This study primarily focuses on comparing coincident ozone profiles, as well as investigating the relationship between the polar vortex and the changes in the ozone layer above Kiruna, Sweden (67.85N 20.22E) during the Arctic winters 2010/2011 and 2018/2019. The instruments used are the Kiruna Microwave Radiometer (KIMRA); a millimeter wave radiometer that allows continuous observations of the evolution of ozone and other trace gases in the Arctic stratosphere, and the Microwave Limb Sounder (MLS) instrument on board the Aura satellite. The KIMRA and MLS measurements are compared to each other over the periods November 2010 to March 2011, as well as November 2018 to March 2019. Overall, the KIMRA and MLS comparison show good agreement, with KIMRA measuring more O3 in the lower stratosphere (around 50hPa) than MLS both during the daytime and nighttime. The O3 time series of KIMRA and MLS, along with the polar vortex edge based on equivalent latitudes, show minimum ozone concentrations when Kiruna was situated well inside the polar vortex.

SIW, Stratospheric Inferred Winds, is one of the upcoming Swedish research satellites, aiming to study the winds in the middle atmosphere by measuring the Doppler shifts in molecules such as O3 with a limb viewing sub-mm spectrometer. By conducting simulations on the expected observations, the pointing sensitivity requirement of the satellite was investigated to be able to optimise the matching of the wind vectors. The development of SIW is in the early phases and therefore few studies of this topic has been conducted. The Python program AMATERASU (Advanced Model for Atmospheric TeraHertz Radiation Analysis and Simulation) developed by P. Baron has been used to calculate the radiative transfer through the atmosphere with the aim of simulating the satellite observations and the induced pointing errors, both horizontal and vertical. The results indicate that the effects of the horizontal pointing errors are neglectable due to their small contributions to the measurements. If horizontal pointing errors were induced the scan bias could be corrected for in the retrieval to a good degree for all species and the wind. If not corrected for, H2O and O3 were the most affected species and something to take into consideration during further development of the satellite design. The optimisation of the wind vectors showed that the bias of the matching could get decreased by changing the angle between the satellite antennas. / SIW, Stratospheric Inferred Winds, är en av de nästkommande svenska forskningssatelliterna som ämnar att studera vindarna i mellanatmosfären genom att mäta dopplerskift från molekyler så som O3 med en sub-mm spektrometer som skannar atmosfären från sidan. Simuleringar av de förväntade observationerna genomfördes för att bestämma gränsen för känsligheten i pekningen i kravspecifikationen och optimera matchningen av vindvektorerna. Utvecklingen av SIW är fortfarande i ett tidigt stadie och studier kring detta är få. Pythonprogrammet AMATERASU (Advanced Model for Atmospheric TeraHertz Radiation Analysis and Simulation) som är utvecklat av P. Baron har använts för att räkna ut strålningstransfern genom atmosfären och därmed kunna simulera satellitens förväntade observationer och de inducerade pekfelen, både horisontella och vertikala. Resultaten indikerar att effekterna av de horisontella pekfelen är försumbara på grund av deras låga påverkan på mätningarna. Vid vertikala pekfel kunde pekfelet korregeras för i återvinningen i hög grad för alla ämnen och vinden. Om pekfelet inte korregerades för var H2O and O3 de mest påverkade molekylerna och något som måste tas i beaktning under vidare utveckling av satellitdesignen. Optimeringen av vindvektorerna visade att skillnaden för matchningen kan minskas genom att ändra vinkeln mellan satellitantennerna.

The main purpose of this thesis is to examine the mineral dust aerosol transport into the Arctic. Two three-dimensional reanalysis datasets of atmospheric composition, the Copernicus Atmosphere Monitoring Service reanalysis (CAMSRA) and the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), are analyzed with regard to dust transport into the Arctic. The reanalyses agree on that the largest mass transport of dust into the Arctic occurs across western Russia during spring and early summer, although large dust transport events can occur across other geographical areas during all seasons. In several aspects, the reanalyses show substantial differences. The transport in CAMSRA is considerably smaller, more concentrated and occurs at lower altitudes. Furthermore, the transport in CAMSRA is to a larger extent than MERRA-2 driven by well-defined events of dust transport in space and time. The reanalysis data are compared with surface measurements of dust in the Arctic and dust extinction satellite retrievals from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The comparison indicates that CAMSRA underestimates the dust transport into the Arctic and that MERRA- 2 likely overestimates it. The discrepancy between CAMSRA and MERRA-2 can in part be explained by the assimilation process where too little dust is assimilated in CAMSRA while MERRA-2 overestimates the production of light particles, causing an excessive transport, and the assimilation process further increases the dust concentration in remote areas. Despite the clear differences between the reanalyses, this study provides new insights into the spatio-temporal distribution of the dust transport into the Arctic and the transported mass is estimated to be within the range 1.5–31 Tg yr-1. The thesis also briefly examines the aerosol transport of all five aerosol species carried by the reanalyses, that in addition to dust are black carbon, organic matter, sea-salt and sulfate. The annual aerosol mass transport to the Arctic in CAMSRA and MERRA-2 are 24 Tg and 50 Tg respectively. The reanalyses show substantial differences regarding the proportions of the different aerosol types — emphasizing that it is crucial that the aerosol module manages to simulate the correct aerosol mass fractions, as the assimilation of AOD alone cannot change the proportions between the aerosols.

Surface gravity waves alter the turbulence of the bottom atmosphere and the upper ocean. Accordingly, they can affect momentum flux, heat fluxes, gas exchange and atmospheric mixing. However, in most state-of-the-art Earth System Models (ESMs), surface wave influences are not fully considered or even included. Here, applying surface wave influences into ESMs is investigated from different aspects. Tuning parameterisations for including instantaneous wave influences has difficulties to capture wave influences. Increasing the horizontal resolution of models intensifies storm simulations for both atmosphere-wave coupled (considering the influence of instantaneous wave-induced stress) and stand-alone atmospheric models. However, coupled models are more sensitive to the horizontal resolution than stand-alone atmospheric models. Under high winds, wave states have a big impact on the sea spray generation. Introducing a wave-state-dependent sea spray generation function and Charnock coefficient into a wind stress parameterisation improves the model performance concerning wind speed (intensifies storms). Adding sea spray impact on heat fluxes improves the simulation results of air temperature. Adding sea spray impact both on the wind stress and heat fluxes results in better model performance on wind speed and air temperature while compared to adding only one wave influence. Swell impact on atmospheric turbulence closure schemes should be taken into account through three terms: the atmospheric mixing length scale, the swell-induced momentum flux at the surface, and the profile of swell-induced momentum flux. Introducing the swell impact on the three terms into turbulence closure schemes shows a better performance than introducing only one of the influences. Considering all surface wave impacts on the upper-ocean turbulence (wave breaking, Stokes drift interaction with the Coriolis force, Langmuir circulation, and stirring by non-breaking waves), rather than just one effect, significantly improves model performance. The non-breaking-wave-induced mixing and Langmuir circulation are the most important terms when considering the impact of waves on upper-ocean mixing. Accurate climate simulations from ESMs are very important references for social and biological systems to adapt the climate change. Comparing simulation results with measurements shows that adding surface wave influences improves model performance. Thus, an accurate description of all important wave impact processes should be correctly represented in ESMs, which are important tools to describe climate and weather. Reducing the uncertainties of simulation results from ESMs through introducing surface gravity wave influences is necessary.

Låga moln definieras av att ha molnbasen från 0 till 2 km ovanför markytan. Molnbildande bygger på att den relativa fuktigheten stiger med höjden tills vattenångan i luften kondenseras. Prognosmodeller för moln bygger på grundläggande termodynamiska och fluiddynamiska ekvationer. Områden delas in i ett rutnät och ekvationerna löses med numeriska metoder. För jämförelse kan mätinstrument samt observationer användas, såsom ceilometrar, radar eller observatörer.  Resultat från fyra olika experiment med prognosmodeller för moln används i detta arbete, som är en litteraturstudie för att undersöka modellers förmåga att simulera låga moln. Olika platser, på global och lokal skala, undersöks. Makroskopiska parametrar såsom molnandel och molnfrekvens är i fokus.  WRF-modellen fungerar bäst med 12 km horisontell upplösning, med en viss överskattning av molnfrekvensen. Modellen CAM5 simulerar molnandel väl men vatteninnehåll och isinnehåll underskattas respektive överskattas. Säsongscykler av låga moln fångas väl av modellerna ECMWF, ARPEGE, RACMO och Met Office, med viss överskattning från samtliga modeller. GFS-modellen överskattar molnandelen långt från ekvatorn med upp mot 80% men underskattar nära ekvatorn med 10–20%. Överskattningar och underskattningar kan bero på faktorer såsom otillräcklig representation av mikrofysik eller möjligtvis felaktiga mätdata. Det denna studie visar är däremot att prognosmodeller på lokal skala kan ge bra simuleringar av makroskopiska parametrar av låga moln. / Cloud types are defined by the height of their bases. Low-level clouds have cloud base heights between 0 and 2 km. They are formed when the relative humidity in the air reaches 100 %, leading to the formation of cloud droplets. Forecast models simulate clouds by integrating thermodynamic and fluid dynamic equations using numerical methods. Instruments and observations, such as ceilometers or observers, are used to assess the accuracy of these simulations.  This study uses four previous works, where forecast models have been used to forecast clouds, to study the accuracy of low-level cloud forecasts. This is done on both local and global scales, focusing on macroscopic characteristics such as cloud fractions and frequencies. The results show that the WRF model works best with a horizontal resolution of 12 km, with slight overestimation of cloud frequencies. The climate model CAM5 simulates cloud fractions well, but liquid- and ice content deviate significantly from measurements. Seasonal cycles are generated well by ECMWF, ARPEGE, RACMO and Met Office Unified Model, with reoccurring overestimations by all models. The GFS model overestimates cloud fractions in higher latitudes by up to 80%, but underestimates near the equator by 10-20%.  Lacking representation of microphysics in the models, or faulty data, can be the causes for deviations in the models. However, this study has shown that forecast models can simulate macroscopic parameters of low-level clouds on a local scale well.

By using climate models based on the Earth’s climate, you can get information about how the climate on exoplanets can look like. ROCKE-3D is a general circulation model based on ModelE2, which is used for simulations of modern and prehistoric Earth’s climate. ROCKE-3D, on the other hand, is used to simulate terrestrial planets both in our solar system and around other stars. The orbital eccentricity affects a planet’s climate, if the eccentricity is high, the planet will be closer to its star certain parts of the year and further away from it for other parts. Because of this, it is interesting to study the eccentricity’s influence on the climate of exoplanets, especially since the boundaries of the habitable zone change. In this report, the climate of an Earth-like planet with varying orbital eccentricity has been investigated using ROCKE-3D. The results show that the annual average temperature increased if the eccentricity increased, even though it was expected to decrease because the planet was further away from its star for longer periods than it was closer. The reason for this was that the ocean dampened the surface temperature drop. The amount of snow and ice was also examined. As eccentricity increased, the ocean ice became thicker and snow accumulated in the northern hemisphere. This can be explained, even though the annual average temperature increased due to the warmer winters, by the fact that the temperature in the summer decreased so much that the snow and ocean ice did not melt away completely and started to accumulate for the years with higher eccentricities.

In many numerical weather prediction models, the presence of lakes is simulated crudely, with their effect being neglected in the resulting simulations. However, it has been shown how lakes effect not only their surrounding climate directly, but have an effect to the overall weather evolution and ecosystem. It is therefore vital to improve existing models to take lakes into account, by coupling with smaller models specificaly compiled for a reas with lakes. There have been several sophisticated models to parameterizelakes in a geographical area, which are, on the other hand, computationally expensive and time consuming. A model built specifically on simple physical assumptions, named FLake, aims to provide a solution that is not heavy computationally, but is accurate enough and contains all the necessary physics surrounding the heat budget and temperature of a given lake. For this project, FLake was tried on a lake close to Uppsala, named Erken, where the validity of the model was tested against data archives from Erken Laboratory’s measurement tower. The resulting simulations were very promising regarding the water temperatures, as well as giving out acceptable results for the surface heat fluxes above the lake and the duration of the ice period, as it was modeled by FLake and compared with ice data archives.

Cirrus clouds play an important role in radiative transfer, and thus have impact on the energy balance of the atmosphere and the climate of the Earth. Furthermore, they occur often and cover large areas globally at any time. Nevertheless, cirrus clouds are poorly studied, especially in the polar regions. Cirrus clouds are present in a large amount of the 14 years of data produced by the lidar at the Swedish Institude of Space Physics (IRF), but has not been studied to a large extent. A lidar is an active remote sensing instrument using a laser. This master's thesis develops and improves programs for analysis of cirrus clouds from this lidar data. It also performs analysis of six case studies chosen from the available data, and statistics of these six cases. The parameters calculated for each date are the cloud top, base and mean altitude, the geometrical thickness, the depolarisation ratio, the backscatter ratio (BSR), the backscatter coefficient, the extinction coefficient, the optical thickness and the number of cloud layers. No clear correlation between the optical thickness and the cloud top, base or mean altitude was found. There seems to be a weak correlation between increased optical thickness and increased geometrical thickness, which is not unreasonable. The mean cloud layer top altitude was 11.82 km and the mean cloud base was 10.36 km. The mean optical thickness for a cloud layer was 1.46 km, and the average of the cloud layer mean altitude was 11.09 km. It should be noted that the statistical analysis is based on only six cases with a total observation time of no more than 37 hours. A far larger dataset is needed in order to obtain any statistically signicant conclusions. The effect of averaging is studied, and it is concluded that averaging over altitude reduced the noise and facilitated the interpolation more than averaging over time did. Different approaches to obtain the molecular backscatter coefficient are compared, as well as the effect on the simulated molecular signal. Two of these approaches calculate the molecular backscatter coeffcient with input of the temperature and pressure either as continuously measured ground vales from the weather station at IRF or as radiosonde profiles for a specific time. In the other two, the molecular backscatter coeffcient is obtained from ECMWF data and from the standard atmosphere. Differences in the range 12-35% between the methods are found. Different approaches to calculate the backscatter ratio (BSR) are also compared. At cirrus altitudes, the decrease in the signal due to the molecular cloudfree part of the atmosphere is still strong, and finding the top and base separately by comparison with the standard deviation of the signal is proven a better method than interpolating between the point where the signal starts to increase and the point where it reaches the same signal value again. Height-normalising the signal provides a more robust method. For thin cirrus, the signal is not significantly attenuated above the cloud layer, and it is found that a method based on the ratios between the measured signal and the simulated molecular signal at cloud top and base did not produce reliable results for the optical thickness. In addition to analysing data and data processing methods, new data processing tools in MATLAB have been developed and existing functions have been improved. These will be valuable for continued studies with the IRF lidar, for cirrus as well as PSCs and thick and/or low-altitude clouds.

<p> </p><p>Meteorologiska förhållanden har en stor påverkan på ljudutbredning utomhus. De atmosfäriska effekterna är absorption, refraktion och turbulens, dessa verkar samtidigt och kan vara svåra att skilja åt. Gradienter i temperaturen och vinden gör att ljudhastigheten varierar med höjden. Ljudet kommer då att böjas av nedåt eller uppåt från marken. Kunskapsläget inom vart och ett av dessa områden presenteras i denna studie.</p><p> </p><p>28 stycken trafikbullermätningar har utförts längs den nya E4:an norr om Uppsala vid varierande meteorologiska förhållanden. Mätningarna visar att den totala meteorologiska inverkan på ljudnivån kan vara så stor som 18 dBA vid 132 meters avstånd över snötäckt mark. Temperaturgradientens påverkan på samma avstånd bedöms kunna vara 6 dBA och turbulensens 2 dBA. Spridningen av ljudnivåerna är större i motvinds- än medvinds-utbredning. Detta kan förklaras genom att markdämpningen får mer varierande inflytande i förstnämnda fall.</p><p> </p><p>Svenska myndigheter har inte tagit hänsyn till meteorologins påverkan på ljudnivåerna, vid bulleranalyser, förrän nyligen. En modell- Nord 2000 har utvecklats som sägs kunna förutsäga vägbuller under varierande meteorologiska förhållanden. Utvärdering av modellen visar dock stora brister. Modellen klarar av att förutsäga medelvärden under ett år med bra noggrannhet, men denna rapport visar att modellen misslyckas med variationerna under kortare tidsperioder. Detta är allvarligt, då det lika ofta som en hög medelnivå är just variationerna i form av toppar i ljudbilden som upplevs som störande. 10 minuters mätningarna i motvindsutbredning visar att modellens fel kring en trafikerad väg kan vara så stort som 8 dBA på 132 m avstånd.</p>

<p>Three different studies have been made; an analysis of the general weather situation at three weather stations in Svalbard, close to the main settlement Longyearbyen; an instrumental comparison between three weather stations operating at nearly the same place during a few days in October 2006; and a case study of a weather station at the mountain Breinosa compared to the station in the valley beneath.</p><p>The analysis of the general weather at the three stations, Adventdalen (data used from 2004-2006), Svalbard Airport (data used from 1994-2004) and Gruvefjellet (data used from 2002-2005) showed that it is clear that the local surroundings do contribute to a more locally produced weather. The mean wind speed in Adventdalen was shown to be 5.1 m/s and the wind direction was mostly from inland towards the coast. Channelling effects dominates the winds in the valley, resulting in high wind speeds. The channelled winds from Adventdalen often reach Svalbard Airport (average wind speed 4.8 m/s). At the Airport there is also a contribution of winds (mostly in summer) originating from the sea, e.g. sea breeze. In times when the weather at Svalbard Airport was more continental, Adventfjorden and Isfjorden were likely to be covered by ice. The higher location of Gruvefjellet most often contributes to low temperatures and an average wind speed of 3.9 m/s. However, the temperature at Adventdalen and the Airport are often colder than at Gruvefjellet due to the frequency of temperature inversions.</p><p>The instrumental comparison concerned three stations in Adventdalen. Data from the stationary weather station was compared with data from two temporarily stations during 4-7th October 2006. It is apparent that the stationary station needs calibration, at least when looking at the pressure measurements, where there clearly is an offset in the data.</p><p>The third study was a case study concerned data from a station at the mountain Breinosa and Adventdalen. A new weather station will be put up during 2007 and data (16th December 2005 until 12th January 2006) from a temporarily station was used when determining the differences from the station down in the valley (Adventdalen). The wind speed is often just as high in the valley as at Breinosa due to channelling effects. The temperature in Adventdalen seems to be affected by the temperature at Breinosa. The air is chilled and sinks down to be channelled through the valley. There are some occasions when the temperature at the mountain is higher than beneath. During those events the wind speed is low and a temperature inversion develops at the ground.</p> / <p>Tre olika studier genomförts; en analysering av data från tre väderstationer på Svalbard;en instrumentell jämförelse mellan tre väderstationer på Svalbard nära huvudorten Longyearbyen; en fallstudie av data från en väderstation på berget Breinosa jämfört med situationen i Adventdalen nedanför.</p><p>Undersökningen av generella vädersituationen vid de tre stationerna, Adventdalen (data från 2004-2006), Svalbard Flygplats (data från 1994-2004) och Gruvefjellet (data från 2002-2005) visade tydligt att den lokala omgivningen bidrar mycket till hur vädret formas. Medelvindhastigheten i Adventdalen var 5,1 m/s och vindriktningen mestadels längs dalen ut mot fjorden. Kanaliseringseffekter dominerar vindarna i dalen och bidrar till de höga vindhastigheterna. Kanaliserade vindar från Adventdalen når ofta Svalbard Flygplats (medel vindhastighet 4,8 m/s). Vid Flygplatsen finns också ett visst bidrag från vindar utifrån havet (mestadels under sommaren), d.v.s. sjöbris. I situationer då vädret vid flygplatsen varit mer kontinentalt så har Adventfjorden mest troligt varit täckt av is.</p><p>Gruvefjellets höga placering bidrar till låga temperaturer och en medelvindhastighet på 3.9 m/s. Dock är temperaturen är ofta lägre i Adventdalen och vid Flygplatsen på grund av att det ofta förekommer temperaturinversioner i marknivå.</p><p>Den instrumentella jämförelsen berörde tre stationer i Adventdalen. Data från den stationära stationen jämfördes under 4-7 oktober 2006 med data från två temporära stationer. Det är tydligt att den stationära stationen är i behov av kalibrering. I alla fall är det uppenbart vid studien av lufttrycket som tydligt är förskjutet och visar ett lägre tryck.</p><p>Tredje studien var en fallstudie och data undersöktes från berget Breinosa och Adventdalen. En ny väderstation kommer att monteras på Breinosa under 2007 och data (16 december 2005 till 12 januari 2006) från en temporär station användes i studien. Vindhastigheten är ofta lika hög i dalen som på berget på grund av kanaliseringseffekter. Temperaturen i dalen förefaller vara påverkad av temperatursituationen på berget. Avkyld luft sjunker och kanaliseras ner i dalen. Det finns några tillfällen då temperaturen på berget Breinosa är högre än nere i dalen. Under de situationerna avtar vindhastigheten och en temperaturinversion bildas i marknivå.</p>