Dissertations / Theses: 'Lower boundary of clouds'

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Новосьол, Катерина Ігорівна. "Математичне та програмне забезпечення для формулювання авіаційної метеодовідки." Master's thesis, КПІ ім. Ігоря Сікорського, 2020. https://ela.kpi.ua/handle/123456789/40116.

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Магістерська дисертація складається зі вступу, чотирьох розділів, висновку та двох додатків, містить 14 рисунків, 29 таблиць та 15 джерел. Повний обсяг магістерської дисертації складає 98 сторінок, з яких додатки – 8 сторінок. До магістерської дипломної роботи Новосьол Катерини Ігорівни на тему: «Математичне та програмне забезпечення для формулювання авіаційної метеодовідки». Актуальність теми. Мета дослідження. Метою магістерської дисертації є дослідження функціонування аеропортів за складних метеорологічних умов, розробка показників функціонування аеропортів при цих умовах, розробка методики їх аналітичного і статистичного моделювання та розробка прикладного програмного забезпечення для формування коду довідки, який можна використати для передачі у повідомленні закритого вигляду. Для досягнення поставленої мети необхідно вирішити комплекс наступних взаємопов’язаних завдань: - проаналізувати існуючі показники метеорологічних умов, котрі впливають на функціонування аеропортів за складних метеорологічних умов; - проаналізувати методи формування метеодовідок та їх залежність від погодних параметрів; - дослідити вплив метеорологічних умов (а саме кліматичних характеристик) на політ літака; - дослідити динамічні процеси розвитку кліматичних характеристик з урахуванням метеорологічних умов; - розробити методику аналітичного та статистичного моделювання показників; - спроектувати та розробити програмне забезпечення для формування довідки із застосуванням запропонованої методики. Об’єктом дослідження є прикладне програмне забезпечення для для формування коду довідки, який можна використати для передачі у повідомленні закритого вигляду. Предметом дослідження є засоби автоматизації формування кодів метеорологіної довідки з урахуванням впливу кліматичних характеристик на політ повітряних суден у складних метеорологічних умовах. Методами дослідженняє загальнонаукові принципи проведення досліджень. В дослідженні використано методи: - наукового аналізу та синтезу для виявлення проблемних аспектів систем моделювання; - методи теорії ймовірності; - метод статистичного моделювання. Наукова новизна. Вперше сформовано метеодовідку, яка відрізняється від існуючих новою методикою виведення горизонтальної дальності видимості, що дозволяє підвищити точність прогнозування польоту. Практичне значення отриманих результатів.Результатом роботи є прикладний програмний застосунок для оцінювання метеорологічних характеристик аеродрому та формулювання авіаційної метеодовідки. Зв'язок роботи з науковими програмами, планами, темами. Дисертаційна робота магістра виконувалась у Національному технічному університеті України "Київський політехнічний інститут ім. Ігоря Сікорського" згідно з планом науково-дослідницьких робіт кафедри а автоматизованих систем обробки інформації та управління. Публікації. Наукові положення дисертації були опублікованіна V всеукраїнській науково-практичній конференції молодих вчених та студентів «Інформаційні системи та технології управління»(ІСТУ-2020).
The master's dissertation consists of an introduction, four chapters, a conclusion and two appendices, contains 14 figures, 29 tables and 15 sources. The full volume of the master's dissertation is 98 pages, of which the appendices are 8 pages. To Kateryna Ihorivna Novosyol's master's thesis on the topic: " Mathematical and software application for aviation meteorological report formulation ". Actuality of theme. The aim of the study. The purpose of the master's dissertation is to study the operation of airports in difficult weather conditions, to develop indicators of airport operation under these conditions, to develop methods for their analytical and statistical modeling and to develop application software for reference code that can be used to transmit in closed message. To achieve this goal it is necessary to solve a set of the following interrelated tasks: - to analyze the existing indicators of meteorological conditions that affect the functioning of airports in difficult meteorological conditions; - to analyze the methods of forming meteorological reports and their dependence on weather parameters; - to investigate the influence of meteorological conditions (namely climatic characteristics) on the flight of the aircraft; - to study the dynamic processes of development of climatic characteristics taking into account meteorological conditions; - to develop a method of analytical and statistical modeling of indicators; - to design and develop the software for formation of the reference with application of the offered technique. The object of the study is application software for generating help code, which can be used for transmission in a closed message. The subject of the research is the means of automating the formation of meteorological reference codes taking into account the influence of climatic characteristics on the flight of aircraft in difficult meteorological conditions. Research methods are general scientific principles of research. The study used the following methods: - scientific analysis and synthesis to identify problematic aspects of modeling systems; - methods of probability theory; - method of statistical modeling. Scientific novelty. For the first time a meteorological report was formed, which differs from the existing ones by a new method of deriving the horizontal range of visibility, which allows to increase the accuracy of flight forecasting. The practical significance of the results. The result of the work is an applied software application for assessing the meteorological characteristics of the aerodrome and the formulation of aviation meteorological information. Connection of work with scientific programs, plans, themes. The dissertation of the master was performed at the National Technical University of Ukraine "Kyiv Polytechnic Institute named after Igor Sikorsky" according to the plan of research work of the department of automated information processing and control systems. Publications. The scientific provisions of the dissertation were published at the V All-Ukrainian scientific-practical conference of young scientists and students "Information systems and management technologies" (ISTU-2020).

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Aronsson, Oskar, and Julia Nyman. "Boundary Representation Modeling from Point Clouds." Thesis, KTH, Bro- och stålbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278543.

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Inspections of bridges are today performed ocularly by an inspector at arm’s lengths distance to evaluate damages and to assess its current condition. Ocular inspections often require specialized equipment to aid the inspector to reach all parts of the bridge. The current state of practice for bridge inspection is therefore considered to be time-consuming, costly, and a safety hazard for the inspector. The purpose of this thesis has been to develop a method for automated modeling of bridges from point cloud data. Point clouds that have been created through photogrammetry from a collection of images acquired with an Unmanned Aerial Vehicle (UAV). This thesis has been an attempt to contribute to the long-term goal of making bridge inspections more efficient by using UAV technology. Several methods for the identification of structural components in point clouds have been evaluated. Based on this, a method has been developed to identify planar surfaces using the model-fitting method Random Sample Consensus (RANSAC). The developed method consists of a set of algorithms written in the programming language Python. The method utilizes intersection points between planes as well as the k-Nearest-Neighbor (k-NN) concept to identify the vertices of the structural elements. The method has been tested both for simulated point cloud data as well as for real bridges, where the images were acquired with a UAV. The results from the simulated point clouds showed that the vertices were modeled with a mean deviation of 0.13− 0.34 mm compared to the true vertex coordinates. For a point cloud of a rectangular column, the algorithms identified all relevant surfaces and were able to reconstruct it with a deviation of less than 2 % for the width and length. The method was also tested on two point clouds of real bridges. The algorithms were able to identify many of the relevant surfaces, but the complexity of the geometries resulted in inadequately reconstructed models.
Besiktning av broar utförs i dagsläget okulärt av en inspektör som på en armlängds avstånd bedömer skadetillståndet. Okulär besiktning kräver därmed ofta speciell utrustning för att inspektören ska kunna nå samtliga delar av bron. Detta resulterar i att det nuvarande tillvägagångssättet för brobesiktning beaktas som tidkrävande, kostsamt samt riskfyllt för inspektören. Syftet med denna uppsats var att utveckla en metod för att modellera broar på ett automatiserat sätt utifrån punktmolnsdata. Punktmolnen skapades genom fotogrammetri, utifrån en samling bilder tagna med en drönare. Uppsatsen har varit en insats för att bidra till det långsiktiga målet att effektivisera brobesiktning genom drönarteknik. Flera metoder för att identifiera konstruktionselement i punktmoln har undersökts. Baserat på detta har en metod utvecklats som identifierar plana ytor med regressionsmetoden Random Sample Consensus (RANSAC). Den utvecklade metoden består av en samling algoritmer skrivna i programmeringsspråket Python. Metoden grundar sig i att beräkna skärningspunkter mellan plan samt använder konceptet k-Nearest-Neighbor (k-NN) för att identifiera konstruktionselementens hörnpunkter. Metoden har testats på både simulerade punktmolnsdata och på punktmoln av fysiska broar, där bildinsamling har skett med hjälp av en drönare. Resultatet från de simulerade punktmolnen visade att hörnpunkterna kunde identifieras med en medelavvikelse på 0,13 − 0,34 mm jämfört med de faktiska hörnpunkterna. För ett punktmoln av en rektangulär pelare lyckades algoritmerna identifiera alla relevanta ytor och skapa en rekonstruerad modell med en avvikelse på mindre än 2 % med avseende på dess bredd och längd. Metoden testades även på två punktmoln av riktiga broar. Algoritmerna lyckades identifiera många av de relevanta ytorna, men geometriernas komplexitet resulterade i bristfälligt rekonstruerade modeller.

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Barber, Claire. "Observations and modelling of tropical marine boundary layer clouds." Thesis, University of Reading, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590117.

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Marine boundary layer (MBL) cloud and fog are ubiquitous over the global oceans, overlying more than 30% of the ocean surface. Due primarily to their large spatial extent, relat ively speaking minor changes in cloud radiative properties have the potential to sub-stantially affect the global radiation budget, and so future climate. Changes to a particular cloud property are often a small residual effect due to many competing processes. Therefore, modelled cloud changes can be associated with large uncertainties, and :MEL clouds were identified in the most recent IPCC report as the largest contributor to the spread in modelled cloud feedbacks . This thesis exploits the existence of long-term (30yr+ ), consistent, global satellite records of cloud extent and properties to evaluate the representation of MBL clouds in the recent Hadley Centre HadGEM-2A global climate model. In general, the position and fraction of MBL clouds is much improved over previous versions of the model. The representation of cloud liquid water path (L\VP), however, still requires improvement, with the model consistently underestimating LWP by as much as 50% relative to microwave-derived observations. Large differences between the retrieval of L\VP from different satellite platforms may contribute to the poorly constrained model representation of L\VP. The final part of this thesis constructs a well-constrained observational climatology of LWP, using microwave and visible-spectrwn derived satellite retrievals, for the West African Stratocwnulus region. For overcast, single layer cloud, latent heat flux (LHF) is found to be the best indicator of observed cloud L\VP compared to other surface and atmospheric measurements of heat and moisture. The advantages of well characterised and accurate measurements from multiple observational platforms for the purposes of model evaluation are emphasised throughout this thesis. ii

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Ehrlich, André, Eike Bierwirth, and Manfred Wendisch. "Airborne remote sensing of Arctic boundary-layer mixed-phase clouds." Universität Leipzig, 2010. https://ul.qucosa.de/id/qucosa%3A16357.

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This article gives an overview on the investigations on Artic boundary-layer mixed-phase clouds conducted within the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) in spring 2007. In particular the horizontal and vertical disribution of ice crystals within the clouds was determined by three independent airborne instruments (lidar, in situ and solar radiation measurements). Spectral measurements of cloud top reflectivity have been utilized to retrieve information on the ice phase by analyzing the spectral pattern of the cloud top reflectance in the wavelength range dominated by liquid water and ice absorption (1400-1700 nm). A new algorithm to derive an ice index which distinguishes pure ice, liquid water, and mixed-phase clouds was developed. The horizontal distribution of the ice index, observed during ASTAR 2007, agrees with airborne lidar and in situ measurements showing patches of glaciated clouds at an air mass transition zone within the investigated mixed-phase cloud fields. Information on the vertical distribution of ice crystals in mixed-phase clouds was derived by comparing the measured cloud top reflectivity in the wavelength band 1400-1700 nm to radiative transfer simulations. To interpret the data, the vertical weighting of the measurements was calculated. In the investigated wavelength range the weightings differ according to the spectral absorption of ice and liquid water. From the observed spectral cloud reflectivity with low values in the ice absorption maximum (1400 nm) and higher values at the liquid water absorption maximum (1700 nm) it was concluded that ice crystals were present in the otherwise liquid dominated cloud top layer. Although in situ measurements (limited due to vertical resolution and detection limits) did confirm these findings only in certain limits, the retrieved vertical structure is in agreement with published ground based remote sensing measurements.

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Paunova, Irena T. "Explicit numerical study of aerosol-cloud interactions in boundary layer clouds." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100670.

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Aerosol-cloud interactions, the mechanisms by which aerosols impact clouds and precipitation and clouds impact aerosols as they are released upon droplet evaporation, are investigated by means of explicit high-resolution (3 km) numerical simulations with the Mesoscale Compressible Community (MC2) model. This model, which is non-hydrostatic and compressible, was extended by including separate continuity equations for dry and activated multi-modal aerosol, and for chemical species. The sources and sinks include: particle activation, solute transfer between drops, generation of extra soluble material in clouds via oxidation of dissolved SO2, and particle regeneration. The cloud processes are represented by an advanced double-moment bulk microphysical parameterization.
Three summertime cases have been evaluated: a marine stratus and a cold frontal system over the Bay of Fundy near Nova Scotia, formed on 1 Sep 1995 and extensively sampled as a part of the Radiation, Aerosol, and Cloud Experiment (RACE); and a continental stratocumulus, formed over the southern coast of Lake Erie on 11 July 2001. The marine stratus and the frontal system have been examined for the effects of aerosol on cloud properties and thoroughly evaluated against the available observations. The frontal system and the continental stratocumulus have been evaluated for the effects of cloud processing on the aerosol spectrum.
The marine stratus simulations suggest a significant impact of the aerosol on cloud properties. A simulation with mechanistic activation and a uni-modal aerosol showed the best agreement with observations in regards to cloud-base and cloud-top height, droplet concentration, and liquid water content. A simulation with a simple activation parameterization failed to simulate essential bulk cloud properties: droplet concentration was significantly underpredicted and the vertical structure of the cloud was inconsistent with the observations. A simulation with a mechanistic parameterization and a bi-modal aerosol, including a coarse mode observed in particle spectra below cloud, showed high sensitivity of droplet concentration to the inclusion of the coarse mode. There was a significant reduction in droplet number relative to the simulation without the coarse mode. A similar change occurred in the precipitating system preceding the stratus formation, resulting in an enhancement of precipitation in the weaker (upstream) part of the system while the precipitation in the more vigorous (downstream) part of the system remained almost unaffected.
Aerosol processing via collision-coalescence and aqueous chemistry in the non-drizzling stratocumulus case suggests that impact of the two mechanisms is of similar magnitude and can be as large as a 3-5 % increase in particle mean radius. A more detailed analysis reveals that the impact of chemical processing is oxidant-limited; beyond times when the oxidant (H 2O2) is depleted (∼ 40 minutes), the extent of processing is determined by supply of fresh oxidant from large-scale advection (fresh gaseous emissions are not considered). Aerosol processing via drop collision-coalescence alone suggests, as expected, sensitivity to the strength of the collection process in clouds. Larger particle growth, up to 5-10 %, is observed in the case of the frontal clouds, which exhibit stronger drop collection compared to that in the stratocumulus case. The processed aerosol exerted a measurable impact on droplet concentrations and precipitation production in the frontal clouds. For the case modeled here, contrary to expectations, the processed spectrum (via physical processing) produced higher droplet concentration than the unprocessed spectrum. The reasons explaining this phenomenon and the resulting impact on precipitation production are discussed.
The current work illustrates the complexity of the coupled system at the cloud system scales, revealed earlier at much smaller large eddy scales. If future parameterizations of the regional effect of aerosols on clouds are to be developed, careful consideration is required of the many of feedbacks in the boundary layer.

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Wang, Zhen, Ramirez Marco Mora, Hossein Dadashazar, Alex B. MacDonald, Ewan Crosbie, Kelvin H. Bates, Matthew M. Coggon, et al. "Contrasting cloud composition between coupled and decoupled marine boundary layer clouds." AMER GEOPHYSICAL UNION, 2016. http://hdl.handle.net/10150/622150.

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Marine stratocumulus clouds often become decoupled from the vertical layer immediately above the ocean surface. This study contrasts cloud chemical composition between coupled and decoupled marine stratocumulus clouds for dissolved nonwater substances. Cloud water and droplet residual particle composition were measured in clouds off the California coast during three airborne experiments in July-August of separate years (Eastern Pacific Emitted Aerosol Cloud Experiment 2011, Nucleation in California Experiment 2013, and Biological and Oceanic Atmospheric Study 2015). Decoupled clouds exhibited significantly lower air-equivalent mass concentrations in both cloud water and droplet residual particles, consistent with reduced cloud droplet number concentration and subcloud aerosol (D-p>100nm) number concentration, owing to detachment from surface sources. Nonrefractory submicrometer aerosol measurements show that coupled clouds exhibit higher sulfate mass fractions in droplet residual particles, owing to more abundant precursor emissions from the ocean and ships. Consequently, decoupled clouds exhibited higher mass fractions of organics, nitrate, and ammonium in droplet residual particles, owing to effects of long-range transport from more distant sources. Sodium and chloride dominated in terms of air-equivalent concentration in cloud water for coupled clouds, and their mass fractions and concentrations exceeded those in decoupled clouds. Conversely, with the exception of sea-salt constituents (e.g., Cl, Na, Mg, and K), cloud water mass fractions of all species examined were higher in decoupled clouds relative to coupled clouds. Satellite and Navy Aerosol Analysis and Prediction System-based reanalysis data are compared with each other, and the airborne data to conclude that limitations in resolving boundary layer processes in a global model prevent it from accurately quantifying observed differences between coupled and decoupled cloud composition.

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Eleuterio, Daniel P. "Coastal stratocumulus topped boundary layers and the role of cloud-top entrainment." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FEleuterio%5PhD.pdf.

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Schäfer, Michael, Eike Bierwirth, André Ehrlich, Evi Jäkel, and Manfred Wendisch. "Three-dimensional radiative effects in Arctic boundary layer clouds above ice edges." Universität Leipzig, 2015. https://ul.qucosa.de/id/qucosa%3A16651.

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Based on airborne spectral imaging observations, three-dimensional (3-D) radiative effects between Arctic boundary layer clouds and highly variable Arctic surfaces have been identified and quantified. A method is presented to discriminate sea ice and open water in cloudy conditions based on airborne upward radiance measurements in the visible spectral range. This separation simultaneously reveals that the transition of radiance between open water and sea ice is not instantaneous in cloudy conditions but horizontally smoothed. In general, clouds reduce the nadir radiance above bright surfaces in the vicinity of open water, while the nadir radiance above open sea is enhanced compared to situations with clouds located above sea ice surfaces. With the help of the observations and 3-D radiative transfer simulations, this effect was quantified. This affected distance deltaL was found to depend on both cloud and sea ice properties. For a low level cloud at 0-200 m altitude, as observed during the Arctic field campaign Vertical Distribution of Ice in Arctic Clouds (VERDI) in 2012, an increase of the cloud optical thickness from tau = 1 to tau = 10 leads to a decrease of deltaL from 600 to 250 m. An increase in cloud base altitude or cloud geometrical thickness results in an increase of deltaL. Furthermore, the impact of these 3-D-radiative effects on a retrieval of cloud optical properties was investigated. The enhanced brightness of a dark pixel next to an ice edge results in uncertainties of up to 90 % in retrievals of tau and up to 30 % in retrievals of the effective radius reff. With the help of detlaL quantified here, an estimate of the distance to the ice edge is given where the retrieval uncertainties due to 3D-effects are negligible.
Mit Hilfe flugzeuggetragener abbildender spektraler Beobachtungen wurden 3-D Strahlungseffekte zwischen arktischen Grenzschichtwolken sowie der hochvariablen arktischen Bodenoberfläche identifiziert und quantifiziert. Eine Methode zur Differenzierung von Meereis und offener Wasserflächen, auf Grundlage flugzeuggetragener Messungen der aufwärtsgerichteten Strahldichte im sichtbaren Spektralbereich, während bewölkter Bedingungen wird vorgestellt. Diese Differenzierung zeigt gleichzeitig auf, dass die Strahldichtereduzierung beim Übergang vom Meereis zu den offenen Wasserflächen nicht unmittelbar erfolgt, sondern horizontal geglättet ist. Allgemein verringern Wolken in der Umgebung von Eiskanten die Nadir-Strahldichte über den hellen Eisflächen und erhöhen sie über dunklen Meeresoberflächen. Mit Hilfe von 3-D Strahlungstransferrechnungen wurde dieser Effekt quantifiziert. Die Reichweite dieses Effektes wird sowohl von den Wolken- als auch den Oberflächeneigenschaften beeinflusst. Für eine flache Wolke zwischen 0 und 200 m, so wie sie während der arktischen Feldkampagne Vertical Distribution of Ice in Arctic Clouds (VERDI), 2012 beobachtet werden konnte, führt eine Erhöhung der wolkenoptischen Dicke von tau = 1 zu tau = 10 zu einer Verringerung in deltaL von 600 zu 250 m. Zudem führt eine Erhöhung der Wolkenhöhe und ihrer geometrischen Dicke zu einer Zunahme von deltaL. Anschließend wurde der Einfluss dieser 3-D Strahlungseffekte auf die Ableitungsergebnisse von tau untersucht. Die Aufhellung eines dunkleren Pixels neben der Eiskante führt zu Unsicherheiten von bis zu 90 % bei der Ableitung von . Beim effektiven Radius zu bis zu 30 %. DeltaL ist ein Maß mit Hilfe dessen die Entfernung zur Eiskante bestimmt werden kann, ab welcher die Unsicherheiten bezüglich der 3-D Effekte vernachlässigt werden können.

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Kanngießer, Franz, André Ehrlich, and Manfred Wendisch. "Observations of glories above arctic boundary layer clouds to identify cloud phase." Universität Leipzig, 2017. https://ul.qucosa.de/id/qucosa%3A16743.

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The glory is an optical phenomenon observed above liquid water clouds and consists of coloured rings around the anti-solar point. Since the glory is caused by scattering on spherical particles it can be used as a proxy to identify liquid water at the cloud top. Images taken with a CANON digital camera equipped with a fish-eye lens on board the research aircraft Polar 5 during the measurement campaign Radiation-Aerosol-Cloud Experiment in the Arctic Circle (RACEPAC) were analysed for glories. To identify glories an algorithm consisting of five criteria was developed by using simulations of the scattering angle dependent radiance and a test data set of measurements. The algorithm was tested and proved to be able to distinguish between images showing a glory and images not showing any glory.
Die Glorie ist eine optische Erscheinung, die über Flüssigwasserwolken beobachtet werden kann und aus farbigen Ringen um den Gegensonnenpunkt besteht. Da die Glorie durch Streuung an sphärischen Partikeln entsteht, kann sie zur Identifikation von Flüssigwasser am Wolkenoberrand genutzt werden. Bilder, die mit einer CANON Digitalkamera, die mit einem Fischaugenobjektiv ausgestattet war, von Bord des Forschungsflugzeugs Polar 5 während der Messkampagne RACEPAC aufgenommen worden, wurden auf das Auftreten von Glorien untersucht. Zur Identifikation wurde ein Algorithmus mit fünf Kriterien entwickelt, die mit Hilfe von Simulationen der streuwinkelabhängigen Radianz und einem Testdatensatz der Messungen erstellt wurden. Der Algorithmus wurde getestet und ist in der Lage zwischen Bildern mit und ohne Glorie zu unterscheiden.

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Teixeira, João Carlos Martins. "WRF sensitivity to lower boundary and urban canopy parametrizations." Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/10175.

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Mestrado em Meteorologia e Oceanografia Física
Ao longo dos anos avanços, na tecnologia de satélite viabilizaram a aquisição de informações sobre a superfície da Terra, tais como elevação e uso do solo, com grande detalhe e resolução. Esta informação pode ser incluída em modelos numérico da atmosfera, atualizando e dando-lhes mais detalhes sobre as condições de fronteira inferior. Assim sendo, este trabalho visa estudar a sensibilidade do Weather Research and Forecasting model a três conjuntos de dados de topografia, e dois de uso do solo diferentes. Um caso de estudo em que a precipitação orográfica foi dominante sobre a Ilha da Madeira foi considerado mostrando que, em geral não existe um aumento significativo da performance do modelo ao usar topografia ou uso do solo de alta resolução. Contudo, existe uma melhor performance do modelo em simular a precipitação a barlavento e o fluxo a sotavento da ilha. Dada a natureza deste estudo, considerou-se também um teste à sensibilidade de três parametrizações de microfísica, sendo que os resultados encontrados não mostram alterações significativas aos resultados encontrados. Além disso, a introdução de um novo conjunto de dados de uso do solo tornou possível realizar simulações usando modelos urbanos acoplados. Assim, de forma a estudar a sensibilidade a estes modelos considerou-se um caso de estudo sobre a região de Lisboa. Ao utilizar um modelo urbano verificou-se que sobre a região urbana existe um arrefecimento à superfície quando comparando com as simulações de controlo. Além disso verificou-se uma grande diferença no escoamento e na energia turbulenta produzida sobre esta zona. Estas diferenças podem por sua vez intaragem com ondas gravíticas, alterando a sua fase e amplitude. Além disso, ao comparar os resultados com dados observados verificou-se que, em geral, não existe melhoria na performance do modelo para este caso de estudo. No entanto o uso do modelo urbano BEP melhora significativamente os resultados relativos à altura da camada de mistura.
Through the years, the advances in satellite technology made feasible the acquisition of information about the Earth surface, such as elevation and land use, with great detail and resolution. This information can be included in numerical atmospheric models, updating and giving them more details about the lower boundary. Given so, this work aims to study the sensitivity of the Weather Research and Forecast model to three different topography datasets as well as two different land use datasets. A test case study in which topography driven precipitation was dominant over Madeira Island was considered. Overall, results show that there is no enhancement of model skill when using higher resolution topography or land use. However, there is a higher model skill simulating precipitation on Madeira leeward and wind flow windward. Additionally, given the nature of this event, a sensitivity test was also performed considering three different microphysics parametrizations. This test showed that the choice of the microphysics parametrizations does not significantly change the results found for this event. Furthermore, the introduction of a new land use dataset turned possible to perform simulations using Urban Canopy Models. Therefore, the sensitivity of the model to these urban parametrizations was also performed. In this work, a case study for the Lisbon region was chosen and showed that the simulations that used a urban canopy model presented a cooling in the urban region. Moreover, larger changes were observed for wind flow and turbulence kinetic energy over the area. In addition, it was shown that these could change the phase and amplitude of gravity waves that were generated in the region. When comparing to observed data it was seen that there is no enhancement of model skill when using these models. However, the planetary boundary layer is better represent by BEP urban model.

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Sotiropoulou, Georgia. "The Arctic Atmosphere : Interactions between clouds, boundary-layer turbulence and large-scale circulation." Doctoral thesis, Stockholms universitet, Meteorologiska institutionen (MISU), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-134525.

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Arctic climate is changing fast, but weather forecast and climate models have serious deficiencies in representing the Arctic atmosphere, because of the special conditions that occur in this region. The cold ice surface and the advection of warm air aloft from the south result in a semi-continuous presence of a temperature inversion, known as the “Arctic inversion”, which is governed by interacting large-scale and local processes, such as surface fluxes and cloud formation. In this thesis these poorly understood interactions are investigated using observations from field campaigns on the Swedish icebreaker Oden: The Arctic Summer Cloud Ocean Study (ASCOS) in 2008 and the Arctic Clouds in Summer Experiment (ACSE) in 2014. Two numerical models are also used to explore these data: the IFS global weather forecast model from the European Center for Medium-range Weather Forecasts and the MIMICA LES from Stockholm University. Arctic clouds can persist for a long time, days to weeks, and are usually mixed-phase; a difficult to model mixture of super-cooled cloud droplets and ice crystals. Their persistence has been attributed to several mechanisms, such as large-scale advection, surface evaporation and microphysical processes. ASCOS observations indicate that these clouds are most frequently decoupled from the surface; hence, surface evaporation plays a minor role. The determining factor for cloud-surface decoupling is the altitude of the clouds. Turbulent mixing is generated in the cloud layer, forced by cloud-top radiative cooling, but with a high cloud this cannot penetrate down to the surface mixed layer, which is forced primarily by mechanical turbulence. A special category of clouds is also found: optically thin liquid-only clouds with stable stratification, hence insignificant in-cloud mixing, which occur in low-aerosol conditions. IFS model fails to reproduce the cloud-surface decoupling observed during ASCOS. A new prognostic cloud physics scheme in IFS improves simulation of mixed-phase clouds, but does not improve the warm bias in the model, mostly because IFS fails to disperse low surface-warming clouds when observations indicate cloud-free conditions. With increasing summer open-water areas in a warming Arctic, there is a growing interest in processes related to the ice marginal zones and the summer-to-autumn seasonal transition. ACSE included measurements over both open-water and sea-ice surfaces, during melt and early freeze. The seasonal transition was abrupt, not gradual as would have been expected if it was primarily driven by the gradual changes in net solar radiation. After the transition, the ocean surface remained warmer than the atmosphere, enhancing surface cooling and facilitating sea-ice formation. Observations in melt season showed distinct differences in atmospheric structure between the two surface types; during freeze-up these largely disappear. In summer, large-scale advection of warm and moist air over melting sea ice had large impacts on atmospheric stability and the surface. This is explored with an LES; results indicate that while vertical structure of the lowest atmosphere is primarily sensitive to heat advection, cloud formation, which is of great importance to the surface energy budget, is primarily sensitive to moisture advection.

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

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McCaa, James Robert. "A new parameterization of marine stratocumulus and shallow cumulus clouds for climate models /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/10019.

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Myers, Timothy Albert. "Investigating the variability of subtropical marine boundary layer clouds in observations and climate models." Thesis, University of California, San Diego, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3714206.

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Low-level clouds found over the eastern subtropical oceans have a substantial cooling effect on Earth’s climate since they strongly reflect solar radiation back to space, and their simulation in climate models contributes to large uncertainty in global warming projections. This thesis aims to increase understanding of these marine boundary layer clouds through observational analysis, theoretical considerations, and an evaluation of their simulation in climate models. Examination of statistical relationships between cloud properties and large-scale meteorological variables is a key method employed throughout the thesis. The meteorological environment of marine boundary layer clouds shapes their properties by affecting the boundary layer’s depth and structure.

It is found that enhanced subsidence, typically thought to promote boundary layer cloudiness, actually reduces cloudiness when the confounding effect of the strength of the temperature inversion capping the boundary layer is taken into account. A conceptual model is able to explain this result. Next, fundamental deficiencies in the simulation of subtropical clouds in two generations of climate models are identified. Remarkably, the newer generation of climate models is in some ways inferior to the older generation in terms of capturing key low-level cloud processes. Subtropical mid- and high-level clouds are also found to contribute more to variability in the radiation budget at the top of the atmosphere than previously thought. In the last portion of the thesis, large inter-model spread in subtropical cloud feedbacks is shown to arise primarily from differences in the simulation of the interannual relationship between shortwave cloud radiative effect and sea surface temperature. An observational constraint on this feedback suggests that subtropical marine boundary layer clouds will act as a positive feedback to global warming.

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Wang, Zhen, and Zhen Wang. "Interactions Between Atmospheric Aerosols and Marine Boundary Layer Clouds on Regional and Global Scales." Diss., The University of Arizona, 2018. http://hdl.handle.net/10150/626640.

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Airborne aerosols are crucial atmospheric constituents that are involved in global climate change and human life qualities. Understanding the nature and magnitude of aerosol-cloud-precipitation interactions is critical in model predictions for atmospheric radiation budget and the water cycle. The interactions depend on a variety of factors including aerosol physicochemical complexity, cloud types, meteorological and thermodynamic regimes and data processing techniques. This PhD work is an effort to quantify the relationships among aerosol, clouds, and precipitation on both global and regional scales by using satellite retrievals and aircraft measurements. The first study examines spatial distributions of conversion rate of cloud water to rainwater in warm maritime clouds over the globe by using NASA A-Train satellite data. This study compares the time scale of the onset of precipitation with different aerosol categories defined by values of aerosol optical depth, fine mode fraction, and Ångstrom Exponent. The results indicate that conversion time scales are actually quite sensitive to lower tropospheric static stability (LTSS) and cloud liquid water path (LWP), in addition to aerosol type. Analysis shows that tropical Pacific Ocean is dominated by the highest average conversion rate while subtropical warm cloud regions (far northeastern Pacific Ocean, far southeastern Pacific Ocean, Western Africa coastal area) exhibit the opposite result. Conversion times are mostly shorter for lower LTSS regimes. When LTSS condition is fixed, higher conversion rates coincide with higher LWP and lower aerosol index categories. After a general global view of physical property quantifications, the rest of the presented PhD studies is focused on regional airborne observations, especially bulk cloud water chemistry and aerosol aqueous-phase reactions during the summertime off the California coast. Local air mass origins are categorized into three distinct types (ocean, ships, and land) with their influences on cloud water composition examined and implications of wet deposition discussed. Chemical analysis of cloud water samples indicates a wide pH range between 2.92 and 7.58, with an average as 4.46. The highest pH values were observed north of San Francisco, coincident with the strongest land mass influence (e.g. Si, B, and Cs). Conversely, the lowest pH values were observed south of San Francisco where there is heavy ship traffic, resulting in the highest concentrations of sulfate, nitrate, V, Fe, Al, P, Cd, Ti, Sb, P, and Mn. The acidic cloud environment with influences from various air mass types can affect the California coastal aquatic ecosystem since it can promote the conversion of micronutrients to more soluble forms. Beyond characterization of how regional air mass sources affect cloud water composition, aircraft cloud water collection provides precious information on tracking cloud processing with specific species such as oxalic acid, which is the most abundant dicarboxylic acid in tropospheric aerosols. Particular attention is given to explore relationship between detected metals with oxalate aqueous-phase production mechanisms. A number of case flights show that oxalate concentrations drop by nearly an order of magnitude relative to samples in the same vicinity with similar environmental and cloud physical conditions. Such a unique feature was consistent with an inverse relationship between oxalate and Fe. In order to examine the hypothesis that oxalate decreasing is potentially related to existing of Fe, chemistry box model simulations were conducted. The prediction results show that the loss of oxalate due to the photolysis of iron oxalato complexes is likely a significant oxalate sink in the study region due to the ubiquity of oxalate precursors, clouds, and metal emissions from ships, the ocean, and continental sources.

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Comstock, Kimberly K. "Mesoscale variability and drizzle in southeast Pacific stratocumulus /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/10013.

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Kawai, Hideaki. "Study on Marine Boundary Layer Clouds and Their Environment for Cloud Parameterizations in Global Climate Models." Kyoto University, 2017. http://hdl.handle.net/2433/226008.

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Park, Sungsu. "ENSO-related marine cloud variation and new single column marine boundary layer cloud modeling /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/10080.

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Klug, Christopher A. "Lower Permian Through Lower Trassic Paleontology, Stratigraphy, and Chemostratigraphy of the Bilk Creek Mountains of Humboldt County, Nevada." Bowling Green State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1184878826.

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Shimelmitz, Ron, Steven L. Kuhn, Avraham Ronen, and Mina Weinstein-Evron. "Predetermined Flake Production at the Lower/Middle Paleolithic Boundary: Yabrudian Scraper-Blank Technology." Public Library of Science, 2014. http://hdl.handle.net/10150/621336.

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UA Open Access Publishing Fund
While predetermined de´bitage technologies are recognized beginning with the middle Acheulian, the Middle Paleolithic is usually associated with a sharp increase in their use. A study of scraper-blank technology from three Yabrudian assemblages retrieved from the early part of the Acheulo-Yabrudian complex of Tabun Cave (ca. 415–320 kyr) demonstrates a calculated and preplanned production, even if it does not show the same complexity and elaboration as in the Levallois technology. These scraper dominated assemblages show an organization of production based on an intensive use of predetermination blank technology already in place at the end of the Lower Paleolithic of the Levant. These results provide a novel perspective on the differences and similarities between the Lower and Middle Paleolithic industries. We suggest that there was a change in the paradigm in the way hominins exploited stone tools: in many Middle Paleolithic assemblages the potential of the stone tools for hafting was a central feature, in the Lower Paleolithic ergonometric considerations of manual prehension were central to the design of blanks and tools.

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Arfaie, Armin. "Numerical modelling of the influence of lower boundary roughness on turbulent sedimentary flows." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/13419/.

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Numerical computations have been performed to evaluate the influence of bedform roughness on turbulent transport of sediments in geophysical flows. Special attention is paid to turbidity currents, which are responsible for the transport of sedimentary rocks far into the deep ocean. It has been suggested that enhanced turbulence mixing in flows over rugose topography contributes to the unexpectedly large runout lengths of naturally occurring turbidity currents. One of the objectives of this study is to provide evidence for against this conjecture. We perform computations over a wide range of periodic arrays of rectangular roughness elements, We find that a strong peak in turbulent mixing occurs when the width-to-height ratio equals a critical value of seven. We also find that a strong peak in resistance to flow occurs at the same critical value. These are competing effects, with the former acting to promote, and the latter acting to diminish runout length. So we are not able to conclude definitively that the enhancement of mixing is responsible for long runout lengths. We continue by considering flows over periodic arrays of shapes which are representative of bedforms that occur in the natural environment. We again find a strong correlation between the optimisation of both turbulence mixing and resistance to the flow. We are unable to distinguish bedform shapes that promote long runout length relative to the flat bed case. However, we are able to distinguish those bedform shapes that have large resistance to flow and large turbulence mixing compared to those that have low resistance and low turbulent mixing, with the latter case occurring for widely spaced asymmetric dunes with a long low angled slope facing the flow. Finally, we develop a model for flow and sediment transport which takes into account erosion and deposition from the bottom boundary. We first apply this model to flow over fixed dune shapes, in order to assess the influence of bedform shape on flow capacity, stratification, and the energy budget. An important result of this study is that flow capacity is optimised for the class of bedform shapes that promote low flow resistance and low turbulent mixing. We conclude by applying the model to the two-way coupled flow of a mobile dune, starting from an initially symmetric inherited dune morphology. We find that, for sufficiently large grain sizes, the dune evolves into a sequence of asymmetric dunes, rather than to a flat bed, and that the long-time evolution tends to be towards those dune shapes that promote large relative flow capacity. However, the model has a discrepancy in that it is unable to prevent the dune shape exceeding the maximum angle of repose. Hence, further work is required before these results can be regarded as reliable.

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Cebi, Ali Can, and Tobias Bauer. "Hierarchical structures in medium-sized manufacturing companies and their lower boundaries." Thesis, Högskolan i Jönköping, Internationella Handelshögskolan, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-30251.

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Application of low hierarchy structures are becoming increasingly popular by enhancing job satisfaction and productivity of employees. On the other hand formation of hierarchy appears to be natural and beneficial in many cases. This study explores how low hierarchies could become and where the boundaries regarding job satisfaction lie as well as how these differ depending on formal position of employees. The inquiry is undertaken with a focus is on medium-sized companies in manufacturing industry in Germany where job satisfaction and productivity via such applications is vital. Extensive qualitative data was collected with a single-case approach; analysis was conducted qualitatively likewise. The lower limits of hierarchy are discovered to lie in various aspects mainly relating to supervision, recognition of good performance and promotion opportunities and to differ significantly with formal position. The study is believed to be unique and assist in shedding light into the area of beneficial and practical low hierarchy applications.

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Reilly, Stephanie Claire [Verfasser], Roel [Gutachter] Neggers, and Susanne [Gutachter] Crewell. "Fast Response of Boundary Layer Clouds to Climate Change / Stephanie Claire Reilly ; Gutachter: Roel Neggers, Susanne Crewell." Köln : Universitäts- und Stadtbibliothek Köln, 2020. http://d-nb.info/1231433345/34.

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23

Nguyen, Van sinh. "3 D Modeling of elevation surfaces from voxel structured point clouds extracted from seismic cubes." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4069/document.

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Dans cette thèse, nous présentons des méthodes pour construire une surface géologique optimal à partir d’une quantité énorme de points 3D extraits de cubes sismiques. Appliquer le processus à l’ensemble des points induit un risque important de contraction de la surface de sorte que l’extraction de la frontière initiale est une étape importante permettant une simplification à l’intérieur de la surface. La forme globale de la surface sera alors mieux respectée pour la reconstruction de la surface triangulaire finale. Nos propositions sont basées sur la régularité des données qui permet, même si des données sont manquantes, d’obtenir facilement les informations de voisinage. Tout d’abord, nous présentons une nouvelle méthode pour extraire et simplifier la frontière d’une surface d’élévation définie par un ensemble de voxels dans un grand volume 3D où des données sont manquantes. Deuxièmement, une méthode pour simplifier la surface à l’intérieur de sa frontière est présentée. Elle comprend une étape de simplification grossière optionnelle suivie par une étape plus fine basée sur l’étude des courbures. Nous tenons également compte du fait que la densité de données doit changer graduellement afin de recevoir à la dernière étape d’une surface triangulée avec de meilleurs triangles. Troisièmement, nous avons proposé une nouvelle méthode rapide pour trianguler la surface après simplification
Reconstructing surfaces with data coming from an automatic acquisition technique always entails the problem of mass of data. This implies that the usual processes cannot be applied directly. Therefore, it leads to a mandatory data reduction process. An effective algorithm for a rapid processing while keeping the original model is a valuable tool for constructing an optimal surface and managing the complex data.In this dissertation, we present methods for building an optimal geological surface from a huge amount of 3D points extracted from seismic cubes. Applying the process to the whole set of points induces an important risk of surface shrinking so that the initial boundary extraction is an important step permitting a simplification inside the surface. The global surface shape will then be better kept for the reconstruction of the final triangular surface. Our proposals are based on the regularity of data which permits, even if data are missing, to easily obtain the neighboring information. Firstly, we present a new method to extract and simplify the boundary of an elevation surface given as voxels in a large 3D volume having the characteristics to be sparse. Secondly, a method for simplifying the surface inside its boundary is presented with a rough optional simplification step followed by a finer one based on curvatures. We also keep into consideration that the density of data must gradually change in order to receive in the last step a triangulated surface with better triangles. Thirdly, we have proposed a new and fast method for triangulating the surface after simplification

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Horner, Michael S. "Determining the fine structure of the entrainment zone in cloud-topped boundary layers." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Mar%5FHorner.pdf.

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Nam, Christine C. W., and Johannes Quaas. "Geographically versus dynamically defined boundary layer cloud regimes and their use to evaluate general circulation model cloud parameterizations." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-177436.

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Regimes of tropical low-level clouds are commonly identified according to large-scale subsidence and lower tropospheric stability (LTS). This definition alone is insufficient for the distinction between regimes and limits the comparison of low-level clouds from CloudSat radar observations and the ECHAM5 GCM run with the COSP radar simulator. Comparisons of CloudSat radar cloud altitude-reflectivity histograms for stratocumulus and shallow cumulus regimes, as defined above, show nearly identical reflectivity profiles, because the distinction between the two regimes is dependent upon atmospheric stability below 700 hPa and observations above 1.5 km. Regional subsets, near California and Hawaii, for example, have large differences in reflectivity profiles than the dynamically defined domain; indicating different reflectivity profiles exist under a given large-scale environment. Regional subsets are better for the evaluation of low-level clouds in CloudSat and ECHAM5 as there is less contamination between 2.5 km and 7.5 km from precipitating hydrometeors which obscured cloud reflectivities.

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Casey, Erin Michelle. "A micro-pulsed LIDAR for the study of the lower troposphere and atmospheric boundary layer." Thesis, Montana State University, 2012. http://etd.lib.montana.edu/etd/2012/casey/CaseyE0812.pdf.

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The current largest unknown variable in global climate models is the effect of aerosols directly and indirectly on radiative forcing. This thesis continues the work of characterizing this effect through the study of aerosols by the use of lidar. A micro-pulsed lidar was designed, fabricated and incorporated into a set of instruments for atmospheric studies at Montana State University. The data collected up to this point shows the usefulness of employing such a system in conjunction with other remote sensing instruments as well as in-situ instruments. This is shown by the retrieval of aerosol backscatter and extinction coefficients as well as lapse rates and atmospheric boundary layer heights.

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Atakul, Ayse. "Lower-middle Carboniferous Boundary In Central Taurides, Turkey (hadim Area): Paleontological And Sequence Stratigraphic Approach." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607033/index.pdf.

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The aim is to delineate the effective boundary between Lower and Middle Carboniferous (mid-Carboniferous boundary) and to study the meter-scale cyclicity and foraminiferal evolution across a stratigraphic section comprising this boundary. In order to perform such a study, a 25,64 m stratigraphic section, which is mainly composed of carbonates has been measured in the Hadim region of the Central Taurides. In this study, calcareous foraminifers have been studied in the measured section. These foraminiferal assemblages contain 62 species. Based on these foraminifers, four biostratigraphic zones have been defined covering the interval from Upper Serpukhovian to Lower Bashkirian. These zones comprise in ascending order, the Eostaffella ex gr. ikensis &
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E. postmosquensis Zone (Zapaltyubinsky Horizon &
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Upper Serpukhovian), the Plectostaffella jakhensis &
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P. bogdanovkensis Zone and the Millerella marblensis Zone (Bogdanovsky Horizon &
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Lower Bashkirian) and the Semistaffella sp. Zone (Syuransky Horizon &
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Lower Bashkirian). In order to construct the sequence stratigraphic framework, detailed microfacies studies were carried out and eleven different microfacies types were identified. Based on the stacking patterns of these microfacies, six main types of cycles, A-F, and ten subcycles are recognized. Twenty-three shallowing upward meter-scale cycles and three sequence boundaries have been determined in the studied section. The duration of cycles has been calculated as 2 my and cycle periodicities correspond to the Milankovitch eccentricity bant. Results of quantitative analysis of benthic foraminifera have been used to demonstrate the biological response to cyclicity. Eostaffellids, archaediscids, unilocular forms and irregularly coiled bilocular forms are the calcareous foraminiferal groups responding the meter-scale cycles.

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Hungershöfer, Katja, and Thomas Trautmann. "Investigations into the impact of the lower boundary condition on the reflected solar radiance field." Universität Leipzig, 2003. https://ul.qucosa.de/id/qucosa%3A15232.

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It is presented how the original isotropic boundary condition in a Gauss-Seidel radiative transfer model is generalized to describe an angular dependent surface reflection. A symmetry about the plane of incidence is assumed since the general case of an arbitrary non-symmetric reflection is to costly. As a result using Hapke\''s BRDF the upward radiance at the surface and the top of the atmosphere are discussed and compared to the results with the original isotropic boundary condition. In addition we discuss the impact of Rayleigh scattering and aerosol extinction on the reflected solar radiance field.
Es wird dargestellt wie die untere Randbedingung in unserem Gauss-Seidel Strahlungstransportmodell erweitert wird, um eine richtungsabhängige Reflexion beschreiben zu können. Da die Beschreibung einer asymmetrischen Bodenreflexion zu aufwendig wäre, beschränken wir uns dabei auf den Fall, bei dem die Reflexion symmetrisch bezüglich der Einfallsebene ist. Als Ergebnisse werden die aufwärtsgerichtete Strahldichte unmittelbar am Erdboden und am Atmosphärenoberrand diskutiert und mit den Ergebnissen für die ursprünglich isotrope Reflexion verglichen. Außerdem wird auf den Einfluß der Rayleigh Streuung und der Extinktion durch die Aerosolpartikel auf das reflektierte solare Strahldichtefeld eingegangen.

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Faizy, Shelly Mardhia. "Assessing a Modeling Standard in Volcanic-Geothermal Systems: the Effects of the Lower System Boundary." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-438664.

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Geothermal energy consumption is projected to increase along with other renewable energy in the future. Therefore, it is important to have a better understanding on the evolution of geothermal systems to optimize the exploitation of such resources. Generally, numerical models are used as a fundamental tool to study a potential geothermal field. However, current modeling practices tend to focus on the shallow area around the heat source, while ignoring the deeper part below the heat source. The purpose of this project is to observe the influence of lower boundary at the bottom of intrusion towards the evolution of geothermal system, while changing the permeability and topography of host rock systematically, using a software from USGS called HYDROTHERM. Simulations differed in three main aspects: 1) having a layer below, or having the bottom boundary directly below intrusion, 2) different topographies with volcanic significance, and 3) varying permeabilities of the host rock. The study is based on a fossil geothermal system, the Cerro Bayo laccolith in Chachahuén volcanic complex (Neuquén Basin), Argentina. The input parameters were obtained in several ways. ILMAT Geothermometry analysis provide the temperature value related to the intrusion. The whole rock data is used to determined density of the intrusion by calculating partial molar volume of the oxides. The other parameters, e.g. densities of the host rock and the impermeable layer, permeability, porosity, and thermal conductivity were obtained from literature. The result from numerical modeling shows that the bottom boundary below intrusion strongly affect the entire system evolution. The added layer (with constant permeability) has strong influence on the life-span of the system. Additionally, while taking into account on the variation of topography and permeabilities, the models show two temperature anomalies: 1) A caldera volcano’s geometry “traps” heat below the caldera, whereas shield and strato-volcano geometries “push” heat away from below the volcanic edifice, and 2) a low temperature anomaly develops beneath the intrusion in all high permeability models with an added layer. Finally, this assessment could prove to be useful as prior knowledge for optimizing the extraction of heat from a given geothermal field, as well as future investigations towards geological applicability of numerical models of geothermal systems, hydrothermal alteration, and ore formation processes.

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Hungershöfer, Katja, and Thomas Trautmann. "Investigations into the impact of the lower boundary condition on the reflected solar radiance field." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-217354.

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It is presented how the original isotropic boundary condition in a Gauss-Seidel radiative transfer model is generalized to describe an angular dependent surface reflection. A symmetry about the plane of incidence is assumed since the general case of an arbitrary non-symmetric reflection is to costly. As a result using Hapke\'s BRDF the upward radiance at the surface and the top of the atmosphere are discussed and compared to the results with the original isotropic boundary condition. In addition we discuss the impact of Rayleigh scattering and aerosol extinction on the reflected solar radiance field
Es wird dargestellt wie die untere Randbedingung in unserem Gauss-Seidel Strahlungstransportmodell erweitert wird, um eine richtungsabhängige Reflexion beschreiben zu können. Da die Beschreibung einer asymmetrischen Bodenreflexion zu aufwendig wäre, beschränken wir uns dabei auf den Fall, bei dem die Reflexion symmetrisch bezüglich der Einfallsebene ist. Als Ergebnisse werden die aufwärtsgerichtete Strahldichte unmittelbar am Erdboden und am Atmosphärenoberrand diskutiert und mit den Ergebnissen für die ursprünglich isotrope Reflexion verglichen. Außerdem wird auf den Einfluß der Rayleigh Streuung und der Extinktion durch die Aerosolpartikel auf das reflektierte solare Strahldichtefeld eingegangen

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31

Daoust, Pascale. "High Resolution Stratigraphy of the Lower Silurian (Rhuddanian-Aeronian) Paleotropical Neritic Carbonates, Anticosti Island, Québec." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36645.

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Anticosti Island, located in Eastern Canada, displays one of the most complete, best exposed, and most fossiliferous carbonate successions spanning the Ordovician-Silurian (O/S) Boundary in the World. This study develops a new high-resolution framework for the post End-Ordovician extinction strata (~ 260 m thick) exposed in coastal outcrops and recovered from a continuous drill core (La Loutre #1), both located in the western part of the island. In total, eight facies, all associated with a storm-dominated carbonate system, were recognized and organized into a multi-order depositional cycles. A new high resolution isotopic curve with more than 300 data points from well-preserved bulk micrite samples covers the late Hirnantian to Early Aeronian time interval and corresponds to the upper Ellis Bay, Becscie, Merrimack and lower Gun River formations. Two distinct positive carbon isotope excursions are present in the late Hirnantian part of the Ellis Bay Formation (+5‰) and in the lower Aeronian part of the Gun River Formation (+2‰). These positive isotopic carbon excursions provide a distinctive chemostratigraphic signature for regional and global correlations with other O/S sections. Like the Quaternary δ18O marine signal, our δ18O record is largely coupled with multi-order cyclic facies changes. This study demonstrates the importance of glacio-eustasy following the End-Ordovician glacial maxima as one of the primary factors controlling the stratigraphic architecture of paleotropical neritic carbonates during the Early Silurian.

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32

Nam, Christine C. W., Johannes Quaas, Roel Neggers, Drian Colombe Siegenthaler-Le, and Francesco Isotta. "Evaluation of boundary layer cloud parameterizations in the ECHAM5 general circulation model using CALIPSO and CloudSat satellite data." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-177343.

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Three different boundary layer cloud models are incorporated into the ECHAM5 general circulation model (GCM) and compared to CloudSat and CALIPSO satellite observations. The first boundary layer model builds upon the standard Tiedtke (1989) parameterization for shallow convection with an adapted convective trigger; the second is a bulk parameterization of the effects of transient shallow cumulus clouds; and lastly the Dual Mass Flux (DMF) scheme adjusted to better represent shallow convection. The three schemes improved (Sub)Tropical oceanic low-level cloud cover, however, the fraction of low-level cloud cover remains underestimated compared to CALIPSO observations. The representation of precipitation was improved by all schemes as they reduced the frequency of light intensity events <0.01 mm d-1, which were found to dominate the radar reflectivity histograms as well as be the greatest source of differences between ECHAM5 and CloudSat radar reflectivity histograms. For both lidar and radar diagnostics, the differences amongst the schemes are smaller than the differences compared to observations. While the DMF approach remains experimental, as its top-of-atmosphere radiative balance has not been retuned, it shows the most promise in producing nonprecipitating boundary layer clouds. With its internally consistent boundary layer scheme that uses the same bimodal joint distribution with a diffusive and an updraft component for clouds and turbulent transport, the ECHAM5_DMF produces the most realistic boundary layer depth as indicated by the cloud field. In addition, it reduced the frequency of large-scale precipitation intensities of <0.01 mm d-1 the greatest.

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33

Nam, Christine C. W., and Johannes Quaas. "Geographically versus dynamically defined boundary layer cloud regimes and their use to evaluate general circulation model cloud parameterizations: Geographically versus dynamically defined boundary layer cloudregimes and their use to evaluate general circulation model cloud parameterizations." American Geophysical Union (AGU), 2013. https://ul.qucosa.de/id/qucosa%3A13460.

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Regimes of tropical low-level clouds are commonly identified according to large-scale subsidence and lower tropospheric stability (LTS). This definition alone is insufficient for the distinction between regimes and limits the comparison of low-level clouds from CloudSat radar observations and the ECHAM5 GCM run with the COSP radar simulator. Comparisons of CloudSat radar cloud altitude-reflectivity histograms for stratocumulus and shallow cumulus regimes, as defined above, show nearly identical reflectivity profiles, because the distinction between the two regimes is dependent upon atmospheric stability below 700 hPa and observations above 1.5 km. Regional subsets, near California and Hawaii, for example, have large differences in reflectivity profiles than the dynamically defined domain; indicating different reflectivity profiles exist under a given large-scale environment. Regional subsets are better for the evaluation of low-level clouds in CloudSat and ECHAM5 as there is less contamination between 2.5 km and 7.5 km from precipitating hydrometeors which obscured cloud reflectivities.

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34

Freitas, Sylvio [Verfasser], and Bernd [Akademischer Betreuer] Leitl. "Investigation of terrain effects on wind dynamics within the lower atmospheric boundary layer / Sylvio Freitas ; Betreuer: Bernd Leitl." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2020. http://d-nb.info/1214370349/34.

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35

Pergaud, Julien. "Étude et paramétrisation de la turbulence et des nuages de couche limite." Toulouse 3, 2008. http://thesesups.ups-tlse.fr/2340/.

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L'objectif principal de cette thèse était de développer une nouvelle paramétrisation améliorant le mélange et la représentation des nuages dans les couches limites convectives. Nous avons développé ainsi une paramétrisation basée sur le concept EDMF pour Eddy-Diffusivity/Mass Flux dans lequel le schéma en flux de masse représente un thermique idéalisé qui peut échanger de l'air avec son environnement et dont les parcelles d'air peuvent condensées. Dans la partie sèche de l'updraft, l'entraînement et le détrainement sont définis comme proportionnels à la flottabilité et inversement proportionnels à la vitesse verticale dans l'updraft. Ce formalisme permet à ces échanges de s'adapter en fonction du type de couche limite ou encore de l'intensité de la convection. Dans le nuage, c'est le formalisme en tri par flottabilité qui a été choisi. Il est en effet bien adapté pour les échanges entre le nuage et son environnement. Les tests dans un modèle unicolonne ont permis de mettre en valeur l'apport d'un tel schéma dans la représentation du mélange mais aussi des nuages de couche limite. Il permet notamment une bonne représentation de la zone à contre-gradient et corrige un défaut bien connu des paramétrisations en coefficient d'échange turbulent. Des résultats 3D pré-opérationnels sont présentés et montrent la nécessité d'un tel schéma pour des modèles à 2. 5km de résolution. Il a été ainsi implémenté dans le nouveau modèle opérationnel de Météo-France, AROME
The main objective of this thesis was to develop a new parameterization enabling to improve the mixing and representation of clouds in convective boundary layers. We thus developed a parameterization based on the concept EDMF for Eddy- Diffusivity/Mass Flux and in which the mass _ux scheme represents idealized thermal which can exchange air with its environment and whose air parcels can condensate. In the dry part of the updraft, entrainment and detrainment are defined as proportional to the buoyancy and inversely proportional to the vertical velocity in the updraft. This formalism allows the exchanges to adapt depending on the type of boundary layer or the intensity of convection. In the cloud, the buoyancy sort formalism was chosen. Indeed, it is well suited to represent exchanges between the cloud and its environment. Tests in a single column model helped highlight the contribution of such a scheme in the representation of the turbulence but also boundary layer clouds. It allows a good representation of the counter-gradient area and corrects a well-knwon defect of eddy-diffusivity parameterizations. 3D results are presented and demonstrate the need for such a scheme for models with 2. 5km resolution. It has been well implemented in the new operational mesoscale model at Météo-France named AROME

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36

Nam, Christine C. W., Johannes Quaas, Roel Neggers, Drian Colombe Siegenthaler-Le, and Francesco Isotta. "Evaluation of boundary layer cloud parameterizations in the ECHAM5 general circulation model using CALIPSO and CloudSat satellite data." American Geophysical Union (AGU), 2014. https://ul.qucosa.de/id/qucosa%3A13458.

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Three different boundary layer cloud models are incorporated into the ECHAM5 general circulation model (GCM) and compared to CloudSat and CALIPSO satellite observations. The first boundary layer model builds upon the standard Tiedtke (1989) parameterization for shallow convection with an adapted convective trigger; the second is a bulk parameterization of the effects of transient shallow cumulus clouds; and lastly the Dual Mass Flux (DMF) scheme adjusted to better represent shallow convection. The three schemes improved (Sub)Tropical oceanic low-level cloud cover, however, the fraction of low-level cloud cover remains underestimated compared to CALIPSO observations. The representation of precipitation was improved by all schemes as they reduced the frequency of light intensity events <0.01 mm d-1, which were found to dominate the radar reflectivity histograms as well as be the greatest source of differences between ECHAM5 and CloudSat radar reflectivity histograms. For both lidar and radar diagnostics, the differences amongst the schemes are smaller than the differences compared to observations. While the DMF approach remains experimental, as its top-of-atmosphere radiative balance has not been retuned, it shows the most promise in producing nonprecipitating boundary layer clouds. With its internally consistent boundary layer scheme that uses the same bimodal joint distribution with a diffusive and an updraft component for clouds and turbulent transport, the ECHAM5_DMF produces the most realistic boundary layer depth as indicated by the cloud field. In addition, it reduced the frequency of large-scale precipitation intensities of <0.01 mm d-1 the greatest.

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37

ANDRONIKOV, ALEXANDRE V., and IRINA E. ANDRONIKOVA. "SEDIMENTS FROM AROUND THE LOWER YOUNGER DRYAS BOUNDARY (SE ARIZONA, USA): IMPLICATIONS FROM LA-ICP-MS MULTI-ELEMENT ANALYSIS." WILEY-BLACKWELL, 2016. http://hdl.handle.net/10150/621537.

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One of the prominent features in sediment sequences formed around the AllerOd-Younger Dryas transition (c. 12.9-12.8 ka bp) in North America is a dark layer of organic-rich material, i.e. the black mat. The black mat sequences in southeast Arizona contain a thin sandy basal layer corresponding to the lower Younger Dryas boundary. Trace element concentrations in the lower Younger Dryas boundary sediments, in the black mat, in the host sediments, and in charcoal from Western Europe and southeast Arizona were studied using LA-ICP-MS. The black mat samples and samples of the underlying host sediments display compositions similar to the average continental crust, while the sediments from the lower Younger Dryas boundary are enriched in rare earth elements, Ni, and Co whereas Ta, Nb, Zr, and Hf are depleted relative to the rare earth elements. Such a difference in compositions between the lower Younger Dryas boundary sediments and other sediments points to a short enigmatic event, which changed conditions of sedimentation just before the onset of the Younger Dryas cooling. The presence of products of biomass burning of still unknown origin is suggested on the basis of trace element features of sediments from the lower Younger Dryas boundary.

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38

Horn, Stefan. "Simulations of complex atmospheric flows using GPUs - the model ASAMgpu -." Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-187994.

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Die vorliegende Arbeit beschreibt die Entwicklung des hochauflösenden Atmosphärenmodells ASAMgpu. Dabei handelt es sich um ein sogenanntes Grobstrukturmodell bei dem gröbere Strukturen mit typischen Skalen von Deka- bis Kilometern in der atmosphärischen Grenzschicht explizit aufgelöst werden. Hochfrequentere Anteile und deren Dissipation müssen dabei entweder explizit mit einem Turbulenzmodell oder, wie im Falle des beschriebenen Modells, implizit behandelt werden. Dazu wurde der Advektionsoperator mit einem dissipativen Upwind-Verfahren dritter Ordnung diskretisiert. Das Modell beinhaltet ein Zwei-Momenten-Schema zur Beschreibung mikrophysikalischer Prozesse. Ein weiterer wichtiger Aspekt ist die verwendete thermodynamische Variable, die einige Vorteile herkömmlicher Ansätze vereint. Im Falle adiabatischer Prozesse stellt sie eine Erhaltungsgröße dar und die Quellen und Senken im Falle von Phasenumwandlungen sind leicht ableitbar. Außerdem können die benötigten Größen Temperatur und Druck explizit berechnet werden. Das gesamte Modell wurde in C++ implementiert und verwendet OpenGL und die OpenGL Shader Language (GLSL) um die nötigen Berechnungen auf Grafikkarten durchzuführen. Durch diesen Ansatz können genannte Simulationen, für die bisher Supercomputer nötig waren, sehr preisgünstig und energieeffizient durchgeführt werden. Neben der Modellbeschreibung werden die Ergebnisse einiger erfolgreicher Test-Simulationen, darunter drei Fälle mit mariner bewölkter Grenzschicht mit flacher Cumulusbewölkung, vorgestellt.

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39

Carrasco, Hugo Alexandre Sacristão. "Higher order boundary value problems on unbounded intervals." Doctoral thesis, Universidade de Évora, 2017. http://hdl.handle.net/10174/21093.

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The relative scarcity of results that guarantee the existence of solutions for BVP on unbounded domains, contrasts with the high applicability on real problems of differential equations defined on the half-line or on the whole real line. It is this gap the main reason that led to this work. The differential equations studied vary from second order to higher orders and they can be discontinuous on time. Different types of boundary conditions will be discussed herein, for example, Sturm- Liouville, homoclinic, Lidstone and functional conditions. The non-compactness of the time interval and the possibility of study unbounded functions will require the redefinition of the admissible Banach spaces. In fact the space considered and the functional framework assumed define the set of admissible solutions for each problem under a main goal: the functions must remain bounded for the space and the norm in consideration. This is achieved by defining some weight functions (polynomial or exponential) in the space or assuming some asymptotic behavior. In addition to the existence, solutions will be localized in a strip. The lower and upper solutions method will play an important role, and combined with other tools like the one-sided Nagumo growth conditions, Green’s functions or Schauder’s fixed point theorem, provide the existence and location results for differential equations with various boundary conditions. Different applications to real phenomena will be presented, most of them translated into classical equations as Duffing, Bernoulli-Eulerv. Karman, Fisher-Kolmogorov, Swift-Hohenberg, Emden-Fowler or Falkner-Skan-type equations. All these applications have a common denominator: they are defined in unbounded intervals and the existing results in the literature are scarce or proven only numerically in discrete problems; RESUMO: Problemas de valor na fronteira de ordem superior em intervalos não limitados A relativa escassez de resultados que garantam a existência de soluções para problemas de valor na fronteira, em domínios ilimitados, contrasta com a alta aplicabilidade em problemas reais de equações diferenciais definidas na semi reta ou em toda a reta real. É esta lacuna o principal motivo que conduziu a este trabalho. As equações diferenciais estudadas variam da segunda ordem a ordens superiores e podem ser descontínuas no tempo. As condições de fronteira aqui analisadas são de diferentes tipos, nomeadamente, Sturm - Liouville, homoclínicas, Lidstone e condições funcionais. A não compacidade do intervalo de tempo e a possibilidade de estudar funções ilimitadas, exigirá a redefinição dos espaços de Banach admissíveis. Na verdade, o espaço considerado e o quadro funcional assumido define o conjunto de soluções admissíveis para cada problema sob um objetivo principal: as funções devem permanecer limitadas para o espaço e norma considerados. Isto é conseguido através da definição de algumas "funções de peso" (polinomiais ou exponenciais) no espaço considerado ou assumindo um comportamento assintótico. Além da existência, as soluções serão localizadas numa faixa. O método da sub e sobre-soluções irá desempenhar aqui um papel importante e, combinado com outras ferramentas como a condição unilateral de Nagumo, as funções de Green ou o teorema de ponto fixo de Schauder, fornecem a existência e localização de soluções para equações diferenciais com diversas condições de fronteira. Apresentam-se também diferentes aplicações a fenómenos reais, a maioria deles traduzidos para equações clássicas como as equações de Duffing, Bernoulli-Euler-v.Karman, Fisher-Kolmogorov, Swift - Hohenberg, Emden-Fowler ou ainda Falkner-Skan. Todas estas aplicações têm um denominador comum: são definidas em intervalos ilimitados e os resultados existentes na literatura são raros ou estão provados apenas numericamente em problemas discretos.

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40

Sener, Johnny, and Anders Svensson. "Effektiv prissättning av OMXS-optioner : En empirisk undersökning." Thesis, Uppsala University, Department of Economics, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7030.

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I uppsatsen har vi undersökt köpoptioner med OMXS30 som underliggande, syftet var att se om det fanns möjligheter till att göra arbitrage. Detta innebär att de är felprissatta. Vi har i vår undersökning testat optioners nedre gräns och köp-sälj paritetsvillkoret. Resultaten tyder på att det finns ett antal tillfällen då marknaden inte är effektiv, antalet tillfällen skiljer sig åt under olika marknadsförhållanden. De slutsatser vi kan dra är att marknaden måste vara mogen och marknadens aktörer måste ha en tydlig bild om i vilken riktning marknaden är på väg för att vi ska kunna säga att optionspriserna är effektivt prissatta. När investerare agerar irrationellt och osäkerheten är hög ökar frekvensen av antalet felprissättningar på finansiella instrument, däribland optioner.

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41

Yost, Samantha L. "Paleocene decapods, survivor taxa of the Kambuehel Formation, Lower Austria, and their relationship to decapod diversity across the K/T boundary." Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent1563376807903551.

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42

FIGUEIRA, Waléria Souza. "Efeito da remoção de umidade da camada limite planetária no desenvolvimento de cúmulos rasos e profundos." Universidade Federal de Campina Grande, 2015. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/673.

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Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-05-14T20:44:44Z No. of bitstreams: 1 WALÉRIA SOUZA FIGUEIRA – DISSERTAÇÃO (PPGMET) 2015.pdf: 2735921 bytes, checksum: c2ab85caa20115480b90d1325acfad13 (MD5)
Made available in DSpace on 2018-05-14T20:44:44Z (GMT). No. of bitstreams: 1 WALÉRIA SOUZA FIGUEIRA – DISSERTAÇÃO (PPGMET) 2015.pdf: 2735921 bytes, checksum: c2ab85caa20115480b90d1325acfad13 (MD5) Previous issue date: 2015-03-05
CNPq
Este trabalho teve como objetivo estudar o efeito da remoção de umidade da camada limite planetária por cúmulos rasos. Para tal, esse efeito foi inserido no código do modelo BRAMS. Foram realizados dois experimentos: no primeiro experimento de controle (EXP_ORI), o modelo foi inicializado em sua forma original e no segundo (EXP_AJUST), o modelo foi integrado para as mesmas condições que o EXP_ORI, porém com o devido ajuste realizado no código do BRAMS. O modelo foi integrado para um período de 774 horas a partir da 00 UTC do dia 1° de janeiro até a 00 UTC do dia 1° de fevereiro de 2011. Para facilitar a análise quanto ao impacto desse ajuste no ciclo diário médio das variáveis termodinâmicas de superfície e da precipitação convectiva, foram feitas médias em duas áreas distintas de 1°x1°, uma área sobre superfície florestada (localizada no sul do Amazonas) e outra área sobre superfície desflorestada (localizada no norte da Bolívia). De forma geral, os resultados mostraram que houve diferenças notáveis no perfil termodinâmico da troposfera inferior devido à implementação do novo ajuste. As taxas de aquecimento e umedecimento, em ambas as áreas, tiveram picos as 09 e 09:30 horas local, embora o seu efeito líquido tenha se mostrado nas horas seguintes, o principal impacto ocorreu no início da tarde. O ciclo diário dos fluxos à superfície também foram sensíveis ao ajuste realizado no modelo. Já o comportamento e a quantidade da precipitação convectiva acumulada ao longo do dia foram melhorados no EXP_AJUST, principalmente na área desflorestada.
The objective of this work was to the effects of moisture removal from the planetary boundary layer by shallow cumulus. To reach this goal, this effect was implemented into the BRAMS model code. Two experiments were performed: in the control experiment (EXP_ORI), the model was initialized in its original form and in the second one (EXP_AJUST) the model was run to the same conditions as the EXP_ORI but with due adjustment made in BRAMS code. The model was run for a period of 774 hours, from 00 UTC of 1 January to 00 UTC of 1 February 2011. To facilitate the analysis of the impact of this adjustment on the mean daily cycle of thermodynamic variables of surface and convective precipitation, averages were performed in two different areas of 1° x 1°, an area of forested area (located in the south of the Amazon) and other deforested area on surface (located in northern Bolivia). Overall, the results showed that there were important differences in the thermodynamic profile of the lower troposphere due to the implementation of new setting in the BRAMS code. Values of moistening and heating rates in both areas peaked around 09 and 09:30 local time, although their net effect were felt later, the impact occurred mainly early afternoon. The daily cycle of surface fluxes were also sensitive to the adjustment performed in the model. Also the behavior and the amount of convective precipitation accumulated during the day in EXP_AJUST were improved, especially in deforested area.

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43

DeSantis, Michael K. "Anatomy of Middle Devonian Faunal Turnover in Eastern North America: Implications for Global Bioevents at the Eifelian-Givetian Stage Boundary." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1289581544.

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44

Downs, Drew Tyler. "In search of the Triassic-Jurassic boundary : palynostratigraphy and carbon-isotope stratigraphy of the lower Dinosaur Canyon Member on the Colorado Plateau (Kanab, Utah) /." Available to subscribers only, 2009. http://proquest.umi.com/pqdweb?did=1879993731&sid=4&Fmt=2&clientId=1509&RQT=309&VName=PQD.

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45

Harrison, Bianca. "Palaeoenvironments and position of the Precambrian–Cambrian boundary within the lower Vanrhynsdorp Group of South Africa: sedimentary facies analysis, U-Pb series zircon geochronology and micropalaeontology." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29450.

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The Vanrhynsdorp Group is a mainly fluvio-marine siliclastic succession that outcrops in the northwestern part of South Africa. The critical Precambrian-Cambrian boundary falls within the group, however the depositional environments across the boundary, its exact stratigraphic position and nature are unresolved. The group was deposited in the Vanrhynsdorp Basin, which has been shown to be the southernmost extension of the Nama Foreland Basin. Consequently, the Vanrhynsdorp Group has been correlated with the world-famous Nama Group, which features diverse Ediacaran-Cambrian fossils. To date, no body fossils have been discovered in the Vanrhynsdorp Group. Through U-Pb dating of detrital zircons using LA-ICP-MS, radiometric ages for the middle part of the Vanrhynsdorp Group (Besonderheid Formation) were obtained in a preliminary study of this project. The radiometric data, yielding a maximum depositional age of 524 to 528 Ma from the youngest zircon grain population, indicated that the Precambrian-Cambrian boundary is stratigraphically lower in the group than it was thought before. To further constrain the age of the lower Vanrhynsdorp Group, and by extension the position of the Precambrian-Cambrian boundary, several detrital zircon samples were processed for age determination from the succession in this study. In addition, using sedimentary facies analysis, the lateral and vertical facies variation in this lower part of the group were (re)documented in order to refine the palaeoenvironmental setting. The current results suggest a dominantly shallow marine, partly storm-dominated depositional environment for the lowermost units as opposed to the previous interpretations of dominantly alluvial settings. Because of the global importance of the Ediacaran-Cambrian transition for diversification of marine biota in the Cambrian, addressing these palaeoenvironmental inconsistencies is the vital outcome of this study. By integrating our sedimentological and geochronological results, the project presents an improved understanding of the depositional history of the Vanrhynsdorp Group during the critical Ediacaran-Cambrian transition.

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46

Brosse, Fabien. "Influence de la couche limite convective sur la réactivité chimique en Afrique de l'Ouest." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30324/document.

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Cette thèse porte sur l'influence de la couche limite convective et nuageuse sur la réactivité chimique en Afrique de l'Ouest. Pour répondre à cette question, des simulations à haute résolution (50m) sont réalisées sur le modèle atmosphérique Méso-NH couplé à un mécanisme chimique détaillé représentant la chimie gazeuse et aqueuse. Cette échelle spatiale permet de représenter explicitement les caractéristiques spatiales et temporelles des structures turbulentes. Les thermiques en couche limite sont identifiés à l'aide d'un échantillonnage conditionnel basé sur l'utilisation d'un traceur passif à décroissance radioactive. L'impact du transport turbulent sur la redistribution d'espèces chimiques dépend du temps de vie chimique de ces espèces. La ségrégation spatiale créée au sein de la couche limite augmente ou réduit les taux de réaction moyens entre composés. La campagne de terrain AMMA, et plus récemment DACCIWA, sont utilisées pour définir des forçages dynamiques et chimiques pour des environnements simulés. Le premier est représentatif d'un environnement biogénique dominé par des émissions naturelles de COV. Le second reproduit un environnement urbain modérément pollué typique du Golfe de Guinée (Cotonou au Bénin). Pour simplifier, l'analyse des simulations est limitée aux réactions chimiques entre OH et l'isoprène dans le cas biogénique, entre les aldéhydes C>2 et OH dans le cas urbain. L'influence de la couche limite convective est étudiée à l'échelle du thermique et du domaine. Cela permet une connexion avec les modèles à résolution plus lâche qui adoptent une hypothèse de mélange parfait et immédiat, négligeant de fait les variabilités spatiales de composés chimiques au sein d'une maille. Les premiers résultats, basés sur la phase gazeuse uniquement, montrent que les nuages en couche limite convective affectent le transport vertical d'espèces chimiques. Les thermiques sont des zones de réactions privilégiées où la réactivité chimique est maximale. La plus grande intensité de ségrégation est calculée au sommet de la couche limite, toutefois de signes opposés entre les deux environnements. En environnement biogénique, le mélange non-homogène de l'isoprène et de OH dans cette zone induit une diminution maximale de 30% du taux de réaction moyen. Dans le cas urbain, la constante de réaction effective entre OH et les aldéhydes est supérieure de 16% à la constante moyenne. La réactivité de OH est supérieure de 15 à 40% dans les thermiques comparé au reste du domaine, dépendant de l'environnement chimique et de l'heure. Comme les thermiques occupent une faible portion du domaine, l'impact des structures turbulentes sur la réactivité totale de OH est une diminution de 9% pour le cas biogénique et une augmentation maximale de 5% dans le cas anthropique. Des simulations LES incluant la réactivité aqueuse révèlent une baisse importante des rapports de mélange de OH associée à la présence de nuages
This thesis focuses on the influence of the convective and cloudy boundary layer on the chemical reactivity in West Africa. To answer this question, high resolution simulations (50m) are performed on the atmospheric model Meso-NH coupled to a detailed chemical scheme representing the gaseous and aqueous phases. This spatial scale allow to explicitly represent the spatial and temporal characteristics of turbulent structures. Thermals in the boundary layer are identified by a conditional sampling based on a radioactive-decay passive scalar. The turbulent transport influence on the redistribution of chemical species depends on the chemical lifetimes of these species. Spatial segregation is created within the convective boundary layer that increases or decreases the mean reaction rates between compounds. AMMA campaign field study, and more recently DACCIWA, are used to define dynamical and chemical forcing of two simulated environments. The first one is representative of a biogenic environment dominated by natural emissions of VOC. The second reproduces a moderately polluted typical urban area of the Guinean Gulf (Cotonou in Benin). For the sake of simplicity, simulations analysis are limited to the chemical reaction between isoprene and OH in the biogenic case, and the reaction between C>2 aldehydes and OH in the anthropogenic case. The convective boundary layer influence is studied at thermal and domain scale. This makes the connection with coarse resolution models for which a hypothesis of perfect and immediate mixing is made, neglecting the spatial variability of chemical species within a grid cell. The first results are based on the gaseous phase only. Cloudy development in the convective boundary layer only affects the vertical transport of chemical species. The simulations show that thermals are preferential reaction zones where the chemical reactivity is the highest. The top of the boundary layer is the region characterized by the highest calculated segregation intensities but of the opposite sign in both environments. In the biogenic environment, the inhomogeneous mixing of isoprene and OH in this zone leads to a maximum decrease of 30% of the mean reaction rate. In the anthropogenic case, the effective rate constant for OH reacting with aldehydes is 16% higher at maximum than the averaged value. The OH reactivity is higher by 15 to 40% inside thermals compared to the surroundings depending on the chemical environment and time of the day. Because thermals occupy a small fraction of the simulated domain, the impact of turbulent motions on the domain-averaged OH total reactivity reaches a maximum 9% decrease for the biogenic case and a maximum of 5% increase for the anthropogenic case. LES simulations including the aqueous reactivity reveal a significant decrease in OH mixing ratios associated to the presence of clouds. Consequently, isoprene and C>2 aldehydes mixing ratios increase at these altitudes

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Young, Alisa H. "The characterization of deep convection in the tropical tropopause layer using active and passive satellite observations." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41210.

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Several studies suggest that deep convection that penetrates the tropical tropopause layer may influence the long-term trends in lower stratospheric water vapor. This thesis investigates the relationship between penetrating deep convection and lower stratospheric water vapor variability using historical infrared (IR) observations. However, since infrared observations do not directly resolve cloud vertical structure and cloud top height, and there has been some debate on their usefulness to characterize penetrating deep convective clouds, CloudSat/Calipso and Aqua MODIS observations are first combined to understand how to best interpret IR observations of penetrating tops. The major findings of the combined CloudSat/Calipso and Aqua MODIS analysis show that penetrating deep convection predominantly occur in the western tropical Pacific Ocean. This finding is consistent with IR studies but is in contrast to previous radar studies where penetrating deep convective clouds predominantly occur over land regions such as equatorial Africa. Estimates on the areal extent of penetrating deep convection show that when using IR observations with a horizontal resolution of 10 km, about two thirds of the events are large enough to be detected. Evaluation of two different IR detection schemes, which includes cold cloud features/pixels and positive brightness temperature differences (+BTD), show that neither schemes completely separate between penetrating deep convection and other types of high clouds. However, the predominant fraction of +BTD distributions and cold cloud features/pixels ≤ 210 K is due to the coldest and highest penetrating tops as inferred from collocated IR and radar/lidar observations. This result is in contrast to previous studies that suggest the majority of cold cloud features/pixels ≤ 210 K are cirrus/anvil cloud fractions that coexist with deep convective clouds. Observations also show that a sufficient fraction of penetrating deep convective cloud tops occur in the extratropics. This provides evidence that penetrating deep convection should be documented as a pathway of stratospheric-tropospheric exchange within the extratropical region. Since the cold cloud feature/pixel ≤ 210 K approach was found to be a sufficient method to detect penetrating deep convection it was used to develop a climatology of the coldest penetrating deep convective clouds from GridSat observations covering years 1998-2008. The highest frequencies of the coldest penetrating deep convective clouds consistently occur in the western-central Pacific and Indian Ocean. Monthly frequency anomalies in penetrating deep convection were evaluated against monthly anomalies in lower stratospheric water vapor at 82 mb and show higher correlations for the western-central Pacific regions in comparison to the tropics. At a lag of 3 months, the combined western-central Pacific had a small but significant anticorrelation, where the largest amount of variance explained by the combined western-central Pacific region was 8.25%. In conjunction with anomalies in the 82 mb water vapor mixing ratios, decreasing trends for the 1998-2008 period were also observed for tropics, the western Pacific and Indian Ocean. Although none of these trends were significant at the 95% confidence level, decreases in the frequency of penetrating deep convection over the 1998-2008 shows evidence that could explain in part some of the 82 mb lower stratospheric water vapor variability.

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Nogueira, Ariadne. "Integrais concentradas na fronteira e aplicações para problemas elípticos semilineares." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/45/45131/tde-06122017-104037/.

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Neste trabalho estudamos propriedades de integrais concentradas, ou seja, integrais cujo integrando atua apenas em uma vizinhança do domínio em questão. Tais termos são utilizados para conhecer o comportamento do integrando em regiões cuja medida de Lebesgue se aproxima de zero quando um parâmetro tende a zero. Ilustraremos estes resultados abstratos através de duas aplicações, ambas em domínios Lipschitz de R2, onde adicionamos um termo de concentração em problemas semilineares elípticos: domínio com fronteira oscilante que tende a um domínio limite fixo; e domínio do tipo fino com fronteira oscilante. Em ambos os casos, provamos a semicontinuidade superior e inferior da família de soluções dos problemas.
In this work we study concentrating integrals properties, in other words, we analyze integrals which function that is been integrated acts only in a neighborhood of the boundary of the domain. Such terms are use to know the behaviour of the integrand in regions which Lebesgue measure tends to zero when a parameter goes to zero. We will illustrate these abstract results through two applications, both in Lipschitz domains of R2, where we add a concentration term in semi linear elliptic problems: oscillating boundary domain which tends to a fixed limit domain; and a thin domain with a oscillatory boundary. In both cases we prove the upper and lower semicontinuity of the family of solutions from these problems.

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Görgen, Klaus. "Sensitivitätsstudien und Analyse von Atmosphäre-Meereis-Wechselwirkungen mit dem regionalen Atmosphärenmodell HIRHAM4 auf Basis eines neu entwickelten beobachtungsgestützten unteren Modellantriebs während ausgewählter Sommer über der Arktis, Laptewsee = Sensitivity studies and analysis of atmosphere-sea-ice-interactions with the regional atmospheric model HIRHAM4 using a newly developed observational lower boundary forcing dataset during selected summers over the Arctic/Laptev Sea /." Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung, 2006. http://www.gbv.de/dms/bs/toc/517265761.pdf.

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Fialho, João Manuel Ferrão. "Existence, localization and multiplicity results for nonlinear and functional." Doctoral thesis, Universidade de Évora, 2012. http://hdl.handle.net/10174/15248.

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In this thesis several problems are addressed. The problems considered vary from second order problems up to high order problems where generaliza- tions to nth order are studied. Such problems range from problems without functional dependence up to problems where the functional dependence is featured both in the equation and on the boundary conditions. Functional boundary conditions include most of the classical conditions as multipoint cases, conditions with delay and/or advances, nonlocal or in- tegral, with maximum or minimum arguments,... Existence, nonexistence, multiplicity and localization results are then discussed in accordance with these conditions. The method used is the lower and upper solutions combined with di¤erent techniques (degree theory, Nagumo condition, iterative technique, Green s function) to obtain such results. Several applications are studied such as the periodic oscillations of the axis of a satellite and conjugate boundary value problems, to emphasize the applicability of the method used; RESUMO:Nesta tese, intitulada em português, Resultados de existência, localiza- ção e multiplicidade para problemas não lineares e funcionais de ordem su- perior com valores na fronteira , diferentes problemas são abordados. Estes problemas variam desde problemas de segunda ordem até problemas de or- dem superior, onde generalizações de ordem n são feitas e onde os problemas apresentados variam desde o caso em que não existe dependência funcional até aos em que esta dependência funcional está presente tanto na equação como nas condições de fronteira. Sobre estas condições, que incluem a maioria das condições clássicas, re- sultados de existência, não existência, multiplicidade e localização de solução são discutidos de acordo com estas condições. O método utilizado é o método da sub e sobre-solução combinado com diferentes técnicas. Várias aplicações são estudadas, nomeadamente as oscilações periódicas do eixo de um satélite e problemas conjugados, de forma a dar ênfase à aplicabilidade do método utilizado.

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Dissertations / Theses on the topic 'Lower boundary of clouds'

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