa tal, S och C togs fram för att indikera vilken av de initiella rörelserna som dominerar i molnet, samt vilken typ av konvektion som dominerar. Båda dessa tal stämde väl överrens med resultat.

Detaljerad information om vindförhållandena på en site är en nödvändighet för att göra beräkningar av lönsamhet i ett vindkraftsprojekt. Mätningarna behöver vara kontinuerliga och så korrekta som möjligt. Därtill bör de göras under minst ett års tid eftersom vindförhållandena på en plats är säsongsberoende. Under vintertid och framför allt på högre latituder eller altituder, kan mätutrustning påverkas av nedisning. En nedisad anemometer kan ge databortfall eller felaktiga mätningar. Identifiering av felaktiga data är en viktig del av analyseringsarbetet eftersom risken annars är att vindförhållandena på platsen underskattas. Då instrumentet är helt fastfruset kan en enklare analys av data göras genom att titta på standardavvikelsen av vindhastigheten. Svårigheten i detektionen är vid lätt till måttlig nedisning då vindstyrkan, och även standardavvikelsen, kan se normal ut trots att felaktiga värden redovisats. I detta arbete analyseras 1 Hz data från skålkorsanemometer för att söka ett matematiskt sätt att avgöra om lätt till måttlig nedisning påverkat instrumentet under mätperioden. I ett experiment har olika typer av nedisning simulerats på skålkorsanemometrar. Därefter har vindhastighetsfördelningen för en ”nedisad” anemometer kunnat jämföras med fördelningen uppmätt med en anemometer som varit opåverkad under samma mätperiod. I denna jämförelse har visats att trots en differens i medelvind-hastighet på upp till 15 % under mätperioden syns ingen, för detektion av nedisning, användbar skillnad i någon av de statistiska parametrar som jämförts i arbetet. Förutom analys av mätdata från egna experiment har även data från Suorva samt från en höghöjdsmast i Norrland analyserats. För analys av mätdata från masten i Norrland har ett en algoritm utarbetats för automatisk detektion av tidpunkter med instrumentell nedisning. Isdetektionen baseras på antaganden om standardavvikelse av vindhastighet och vindriktning, förändring av vindriktning samt en regression mellan vindhastigheten på två höjder. / Detailed information about the wind conditions on a site is a necessity for calculations of profitability from a wind power project. Hence the continuity and the correctitude of the measurements are crucial when making the site evaluations. Due to the season dependence of the wind conditions the measurements also needs to be done for at least a whole year. During wintertime and particularly on higher altitudes and/or latitudes the instruments may be affected by icing. An iced up anemometer often underestimates the wind speed and severe icing can lead to instrument breakage and loss of data. Identification of inaccurate measurements is of great importance in the analysis of the site’s energy potential. The difficulty in detecting light to moderate icing lies in that the wind speed and the standard deviation of the wind may seem normal, although the anemometer is underestimating the wind speed due to icing. In this thesis 1 Hz data from cup anemometers are analysed in search for a mathematical way to determine whether the instrument has been affected by icing during the measurement. An experiment has been performed simulating different types of icing on anemometers. The wind velocity distribution of an “iced up” anemometer has been compared to the wind velocity distribution of an unaffected anemometer for the same measuring period. Also the turbulence intensity and the change of mean wind velocity between observations have been evaluated. The comparison of these statistical variables between the instruments has showed that none of them are applicable for detection of icing. In addition to analysing data from the experiment a pre-study on the subject has been made analysing measurements with possible icing from the Suorva valley. Also, the results from the experiment have been compared to results from a conventional measuring mast placed in the northern part of Sweden. For the analysis of the mast data an algorithm for detection of icing during measurements has been implemented. This automatic detection of icing is based on assumptions about the standard deviation of wind speed, the standard deviation of the wind direction, the change of wind direction and regression between wind velocities of two heights.

I detta arbete studeras hur vinterklimatet i Sverige kommer att skilja sig åt mellan perioderna 2071-2100 och 1971-2000, med avseende på parametrarna temperatur, nederbörd, vind, snödjup och snöutbredning. Klimatmodelldata (CORDEX) i upplösningen 12.5 km baserade på tre olika strålningsdrivningsscenarier (RCP-scenarier) behandlades i Matlab och modellerades över Sverige. För att analysera upplösningens betydelse tillhandahölls även data i upplösningen 50 km för en tioårsperiod. Scenariot RCP 8.5 kan ge så mycket som 10 grader varmare vintrar, med uppemot 50% mer nederbörd. För RCP 2.6 förändras nederbörden med -5 till 20%, och temperaturen ökar med 1-4 grader. Antalet dygn med nederbördstillfällen kommer att vara oförändrat oavsett RCP-scenario; istället kommer mängden nederbörd per tillfälle generellt att bli större. Detta bekräftas av antalet dygn med kraftig nederbörd, som kommer att öka med 20%, 37% respektive 68% för RCP 2.6, 4.5 respektive 8.5. Temperaturökningen blir mer påtaglig i norr än i söder. Vinden uppvisar inga tydliga mönster, vilket korresponderar med historiska observationer. Även RCP 2.6 innebär en förminskning av snödjup och -utbredning, vilket kraftigt förstärks med RCP 8.5. Dessa förändringar kommer bland annat att medföra ökade vintervattenflöden och större risk för laviner och översvämningar, och snöberoende näringslivsaktörer som exempelvis skidanläggningar kommer att drabbas hårt av förändringarna. Regionala klimatmodeller med grövre upplösningar kan inte illustrera lokala geografiska variationer, vilket har i särklass störst betydelse för nederbörden och snödjupet. / How the winter climate in Sweden will differ between the time periods 2071-2100 and 1971-2000 is reviewed in this work. The investigated parameters are temperature, precipitation, wind, snow depth and snow distribution. Climate model data (CORDEX) with the resolution 12.5 km based on three different representative concentration pathways (RCP scenarios) were processed in Matlab and projected over Sweden. For a thorough analysis of the significance of the regional model resolution, data with the resolution 50 km was provided for a ten year period. The RCP 8.5 scenario could implicate a 10 degree increase in temperature, and upto 50% more precipitation. For the RCP 2.6 scenario, the precipitation alters with -5 to 20%, and the temperature increases with 1-4 degrees. The number of days with precipitation events remain unaltered regardless of RCP scenario, instead the amount of precipitation in general increases for each precipitation event. This is verified when looking at the amount of days with heavy precipitation, which will increase with 20%, 37% and 68% for RCP 2.6, 4.5 and 8.5, respectively. The temperature change will be more substantial in the north than in the south. The wind does not show any distinct patterns, which corresponds with historical observations. Even RCP 2.6 implies a diminishment of snow depth and snow distribution, which drastically amplifies for RCP 8.5. These changes will among others bring about increased winter water flow and a bigger risk for avalanches and floodings. Snow dependent businesses, for instance ski resorts, will be heavily affected by the changes. Regional low resolution climate models cannot illustrate local geographical variations, which by far has the biggest importance for modelling precipitation and snow depth.