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Panyametheekul, Sirima. "Assessment and modelling of the distribution of mercury around combustion processes." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271413.
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Titov, Mikhail. "Application of an atmospheric mesoscale modelling system to analysis of air pollution dispersion in the Christchurch area." Thesis, University of Canterbury. Department of Geography, 2004. http://hdl.handle.net/10092/3920.
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The study is concerned with the significant and historically well-known problem of winter
air pollution in Christchurch and its vicinity (especially associated with particulate matter-PMlO)
during nights dominated by stagnant synoptic weather situations. This pollution results from
active use of domestic log-burners and open-fires, on nights of strong near-surface temperature
inversion.
In this study, a numerical modelling research approach is used with the application of a
regional atmospheric model (Mesoscale Model, 5th generation-MM5) and an air quality-air
pollution model (Comprehensive Air quality Model with extensions, version 4-CAMx4),
coupled together for more sophisticated investigation of space-time PMlO dispersion over the
Christchurch region during heavy smog nights.
In the thesis, the theoretical and practical background of limited area models is described,
with reference to basic limited area meteorological models such as MM5, RAMS and WRF. The
potential of limited area meteorological modelling (MM5) , air pollution chemical modelling
(CAMx4), and the use of coupled numerical systems (MM5-CAMx4) for numerical
investigations are also discussed. The basic types of coupled meteorological-chemical models,
the application of the main limited area models, and the level of precision of the various
modelling systems are briefly discussed.
The factors controlling atmospheric circulation over Canterbury and the Christchurch
region are described, and their influence on heavy night-time air pollution in Christchurch and its
vicinity, with particular reference to the winter situation and the possibility of prediction and
control of the aerosol air pollution. The study analyses input data for numerical modelling,
including global analysis data, the CAPS2000 and winter 2003 field experimental sites, and
particulate monitoring observations.
Several methods of MM5 modelling are applied to replicate the local air circulation over
Christchurch and its environs: single run modelling, series of runs with different levels of nesting
with use of the CAPS2000 observed data for MM5 fine tuning. Particulars of 2003 winter MM5
modelling using global analysis input data, and Meteorological Service input data are covered
separately.
The numerical modelling system (meteorological-chemical) was created with application
of CAMx4 as a basic air quality model. The procedures for assimilation of MM5 data as basic
input meteorology for the chemistry model, and use of particulate matter monitoring data were
investigated. Different versions of MM5-CAMx4 optimal combination have been compared, and
quasi-operation possibilities of the MM5-CAMx4 modelling system have also been considered on the basis of winter 2000 and winter 2003 PMlO experimental modelling.
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Titov, Mikhail. "Investigation of winter aerosol dispersion using the MM5/WRF-CAMx4 numerical modelling system : application to the aerosol abatement strategy for the city of Christchurch : a thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy in Environmental Science at the University of Canterbury /." Thesis, University of Canterbury. Geography, 2008. http://hdl.handle.net/10092/1581.
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Air circulation and air pollution dispersion models are used by a range of stakeholders involved in managing air quality in New Zealand following the recent establishment and implementation of the National Environmental (Air Quality) Standards by the Ministry for the Environment. MM5-CAMx4 and WRF-CAMx4 numerical modelling systems were utilized to air circulation over the complex terrain of the Christchurch area for investigation applied to winter aerosol pollution, following the recent establishment and implementation of the National Environmental Standards. A new method using several different chemical scenarios is developed to calculate optimal chemical composition of the input gridded aerosol emissions. This method improves the accuracy of predicted PM concentrations. The MM5-CAMx4.2 numerical system is evaluated to predict aerosol concentrations over a 48-72 hour time period for Christchurch for winter 2005. The aerosol concentrations are obtained for four different chemical compositions of the input aerosol emissions. The fine-total PM regression error between observed and modelled aerosol is used to find the minimum difference between modelled and ambient aerosol. Combination of the chemical scenarios with the minimum error between modelled and ambient data is employed to create a new complex chemical scenario. A reduction of the systematic error in the scenario method is achieved by applying the MM5/WRF - CAMx4.2 numerical system and observations for winter 2006, aerosol data from 2 observation sites. Assessment of the efficiency of PM abatement strategies for the period 2005- 2013 is undertaken using winter 2005 meteorology and application of a linear reduction in emissions according to Environment Canterbury proposed plan for aerosol reduction. A new numerical approach to selection of PM monitoring sites optimal localisation is also developed and could be applied to any air pollutant to find the optimal positions for installing new observation sites.
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Mokalled, Tharwat. "The impact of Beirut Rafic Hariri International Airport’s activities on the air quality of Beirut & its suburbs : measurements and modelling of VOCs and NO2." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF041.
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Cette thèse étudie l’impact de l’Aéroport international de Beyrouth sur la qualité de l’air de Beyrouth et ses banlieues par mesures et modélisation des COVs et NO2. Il s’agit de la première étude qui identifie les signatures des émissions (COVs) issues des avions sous opération réelle. Grâce aux signatures détectées lors de 4 campagnes réalisées, nous constatons que l’aéroport a un impact sur la qualité de l’air de son voisinage, la zone côtière (trajectoire d’atterrissage), et les zones montagneuses. Ces résultats sont confirmés via le modèle ADMS-Airport, utilisé pour la première fois au Moyen-Orient et validé pour les conditions libanaises (r = 0.86). Par ailleurs, les concentrations de 47 COVs ont été mesurées pour la première fois à l'intérieur d’un bâtiment de l'aéroport. Les teneurs en COVs qui sont corrélées au nombre d’avions sont en dessous des valeurs seuils sauf pour l'acroléine alors que la celle de NO2 peut constituer un danger pour la santéThis work mainly investigated the impact of Beirut Airport on the air quality of Beirut and its suburbs via both measurements and modeling of VOCs and NO2. This is the first study to determine VOC signatures of exhaust emissions from aircraft under real operation. Using these signatures, the impact of the airport activities was tracked in 4 transect campaigns, where it was found that the airport impacts air quality not only in its vicinity, but also on the seashore (landing jet trajectory) and in mountainous areas. These results were confirmed via modeling with ADMS-Airport, implemented for the first time in the Middle East, after being validated in the Lebanese conditions (r = 0.86). As a secondary goal, and for the first time, 47 VOCs were assessed inside an airport building. Measured VOC levels did not present any risks except for acrolein. In the arrivals hall, NO2 levels indicated a health hazard; while a direct relationship was found between aircraft number and VOC concentrations
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McClure, John Douglas. "Sensitivity and uncertainty analysis in atmospheric dispersion models." Thesis, University of Glasgow, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270992.
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Cook, Sarah Elizabeth. "Multi level Monte Carlo methods for atmospheric dispersion modelling." Thesis, University of Bath, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616582.
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The Met Office uses the NAME dispersion model to solve stochastic differential equations (SDEs) for predicting the transport and spread of atmospheric pollutants. Time stepping methods for this SDE dominate the computation time. In particular the slow convergence of the Monte Carlo Method imposes limitations on the accuracy with which predictions can be made on operational timescales. We review the theory of both the Standard and Multi Level Monte Carlo Methods, and in particular the complexity theorems discussed in [9] in a more general context. We then argue how it can potentially give rise to significant gains for this problem in atmospheric dispersion modelling. To verify these theoretical arguments numerically, we consider two model problems; a simplified problem which corresponds to homogeneous turbulence and is used by the Met Office for long term predictions, as well as a full non-linear model problem close to that used by the Met Office for atmospheric dispersion modelling. For both model problems we performed numerical tests in which we observed significant speed-up as a result of the implementation of the Multi Level Monte Carlo Method. The numerically observed convergence rates are also confirmed by a full theoretical analysis for the simplified model problem.
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Kukkonen, Jaakko. "Modelling source terms for the atmospheric dispersion of hazardous substances." Helsinki : Societas Scientiarum Fennica, 1990. http://catalog.hathitrust.org/api/volumes/oclc/57930643.html.
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Dingwell, Adam. "Dispersion modelling of volcanic emissions." Doctoral thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-303959.
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Gases and particles released by volcanoes pose a serious hazard to humans and society. Emissions can be transported over long distances before being reduced to harmless concentrations. Knowing which areas are, or will be, exposed to volcanic emissions is an important part inreducing the impact on human health and society. In this thesis, the dispersion of volcanic emissions is studied using a set of atmospheric models. The work includes contribution to the development of the Lagrangian Particle Dispersion Model FLEXPART-WRF. Three case studies have been performed, one studying potential ash emissions from potential future eruptions on Iceland, a second covering SO2 emissions from Mt. Nyiragongo in D.R. Congo, and a third studying the SO2 emission rate of the Holuhraun eruption (Iceland) in 2014–2015. The first study covers volcanic ash hazard for air traffic over Europe. Three years of meteorological data are used to repeatedly simulate dispersion from different eruption scenarios. The simulations are used to study the probability of hazardous concentrations in ash in European airspace. The ash hazard shows a seasonal variation with a higher probability of efficient eastward transport in winter, while summer eruptions pose a more persistent hazard. In the second study, regional gas exposure around Mt. Nyiragongo is modelled using flux measurements to improve the description of the emission source. Gases are generally transported to the north-west in June–August and to the south-west in December–January. A diurnal variation due to land breeze around lake Kivu contributes to high concentrations of SO2 along the northern shore during the night. Potentially hazardous concentrations are occasionally reached in populated areas in the region, but mainly during the nights. The third study uses inverse dispersion modelling to determine the height and emission rates based on traverse measurements of the plume at 80–240 km from the source. The calculated source term yields better agreement with satellite observations compared to commonly used column sources. The work in this thesis presents improvements in dispersion modelling of volcanic emissions through improved models, more accurate representation of the source terms, and through incorporating new types of measurements into the modelling systems.Gas- och partikelutsläpp från vulkaner utgör en fara för människor och för vårt samhälle. Utsläppen kan transporteras över långa avstånd innan de reduceras till oskadliga halter. Att känna till vilka områden som utsätts för, eller kommer utsättas för, utsläppen är ett viktigt verktyg föratt minska påverkan på folkhälsa och samhälle. I avhandlingen studeras spridningen av utsläpp från vulkanutbrott med hjälp av en uppsättning numeriska atmosfärsmodeller. Den Lagrangiska Partikelspridningsmodellen FLEXPART-WRF har förbättrats och applicerats för spridningsmodellering av vulkanutbrott. Tre studier har utförts, en fokuserar på vulkanaska från potentiella framtida utbrott på Island, den andra studerar SO2-ustläpp från vulkanen Nyiragongo i Demokratiska Republiken Kongo, och den tredje studerar SO2-ustläpp från utbrottet i Holuhraun (Island) 2014–2015. Den första studien uppskattar sannolikheten för att vulkanaska från framtida vulkanutbrott på Island ska överskrida de gränsvärden som tillämpas för flygtrafik. Tre år av meteorologisk data används för att simulera spridningen från olika utbrottsscenarier. Sannolikheten för skadliga halter aska varierar med årstid, med en högre sannolikhet för effektiv transport österut under vintermånaderna, sommarutbrott är istället mer benägna att orsaka långvariga problem överspecifika områden. In den andra studien undersöks spridningen av SO2 från Nyiragongo över en ettårsperiod. Flödesmätningar av plymen används för att förbättra källtermen i modellen. Gaserna transporteras i regel mot nordväst i juni–augusti och mot sydväst i december–februari En dygnsvariation, kopplad till mesoskaliga processer runt Kivusjön, bidrar till förhöjda halter av SO2 nattetid längs Kivusjöns norra kust. Potentiellt skadliga halter av SO2 uppnås av och till i befolkade områden men huvudsakligen nattetid. Den tredje studien utnyttjar inversmodellering för att avgöra plymhöjd och gasutsläpp baserat på traversmätningar av plymen runt 80–240 km från utsläppskällan. Den beräknade källtermen resulterar i bättre överensstämmelse mellan modell- och satellitdata jämfört med enklare källtermer. Arbetet i den här avhandlingen presenterar flertalet förbättringar för spridningsmodellering av vulkanutbrott genom bättre modeller, nogrannare beskrivning av källtermer, och genom nya metoder för tillämpning av olika typer av mätdata.
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Sachdev, Jai Singh. "A review of dispersion modelling and particle trajectories in atmospheric flows." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0017/MQ53327.pdf.
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廖俊豪 and Chun-ho Liu. "Numerical modelling of atmospheric boundary layer with application to air pollutant dispersion." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31239018.
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Liu, Chun-ho. "Numerical modelling of atmospheric boundary layer with application to air pollutant dispersion /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20158695.
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Assimakopoulos, Vasiliki. "Numerical modelling of dispersion of atmospheric pollution in and above urban canopies." Thesis, Imperial College London, 2002. http://hdl.handle.net/10044/1/8046.
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Plainiotis, Stylianos. "Atmospheric dispersion modelling of particulate and gaseous pollutants affecting the trans-Manche region." Thesis, University of Greenwich, 2006. http://gala.gre.ac.uk/6269/.
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This thesis describes the development of a methodology to determine large-scale and meso-scale atmospheric dispersion patterns. The research is only concerned with outdoor exposure to atmospheric pollutants and aims to identify pollution sources using dispersion modelling with the assistance of ground level measurements from British, French and other monitoring stations and remote sensing technology. Lagrangian Particle Dispersion (LPD) models compute trajectories of a large number of notional particles and can be used to numerically simulate the dispersion of a pollutant (passive tracer) in the planetary boundary layer. Two widely used atmospheric dispersion models were employed: the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model by R. Draxler, and the model FLEXPART by Stohl et al. Both models possess forward tracking and inverse (or receptor-based) modes. Meteorological data output from the PSU/NCAR Mesoscale model (known as MM5), or datasets from the European Centre of Medium-range Weather Forecast (ECMWF) are used to drive the dispersion models. Linkage routines were developed to interpret the LPD codes with the required meteorological information. This study aims to determine whether current approaches and practice for atmospheric dispersion modelling are reliable, consistent and up-to-date. An intercomparison of the models FLEXPART and HYSPLIT is performed for known episodes to determine their accuracy, ease of use, effect of source specification and to investigate their sensitivity to input data and mesh resolution, and in particular the effect of different model formulations and assumptions followed by the models. The possibility of identifying emission sources in the near and far field is investigated, by modelling dispersion backwards in time, in particular the discrimination of multiple sources from receptor data is discussed. The effect of meteorological data resolution on the output of LPD models was evaluated and the most suitable methodology for better source definition was determined for different modelling scales, ranging from the intercontinental transport of airborne pollutants to simulating pollution episodes caused by local sources.
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Apsley, David D. "Numerical modelling of neutral and stably stratified flow and dispersion in complex terrain." Thesis, University of Surrey, 1995. http://epubs.surrey.ac.uk/649/.
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Papageorgiou, I. G. "Mesoscale modelling of the atmospheric boundary layer including pollutant dispersion of a coastal area." Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356134.
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Zubas, Laimonas. "Modelling of methane emissions utilising a Lagrangian atmospheric dispersion model in combination with Earth observation data." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/31998.
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Space-borne methane observations provide increased spatial coverage and complement the precise, but sparse network of in-situ measurement sites. In this study, a method has been developed to investigate regional-scale methane budgets using space-borne methane observations, utilising the UK Met Office Numerical Atmospheric Modelling Environment (NAME). Lagrangian atmospheric dispersion models, such as NAME, allow us to investigate fluxes at a lesser computational cost and potentially, a higher spatial resolution. An inversion algorithm was created and tested on synthetic ground measurement data. The NAME based inversion algorithm was then developed to utilise column CH4 concentrations, with an intention of applying it to Greenhouse Gases Observing SATellite (GOSAT) observations. A study utilising synthetic GOSAT-like observations was carried out, as well as synthetic inversions quantifying the performance of future methane sensing space-borne missions (CarbonSat and Sentinel-5 Precursor), when used to study fluxes over the British Isles. The results were obtained for 2 months, January and July, 2011. Sentinel-5 Precursor can reduce the flux uncertainty over England by 30% over England and Wales in July, with the remaining regions (Scotland, Republic of Ireland, Northern Ireland and northern France) achieving a reduction of 8-14%. In contrast, CarbonSat error reduction values are expected to range from 3% to 18%. Finally, we used the forward model to relate bottom-up inventories to satellite observations of atmospheric XCH4 from GOSAT. For selected regions, we have inferred patterns in atmospheric XCH4 from the spatial distribution of the surface emissions, factoring in the atmospheric transport using an atmospheric dispersion model. The forward model was found to perform poorly over Western Europe (r=0.43) and North America (r=0.48). The agreement between the observations and simulations of r=0.72 were calculated over South America, r=0.60 over South East Asia and r=0.60 over Australasia.
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Wilkins, Kate L. "On simulating volcanic ash transport using data insertion : combining atmospheric dispersion modelling and satellite remote sensing." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.705463.
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MacKenzie, Angus Robert. "'Small system' modelling of the polluted planetary boundary layer." Thesis, University of Essex, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235597.
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Beard, Thomas. "CFD modelling of hydrogen safety aspects for a residential refuelling system." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/25723.
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This work concerns the modelling of scenarios for a residential hydrogen refuelling system. Such a system is under construction within the Engineering Safe and Compact Hydrogen Energy Reserves (ESCHER) project. Non-reacting and reacting simulations are compared against experimental data before being applied to a residential garage scenario. The non-reacting simulations utilise natural ventilation, which utilises the natural buoyancy of hydrogen and vent locations to disperse flammable mixtures. This is favoured over mechanical ventilation, which could fail. The non-reacting work focuses on investigating the most suitable venting configuration for a release of hydrogen from a refuelling system located within a residential garage. Different vent configurations are examined initially before proceeding to take into account atmospheric conditions, wind, and the presence of a vehicle for the two best venting configurations. This is to determine the venting configuration that would diminish the accumulation of a flammable mixture, as well as dissipating the mixture quickest after the release has stopped. The modelling strategy utilised for this work is validated against two different sets of experimental data, prior to the investigation into residential garages. The predicted and experimental results show good agreement for the modelling procedure suggested. The reacting investigations are for both premixed and non-premixed combustion. The non-premixed combustion investigates the temperature distributions and as such the possible harm to people for such a scenario, compared against experimental data. The results show some over predictions of the temperatures. The premixed combustion investigates the potential overpressures that may occur if a homogeneous mixture was to form and ignite, within a residential garage. This work is preceded by a validation of the combustion model with the predicted results compared to data from The University of Sydney. The validation results show that the modelling strategy matches the peak overpressures accurately. The non-reacting studies show that having a lower vent opposite the release and an higher vent near the release produces the smallest flammable mixture as well as dissipating the mixture to the external surroundings quickest. The non-premixed reacting work shows good agreement with experimental results. The premixed reacting work shows that the garage would destruct with major consequences to people and surroundings. This work would be applicable to any potential usage of indoor refuelling for hydrogen vehicles, helping to determine a suitable configuration for mitigating hydrogen releases. It should be noted that all such work is geometrically dependent and as such the strategy proposed would be useful for investigating individual scenarios.
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Meyer, Marcel. "Modelling atmospheric dispersal of fungal pathogens on continental scales to safeguard global wheat production." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/286586.
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The recent emergence of highly virulent strains of the pathogen causing wheat stem rust has been acknowledged as a threat to global food security. In infected wheat fields, vast amounts of pathogenic fungal spores are produced that can be carried away by wind. For targeted disease surveillance and control it is important to estimate when, where and how many fungal spores are dispersed from infected to susceptible wheat fields. In this study, high-performance computational resources are used to investigate long-distance dispersal revealing atmospheric pathways that connect entire continents. Mechanistic simulations of turbulent atmospheric spore dispersal are conducted. The analyses bring together a variety of data, including international field disease surveys and finely resolved meteorological model data. The UK Met Office's Langrangian stochastic particle dispersion model, NAME, is applied, extended and coupled to other models in a set of case studies. In the first case study, spore dispersal is analysed across Southern/East Africa, the Middle East, and Central/South Asia by simulating billions of stochastic trajectories of fungal spores over dynamically changing host and environmental landscapes. The circumstances under which virulent strains, such as Ug99, pose a risk to globally important wheat producing areas are identified. Simulation results indicate a negligible risk for dispersal from key wheat producing countries on the East African continent (Ethiopia, Kenya) directly to India and Pakistan. However, there is a considerable risk for atmospheric transport from the Arabian Peninsula to South Asia. Spore dispersal trends are quantified between all countries in the domain providing estimates which can be used to improve targeted sampling and control. In the second case study, dispersal from southern Africa to Australia is analysed. Simulation results, as well as data from phenotypic and genotypic analyses, support the hypothesis that extremely long-distance airborne dispersal across the Indian Ocean is possible, albeit rare. This indicates that the pathogen populations on the two continents are connected and underlines the importance of sharing surveillance intelligence between continents. The third case study focusses on Ethiopia, determining likely origins of strain TKTTF that recently caused severe epidemics in East Africa's largest wheat producing country. The analyses suggest inflow into Ethiopia from the Middle East via Yemen, consistent with field survey data. The risk for inflow of pathogens into Ethiopia from key neighbouring countries is ranked for different months of the wheat season. In the last results chapter a pilot study is summarized testing the feasibility of an automated short-term forecasting system for spore dispersal from the latest field disease detection sites. Whilst the functionality and practical relevance of the forecasting system is demonstrated, considerable challenges remain for testing the forecasts. The predictive simulation framework described in this thesis can be applied to any wheat producing area worldwide to assess dispersal risks. The research has broader relevance because long-distance dispersal is a key mechanism for the transmission of several crop and livestock diseases, and also plays an important role in other areas of ecology.
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Winiarek, Victor. "Dispersion atmosphérique et modélisation inverse pour la reconstruction de sources accidentelles de polluants." Phd thesis, Université Paris-Est, 2014. http://tel.archives-ouvertes.fr/tel-01004505.
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Les circonstances pouvant conduire à un rejet incontrôlé de polluants dans l'atmosphère sont variées : il peut s'agir de situations accidentelles, par exemples des fuites ou explosions sur un site industriel, ou encore de menaces terroristes : bombe sale, bombe biologique, notamment en milieu urbain. Face à de telles situations, les objectifs des autorités sont multiples : prévoir les zones impactées à court terme, notamment pour évacuer les populations concernées ; localiser la source pour pouvoir intervenir directement sur celle-ci ; enfin déterminer les zones polluées à plus long terme, par exemple par le dépôt de polluants persistants, et soumises à restriction de résidence ou d'utilisation agricole. Pour atteindre ces objectifs, des modèles numériques peuvent être utilisés pour modéliser la dispersion atmosphérique des polluants. Après avoir rappelé les processus physiques qui régissent le transport de polluants dans l'atmosphère, nous présenterons les différents modèles à disposition. Le choix de l'un ou l'autre de ces modèles dépend de l'échelle d'étude et du niveau de détails (topographiques notamment) désiré. Différentes méthodes de modélisation inverse pour reconstruire des sources accidentelles sont ensuite présentées, de même que des méthodes d'estimations des erreurs a priori, auxquelles les résultats de l'inversion sont particulièrement sensibles. Plusieurs cas d'application, en utilisant des données synthétiques et des données réelles, sont proposés, notamment l'estimation de termes sources consécutifs à l'accident de Fukushima en mars 2011. Par nos méthodes, nous avons estimé que les rejets de césium-137 se situent en 12 et 19 PBq, avec une incertitude comprise en 15 et 65%, et que les rejets d'iode-131 se situent entre 190 et 380 PBq avec une incertitude comprise entre 5 et 10%. En ce qui concerne la localisation d'une source inconnue, deux stratégies sont envisageables : les méthodes dites paramétriques et les méthodes non-paramétriques. Les méthodes paramétriques s'appuient sur le caractère particulier des situations accidentelles dans lesquelles les émissions de polluants sont généralement d'étendue limitée. La source à reconstruire est alors paramétrisée et le problème inverse consiste à estimer ces paramètres, en nombre réduit. Dans les méthodes non-paramétriques, aucune hypothèse sur la nature de la source (ponctuelle, localisée, ...) n'est réalisée et le système cherche à reconstruire un champs d'émission complet (en 4 dimensions). Plusieurs méthodes sont proposées et testées sur des situations réelles à l'échelle urbaine avec prise en compte des bâtiments, pour lesquelles les méthodes que nous proposons parviennent à localiser la source avec une erreur moyenne de 20m (soit 10% de la taille du domaine d'étude), suivant les situations modélisées et les méthodes inverses utilisées.
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Ben, Salem Nabil. "Modélisation directe et inverse de la dispersion atmosphérique en milieux complexes." Thesis, Ecully, Ecole centrale de Lyon, 2014. http://www.theses.fr/2014ECDL0023.
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La modélisation inverse de la dispersion atmosphérique consiste à reconstruire les caractéristiques d’une source (quantité de polluants rejetée, position) à partir de mesures de concentration dans l’air, en utilisant un modèle direct de dispersion et un algorithme d’inversion. Nous avons utilisé dans cette étude deux modèles directs de dispersion atmosphérique SIRANE (Soulhac, 2000; Soulhac et al., 2011) et SIRANERISK (Cierco et Soulhac, 2009a; Lamaison et al., 2011a, 2011b). Il s’agit de deux modèles opérationnels de « réseau des rues », basés sur le calcul du bilan de masse à différents niveaux du réseau. Leur concept permet de décrire correctement les différents phénomènes physiques de dispersion et de transport de la pollution atmosphérique dans des réseaux urbains complexes. L’étude de validation de ces deux modèles directs de dispersion a été effectuée après avoir évalué la fiabilité des paramétrages adoptés pour simuler les échanges verticaux entre la canopée et l'atmosphère, les transferts aux intersections de rues et la canalisation de l’écoulement à l’intérieur du réseau de rues. Pour cela, nous avons utilisé des mesures en soufflerie effectuées dans plusieurs configurations académiques. Nous avons développé au cours de cette thèse un système de modélisation inverse de dispersion atmosphérique (nommé ReWind) qui consiste à déterminer les caractéristiques d’une source de polluant (débit, position) à partir des concentrations mesurées, en résolvant numériquement le système matriciel linéaire qui relie le vecteur des débits au vecteur des concentrations. La fiabilité des résultats et l’optimisation des temps de calcul d’inversion sont assurées par le couplage de plusieurs méthodes mathématiques de résolution et d’optimisation, bien adaptées pour traiter le cas des problèmes mal posés. L’étude de sensibilité de cet algorithme d’inversion à certains paramètres d’entrée (comme les conditions météorologiques, les positions des récepteurs,…) a été effectuée en utilisant des observations synthétiques (fictives) fournies par le modèle direct de dispersion atmosphérique. La spécificité des travaux entrepris dans le cadre de ce travail a consisté à appliquer ReWind dans des configurations complexes de quartier urbain, et à utiliser toute la variabilité turbulente des mesures expérimentales obtenues en soufflerie pour qualifier ses performances à reconstruire les paramètres sources dans des conditions représentatives de situations de crise en milieu urbain ou industriel. L’application de l’approche inverse en utilisant des signaux instantanés de concentration mesurés en soufflerie plutôt que des valeurs moyennes, a montré que le modèle ReWind fournit des résultats d’inversion qui sont globalement satisfaisants et particulièrement encourageants en termes de reproduction de la quantité de masse totale de polluant rejetée dans l’atmosphère. Cependant, l’algorithme présente quelques difficultés pour estimer à la fois le débit et la position de la source dans certains cas. En effet, les résultats de l’inversion sont assez influencés par le critère de recherche (d’optimisation), le nombre de récepteurs impactés par le panache, la qualité des observations et la fiabilité du modèle direct de dispersion atmosphériqueThe aim of this study is to develop an inverse atmospheric dispersion model for crisis management in urban areas and industrial sites. The inverse modes allows for the reconstruction of the characteristics of a pollutant source (emission rate, position) from concentration measurements, by combining a direct dispersion model and an inversion algorithm, and assuming as known both site topography and meteorological conditions. The direct models used in these study, named SIRANE and SIRANERISK, are both operational "street network" models. These are based on the decomposition of the urban atmosphere into two sub-domains: the urban boundary layer and the urban canopy, represented as a series of interconnected boxes. Parametric laws govern the mass exchanges between the boxes under the assumption that the pollutant dispersion within the canopy can be fully simulated by modelling three main bulk transfer phenomena: channelling along street axes, transfers at street intersections and vertical exchange between a street canyon and the overlying atmosphere. The first part of this study is devoted to a detailed validation of these direct models in order to test the parameterisations implemented in them. This is achieved by comparing their outputs with wind tunnel experiments of the dispersion of steady and unsteady pollutant releases in idealised urban geometries. In the second part we use these models and experiments to test the performances of an inversion algorithm, named REWind. The specificity of this work is twofold. The first concerns the application of the inversion algorithm - using as input data instantaneous concentration signals registered at fixed receptors and not only time-averaged or ensemble averaged concentrations. - in urban like geometries, using an operational urban dispersion model as direct model. The application of the inverse approach by using instantaneous concentration signals rather than the averaged concentrations showed that the ReWind model generally provides reliable estimates of the total pollutant mass discharged at the source. However, the algorithm has some difficulties in estimating both emission rate and position of the source. We also show that the performances of the inversion algorithm are significantly influenced by the cost function used to the optimization, the number of receptors and the parameterizations adopted in the direct atmospheric dispersion model
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Akinshipe, Oladapo Bola. "The development of an ‘emission inventory tool’ for brickmaking clamp kilns." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/40846.
Full textAbstract:
An emission inventory tool for estimating SO2, NO2, and PM10 emissions from brick clamp kiln sites
was developed from investigations performed on three representative South African clamp kiln
sites in order to facilitate application for Atmospheric Emission Licenses (AELs) from these sources.
The tool utilizes readily available site-specific parameters to generate emission factors for
significant activities that emit the aforementioned pollutants. PM10 emission factors for significant
processes were developed using empirical expressions from the Compilation of Air Pollutant
Emission Factors (AP-42) documents.
SO2 emission factor for clamp kiln firing was obtained from “reverse-modelling”, a technique that
integrates ambient monitoring and dispersion modelling (using Atmospheric Dispersion Modelling
System software) to “standardize” actual emission rate from an assumed rate of 1 g/s. The use of
multiple point sources proved to improve the simulation of the buoyancy-induced plume rise;
therefore, a “bi-point” source configuration was adopted for the kiln. The “reverse-modelling”
technique and “bi-point” source configuration produced SO2 emission rates differing from -9 % to
+22 % from mass balance results, indicating that the “reverse-modelling” calculations provide
reliable emission estimates for SO2.
An NO2 emission factor could not be obtained from the “reverse-modelling” technique due to
experimental errors and the significant effect of NO2 emissions from other onsite air emission
sources such as internal combustion engines. The NO2 emission factor was obtained from previous
comprehensive study on a similar clamp kiln site.
The emission factors obtained from this study were utilized in developing an “emission inventory
tool” which is utilized by clay brick manufacturers in quantifying air emissions from their sites.
Emissions quantification is a requirement for brick manufacturers to obtain an AEL which is
regulated under South African environmental laws.
It is suggested that the technique used here for SO2 emission confirmation could be used to
estimate emissions from a volume or area source where combustion occurs and where knowledge
of the source parameters is limited.Dissertation (MSc)--University of Pretoria, 2013.
gm2014
Chemical Engineering
unrestricted
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Xia, Qian [Verfasser], Yaping [Gutachter] Shao, Karl [Gutachter] Schneider, and Susanne [Gutachter] Crewell. "Development and Application of a Coupled Atmospheric and Hydrological Modelling System / Qian Xia ; Gutachter: Yaping Shao, Karl Schneider, Susanne Crewell." Köln : Universitäts- und Stadtbibliothek Köln, 2018. http://d-nb.info/1182533310/34.
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LOUBET, Benjamin. "Modélisation du dépôt sec d'ammoniac atmosphérique à proximité des sources." Phd thesis, Université Paul Sabatier - Toulouse III, 2000. http://tel.archives-ouvertes.fr/tel-00003250.
Full textAbstract:
L'ammoniac atmosphérique (NH3) est émis en majeure partie par l'agriculture. Etant très soluble, il se dépose rapidement sur la végétation par absorption foliaire et dépôt sur les surfaces (dépôt cuticulaire). Ces dépôts constituent une source de pollution importante pour les écosystèmes dits sensibles. Afin d'étudier la variabilité des dépôts secs d'ammoniac à proximité des sources agricoles, en réponse aux conditions climatiques et au type d'écosystème, un modèle mécaniste de dispersion et de dépôt d'NH3 a été développé. Il repose sur le couplage d'un modèle de dispersion de gaz-traces, de type marche aléatoire, et d'un modèle d'échange à l'échelle foliaire prenant en compte les voies stomatiques et cuticulaires, et incluant le point de compensation stomatique. Le modèle a été validé à partir de données expérimentales mesurées sur un couvert de maïs et de deux autres jeux de données sur prairie. Le modèle simule bien les concentrations dans le cas de la prairie mais il est biaisé dans le cas du maïs. Le biais semble provenir de l'orientation moyenne de la direction du vent et met en avant la nécessité d'utiliser un modèle en 3 dimensions pour l'étude de la dispersion à l'échelle locale. L'application du modèle montre que les dépôts secs cumulés peuvent varier entre quelques dixièmes de % et quasiment 20% de la quantité émise à 400 m en aval d'une source ligne. Le modèle indique que les facteurs les plus influents sur le dépôt sont la hauteur de la source par rapport au couvert, la vitesse du vent et la stratification thermique, ainsi que les résistances stomatiques et cuticulaires. Sous un climat chaud et sec, le dépôt sec local d'ammoniac emprunte prioritairement la voie stomatique, tandis que sous un climat tempéré et humide, il se fait par voie cuticulaire. Il en ressort que pour améliorer les estimations du dépôt sec local, il sera nécessaire de mieux comprendre et paramétrer le dépôt cuticulaire, et le point de compensation stomatique.
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Burgin, Laura Elizabeth. "The impacts of weather and climate change on the spread of bluetongue into the United Kingdom." Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3208.
Full textAbstract:
A large epizootic of the vector-borne disease bluetongue occurred in northern Europe from 2006-2009, costing the economies of the infected countries several hundreds of millions of euros. During this time, the United Kingdom (UK) was exposed to the risk of bluetongue by windborne incursions of infected Culicoides biting midges from the northern coast of mainland Europe. The first outbreaks which occurred in the UK in 2007 were attributed to this cause. Although bluetongue virus (BTV) no longer appears to be circulating in northern Europe, it is widely suggested that it and other midge-borne diseases may emerge again in the future, particularly under a changing climate. Spread of BTV is strongly influenced by the weather and climate however limited use has been made of meteorologically based models to generate predictions of its spread to the UK. The extent to which windborne BTV spread can be modelled at timescales from days to decades ahead, to inform tactical and strategic decisions taken to limit its transmission, is therefore examined here. An early warning system has been developed to predict possible incursion events on a daily timescale, based on an atmospheric dispersion model adapted to incorporate flight characteristics of the Culicoides vectors. The system’s warning of the first UK outbreak in September 2007 was found to be greatly beneficial to the UK livestock industry. The dispersion model is also shown to be a useful post-outbreak epidemiological analysis tool. A novel approach has been developed to predict BTV spread into the UK on climate-change timescales as dispersion modelling is not practical over extended periods of time. Using a combination of principal component and cluster analyses the synoptic scale atmospheric circulations which control when local weather conditions are suitable for midge incursions were determined. Changes in the frequency and timing of these large scale circulations over the period 2000 to 2050 were then examined using an ensemble of regional climate model simulations. The results suggest areas of UK under the influence of easterly winds may face a slight increase in risk and the length of the season where temperatures are suitable for BTV replication is likely to increase by around 20 days by 2050. However a high level of uncertainty is associated with these predictions so a flexible decision making approach should be adopted to accommodate better information as it becomes available in the future.
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Habarulema, John Bosco. "A contribution to TEC modelling over Southern Africa using GPS data." Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1005241.
Full textAbstract:
Modelling ionospheric total electron content (TEC) is an important area of interest for radio wave propagation, geodesy, surveying, the understanding of space weather dynamics and error correction in relation to Global Navigation Satellite Systems (GNNS) applications. With the utilisation of improved ionosonde technology coupled with the use of GNSS, the response of technological systems due to changes in the ionosphere during both quiet and disturbed conditions can be historically inferred. TEC values are usually derived from GNSS measurements using mathematically intensive algorithms. However, the techniques used to estimate these TEC values depend heavily on the availability of near-real time GNSS data, and therefore, are sometimes unable to generate complete datasets. This thesis investigated possibilities for the modelling of TEC values derived from the South African Global Positioning System (GPS)receiver network using linear regression methods and artificial neural networks (NNs). GPS TEC values were derived using the Adjusted Spherical Harmonic Analysis (ASHA) algorithm. Considering TEC and the factors that influence its variability as “dependent and independent variables” respectively, the capabilities of linear regression methods and NNs for TEC modelling were first investigated using a small dataset from two GPS receiver stations. NN and regression models were separately developed and used to reproduce TEC fluctuations at different stations not included in the models’ development. For this purpose, TEC was modelled as a function of diurnal variation, seasonal variation, solar and magnetic activities. Comparative analysis showed that NN models provide predictions of GPS TEC that were an improvement on those predicted by the regression models developed. A separate study to empirically investigate the effects of solar wind on GPS TEC was carried out. Quantitative results indicated that solar wind does not have a significant influence on TEC variability. The final TEC simulation model developed makes use of the NN technique to find the relationship between historical TEC data variations and factors that are known to influence TEC variability (such as solar and magnetic activities, diurnal and seasonal variations and the geographical locations of the respective GPS stations) for the purposes of regional TEC modelling and mapping. The NN technique in conjunction with interpolation and extrapolation methods makes it possible to construct ionospheric TEC maps and to analyse the spatial and temporal TEC behaviour over Southern Africa. For independent validation, modelled TEC values were compared to ionosonde TEC and the International Reference Ionosphere (IRI) generated TEC values during both quiet and disturbed conditions. This thesis provides a comprehensive guide on the development of TEC models for predicting ionospheric variability over the South African region, and forms a significant contribution to ionospheric modelling efforts in Africa.
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Martire, Léo. "Characterisation of Infrasound in the Coupled Solid-Atmosphere System : Numerical Modelling, Terrestrial and Planetary Applications." Thesis, Toulouse, ISAE, 2020. http://www.theses.fr/2020ESAE0028.
Full textAbstract:
Cette thèse porte sur le couplage mécanique entre le corps solide d’une planèteet son atmosphère. Nous étudions les événements géophysiques naturels et anthropiquesgrâce aux ondes sismiques et infrasonores. Ces phénomènes sont clés pour découvrir lastructure atmosphérique de la Terre, l’intérieur de Vénus, et Mars dans son intégralité.Les formes d’ondes acoustiques et sismiques contiennent des informations importantes, à lafois sur l’événement source et sur le milieu de propagation. L’objet de ce travail est double.Premièrement, nous développons un logiciel de simulation numérique pour le systèmecouplé sol-atmosphère. Nous nous appuyons sur les équations linéarisées de Navier-Stokespour modéliser l’atmosphère, et sur la visco-élastodynamique pour modéliser le sous-sol.Nous utilisons la méthode des éléments finis spectraux discontinus, permettant la simulationcomplète des formes d’ondes. L’implémentation est validée à l’aide de deux techniques :les solutions analytiques et manufacturées. Le logiciel permet de modéliser tous les types decouplages air-sol, et prend en compte avec précision la propagation des ondes acoustiqueset sismiques. Des topographies complexes peuvent être utilisées, ainsi que des modèles atmosphériques variant latéralement. Il est donc particulièrement bien adapté à l’étude de laplupart des phénomènes géophysiques dans les atmosphères planétaires. Parmi les exemplesd’événements, nous pouvons citer les ondes sismiques, les microbaroms, les explosionssouterraines ou aériennes, ou encore les ondes de gravité. Deuxièmement, nous étudionsde nombreux cas d’application liés à la planétologie. En vue de l’exploration de l’intérieurde Vénus, nous menons des expériences terrestres dont le but est d’étudier les infrasonsinduits par les séismes, et utilisons notamment des instruments sous ballons. Nous montronsqu’il est possible de déduire les propriétés et la structure du sous-sol grâce à ces ondesinfrasonores. Ces ballons instrumentés permettent également de localiser les événements ausol. Ce sujet est crucial pour l’exploration planétaire, mais également pour la surveillancede la Terre depuis l’atmosphère. Enfin, nous démontrons que des infrasons sont présentsdans l’atmosphère de Mars, établissant pour la première fois l’existence d’infrasons sur uneautre planète. Ceci est possible grâce au sismomètre SEIS d’InSight, capable de mesurer lesinfimes mouvements du sol causés par le passage des infrasonsThis thesis focuses on the mechanical coupling between a planet’s solid bodyand its atmosphere. We study natural and anthropogenic geophysical events under thescope of seismic waves and infrasound. These phenomena are keys to uncover the atmosphericstructure of Earth, the interior of Venus, and Mars as a whole. Acoustic and seismicwaveforms contain valuable information, about both the source event and the propagationmedium. Our work is two-fold. Firstly, we develop a numerical simulation software for thecoupled ground-atmosphere system. We rely on the linearised Navier-Stokes equations tomodel the atmosphere, and on visco-elastodynamics to model the sub-surface. We employa discontinuous spectral finite elements method, allowing the simulation of full waveforms.The implementation is validated using two techniques: analytical and manufactured solutions.Our software can model all types of air-ground couplings, and accurately accountsfor acoustic and seismic wave propagation. Complex topographies can be used, as well asrange-dependant atmospheric models. As a result, it is particularly well suited to studymost geophysical phenomena in planetary atmospheres. Example events include seismicwaves, microbaroms, underground and overground explosions, or gravity waves. Secondly,we study numerous application cases related to the aforementioned planetary science objectives.With the exploration of Venus’ interior in mind, we conduct terrestrial experiments tostudy seismically-induced infrasound, and involve balloon-borne instruments. We show thatit is possible to infer the properties and structure of the sub-surface from these infrasonicwaves. These instrumented balloons also render the localisation of ground events possible,which is crucial both for planetary exploration and for the airborne monitoring of the Earth.Finally, we demonstrate that the Martian atmosphere features infrasound, establishing forthe first time the existence of infrasound on another planet. This is achieved thanks toInSight’s seismometer SEIS, able to measure the faint ground motion caused by passingairwaves
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Pandya, Nishant. "Analyse de sensibilité paramétrique d’un outil de modélisation des conséquences de scénarios d’accidents. Application à la dispersion atmosphérique de rejets avec le logiciel Phast." Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT031G/document.
Full textAbstract:
L’objectif de la thèse est d’effectuer l’analyse de sensibilité paramétrique du logiciel Phast de modélisation de la dispersion atmosphérique de gaz toxiques et/ou inflammables. La technique a consisté à coupler Phast et l’outil d’analyse de sensibilité SimLab, ce qui permet d’exécuter automatiquement un grand nombre de simulations en faisant varier l’ensemble des paramètres du modèle de façon simultanée. La méthode d’analyse de sensibilité globale choisie, E-FAST, est basée sur l’analyse de la variance des sorties du modèle pour le calcul des indices de sensibilité. Nous avons étudié des scénarios de rejet continus pour six produits différents (monoxyde d’azote, ammoniac, chlore, azote, n-hexane et fluorure d’hydrogène), sélectionnés pour couvrir une large gamme de caractéristiques physiques et de conditions de stockage. L’analyse du modèle de dispersion de Phast, Unified Dispersion Model, a été séparée en deux étapes : étape de « screening » avec pour but de comparer l’influence de l’ensemble des paramètres puis étude de l’influence globale des paramètres de modélisation, autres que les paramètres météo et du terme source, sur une plage large de valeurs. Pour chaque produit, nous avons décomposé les scénarios de base en sous-scénarios correspondant à des conditions de rejet différentes. Ce travail a notamment permis de classifier les paramètres du modèle selon leur degré d’influence sur la variabilité de différentes sorties et d’effectuer une analyse comparative par produit indiquant, pour des conditions de rejet données, quels paramètres sont les plus influents sur les sorties. Une étude complémentaire a consisté à effectuer une analyse de sensibilité locale de ces paramètres autour de leur valeur par défautWe have undertaken a parametric sensitivity analysis of the Phast software tool’s models for atmospheric dispersion of toxic and/or inflammable gases. We have coupled Phast with the sensitivity analysis tool SimLab, and have automated the execution of a large number of simulations while varying simultaneously selected model parameters. The global sensitivity analysis method used, E-FAST, is based on analysis of the variance of model outputs, and allows us to estimate sensitivity indices. We have studied continuous release scenarios for six different products (nitric oxide, ammonia, chlorine, nitrogen, n-hexane and hydrogen fluoride), which were chosen to cover a wide range of physical characteristics and storage conditions. Our analysis of Phast’s Unified Dispersion Model comprises two phases: a screening phase which allows the sensitivity of a wide range of parameters to be compared, followed by a phase focusing on the sensitivity of internal model parameters (excluding weather and source term variables), over a wide input range. For each product, we have broken down base-case scenarios into a number of sub-scenarios corresponding to different release conditions. This work has allowed us to rank model parameters according to their influence on the variability of a number of model outputs. It also includes a per-product comparative analysis indicating, for each release condition studied, which parameters have the most influence on the outputs. In the final part of the work, we have analyzed the local sensitivity of these parameters in a narrow range around their default values
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Eyring, Veronika. "Modelling of the coupled chemistry climate system : projections of stratospheric ozone in the 21st century and impact of shipping on atmospheric composition and climate /." Köln : DLR, Bibliotheks- und Informationswesen, 2008. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016556630&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Warthen, Seth Tyler. "Attempting to Recreate the Late Ordovician Glaciation with the University of Victoria Earth System Climate Model." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1465828293.
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Lesouëf, Dorothée. "Étude numérique des circulations locales à la Réunion : application à la dispersion de polluants." Phd thesis, Université de la Réunion, 2010. http://tel.archives-ouvertes.fr/tel-00633096.
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Les régimes dynamiques dans les basses couches de l'atmosphère à l'île de la Réunion sont conditionnés par l'action du relief et du rayonnement sur l'écoulement synoptique. L'île est située en permanence dans le flux des alizés de sud-est et son relief élevé, culminant à 3000 m dans le centre de l'île et 2600 m au sud, constitue un obstacle important pour l'écoulement moyen. Le relief, le chauffage différentiel des pentes et le contraste thermique avec l'océan influent sur les échanges locaux entre la couche limite marine et la troposphère libre.L'analyse des phénomènes complexes de l'écoulement atmosphérique au niveau de l'île a pour but initial de caractériser les transferts de polluants émis localement. Cette étude a deux applications : * La première rentre dans le cadre préparatoire à la mise en place, à 2200 m d'altitude sur le Piton Maïdo, de l'observatoire atmosphérique de l'OPAR, à l'horizon 2011. L'objectif est de comprendre les circulations locales induites par le relief et les transports associés afin de discriminer d'éventuelles pollutions par les sources locales sur le signal qui sera mesuré in situ au sommet du Maïdo.* La seconde vise à étudier la diffusion des panaches volcaniques du Piton de la Fournaise. L'éruption majeure d'avril 2007 du volcan réunionnais a montré que des panaches pouvaient générer d'importantes pollutions dans diverses parties de l'île allant jusqu'à poser de réels problèmes environnementaux et de santé publique.Ces applications s'appuient sur une étude par modélisation numérique à haute résolution des écoulements atmosphériques dans les basses couches au niveau de l'île, au moyen du modèle météorologique de recherche MésoNH, permettant de conduire un ensemble de simulations sur cas idéalisés puis sur cas réels avec diffusion de traceurs passifs.
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Papatsoris, Anastassios Dimitriou. "Improvements to the modelling of radiowave propagation at millimetre wavelengths : in-depth studies are reported on resonance phenomena in the scattering of spherical ice particles, extinction and backscattering properties of clouds and on the absorption and dispersion spectra of atmospheric gases." Thesis, University of Bradford, 1993. http://hdl.handle.net/10454/4213.
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Various physical mechanisms that affect radiowave propagation at millimetre wavelengths are considered. Current modelling weaknesses are highlighted and new improved models or more appropriate modelling approaches are suggested. Interference and resonance phenomena in the scattering of spherical ice and water particles are reviewed. The long standing problem of the numerous resonances observed in the scattering diagrams of dielectric spheres is answered. The spatial structure and the physical characteristics of non-precipitable ice and water clouds are reviewed. Extinction and back scattering calculations for a wide variety of cloud models over the entire millimetre frequency spectrum are given. Multiple scattering and the effects of super-large drops in clouds are also dealt with. The potential of a spaceborne instrument in deducing information about the vertical structure of various cloud types is examined. Attenuation and reflectivity profiles resulting from various cloud types are calculated for a nadir pointing fixed beam millimetre wave radar operating at 94 GHz. The physics and application of the equation of radiative transfer to millimetre wave propagation in the earth's atmosphere are given and also is the solution of this equation for a typical millimetre wave remote sensing application. The theory of gaseous absorption at millimetre wavelengths is presented and an improved modelling approach is proposed for the calculation of the absorption and dispersion spectra of atmospheric gases. The effects of trace gases on communication systems operating at high altitudes are for the first time reported. Finally the use of the 60 GHz oxygen absorption band for top-side air traffic control/navigation and broadband transmission purposes is studied.
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Hodosán, Gabriella. "Lightning on exoplanets and brown dwarfs." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/12079.
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Lightning is an important electrical phenomenon, known to exist in several Solar System planets. Amongst others, it carries information on convection and cloud formation, and may be important for pre-biotic chemistry. Exoplanets and brown dwarfs have been shown to host environments appropriate for the initiation of lightning discharges. In this PhD project, I aim to determine if lightning on exoplanets and brown dwarfs can be more energetic than it is known from Solar System planets, what are the most promising signatures to look for, and if these "exo-lightning" signatures can be detected from Earth. This thesis focuses on three major topics. First I discuss a lightning climatology study of Earth, Jupiter, Saturn, and Venus. I apply the obtained lightning statistics to extrasolar planets in order to give a first estimate on lightning occurrence on exoplanets and brown dwarfs. Next, I introduce a short study of potential lightning activity on the exoplanet HAT-P-11b, based on previous radio observations. Related to this, I discuss a first estimate of observability of lightning from close brown dwarfs, with the optical Danish Telescope. The final part of my project focuses on a lightning radio model, which is applied to study the energy and radio power released from lightning discharges in hot giant gas planetary and brown dwarf atmospheres. The released energy determines the observability of signatures, and the effect lightning has on the local atmosphere of the object. This work combines knowledge obtained from planetary and earth sciences and uses that to learn more about extrasolar systems. My main results show that lightning on exoplanets may be more energetic than in the Solar System, supporting the possibility of future observations and detection of lightning activity on an extrasolar body. My work provides the base for future radio, optical, and infrared search for "exo-lightning".
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Du, Preez Chrisna Barbara. "A mesoscale investigation of the sea breeze in the Stellenbosch winegrowing district." Diss., Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-02092007-093317.
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Mkhonto, Prince Dominican Maphisa. "Atmospheric dispersion modelling study of a township within a declared national priority area." Thesis, 2014. http://hdl.handle.net/10210/11355.
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M.Sc. (Environmental Management)The use of atmospheric dispersion models to predict ground level pollutants concentrations has been on an increase in South Africa in the last decade. At this stage National Department of Environmental Affairs has published a draft document to provide guidelines on the type or use of models. Most Air Quality Specialists in the country make use of the United States Environmental Protection Agency approved atmospheric dispersion models to conduct air quality investigations. These models were developed in the United States of America after having considered the environmental set up and monitoring capabilities. In light of the above, much of the required input data are not readily available and calculations have been conducted to make up for the shortfall. For domestic emissions, quantifying the emissions factors is proving to be a challenge for modellers. They calculate emissions factors using different data sets from variable sources – sometimes the data are not up to date. This variability could potentially compromise the output of the model. This study aim was to model domestic emissions from an isolated rural township, Leandra, in the Mpumalanga Province – located within a nationally declared Highveld air quality management priority area – for two one month periods – in both the winter – July 2008 – and the summer – October 2008. This was achieved by using a United States Environmental Protection Agency approved AERMOD atmospheric dispersion model. Hourly surface measured meteorology data were obtained from the Langverwacht ambient air quality monitoring station and upper air data from the Irene monitoring station. The data were screened for any suspect values, formatted and then pre-processed by AERMET to be used by AERMOD. The study also investigated and compared the modelled time-series and monitored time-series data. This study calculated the effective emissions rate of 0.3 g PM10 s-1 m-2 by using a combination of monitored hourly PM10 concentrations and dispersion modelling time series data, for a typical Highveld township. Furthermore, the study revealed that, during winter when air is stagnant, Leandra was demonstrably isolated from other emissions sources of strength in the region – i.e. power station and domestic emissions were the dominant emissions sources. Under these circumstances, indoor and outdoor emissions were above the acceptable standards – i.e. they constituted unhealthy ambient air conditions. During summer – with the higher average wind speeds – Leandra was under the influence of industrial sources and the argument of isolation was not valid.
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Van, der Merwe Nicolene Magdalena. "Mesoscale dispersion modelling of SO₂ over the South African Highveld." Thesis, 2012. http://hdl.handle.net/10210/6272.
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HENDRYCH, Adam. "Porovnání výstupů z programů ALOHA a TerEx při jejich modelování rozptylu vybraných nebezpečných látek." Master's thesis, 2012. http://www.nusl.cz/ntk/nusl-136475.
Full textAbstract:
In the context of an increasing production of industrial toxic substances (TIC; Toxic Industrial Compound), the risk of accidental release of hazardous substances is growing in spite of the gradual implementation of safer technological processes and safety improvement measures. To mitigate the consequences of chemical accidents or to prepare preventive protective measures before the accident, it is necessary to know or at least estimate the course of accidents. In particular, it applies to the range of traumatic events and fatal accidents. One of the tools that can express the impact of accidents is modelling programs. This diploma thesis presents a comparison of outputs from two special types of software ? a foreign program the ALOHA and the TerEx developed in the Czech Republic. The purpose of the thesis was to indicate theoretical aspects related to gaseous toxic substances diffusion in the ground atmospheric layer and to describe modelling of their ill effects range. To achieve this objective, scientific literature and consultation with experts were used. The practical section of the thesis aimed at determining to what extent the results of both programs differ when initial conditions were identical. To achieve this goal, the intercomparison of outputs (e.g. hurtful concentration range) of the two programs that provided results for the same input data sets (type and quantity of hazardous substances, environmental temperature, wind speed, degree of cloud cover, weather stability class, type of ground surface) was used. After the assessment of the comparison it is possible to generalize the results stating that the software ALOHA compared to the TerEx is more conservative, which means that the ALOHA software provides longer anticipated ranges of danger. Therefore, it depends on the user (the person responsible ? crisis manager, intervention commander, mayor of the village), which approach they select or recommend ? to prepare a greater or a smaller area for a possible accident (to ensure public awareness, to implement technical measures to mitigate the impact of that accident, to assess the amount of financial resources, etc.). As a subsequent step it would be appropriate to verify the theoretical results experimentally, by field testing, which would be conducted under the same meteorological conditions under which the modelling was made by the mentioned programs. This would thus confirm the legitimacy of the special software use for the purpose of estimating the range of negative effects of chemical accidents.
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Chaloupecká, Hana. "Proudění a difúze uvnitř městské zástavby." Master's thesis, 2012. http://www.nusl.cz/ntk/nusl-305880.
Full textAbstract:
Title: Flow and diffusion characteristics inside the urban area Author: Hana Chaloupecká Department: Department of meteorology and enviroment protection Supervisor: prof. RNDr. Zbyněk Jaňour, DrSc., IT AS CR, v. v. i. Supervisor's e - mail: janour@it.cas.cz Abstract: Uniqueness of different towns, consists of various shapes of buildings. The main topic of this work is to compare concentration diffusion within groups of buildings of various types. We pursued houses made of single blocks of two different lengths - they were placed parallel or in courtyards. For research of pollution diffusion within the housing estates a method of physical modelling has been used. For this purpose we summarized a theory of atmospheric boundary layer and physical modelling at first. Then we pursued experiments. Measuring took place in a model in scale 1 : 300 inside an aerodynamic wind tunnel of the Institute of Thermomechanics AS in Nový Knín. We checked out the requirements placed on similarity of the real boundary layer and boundary layer modelled in the tunnel. By the measuring of concentration in urban areas we weren't watching a plume from the pollution source but we were studying an inversion task. We measured concentrations in two fixed points from different point sources inside the defined areas. A sensitivity of...
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Aneesh, C. S. "Data Assimilation Experiments Using An Indian Ocean General Circulation Model." Thesis, 2006. http://hdl.handle.net/2005/358.
Full textAbstract:
Today, ocean modeling is fast developing as a versatile tool for the study of earth’s climate, local marine ecosystems and coastal engineering applications. Though the field of ocean modeling began in the early 1950s along with the development of climate models and primitive computers,
even today, the state-of-the-art ocean models have their own limitations. Many issues still remain such as the uncertainity in the parameterisation of essential processes that occur on spatial and
temporal scales smaller than that can be resolved in model calculations, atmospheric forcing of the ocean and the boundary and initial conditions.
The advent of data assimilation into ocean modeling has heralded a new era in the field of ocean modeling and oceanic sciences. “Data assimilation” is a methodology in which observations
are used to improve the forecasting skill of operational meteorological models.
The study in the present thesis mainly focuses on obtaining a four dimensional realization (the spatial description coupled with the time evolution) of the oceanic flow that is simultaneously consistent with the observational evidence and with the dynamical equations of motion and to
provide initial conditions for predictions of oceanic circulation and tracer distribution.
A good implementation of data assimilation can be achieved with the availability of large number of good quality observations of the oceanic fields as both synoptic and in-situ data. With the technology in satellite oceanography and insitu measurements advancing by leaps over the past two decades, good synoptic and insitu observations of oceanic fields have been achieved. The current and expected explosion in remotely sensed and insitu measured oceanographic data is ushering a new age of ocean modeling and data assimilation. The thesis presents results of analysis
of the impact of data assimilation in an ocean general circulation model of the North Indian Ocean.
In this thesis we have studied the impact of assimilation of temperature and salinity profiles from Argo floats and Sea Surface height anomalies from satellite altimeters in a Sigma-coordinate Indian Ocean model. An ocean data assimilation system based on the Regional Ocean Modeling System (ROMS) for the Indian Ocean is used. This model is implemented, validated and applied
in a climatological simulation experiment to study the circulation in the Indian Ocean. The validated model is then used for the implementation of the data assimilation system for the Indian Ocean region. This dissertation presents the qualitative and quantitative comparisons of the model
simulations with and without subsurface temperature and salinity profiles and sea surface height anamoly data assimilation for the Indian Ocean region. This is the first ever reported data assimilation studies of the Argo subsurface temperature and salinity profile data with ROMS in the Indian
Ocean region.