Dissertations / Theses on the topic 'Engineering meteorology'

In the presence of a sufficient temperature gradient, snow evolves from an isotropic network of ice crystals to a transversely isotropic system of depth hoar chains. This morphology is often the weak layer responsible for full depth avalanches. Previous research primarily focused on quantifying the conditions necessary to produce depth hoar. Limited work has been performed to determine the underlying reason for the microstructural changes. Using entropy production rates derived from nonequilibrium thermodynamics, this research shows that depth hoar forms as a result of the snow progressing naturally toward thermal equilibrium.

Laboratory experiments were undertaken to examine the evolution of snow microstructure at the macro scale under nonequilibrium thermal conditions. Snow samples with similar initial microstructure were subjected to either a fixed temperature gradient or fixed heat input. The metamorphism for both sets of boundary conditions produced similar depth hoar chains with comparable increases in effective thermal conductivity. Examination of the Gibbs free energy and entropy production rates showed that all metamorphic changes were driven by the system evolving to facilitate equilibrium in the snow or the surroundings. This behavior was dictated by the second law of thermodynamics.

An existing numerical model was modified to examine depth hoar formation at the grain scale. Entropy production rate relations were developed for an open system of ice and water vapor. This analysis showed that heat conduction in the bonds had the highest specific entropy production rate, indicating they were the most inefficient part of the snow system. As the metamorphism advanced, the increase in bond size enhanced the conduction pathways through the snow, making the system more efficient at transferring heat. This spontaneous microstructural evolution moved the system and the surroundings toward equilibrium by reducing the local temperature gradients over the bonds and increasing the entropy production rate density.

The employment of nonequilibrium thermodynamics determined that the need to reach equilibrium was the underlying force that drives the evolution of snow microstructure. This research also expanded the relevance of nonequilibrium thermodynamics by applying it to a complicated, but well bounded, natural problem.

There has been much success in atmospheric boundary layer simulation with medium sized closed-circuit wind tunnels with test section dimensions of approximately 1 x 1 m. However, smaller, blower-type wind tunnels are more common in university laboratories due to the lower cost and smaller space requirements. A small size, open flow wind tunnel with a 1 x 1 foot test section was modified to simulate the atmospheric boundary layer with a combination of upstream spires and cubic roughness elements. The primitive spire geometry detailed in the literature was found to yield poor agreement with the power law velocity profile of interest, and a novel iterative algorithm was developed to produce nonlinear spire geometry. The geometry generated by the algorithm was tested in the wind tunnel and found to simulate the desired velocity profile based on a Hellman exponent of 0.20 with a high degree of agreement, having a maximum velocity error of 4%. This confirmed the suitability of small-sized wind tunnels for simulating the atmospheric boundary layer.

The Radar-based Quantitative Precipitation Estimates (QPE) is one of the NEXRAD products that are available in a high temporal and spatial resolution compared with gauges. Radar-based QPEs have been widely used in many hydrological and meteorological applications; however, a few studies have focused on using radar QPE products in deriving of Precipitation Frequency Estimates (PFE). Accurate and regionally specific information on PFE is critically needed for various water resources engineering planning and design purposes. This study focused first on examining the data quality of two main radar products, the near real-time Stage IV QPE product, and the post real-time RFC/MPE product. Assessment of the Stage IV product showed some alarming data artifacts that contaminate the identification of rainfall maxima. Based on the inter-comparison analysis of the two products, Stage IV and RFC/MPE, the latter was selected for the frequency analysis carried out throughout the study. The precipitation frequency analysis approach used in this study is based on fitting Generalized Extreme Value (GEV) distribution as a statistical model for the hydrologic extreme rainfall data that based on Annual Maximum Series (AMS) extracted from 11 years (2002-2012) over a domain covering Louisiana. The parameters of the GEV model are estimated using method of linear moments (L-moments). Two different approaches are suggested for estimating the precipitation frequencies; Pixel-Based approach, in which PFEs are estimated at each individual pixel and Region-Based approach in which a synthetic sample is generated at each pixel by using observations from surrounding pixels. The region-based technique outperforms the pixel based estimation when compared with results obtained by NOAA Atlas 14; however, the availability of only short record of observations and the underestimation of radar QPE for some extremes causes considerable reduction in precipitation frequencies in pixel-based and region-based approaches.

The potential for wind power development in Greenland is evaluated based on the analysis of 58 years of data (1957-2015) from RACMO 2.3 (Regional Atmospheric Climate Model). In order to create a wind power development tool, mesoscale maps based on RACMO 2.3 model were created containing the following characteristics: mean wind speeds (at 10 m), averaged maximum wind speed (with and without gusts at 10 m), temperature, humidity, geopotential, ice sheet mask and land sheet mask. A relevant aspect for this thesis is the mean wind speed. Over Greenland, the lower mean wind speeds range from 2-3 m/s on the tundra areas near the coast. This is influenced by high temperature inversion over the arctic tundra which disintegrates the predominant katabatic flow leading to lower wind speeds. On the other hand, the highest mean wind speeds range from 6 to 10 m/s and are observed in the northeastern region, due to cyclonic activity over the Greenland Sea. Maps of both the mean wind speed and averaged maximum wind speed are combined in order to achieve the highest mean wind speed value while at the same time avoiding maximum wind speeds higher than the cut-off value of the selected turbine model. This map combination is synchronized with pre-determined construction constraints, resulting in the suggestion of three different sites (sites 4, 5 and 6) as potential targets for wind power development. Multi-level data is sorted for different heights (10, 35, 70, 100 and 120 m) to perform a micro-scale analysis exercise for the three different site suggestions. A Vestas V90 3MW with an 80 meter hub height is selected as the standard turbine model to be deployed at the three recommended positions and for use in further simulations using WindSim. Annual Energy Production (AEP) for these three turbines in the recommended locations is calculated based on the interpolation from the climatology data at 70 m which is closest to the turbines’ hub heights. The AEP results are compared and show that site suggestion 4 presents the best potential for wind power development, surpassing by 79% and 23% the production results from sites 5 and 6, respectively. Based on the study developed, it is concluded that the in terms of wind resource assessment the potential for wind power development in Greenland exists. However the selection of possible deployment sites should be carefully done and real measurements must be performed.

Antarctic Wind Engineering deals with the effects of wind on the built environment. The assessment of wind induced forces, wind resource and wind driven snowdrifts are the main tasks for a wind engineer when participating on the design of an Antarctic building. While conventional Wind Engineering techniques are generally applicable to the Antarctic environment, there are some aspects that require further analysis due to the special characteristics of the Antarctic wind climate and its boundary layer meteorology.

The first issue in remote places like Antarctica is the lack of site wind measurements and meteorological information in general. In order to complement this shortage of information various meteorological databases have been surveyed. Global Reanalyses, produced by the European Met Office ECMWF, and RACMO/ANT mesoscale model simulations, produced by the Institute for Marine and Atmospheric Research of Utrecht University (IMAU), have been validated versus independent observations from a network of 115 automatic weather stations. The resolution of these models, of some tens of kilometers, is sufficient to characterize the wind climate in areas of smooth topography like the interior plateaus or the coastal ice shelves. In contrast, in escarpment and coastal areas, where the terrain gets rugged and katabatic winds are further intensified in confluence zones, the models lack resolution and underestimate the wind velocity.

The Antarctic atmospheric boundary layer (ABL) is characterized by the presence of strong katabatic winds that are generated by the presence of surface temperature inversions in sloping terrain. This inversion is persistent in Antarctica due to an almost continuous cooling by longwave radiation, especially during the winter night. As a result, the ABL is stably stratified most of the time and, only when the wind speed is high it becomes near neutrally stratified. This thesis also aims at making a critical review of the hypothesis underlying wind engineering models when extreme boundary layer situations are faced. It will be shown that the classical approach of assuming a neutral log-law in the surface layer can hold for studies of wind loading under strong winds but can be of limited use when detailed assessments are pursued.

The Antarctic landscape, mostly composed of very long fetches of ice covered terrain, makes it an optimum natural laboratory for the development of homogeneous boundary layers, which are a basic need for the formulation of ABL theories. Flux-profile measurements, made at Halley Research Station in the Brunt Ice Shelf by the British Antarctic Survery (BAS), have been used to analyze boundary layer similarity in view of formulating a one-dimensional ABL model. A 1D model of the neutral and stable boundary layer with a transport model for blowing snow has been implemented and verified versus test cases of the literature. A validation of quasi-stationary homogeneous profiles at different levels of stability confirms that such 1D models can be used to classify wind profiles to be used as boundary conditions for detailed 3D computational wind engineering studies.

A summary of the wind engineering activities carried out during the design of the Antarctic Research Station is provided as contextual reference and point of departure of this thesis. An elevated building on top of sloping terrain and connected to an under-snow garage constitutes a challenging environment for building design. Building aerodynamics and snowdrift management were tested in the von Karman Institute L1B wind tunnel for different building geometries and ridge integrations. Not only for safety and cost reduction but also for the integration of renewable energies, important benefits in the design of a building can be achieved if wind engineering is considered since the conceptual phase of the integrated building design process.

Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

Rapid urbanization of cities has greatly modified the thermal and dynamic profile in the urban boundary layer. This thesis attempts to study the effect of urban heating on the local climate and air quality for a tropical coastal urban agglomeration, Greater Kuala Lumpur (GKL) in Malaysia. A state-of-art numerical model, Weather Research and Forecast Model (WRF) is used to identify the influence of urbanization through modification of urban surfaces. In order to thoroughly study the environmental impact of land use change in GKL, this thesis begins with the local urban heating on the surface layer before extending to the influence on the boundary layer circulation and its atmospheric composition. The WRF model is tested for its applicability to reproduce the urban heating condition. The model verification hence incorporates sensitivity analysis of physics pertinent to the simulation of land surface and boundary layer dynamics condition, namely the land use map, urban canopy model (UCM) and planetary boundary layer (PBL) physics options. Result shows that the urban surface representation and parameterization models in WRF are of great importance for the high resolution urban climate in the region. The locally calibrated land use map and urban parameters have substantially improved the near-surface weather and urban heating prediction. The local PBL scheme also predicts a generally good agreement for the studied region in terms of near-surface environment and vertical profile during the morning and evening transitional period. Incorporating the optimum physics settings, the control study found that urbanization due to land use change has induced a modelled daily mean urban heat island intensity (UHII) of 0.9 °C with a more severe heating of 1.9 °C at night. The heating condition induces urban thermal circulation that interacts with the local topographic flow, namely sea/land breeze and downhill/uphill breeze for the coastal urban agglomeration sheltered by the mountain ranges on the other side. Depending on the cloud cover and prevailing synoptic flow, the immense heat forcing on the surface accelerates/decelerates the moisture-bearing sea breeze during the day. It also induces vertical lifting which creates a conducive environment for convective precipitation on the upwind region. The subsequent control study with chemical weather prediction model (WRF-Chem) shows that the urban heating condition reduces the ground ozone level by around 20 ppbv throughout the day. Analysis shows that the reduced ozone level is closely correlated to the stronger horizontal sea breeze front (SBF) advection in the morning and urban-enhanced vertical mixing during the night which disperse the ground ozone and its precursors. Despite the reduction of ozone level, the air quality monitoring result identifies GKL as NOx-sensitive region which is prone to higher level of ozone with the continuous expansion of urban. The thesis explores the ability of WRF software to reproduce the high resolution urban climate. The model evaluation has realistically discovered that WRF is able to produce good approximation of the near-surface weather condition and fairly reasonable vertical boundary layer profiles. However, the atmospheric chemistry composition of the local surface pollutants is greatly underestimated. Continuous effort is required to improve the regional prediction on the chemistry weather prediction tool.

The New European Wind Atlas (NEWA) was developed with an aim to provide high accuracy wind climate data for the region of EU and Turkey. Wind industry always seek for solid performance in wind resource assessment, and it is highly affected by the quality of modelled data. The aim of this study is to validate the newly developed wind atlas for two onshore sites in Sweden. Wind resource assessment is conducted using NEWA mesoscale data as wind condition of the sites. AEP estimation is performed using two different simulation tools, and the results of estimation are compared to the actual SCADA data for the validation of NEWA. During the process of simulation, downscaling is executed for the mesoscale data to reflect micro terrain effects. The result of the current study showed that NEWA mesoscale data represents wind climate very well for the onshore site with simple terrain. On the other hand, NEWA provided overestimated wind speeds for the relatively complex onshore site with forested areas. The overestimation of wind speed led to predict AEP significantly higher than the measurements. The result of downscaling showed only little difference to the original data, which can be explained by the sites’ low orographic complexity. This study contributes to a deeper understanding of NEWA and provides insights into its validity for onshore sites. It is beyond the scope of this study to investigate whole region covered by NEWA. A further study focusing on sites with higher orographic complexity or with cold climate is recommended to achieve further understanding of NEWA.

Today, mainframes contain a considerable portion of business applications worldwide. It is estimated that the current inventory of production COBOL running on mainframes is 150 to 200 billion lines of code. Despite the efforts to change within the mainframe environment, these mainframes, nowadays, face major problems for host organizations due to a combined set of financial, business related, technical and organizational problems. Moreover, the factors like diminishing resources (COBOL programmers), lack of documentation, inability to integrate with other systems, increasing maintenance costs, etc. have caused the organizations search for migration solutions. To overcome this problem within the context of modernization, over the years several main migration approaches that ranges from simple screen scraping methods to complete re-write of applications or re-hosting of platforms have been developed. To contribute to the solution of this overall problem, this thesis proposes a methodology framework specifically for the COBOL/CICS based mainframes. The research studies in this topic within this field are mainly focused on the technical aspects whereas our concentration is covering not only that but the other essential aspects of the problem domain. These are organizational view, project management view and process view. Within the thesis study, a special interest is given to the modernization strategy selection among migration, rewrite, packaged and do-nothing alternatives. Experimental results are also provided within the thesis to prove the usability of the approach for this selection.

Extreme rainfall events and consequent floods are being observed more frequently in the Western Black Sea region in Turkey as climate changes. In this study, application of a flood early warning system is intended by using and calibrating a combined model system. A regional-scale hydro-meteorological model system, consisting of Weather Research and Forecasting (WRF) model, NOAH land surface model and fully distributed NOAH-Hydro hydrologic models, is used for simulations of 25 heavy-rainfall and major flooding events observed in the Western Black Sea region between years 2000 and 2011. The performance of WRF model system in simulating precipitation is tested with 3-dimensional variational (3DVAR) data assimilation scheme. WRF-derived precipitation with and without data assimilation and Multi Precipitation Estimates (MPE) are used in NOAH-Hydro model to simulate streamflow for flood events. Statistical precipitation analyses show that WRF model with 3DVAR improved precipitation up to 12% with respect to no-assimilation. MPE algorithm generally underestimates rainfall and it also showed lower performance than WRF model with and without data assimilation. Depending on reliability of precipitation inputs, NOAH-Hydro model produces reasonable flood hydrographs both in structure and volume. After model calibration is performed using assimilated precipitation inputs in Bartin Basin, NOAH-Hydro model reduced the average error in streamflow by 23.24% and 53.57% with calibration for testing events. With calibrated parameters, NOAH-Hydro model forced by WRF non-assimilated precipitation input also reduced the error in streamflow but with lower rates (16.67% and 40.72%). With a proper model calibration and reliable precipitation inputs, hydrologic modeling system is capable of simulating flood events.

The energy exchanged between the atmosphere and the ocean is an important parameter in understanding the Earth’s climate. One way of quantifying this energy exchange is through the use of “wind work,” or the work done on the ocean by the wind. Since wind work is calculated according to the interaction between ocean surface currents and surface wind stress, a number of surface current decompositions can be used to decompose wind work calculations. In this research, geostrophic, ageostrophic, Ekman, and total current decompositions are all used to calculate wind work. Geostrophic currents are formed by the balance of surface pressure gradients and the Coriolis effect. Ageostrophic currents, on the other hand, are difficult to calculate because they are made up of many types of currents, and are generally defined as any current not in geostrophic balance. The main component of ageostrophic currents, Ekman currents, are used in this work to approximate ageostrophic currents. Ekman currents are formed by the balance of surface wind stress and the Coriolis effect. Finally, total currents are the sum of all currents in the ocean. Using high resolution, global NASA ocean models, the wind work on the global oceans is estimated via a number of decompositions, with results finding about 3.2 TW, .32 TW, and 3.05 TW for total, geostrophic, and Ekman wind work respectively, when taking a 7 day window average of surface currents and a 1 day average of surface stress. Averaging period for currents is found to significantly affect the resulting calculated wind work, with greater than 50 percent difference between 1 and 15 days of averaging. Looking at the same total, geostrophic, and Ekman wind work results for 1 day averages of wind stress and surface currents finds 5.5 TW, .03 TW, and 6.3 TW respectively. This result indicates that high frequency currents are very important to wind work. Seasonally, wind work is found to be at a maximum during the Northern Hemisphere (NH) summer, and at a minimum during the NH winter months. To help motivate the funding of a Doppler Scatterometer, simulations are used to show the capabilities of such an instrument in measuring wind work. DopplerScat simulations find that a satellite capable of measuring coincident surface vector winds and surface vector currents, with 1.1 m/s wind speed error and .5 m/s current speed error, could estimate global wind work to within 2 percent accuracy on an 8 day average with daily global snapshots.

Studien undersökte implementeringen och undervisningen av klimat och väder som år 2011 lades till under Fysik 1 i den svenska gymnasieskolan. Undersökningen använde sig av metodkombination som omfattade lärarintervjuer kompletterade med intervju av ett undervisningsråd på Skolverket och med textanalys av kursböcker. Lärarna upplevde en del problem kopplat till vad det nya ämnesområdet skulle innehålla. Oklarheten kring vad området skulle innehålla märktes också i kursböckernas framställning. Intervjupersonerna var överens om att viktiga aspekter inom ämnesområdet var växthuseffekten och global uppvärmning. Växthuseffekten och global uppvärmning hade även en framträdande roll i kursböckernas framställning. Från lärarintervjuerna framkom att lärarna gärna inkluderade Samhällsfrågor med Naturvetenskapligt Innehåll (SNI) i sin undervisning, men i bedömningen av elevernas lärande var det fysikalisk begreppsförståelse som accentuerades. Ämnesöverskridande samarbeten beskrevs av lärarna som önskvärt och förekom ofta.
This study examined the implementation and teaching of climate and weather which was added in the year 2011 under Physics 1 in the Swedish upper secondary school. The study performed a mixed-methods approach consisting of teacher interviews supplemented with an interview with an official at the Swedish National Agency for Education and with text analysis of course books. The teacher’s experienced some problems related to what the new subject area would contain. The uncertainty about what the area would contain was also seen in the course books. The interviewees’ opinion that the important issues in the subject area were the greenhouse effect and global warming were shared among the teachers. The greenhouse effect and global warming also had prominent roles in the course books. From the interviews it was found that teachers were positive to include Socio-Scientific Issues (SSI) into their teaching, but when assessing students learning the concepts of physics were emphasized. Cross-disciplinary cooperation was described by the teachers as desirable and often occurring.

In this study, the plant layout problem of a worldwide Printed Circuit Board (PCB) producer company is analyzed. Machines are grouped into cells using grouping methodologies of Tabular Algorithm, K-means clustering algorithm, and Hierarchical grouping with Levenshtein distances. Production plant layouts, which are formed by using different techniques, are evaluated using technical and economical indicators.

Atmospheric features, such as tropical cyclones, act as a driving mechanism for many of the major hazards affecting coastal areas around the world. Accurate and efficient quantification of tropical cyclone surge hazard is essential to the development of resilient coastal communities, particularly given continued sea level trend concerns. Recent major tropical cyclones that have impacted the northeastern portion of the United States have resulted in devastating flooding in New York City, the most densely populated city in the US. As a part of national effort to re-evaluate coastal inundation hazards, the Federal Emergency Management Agency used the Joint Probability Method to re-evaluate surge hazard probabilities for Flood Insurance Rate Maps in the New York – New Jersey coastal areas, also termed the New York Bight. As originally developed, this method required many combinations of storm parameters to statistically characterize the local climatology for numerical model simulation. Even though high-performance computing efficiency has vastly improved in recent years, researchers have utilized different “Optimal Sampling” techniques to reduce the number of storm simulations needed in the traditional Joint Probability Method. This manuscript presents results from the simulation of over 350 synthetic tropical cyclones designed to produce significant surge in the New York Bight using the hydrodynamic Advanced Circulation numerical model, bypassing the need for Optimal Sampling schemes. This data set allowed for a careful assessment of joint probability distributions utilized for this area and the impacts of current assumptions used in deriving new flood-risk maps for the New York City area.

Thesis (S.M.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), 2005.
Includes bibliographical references (leaves 70-72).
The uncertainty in the determination of the momentum and scalar fluxes remains one of the main obstacles to accurate numerical forecasts in low to moderate wind conditions. For example, latent heat fluxes computed from data using direct covariance and bulk aerodynamic methods show that there is good agreement in unstable conditions when the latent heat flux values are generally positive. However, the agreement is relatively poor in stable conditions, particularly when the moisture flux is directed downward. If the direct covariance measurements are indeed accurate, then they clearly indicate that the bulk aerodynamic formula overestimate the downward moisture flux in stable conditions. As a result, comparisons of the Dalton number for unstable and stable conditions indicate a marked difference in value between the two stability regimes. Investigations done for this thesis used data taken primarily at the Air-Sea Interaction Tower (ASIT) during the Coupled Boundary Layers and Air-Sea Transfer (CBLAST) Experiment 2003 from the 20-27 August 2003. Other data from the shore based Martha's Vineyard Coastal Observatory (MVCO) and moored buoys in the vicinity of the ASIT were also incorporated.
(cont.) During this eight day period, the boundary layer was often characterized by light winds, a stably stratified surface layer and a swell dominated wave field. Additionally, the advection of warm moist air over cooler water resulted in fog formation and a downward flux of moisture on at least three occasions. Therefore, a primary objective of this thesis is to present a case study to investigate the cause of this shortcoming in the bulk formula under these conditions by examining the physical processes that are unique to these boundary layers. Particular attention will be paid to the behavior of the Dalton number in a stable marine atmospheric boundary layer under foggy conditions using insights derived from the study of fog formation and current flux parameterization methods.
by Robert Farrington Crofoot.
S.M.

The goal of this thesis was to adopt a reverse flow injection analysis (rFIA) technique to the fluorometric analysis of the reaction o-phthaldialdehyde (OPA) with ammonium, allowing accurate measurements of ammonium concentrations lower than the detection limit of the widely used indophenol blue (IPB) colorimetric method while accounting for the background fluorescence of seawater. Ammonium is considered an essential nutrient for primary productivity, especially in the nutrient depleted surface ocean where as the most reduced form of dissolved inorganic nitrogen, it is readily assimilated via metabolic pathways. Challenges in the quantification of ammonium require more sensitive analytical techniques for a greater understanding of the biogeochemical cycling of ammonium in the oligotrophic ocean. On-line and automated flow analysis techniques are capable of mitigating some of the challenges. Fluorescent-based methods out-perform colorimetric methods in terms of detection limits and sensitivity. Presented here is the development of an rFIA technique paired with an OPA-sulfite chemistry. For this method, a sulfite-formaldehyde reagent is mixed with the sample stream and then injected with the OPA reagent before being heated. Fluorescence is measured before and at the peak of the OPA injection, differentiating the background fluorescence from the analyte signal. Experiments to optimize reaction parameters and characterize the effects of salinity and potentially interfering species were conducted. The newly developed method offers a reasonable throughput (18 samples per hour), low limit of detection (1.1 nM) ammonium analysis technique with automatic background fluorescence correction suitable for oligotrophic seawater as a preferable alternative to the low sensitivity and high limit of detection IPB colorimetric method.

This thesis focuses on the main processes in positive ground flashes and the distant lightning environment for both positive and negative ground flashes. It presents the characteristics of the preliminary breakdown pulses (PBPs), the characteristics of the electric field pulses observed during leader propagation, and the characteristics of the electric fields produced by the first and the subsequent return strokes. It also features the observations of distant positive and negative ground flashes at distances up to 1000 km. The results were based on electric field measurements conducted remotely during summer thunderstorms in Sweden in 2014. We found that the majority of the positive ground flashes were preceded by PBPs. Some were preceded by more than one PBP train, and the parameter values for the subsequent PBP trains were found to be smaller than the values for the first PBP train. Three types of PBPs were also identified. The results suggest that the PBPs in positive ground flashes during summer thunderstorms in Sweden are weak, and the inverted dipole charge cloud configuration is consistent with our observation. A small percentage of these positive ground flashes were observed to be preceded by pronounced leader pulses. The presence of these pulses suggests that the leaders propagate in a stepped manner. We inferred that these pulses were due to the upward-connecting negative leader since their characteristics were similar to those of a negative stepped leader. On the basis of the leader pulses’ time of initiation and the average speed of the leader, we estimated the distance travelled by the leader. One case of positive return stroke preceded by negative leader pulses was also observed, and the occurrence of these pulses was the first in positive ground flashes to be reported. The majority of these positive ground flashes were found to be single-stroke. Comparison between the first and the subsequent return strokes showed that the average durations of the subsequent stroke parameters were smaller than that of the first strokes. The distances reported by the lightning location system suggest that the subsequent strokes probably created new terminations to ground. Two possible reasons were given to explain the reason for the shorter duration of the subsequent return strokes parameters compared to the first strokes. Finally, observations of distant positive and negative ground flashes showed that the electric field waveforms have a typical shape, like a distorted ‘W’ (or distorted ‘M’ for negative ground flashes) followed by small oscillations. These small oscillations were more pronounced in negative ground flashes, especially at a greater distance. The heights of the ionospheric reflections estimated for both ground flashes were found to likely correspond to a D-layer of the ionosphere. Two possible reasons were suggested for the small oscillations observed in the waveforms.

Si la pertinence de la prise en compte de la météorologie dans la gestion du trafic est bien admise, son intégration dans les outils d'aide à la décision et les stratégies de contrôle représente encore un enjeu réel pour les gestionnaires d'infrastructures. En effet, cette avancée semble légitimée par les effets significatifs d'une météorologie dégradée sur la sécurité des usagers et le comportement des conducteurs. Ainsi, au niveau de la sécurité, un sur-risque d'accident a été mis en évidence par de nombreux travaux. Or, l'étiologie de ce risque augmenté ne permet pas seulement de démontrer l'impact d'évènements météorologiques extrêmes et ponctuels (ex : tempêtes de neige), mais égalementcelui de phénomènes récurrents (ex : la pluie). La baisse de la sécurité des conducteurs se traduit concrètement par un changement de comportements des usagers (vitesses, temps inter-véhiculaires) mais aussi du flot de véhicules en général (vitesse, débit, concentration), ceci influant de manière conséquente sur la mobilité. De fait, la pluie représente ainsi la seconde cause de congestion ponctuelle.Pourtant, malgré ces enjeux indéniables, les effets de la météorologie sur le trafic demeurent mal quantifiés et ne sont guère intégrés à la modélisation ou l'estimation du trafic. Ce travail de thèse se propose ainsi de contribuer à une meilleure compréhension des effets météorologiques sur le trafic, en se focalisant sur des phénomènes de précipitations en milieu interurbain. Partant d'un état de l'art de l'impact météorologique sur le trafic, il nous est apparu que les études existantes, par leurs carences, soulèvent le besoin de fonder une méthodologie d'analyse plus rigoureuse. Cette méthodologie, une fois clairement définie, a ensuite été appliquée à des données opérationnelles. Elle nous a permis de quantifier les effets de la pluie à plusieurs niveaux selon l'échelle de représentation abordée : au niveau microscopique, considérant le comportement individuel des conducteurs, les analyses statistiques mettent en lumière des effets sur les vitesses, les temps et les distances inter-véhiculaires. Ces effets se reflètent au niveau macroscopique (celui du flot de véhicules) avec des variations de débits, de vitesses du flot et, de façon générale, de l'ensemble des paramètres formant le diagramme fondamental du trafic. Les résultats empiriques nous semblent ainsi ouvrir la voie à l'intégration du phénomène météorologique à la modélisation du trafic.Partant, nous avons développé, à ce stade de notre travail, une contribution théorique à la modélisation du trafic se fondant sur une formulation Vlasov qui permet de dériver un modèle macroscopique à deux équations à partir d'une formulation cinétique. Le modèle ainsi proposé offre un cadre propice à l'intégration d'un paramètre météorologique. La discrétisation numérique du modèle s'effectue à l'aide d'une méthode à pas fractionnaire qui permet de traiter successivement le terme source et la partie homogène du système. Pour la partie homogène du système, nous avons fait l'usage d'un schéma de type Lagrange+remap. Le comportement du modèle, couplé à une équation de transport sur les temps inter-véhiculaires, a ensuite été illustré à travers une série d'expérimentations numériques qui ont mis en évidence ses aptitudes face à des conditions météorologiques changeantes.Dans un ultime volet, notre travail s'est orienté vers de futures applications en temps réel qui se placeraient dans un cadre bayesien d'assimilation de données. Le défi à relever est celui de l'estimation en ligne du vecteur d'état du trafic au fur et à mesure de l'arrivée de nouvelles observations. Une méthode de filtrage particulaire (Monte Carlo séquentielle) nous a paru judicieuse à mobiliser, car elle s'adapte bien à la problématique du trafic routier. Plusieurs scénarios fondés sur des données opérationnelles permettent ensuite de montrer les bénéfices de l'intégration du phénomène météorologique à de telles approches. Une meilleure connaissance du phénomène météorologique doit ainsi mener à son insertion dans les modèles de trafic qui forment le substrat des outils d'aide à la décision destinés aux gestionnaires.Le travail proposé ouvre donc des perspectives pour le développement de stratégies de gestion de trafic météo-sensibles.

Climate change is ecologically and socially complex, deemed the most important issue of our generation. Through this dissertation I have approached climate change research through an interdisciplinary perspective, investigating how this phenomenon will affect marine ecological systems, how we can better develop experimental systems to answer ecological questions, and how we can effectively educate about this issue. In Chapter 2, I provided accessible alternatives for researching the effects of climate change (elevated temperatures and pCO2) on marine ecosystems. I designed, built, and troubleshooted two accurate and inexpensive climate-controlled experimental systems capable of maintaining target conditions: a temperature-controlled system and an ocean acidification system. The temperature-controlled system was designed to manipulate experimental tank temperatures indirectly by controlling the temperature in a surrounding water bath, which buffered fluctuations and resulted in a high level of control. The ocean acidification experimental system was designed to elevate normally fluctuating pCO2 levels by a constant factor, which allowed pCO2 to fluctuate as expected in natural environments and made it more ecologically relevant than active pCO2-controlled systems. In Chapter 3, I experimentally tested the morphological responses of southern ribbed mussels Geukensia granosissima to two simultaneous stressors (elevated temperatures and the presence of water-borne predation cues from blue crab Callinectes sapidus) and if any effects of these treatments led to differences in handling times by predatory crabs. Bivalves may become more susceptible to predation as increased temperatures decrease the protection afforded by their shells, but few studies have tested the effects of elevated temperatures on inducible defenses in bivalves. Results showed that chronic heat stress can have detrimental morphological effects on intertidal mussels. Mussels reared in elevated temperatures manifested elongated shell shapes, exhibited a disruption of the predator effect on inducible defenses, and experienced decreased predator handling times. The observed responses to elevated temperatures could make southern ribbed mussels more vulnerable to predation. In Chapter 4, I experimentally tested the morphological responses of southern ribbed mussels to elevated pCO2 levels and the presence of water-borne predation cues from blue crabs, and if these effects led to differences in handling times by predatory crabs. Elevated pCO2 can have negative effects on bivalves’ morphology and physiology, but the consequences of these effects on predator-prey interactions are still unclear. I found that adult southern ribbed mussels’ inducible defenses were not affected by a medium-term exposure to elevated pCO2. Mussels grew more in shell length and width as a response to predation cues, independent of pCO2 conditions. However, and unexpectedly, mussels reared under elevated pCO2 exhibited greater growth in shell width independent of predator treatment, driving mussels reared in the presence of a predator under elevated pCO2 conditions to develop rounder shapes. On average, these effects on mussel morphometrics did not affect crab handling times, but mussels reared in the presence of a predator under elevated pCO2 conditions had highly variable handling times. It is important to consider the complexity of animal physiology, morphology, and interspecies relationships when making deductions on predator-prey relationships in a changing ocean. In Chapter 5, I analyzed the effectiveness of using an interdisciplinary approach to climate change education. Literature suggests that an interdisciplinary instructional framework in an outdoor setting, using tools from the experiential, active, and inquiry- and place-based learning approaches, as well as the socioscientific issues pedagogical framework, would be an excellent approach for climate change education. I found that students: increased their content knowledge on climate change causes and consequences, exhibited a deeper understanding of climate change through the words they used to describe it, and corrected common climate change misconceptions. This work can serve as an example for the development of effective climate change programs that uses already available instructional materials with intentional interdisciplinary goals. Our search to understand how marine ecosystems will cope with a changing climate has emphasized emerging issues in the way we gather data, the questions we seek to answer through research, and how we translate science of social importance to the public. Through this dissertation I strove to seek the answers to some of these questions and provide feasible solutions to some of the problems in climate change research and education through an interdisciplinary approach. As science continues to move towards answering questions of concern for both science and society, science research is moving towards more interdisciplinary approaches. This dissertation is an example of how this can be an efficient and comprehensive approach.

Översvämningar till följd av skyfall har blivit allt vanligare och förväntas att öka i takt med klimatförändringarna. Översvämningar kan ställa till stora skador för ett samhälle, framförallt när de samhällsviktiga verksamheterna blir drabbade. För att undvika att detta sker bör samhället vara byggt för att tåla stora volymer vatten som faller vid ett skyfall. Ett steg för att nå dit är att göra en skyfallskartering där flödesvägar, vattenvolymer och översvämningens utbredning tas fram genom hydraulisk modellering. Utifrån skyfallskarteringen kan sårbara områden upptäckas och förebyggande åtgärder kan utföras för att minska översvämningens negativa påverkan. Akademiska sjukhuset i Uppsala är en samhällsviktig verksamhet och har tidigare haft problem med översvämningar. I den här studien har en skyfallskartering utförts på Akademiska sjukhusets område för att ta reda på översvämningens utbredning vid ett skyfall och vilka åtgärder som lämpar sig för att förhindra översvämningar. Skyfallskarteringen utfördes i det tvådimensionella (2D) hydrauliska modelleringsprogrammet MIKE 21 Flow Model. Eftersom en skyfallskartering baseras på många generaliseringar finns det vissa osäkerheter kring valet av parametrar. Därför har även en känslighetsanalys utförts kring valet av regntyp (Chicago Design Storm (CDS) jämfört med ett blockregn), regnets varaktighet, grönytornas avrinningskoefficient och markens infiltrationshastighet. Indata till modellen baserades på olika kartdata som bearbetades i GIS-programmet ArcMap. Flera olika regn med varierande återkomsttid simulerades. Resultaten visade att det blir översvämning inne på sjukhusområdet vid ett 100-årsregn som förvärras när återkomsttiden ökar. Åtgärdsanalysen utfördes genom att lägga in förändringar i höjdmodellen för att se hur det påverkar översvämningens utbredning. Analysen visade att åtgärder som jordvallar och höjdsättning av marken kan tillämpas på området för att minska översvämningsrisken. Resultatet från känslighetsanalysen visade att ett CDS-regn ger större översvämningskonsekvenser i modelleringen än om ett blockregn av samma återkomsttid och varaktighet används. Känslighetsanalysen av varaktigheterna visade att en lång varaktighet kan leda till låga flödestoppar som inte representerar ett skyfall väl. En avrinningskoefficient på 0,4 beskriver infiltrationen i området väl och när en större avrinningskoefficient används tenderar översvämningen att bli större på grönytorna. Till sist visade resultatet att infiltrationshastigheten är en känslig parameter som bör väljas efter mer noggrann analys av marken i modelleringsområdet.
Flooding as a cause of cloudbursts have become more common and is expected to increase with climate change. Floods can cause substantial damage to a society, especially when the critical societal functions are affected. To avoid this the city should be built to tolerate large volumes of water from cloudbursts. As a step on the way to accomplish this, a cloudburst mapping could be made where flow paths, water volumes and the extent of the flooding are studied through hydraulic modelling. Through the cloudburst mapping, vulnerable areas can be spotted, and flood prevention measures can be taken to lessen the extent of the floods negative impact. Uppsala University Hospital serves a critical societal function and has previously had problems with flooding. In this project a cloudburst mapping has been made in the two dimensinoal (2D) hydraulic modelling program, MIKE 21. This was done to find out the extent of a flood caused by a cloudburst event and what measures that can be taken to prevent floods. A cloudburst mapping is based off many generalized assumptions and there are some uncertainties when selecting the parameters. Because of this, a sensitivity analysis was performed on the selection of rain-type (Chicago Design Storm (CDS) vs. block-rain), rain duration, the runoff coefficient and the soil's infiltration capacity. The inputs of the model were based off different geographic data and then constructed in the GIS-program ArcMap. Several different rain events with varying duration and return periods were simulated. The results showed that there is considerable flooding in the area after a rain with a 100-year return period and it gets worse when the return period increases. The flood prevention analysis was made by editing the terrain to mimic flood prevention measures and study how the extent of the flood responds to the edits. The analysis showed that measures like soil barriers and changes in elevation were effective in lessening the risk of flooding. The results from the sensitivity analysis showed that a CDS-rain causes a more significant flooding compared to a block-rain of the same return period and duration. The sensitivity analysis of the rain duration proved that a long duration can lead to flat flow curves that doesn't resemble a flow curve from a cloudburst event. A runoff coefficient of 0.4 describes the infiltration in the area well and with a larger coefficient the flooding on greenery tend to grow. Lastly, the infiltration capacity proved to be a sensitive parameter that needs to be selected carefully, preferably after a thorough soil analysis.

Currently, the South Pole has a large data problem. It is estimated that 1.2 TB of data is being produced every day, but less than 500 GB of that data is being uploaded via aging satellites to researchers in other parts of the world. This requires those at the South Pole to analyze the data and carefully select the parts to send, possibly missing out on vital scientific information. The South Pole Carrier Pigeon will look to bridge this data gap. The Carrier Pigeon will be a small unmanned aerial vehicle that will carry a 30 TB solid-state hard drive from the South Pole to various destinations in the Southern Hemisphere, but it has been designed to y to Christchurch, New Zealand. This 87 lb. UAV will be able to y 3,650 nmi. up to 25,000 ft., using a 5.7 hp. engine. It will feature an de-icing system on the leading edge of its 8 ft. span wing to allow it to y through cold, moist climates. It will have a 39 in. long fuselage with a tail boom of 33 in. The aircraft has been designed to be made out of composites, thus reducing both the weight of the aircraft as well as its drag. It has been designed to come apart in order to be shipped successfully to the South Pole. There, it will be assembled and launched via a custom pneumatic launcher. It will y autonomously to 15,000 ft. and cruise climb throughout the flight to 25,000 ft., before descending to its destination. There, it will be caught by a net restraint system, where the hard drive will be extracted. The Carrier Pigeon is truly a unique vehicle for its size, range, and robustness.

The objective of this project was to determine if the electromagnetic field (EMF) emissions from undersea power cables impacted the local and transient marine life, with an emphasis on reef fishes. The work was done at South Florida Ocean Measurement Facility of Naval Surface Warfare Center, Carderock Division, Broward County, Florida. This facility functions as the hub for a range of active undersea detection and data transmission cables. It has multiple active submarine power cables that extend several miles offshore and which can deliver power and enable data transmission to and from a range of acoustic and EMF sensors. The cables lie directly on the seabed, are buried in the sand, or are suspended in the water column. EMF emissions from a selected cable were created during SCUBA fish surveys. During the surveys the transmission of either alternating current (AC) or Direct Current (DC) was randomly intiated by the facility with no transmitted current (OFF) provided a control. The surveys were conducted using standardized transect and stationary point count methods to acquire reef fish abundances prior to and immediately after a change in transmission frequency (the divers were aware of the time of frequency change but not the specific frequencies). The divers were also tasked to note the reaction of the reef fishes to the immediate change in the EMFs emitting from the cable during a power switch. The surveys were conducted on a quarterly basis at three sampling sites offshore on the same cable. These sites were in water depths of approximately 5, 10, and 15 m, respectively and were selected based on their robust reef fish community and are representative of each of the three primary hardbottom coral reef habitats in the local offshore environment: the Inner (Shallow), Middle, and Outer (Deep) reef tracts. A total of 263 surveys were conducted: 132 transect-counts and 131 point-counts over 15 months. There were 24,473 fishes counted during transect-count surveys and with point-counts, 36,115 fishes were counted. With count types and sites combine a total of 151 species representing 35 families were recorded. An analysis of the data primarily did not find statistical differences among power states and any variables. However, this may be a Type II error as there are strong indications of a potential difference of a higher abundance of reef fishes at the sites when the power was off. There are a number of caveats to consider with this finding: the data set needs to be larger in terms of numbers of: counts, sites and eletro-sensitive species to allow for rigorous statistical analysis; also a longer time between frequency changes to allow for slower, but nonetheless important, reactions to differing EMFs might lead to differing conclusions. Obviously, more research is required to confirm the results of this study.

In the forecast data post-processing at the Swedish Meteorological and Hydrological Institute (SMHI) a regular Kalman filter is used to debias the two meter air temperature forecast of the physical models by controlling towards air temperature observations. The Kalman filter however diverges when encountering greater nonlinearities in shifting weather patterns, and can only be manually reset when a new air mass has stabilized itself within its operating region. This project aimed to automate this process by means of a machine learning approach. The methodology was at its base supervised learning, by first algorithmically labelling the air mass shift occurrences in the data, followed by training a logistic regression model. Observational data from the latest twenty years of the Uppsala automatic meteorological station was used for the analysis. A simple pipeline for loading, labelling, training on and visualizing the data was built. As a work in progress the operating regime was more of a semi-supervised one - which also in the long run could be a necessary and fruitful strategy. Conclusively the logistic regression appeared to be quite able to handle and infer from the dynamics of air temperatures - albeit non-robustly tested - being able to correctly classify 77% of the labelled data. This work was presented at Uppsala University in June 1st of 2018, and later in June 20th at SMHI.

Nitrate pollution is a widespread problem that affects water bodies in many regions of the world, undermining water quality and therefore its safe use. Despite the application of improved management practices, nitrate pollution seems to increase, particularly in groundwater. The Nitrate Vulnerable Zone (NVZ) designation in Europe, for instance, has increased from 35.5% of the EU-15 territory at the end of 1999 to 44% at the end of 2003, and the Commission’s report for the period 2004-2007 revealed that 15% of groundwater monitoring stations in the EU-27 territory showed nitrate levels above the limit of 50 mg of nitrates per liter. Some trends towards nitrate attenuation are observed, but at least 33% of water bodies will clearly fail in achieving the 2015 goals set by the Water Framework Directive. Several efforts have been addressed to either reduce nitrogen inputs or to decrease its already accumulated levels, particularly by designing nitrate-removal technologies aimed at recovering drinking-water standards. This PhD thesis, hence, focuses on the optimization of an already existing technology for nitrate­removal: enhanced in situ biodenitrification (EISB), which is now regaining attention due to its economic and environmental benefits and its potential for scale-up and design of case­specific solutions. EISB is an engineered application of microbial heterotrophic denitrification aimed at in situ nitrate removal from groundwater. Aimed at stimulating facultative denitrifiers, EISB is based on the injection of a C source into the aquifer. Microbial denitrification is then enhanced in a designated area of the aquifer, creating a biologically active zone (often referred as biowall) which removes nitrate from the naturally-flowing groundwater. Among the different factors that affect the technical feasibility of EISB, the type and quantity of the injected C source is a key issue, particularly due to its influence upon the microbial processes that determine the treatment performance. The understanding of the subsurface geology and hydrogeology is also an issue of concern, particularly if highly heterogeneous media, such as fractured aquifers, are meant to be remediated. Aimed at achieving our research goal, several EISB experiments were developed at different scales -batch, flow-through column and pilot scale-and involving different geological media -granular and fractured-. Combined chemical, microbial and isotope monitoring tools where applied to gain a better insight on the denitrification process and thus improve technology design and optimization. The first set of batch-scale experiments focused on testing the viability of in situ heterotrophic denitrification and determining the most suitable biostimulants for a case­specific scenario in the Osona region, a Catalan NVZ showing historic nitrate pollution up to 200 mg/L. Native microbiota was stimulated and nitrate reduction was effectively achieved by addition of a carbon source (ethanol or glucose) as well as a phosphorous source (disodium hydrogen phosphate). Transient nitrite accumulation was observed, especially when using glucose as the C source. The N and O isotope fractionation was determined to be -13.0‰ and -17.1‰ for eN and -8.9‰ and -15.1‰ for eO in ethanol and glucose-amended experiments respectively, resulting in eN/eO values of 1.46 (ethanol-amended experiment), and 1.13 (glucose-amended). Organic carbon (OC) consumption in batch­scale experiments, expressed as .C/.NO3 -, varied slightly depending on the type of C source used: 1.6 mmolOC/mmolNO3 -for ethanol and 2.2 for the glucose, similarly to stoichiometric values associated with nitrate respiration (0.83 and 1.25 mmolOC/mmolNO3 ­respectively). When deriving stoichiometric reactions that accounted not only for the amount of electron donor used for nitrate respiration but also for cell synthesis, the following values were determined: 1.9 and 2.0 mmolOC/mmolNO3 -for ethanol and glucose­induced biodenitrification respectively. These values were used for the numerical modeling of batch-scale experiments, aimed at quantifying microbial kinetics by applying the modified Monod expression. The (geochemical) numerical model also indicated a different effect of mineral precipitation on ethanol or glucose-induced denitrification, an effect that is linked to a different alkalinity production. Such effect could be taken into account when designing and/or optimizing EISB systems, particularly as a way to control geochemical clogging. A pilot-scale application was then performed at the site, aimed at assessing the viability of EISB in a fractured aquifer. Ethanol was now used as the main C source, and based on lab­scale results, P was also added. Again, transient nitrite accumulation was detected, and evidences for incomplete denitrification and coexistence of other respiration processes (such as iron or sulfate reduction) and autotrophic denitrification were observed. Sulfate isotope characterization proved that autotrophic denitrification linked to sulfide oxidation could be occurring along with heterotrophic denitrification, while sulfate­reduction couldn’t be verified. Overall, results suggested that stimulated heterotrophic denitrification could be applied as a remedial alternative in a fractured media and despite the complexity of the formation. However, a deep understanding of the system is required and efforts must be addressed to control microbial population and stability as a key issue to avoid the decrease of groundwater quality due to incomplete denitrification or secondary respiratory processes. Different engineering approaches such as feeding or pumping strategies could help improving the system performance. Aimed at testing the impact of such engineering approaches upon resulting water quality, a second study-case was studied, now in an alluvial media. . A flow-through experiment was built to simulate an EISB system and assess the influence of different C addition strategies upon the denitrification process. Heterotrophic denitrification was stimulated by the periodic addition of a C source (ethanol), and 4 different addition strategies were evaluated, being the first-one a weekly injection, and the others a daily injection with decreasing amounts of C. Enhanced denitrification was stimulated following the first C addition, easily achieving drinking water standards for both nitrate and nitrite. Water quality in terms of remaining C, denitrification intermediates and other anaerobic respiration products varied during the experimental time. Ethanol, for instance, showed a cyclic behavior during the weekly feeding strategy while it was completely depleted when injected daily. A quasi steady­state nitrate outflow, similar to ethanol’s, was obtained in daily injection scenarios, with nitrate levels ranging from non-detected values and up to 10 mg/L, and nitrite’s remaining undetected. No dissimilatory nitrate reduction to ammonium was ever detected and some secondary microbial respiration processes, mainly manganese reduction, were suspected to occur temporarily. Overall, results showed that biodenitrification could be successfully achieved by a daily addition of a C source slightly higher than the stoichiometric value, diminishing the accumulation of non-desired products and the biofilm growth and still obtaining the required denitrification results. Reducing the C/N ratio enables us to reduce treatment costs while achieving a better water quality in terms of remaining C and residual microflora, and potentially reducing the biofouling effect due to the increase of endogenous respiration. Endogenous activity –that provides internal C for denitrification-may become important when low C/N values are used, keep denitrification temporarily ongoing and reducing the biofilm growth, but may affect the biodenitrification performance at longer operation times. Such aspects should be further evaluated using modeling and/or experimental tools. Furthermore, results suggested that not only the feeding strategy but also the biofilm life-time have a direct effect on microbial population structure and hence on the biodenitrification performance, reducing the accumulation of nitrite over time. The obtained eN/eO fractionation values for the flow-through experiment (1.01) fell within the low-end of previously reported data (varying from 0.9 to 2.3), an effect that may be linked to faster microbial kinetics in enhanced vs. natural biodenitrification. Similar low values were observed in our previous batch-scale experiments as well as in other work conducted in our lab. Concerning ethanol’s fractionation, on the other side, a two-trend behavior was observed, probably indicating a change in the dominating C­consuming population. Interestingly, the second trend suggests an inverse fractionation of the C source that got depleted while being consumed.
Esta tesis se destina a la evaluación de la viabilidad técnica de la biodesnitrificación in situ de aguas subterráneas contaminadas por nitratos, con el objetivo de optimizar las estrategias de bioestimulación y mejorar los resultados del proceso microbiano. El proyecto evalúa la aplicación de la tecnología en dos entornos geológicos distintos: un medio fracturado de baja porosidad y un aluvial arenoso. Se desarrollan ensayos a tres escalas distintas: batch, columna de laboratorio de flujo continuo y piloto. El seguimiento y estudio del proceso se desarrolla mediante la combinación de herramientas de análisis químico y microbiológico y la aplicación de isótopos estables del nitrato, el sulfato y el C.

Dans la troposphère, le rayonnement électromagnétique hyperfréquence interagit avec la matière suivant trois processus : l'absorption par les molécules de gaz et d'eau, la diffusion due à la redirection de l'onde par les hydrométéores, et l'émission par les particules absorbantes d'un rayonnement naturel incohérent. Mes travaux ont pour base commune ces processus d'interaction des ondes électromagnétiques avec l'atmosphère, et concernent deux domaines distincts : la télédétection spatiale de l'atmosphère et les télécommunications Terre-satellite. J'ai développé une méthodologie originale de mise au point d'algorithmes neuronaux pour l'observation de l'atmosphère à partir de capteurs hyperfréquences passifs. Mes travaux ont mis en évidence la capacité des réseaux de neurones à restituer les paramètres physiques des phénomènes sous-jacents aux observations. Une amélioration des performances globales de la restitution des grandeurs atmosphériques est obtenue grâce à la modélisation de relations non linéaires que permet cette approche. Les perspectives multiples qu'offrent, en géophysique, l'emploi d'une architecture neuronale modulaire, ou l'utilisation des cartes de Kohonen, sont soulignées. L'évolution des systèmes de télécommunication hyperfréquence par satellites, pousse à utiliser des fréquences de plus en plus élevées. Aux fréquences supérieures à 20 GHz l'atmosphère est à l'origine de la dégradation de la qualité des liaisons. Je présenterai les campagnes de mesures, et les travaux de modélisation réalisés, dans le cadre de la mise au point de nouvelles techniques de lutte contre les affaiblissements (Fade Mitigation Technique). L'originalité de mes recherches relatives à la modélisation du canal de propagation réside dans l'usage de modélisations statistiques du type TARIMA GARCH, qui s'attachent, plutôt que de prévoir le comportement moyen du processus, à prévoir la variabilité et donc le risque d'un comportement extrême.

Ce travail a consisté à developper un modèle de canopée (CIM), qui pourrait servir d'interface entre des modèles méso-échelles de calcul du climat urbain et des modèles micro-échelles de besoin énergétique du bâtiment. Le développement est présenté en conditions atmosphériques variées, avec et sans obstacles, en s'appuyant sur les théories précédemment proposées. Il a été, par exemple, montré que, pour être en cohérence avec la théorie de similitude de Monin-Obukhov, un terme correctif devait être rajouté au terme de flottabilité de la T.K.E. CIM a aussi été couplé au modèle méso-échelle WRF. Une méthodologie a été proposée pour profiter de leurs avantages respectifs (un plus résolu, l'autre intégrant des termes de transports horizontaux) et pour assurer la cohérence de leurs résultats. Ces derniers ont montré que ce système, en plus d'être plus précis que le modèle WRF à la même résolution, permettait, par l'intermédiaire de CIM, de fournir des profils plus résolus près de la surface.

På SMHI hanteras stora mängder geografisk information som idag studeras med tvådimensionella metoder. Flerdimensionella metoder används mycket sparsamt inom verksamheten, trots att de atmosfäriska processerna sker i alla tre rumsdimensionerna och förändras med tiden. Inom SMHI är de allra flesta vana och nöjda med de tvådimensionella visualiseringsmetoderna och känner stor arbetsglädje i dagens arbetssätt. Bland annat är meteorologernas utbildning helt anpassad efter dagens 2D-visualiseringar. Många tycker heller inte att det finns tid att lära sig nya metoder och verktyg samtidigt som det dagliga arbetet måste utföras. De exempel på flerdimensionell visualisering som man haft tidigare, har inte slagit igenom bland annat på grund av ogenomtänkta användargränssnitt samt begränsad prestanda och hastighet hos systemen. De höga kostnader som visualiseringarna tidigare har inneburit i form av dyr hårdvara och mjukvara är en ytterligare orsak till varför flerdimensionella visualiseringar inte används inom SMHI.

För att ta ställning till användandet av flerdimensionella visualiseringar måste dess mervärde definieras. Mervärde handlar om att addera mer värde till någonting. Det är ett positivt begrepp i bemärkelsen att det möjliggör, avlastar eller ger tydliga fördelar. Gällande mervärdet med 3D är det mycket viktigt att 3D inte användas för sakens skull utan för att förbättra trovärdigheten, förståelsen och förmedlingen av informationen. Flerdimensionella visualiseringar ska ge en ökad effektivitet och ökad kvalitet jämfört med 2D om de ska vara värdefulla att använda. Ofta är det så att kombinationen av 2D tillsammans med 3D ger styrkan. Det handlar alltså inte om att strikt använda det ena eller andra visualiseringssättet.

Andra företag liknande SMHI har gjort seriösa försök att införa flerdimensionella visualiseringar i det dagliga arbetet. Exempel på tillämpningar där dessa företag har upptäckt det största mervärdet är bland annat vid visualisering av lokala prognoser med högupplöst data (1-16 km upplösning). Andra exempel är när man vill få eller ge mer information, snabbt unna överblicka mycket data, eller i utbildnings-sammanhang och marknadsföringssyften. Flerdimensionella visualiseringar passar också mycket bra när man vill gå tillbaka och kontrollera ett fel i exempelvis en prognos eller modell.

Slutsatsen från utvärderingarna av de flerdimensionella applikationerna Vis5D och RAVE i 3D visar att systemen skulle vara användbara för speciella sammanhang inom SMHI, som komplement till dagens tvådimensionella visualiseringssystem. Systemen underlättar upptäckten av vissa väderfenomen samt ger entydlig uppfattning om vädrets fördelning i rummet.

För att införa flerdimensionella visualiseringar i större utsträckning på SMHI är det viktigt att tänka på den inlärningstid och förändringsprocess som krävs för att man ska kunna lära sig att hantera en tredje rumsdimension. Personalen måste se användandet av visualiseringarna som en kompetenshöjning och något som kan tillföra arbetet något positivt. Att hitta fler goda exempel genom pilotstudier eller exjobb är ett sätt som fler kan få upp ögonen för hur flerdimensionella visualiseringar kan se ut och användas.

abstract: Conformance of a manufactured feature to the applied geometric tolerances is done by analyzing the point cloud that is measured on the feature. To that end, a geometric feature is fitted to the point cloud and the results are assessed to see whether the fitted feature lies within the specified tolerance limits or not. Coordinate Measuring Machines (CMMs) use feature fitting algorithms that incorporate least square estimates as a basis for obtaining minimum, maximum, and zone fits. However, a comprehensive set of algorithms addressing the fitting procedure (all datums, targets) for every tolerance class is not available. Therefore, a Library of algorithms is developed to aid the process of feature fitting, and tolerance verification. This paper addresses linear, planar, circular, and cylindrical features only. This set of algorithms described conforms to the international Standards for GD&T.; In order to reduce the number of points to be analyzed, and to identify the possible candidate points for linear, circular and planar features, 2D and 3D convex hulls are used. For minimum, maximum, and Chebyshev cylinders, geometric search algorithms are used. Algorithms are divided into three major categories: least square, unconstrained, and constrained fits. Primary datums require one sided unconstrained fits for their verification. Secondary datums require one sided constrained fits for their verification. For size and other tolerance verifications, we require both unconstrained and constrained fits
Dissertation/Thesis
M.S. Mechanical Engineering 2014

This document presents an approach using the maximum likelihood formulation to estimate vector velocities in real-time by a network of Doppler radars. Relationships between the estimated vector velocity, the statistics of the measured signals, the characteristics of the observing geometry, and the hardware and signal processing parameters is derived. Metrics to gauge the quality of vector velocity retrievals are presented, and their utilization for network design and operation is provided. The thesis concludes with a software architecture for real-time implementation of the vector velocity estimation and its demonstration within the framework of the CASA IP1 four node radar network.

Weather radar provides a detailed spatial representation of rainfall over a large area and in a real time basis. It has proven to be a valuable tool for hydrologists, agriculturalists and organisations that require accurate and real time information of rainfall and overcomes many of the disadvantages associated with the traditional raingauge estimate. However one of the shortcomings of the rainfall estimates supplied by weather radars is that there are quality problems associated with radar rainfall images that include ground clutter, beam blocking and anomalous propagation to name a few. To obtain the best rainfall estimate possible, techniques for removing ground clutter (non-meteorological echoes that influence radar data quality) on two-dimensional (20) and three-dimensional (3D) radar rainfall image data sets were developed in this study. The chosen method for estimating the "true" values behind the contaminated data was Kriging, which is considered to be the optimal technique for the spatial prediction of Gaussian data. Kriging has various advantages and disadvantages, which need to be taken into consideration in this type of application. For the radar rainfall images to be repaired in real time a computationally fast and efficient method of estimating the missing contaminated data was needed. This is achieved by exploiting the various properties associated with Kriging. In South Africa, radar volume scan data are currently only available on one-kilometre horizontal grids at one-kilometre intervals above the earth's surface. This may not be an accurate representation of the rainfall that actually reaches ground level. To provide an estimate of the "true" rainfall reaching the earth's surface, an algorithm has been developed that extrapolates the radar data down to ground level. The extrapolation is carried out using a combination of 3D Universal and Ordinary Kriging which is preceded by a rainfall classification algorithm developed and calibrated in this study. The techniques proposed for ground clutter infilling and the extrapolation of radar data to ground level have been tested for their effectiveness and efficiency on a wide range of selected rainfall events and indicate that the methodology is practically useful. The South African Weather Service (SAWS) has recently installed the software to "cleanse" the radar data as it is received in real time.
Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2005.

Floods cannot be prevented, but their devastating effects can be minimized if advance warning of the event is available. The South African Disaster Management Act (Act 57 of 2002) advocates a paradigm shift from the current "bucket and blanket brigade" response-based mind set to one where disaster prevention or mitigation are the preferred options. It is in the context of mitigating the effects of floods that the development and implementation of a reli able flood forecasting system has major significance. In the case of flash floods, a few hours lead time can afford disaster managers the opportunity to take steps which may significantly reduce loss of life and damage to property. The engineering challenges in developing and implementing such a system are numerous. In this thesis, the design and implement at ion of a flash flood forecasting system in South Africa is critically examined. The technical aspect s relating to spatio-temporal rainfall estimation and now casting are a key area in which new contributions are made. In particular, field and optical flow advection algorithms are adapted and refined to help pred ict future path s of storms; fast and pragmatic algorithms for combining rain gauge and remote sensing (rada r and satellite) estimates are re fi ned and validated; a two-dimensional adaptation of Empirical Mode Decomposition is devised to extract the temporally persistent structure embedded in rainfall fields. A second area of significant contribution relates to real-time fore cast updates, made in response to the most recent observed information. A number of techniques embedded in the rich Kalm an and adaptive filtering literature are adopted for this purpose. The work captures the current "state of play" in the South African context and hopes to provide a blueprint for future development of an essential tool for disaster management. There are a number of natural spin-offs from this work for related field s in water resources management.
Thesis (Ph.D.Eng.)-University of KwaZulu-Natal, Durban, 2007.

This thesis has investigated radioclimatological study in a clear-air environment as applicable to terrestrial line of sight link design problems. Radioclimatological phenomena are adequately reviewed both for the precipitation effect and clear-air effect. The research focuses more on the clear-air effect of radioclimatological studies. Two Southern African countries chosen for case study in the report are Botswana and South Africa. To this end, radiosonde data gathered in Maun, Botswana and Durban, South Africa are used for model formulation and verification. The data used in the thesis ranges from three years to ten years in these two stations. Three to ten years of refractivity data gathered in Botswana and South Africa is used for the model formulation. On the other hand, eight months signal level measurement data recorded from the terrestrial line of sight link set up between Howard College and Westville Campuses of the University of KwaZulu-Natal, Durban South Africa is used for model verification. Though various radioclimatic parameters could affect radio signal propagation in the clear-air environment, this report focuses on two of these parameters. These two parameters are the geoclimatic factor and effective earth radius factor (k-factor). The first parameter is useful for multipath fading determination while the second parameter is very important for diffraction fading, modeling and characterization. The two countries chosen have different terrain and topographical structures; thus further underlying the choice for these two parameters. While Maun in Botswana is a gentle flat terrain, Durban in South Africa is characterized by hilly and mountainous terrain structure, which thus affects radioclimatological modeling in the two countries. Two analytical models have been proposed to solve clear-air radioclimatic problems in Southern Africa in the thesis. The first model is the fourth order polynomial analytical expression while the second model is the parabolic equation. The fourth order polynomial model was proposed after an extensive analysis of the eight month signal level measurement data gathered in Durban, South Africa. This model is able to predict the fade exceedance probabilities as a function of fade depth level. The result from the fourth order polynomial model is found to be comparable with other established multipath propagation model reviewed in the thesis. Availability of more measurement data in more location will be necessary in future to further refine this model. The second model proposed to solve clear-air propagation problem in the thesis is the modified parabolic equation. We chose this technique because of its strength and its simplistic adaptation to terrestrial line of sight link design problem. This adaptation is possible because, the parabolic equation can be modified to incorporate clear-air parameters. Hence this modification of the parabolic equation allows the possibility of a hybrid technique that incorporates both the statistical and mathematical procedures perfectly into one single process. As a result of this, most of the very important phenomena in clear-air propagation such as duct occurrence probabilities, diffraction fading and multipath fading is captured by this technique. The standard parabolic equation (SPE) is the unmodified parabolic equation which only accounts for free space propagation, while the modified parabolic equation (MPE) is the modified version of the parabolic equation. The MPE is classified into two in the thesis: the first modified parabolic equation (MPE1) and second modified parabolic equation (MPE2). The MPE1 is designed to incorporate the geoclimatic factor which is intended to study the multipath fading effect in the location of study. On the other hand, MPE2 is the modified parabolic equation designed to incorporate the effective earth radius factor (k-factor) intended to study the diffraction fading in the location of study. The results and analysis of the results after these modifications confirm our expectation. This result shows that signal loss is due primarily to diffraction fading in Durban while in Botswana, signal loss is due primarily to multipath. This confirms our expectation since a flatter terrain attracts signal loss due to multipath while hilly terrain attracts signal loss due to diffraction fading.
Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2010.

abstract: This study considered the impact of grid resolution on wind velocity simulated by the Weather Research and Forecasting (WRF) model. The period simulated spanned November 2009 through January 2010, for which, multi-resolution nested domains were examined. Basic analysis was performed utilizing the data assimilation tools of NCEP/NCAR (National Center for Environmental Prediction/National Center for Atmospheric Research) to determine the ideal location to examine during the simulation was the Pacific Northwest portion of the United States, specifically the border between California and Oregon. The simulated mutli-resolution nested domains in this region indicated an increase in apparent wind speed as the resolution for the domain was increased. These findings were confirmed by statistical analysis which identified a positive bias for wind speed with respect to increased resolution as well as a correlation coefficient indicating the existence of a positive change in wind speed with increased resolution. An analysis of temperature change was performed in order to test the validity of the findings of the WRF simulation model. The statistical analysis performed on temperature change throughout the increased grid resolution did not indicate any change in temperature. In fact the correlation coefficient values between the domains were found in the 0.90 range, indicating the non-sensitivity of temperature across the increased resolutions. These results validate the findings of the WRF simulation: increased wind velocity can be observed at higher grid resolution. The study then considered the difference between wind velocity observed over the entire domains and the wind velocity observed solely over offshore locations. Wind velocity was observed to be significantly higher (an increase of 68.4%) in the offshore locations. The findings of this study suggest simulation tools should be utilized to examine domains at a higher resolution in order to identify potential locations for wind farms. The results go further to suggest the ideal location for these potential wind farms will be at offshore locations.
Dissertation/Thesis
M.S. Mechanical Engineering 2012

Thesis (M. Sc.)--University of Alberta, 2010.
Title from pdf file main screen (viewed on July 14, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Mechanical Engineering, University of Alberta. Includes bibliographical references.

abstract: Climate change has been one of the major issues of global economic and social concerns in the past decade. To quantitatively predict global climate change, the Intergovernmental Panel on Climate Change (IPCC) of the United Nations have organized a multi-national effort to use global atmosphere-ocean models to project anthropogenically induced climate changes in the 21st century. The computer simulations performed with those models and archived by the Coupled Model Intercomparison Project - Phase 5 (CMIP5) form the most comprehensive quantitative basis for the prediction of global environmental changes on decadal-to-centennial time scales. While the CMIP5 archives have been widely used for policy making, the inherent biases in the models have not been systematically examined. The main objective of this study is to validate the CMIP5 simulations of the 20th century climate with observations to quantify the biases and uncertainties in state-of-the-art climate models. Specifically, this work focuses on three major features in the atmosphere: the jet streams over the North Pacific and Atlantic Oceans and the low level jet (LLJ) stream over central North America which affects the weather in the United States, and the near-surface wind field over North America which is relevant to energy applications. The errors in the model simulations of those features are systematically quantified and the uncertainties in future predictions are assessed for stakeholders to use in climate applications. Additional atmospheric model simulations are performed to determine the sources of the errors in climate models. The results reject a popular idea that the errors in the sea surface temperature due to an inaccurate ocean circulation contributes to the errors in major atmospheric jet streams.
Dissertation/Thesis
M.S. Mechanical Engineering 2014

Indiana University-Purdue University Indianapolis (IUPUI)
Although many studies have investigated the impact of tile drainage on nitrate and pesticide export from cropland to streams, little information is known about the primary hydrological controls of tile flow response to precipitation events and its impact on N, P and C transport in artificially drained landscapes of the US Midwest. This study investigated 1) the relationship between precipitation characteristics and tile flow response at a high temporal resolution during storms; 2) the relative importance of macropore and matrix flow in tile flow and in N, P and C transport to tile drains; and 3) the impact of storm characteristics in N, P and C fluxes/export rates. The study was conducted between April and June 2008, in an agricultural tile drained soybean field, representative of agro-ecosystems of the US Midwest near Indianapolis, IN. For the 8 storms analyzed, results showed that bulk precipitation amount was the best predictor of mean and maximum tile flow, time to peak and runoff ratio. The contribution of macropore flow to total flow increased with precipitation amount, representing between 11% and 50% of total drain flow, with peak contributions between 15% and 74% of flow. For large storms (> 6 cm rainfall), cations data indicated a dilution of groundwater with new water as discharge peaked. Although no clear indication of dilution was observed for smaller storms (< 4 cm rainfall), macropore flow still contributed between 11% and 17% of total flow. For large storms, the transport of dissolved organic carbon (DOC), total phosphorous (TP) and soluble reactive phosphorus (SRP) was found to be regulated mainly by macropore flow while nitrate transport was regulated mainly by matrix flow. For smaller storms, macropore flow dominated DOC and TP transport while SRP and nitrate transport was dominated by matrix flow. These results significantly increase our understanding of the hydrological functioning of tile drained fields and its interaction with N, P and C transport in spring, which is the time of the year during which most water and N losses from tile drains occur in the Midwest.