Dissertations / Theses on the topic 'Clouds'
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Riley, Emily Marie. "A Global Survey of Clouds by CloudSat." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_theses/198.
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With the launch of CloudSat, direct observations of cloud vertical structure became possible on the global scale. This thesis utilizes over two years of CloudSat data to study large-scale variations of clouds. We compose a global data set of contiguous clouds (echo objects, EOs) and the individual pixels comprising each EO. For each EO many attributes are recorded. EOs are categorized according to cloud type, time of day, season, surface type, and region. From the categorization we first look at gross global climatology of clouds. Maps of cloud cover are subdivided by EO (cloud) type, and results compare well with previous CloudSat work. The seasonality of cloud cover is also examined. Focus topics studied in this thesis include: (1) mid-level clouds, (2) stratocumulus clouds, and (3) clouds across the Madden-Julian Oscillation (MJO). The mid-level cloud work found an unexpected frequency peak in EO top heights between 7-8 km in the tropics, further shown to correspond to a global peak in EO top temperature between -15°C ? -20°C. Hypotheses are discussed regarding cause of this feature. Stratocumulus clouds are defined as low-level (tops < 4.5 km), wide (width > 11 km) EOs. Stratocumulus cloud cover agrees (with understandable differences) with other estimates (ISCCP and CALIPSO). The seasonal cycle of stratocumulus over the main stratocumulus decks is examined. The Peruvian and Namibian decks have increased cloud cover in austral spring in 2007 vs. 2006, corresponding sensibly to sea surface temperature differences and changes in lower static stability. Looking at rain and drizzle statistics, wider EOs are found to drizzle more. Clouds across the MJO are defined relative to temporally filtered OLR data. Cloud cover (volume) doubles (triples) from suppressed to active MJO phases, with some shifts of the relative contributions of different EO types from the front to back of the MJO. Pixel statistics in dBZ-height space correspond to these cloud-type shifts. High anvils and low clouds in front lead deep convection followed by relatively lower anvils in the back.
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Fallas, German Vidaurre. "Characterization of mixed-phase clouds." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3275833.
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Ovtchinnikov, Mikhail. "An investigation of ice production mechanisms using a 3-D cloud model with explicit microphysics /." Full-text version available from OU Domain via ProQuest Digital Dissertations, 1997.
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Brooks, Christopher David. "Underwater Clouds Utilizing Private Cloud Architecture Aboard U.S. Submarines." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/7312.
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The Consolidated Afloat Network and Enterprise Systems (CANES) program was tasked with replacing computer networks afloat, to both improve productivity and functionality of the fleets Information Technology infrastructure. The program, in its first iteration, fails to include half the ships currently in service and is limited to a small number of specific platforms. Upgrading the existing software on the current platforms may pose a useful resolution to this issue. The computer networks on board submarines provide a good opportunity to explore how cloud computing could benefit older platforms. This thesis presents a proof of concept for the use of a Private Cloud architecture on board U.S. submarines and how improving computer networks may be possible by leveraging the currently installed hardware without requiring a complete system reconfiguration. We use the Ubuntu Server Private Cloud as a basic example to illustrate and explore potential benefits and limitations of the Platform as a Service (PAAS) model. The revised system is examined in terms of its application aboard a submarine and explores how it compares to previous network architectures, such as the Client/Server model. The Ubuntu model was chosen for its usability and robust features and because it is open source and free.
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Beletsky, Yuri. "Extragalactic molecular clouds and chemistry of diffuse interstellar clouds." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-105670.
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Beesley, John Anthony. "The climatic effects and requirements of arctic clouds /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/10056.
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Ng, Alexander CB. "Decision Modelling and Optimization for Enterprise Migration to Clouds." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31719.
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Many enterprises are currently exploring the possibility of migrating some or all of their IT functionalities to public clouds with the objective of reducing their overall IT service costs or to open new business frontiers. Unfortunately, making such a decision is not a straightforward task; it requires a vigorous evaluation of the various benefits, risks and costs associated with the migration of their diverse business processes that comprise of their current IT services. Yet, this problem has received very little attention in the literature, mainly due to its interdisciplinary nature.
This thesis aims at filling this gap by aiding the enterprises during the phase of making their cloud migration decision. The contributions of this work are twofold. First, a novel cloud-migration framework is introduced to guide the enterprises through a sequence of well-defined recommended analysis steps. These steps culminate with the formulation of the migration decision problem as a mathematical optimization one. The second contribution is a decision engine that efficiently solves this optimization problem.
More precisely, the proposed framework gradually guides the enterprise to first identify the various business processes that are related to their IT services and then to determine the relationship and the communication needed among those processes. The identified inter-process communication represents an indicator of how tightly coupled these business processes are to each other. When outsourcing business processes, tightly coupled processes add a high communication cost and may introduce service latency if they are not co-located. As such, inter-process communication becomes an important input parameter that affects the migration decision.
Enterprises can then determine to partially or completely migrate IT services to clouds. Furthermore, multiple vendors can be used for different services. However, when different vendors are involved, the communication cost between different processes increases. The objective is to maximize profit for an organization which includes lowering IT expenses in the long term without compromising data integrity or security. An optimization formula is finally constructed to help the enterprise determine which services to migrate given input parameters of the cost of doing business in-house, cost of outsourcing, and communication costs.
Finally, a case study is utilized to demonstrate the performance of the proposed work by analyzing the process of migrating the services to clouds for an IPTV service provider. More specifically, the case study focuses on the content delivery network (CDN) within the IPTV provider’s infrastructure which is responsible for delivering contents to viewers. The CDN network can use the proposed profit-optimization formula to determine whether to utilize a cloud service or to use its internal resource to deliver the content. A performance evaluation from a simulation is presented to demonstrate the proposed profit-optimization formula can return a set of optimal mix of both internal and external services to maximize profits.
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Karlsson, Karl-Göran. "The use of a satellite-derived cloud climatology for studying cloud-aerosol processes and the performance of regional cloud climate simulations." Doctoral thesis, Stockholm University, Department of Meteorology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-1364.
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The entry of satellite-derived decadal cloud datasets with homogeneous coverage in time and space enables studies not possible before. This thesis presents two such applications. The first study deals with cloud-aerosol processes and the second with an evaluation of cloud simulations from a regional climate model.
The first part of the thesis describes the used satellite-derived dataset based on imagery from the Advanced Very High Resolution Radiometer (AVHRR) on the polar orbiting NOAA satellites. A method for cloud retrieval and the compilation of a 1991-2000 Scandinavian cloud climatology are described.
The second part reveals an intriguing anti-correlation between monthly mean satellite-derived cloudiness and the concentration of the cosmogenetic isotope Beryllium-7 in near-surface aerosol samples for three measurement sites in Sweden. Large-scale transport processes are suggested as the most likely physical mechanism for this behaviour but more complex relations to cloud microphysical processes are not ruled out.
The final part presents a thorough evaluation of cloud simulations of the SMHI Rossby Centre regional atmospheric model (RCA3). Several model-to-satellite adaptations are applied to avoid artificial biases of results. The study stresses the necessity to account for initial differences between observed and modelled clouds caused by satellite cloud detection limitations. Results show good agreement of modelled and observed cloud amounts while the vertical distribution of clouds appears largely different. RCA3 underestimates medium-level clouds while overestimating low- and high-level clouds. Also, the current use of the Maximum cloud overlap approach in the radiation scheme and an indicated excess of cloud condensate in modelled clouds appear to create excessive cloud optical thicknesses with serious implications for the surface radiation budget.
Future applications are outlined based on greatly enhanced satellite-derived cloud and radiation budget datasets.
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Sotiriadis, Stelios. "The inter-cloud meta-scheduling." Thesis, University of Derby, 2013. http://hdl.handle.net/10545/299501.
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Inter-cloud is a recently emerging approach that expands cloud elasticity. By facilitating an adaptable setting, it purposes at the realization of a scalable resource provisioning that enables a diversity of cloud user requirements to be handled efficiently. This study’s contribution is in the inter-cloud performance optimization of job executions using metascheduling concepts. This includes the development of the inter-cloud meta-scheduling (ICMS) framework, the ICMS optimal schemes and the SimIC toolkit. The ICMS model is an architectural strategy for managing and scheduling user services in virtualized dynamically inter-linked clouds. This is achieved by the development of a model that includes a set of algorithms, namely the Service-Request, Service-Distribution, Service-Availability and Service-Allocation algorithms. These along with resource management optimal schemes offer the novel functionalities of the ICMS where the message exchanging implements the job distributions method, the VM deployment offers the VM management features and the local resource management system details the management of the local cloud schedulers. The generated system offers great flexibility by facilitating a lightweight resource management methodology while at the same time handling the heterogeneity of different clouds through advanced service level agreement coordination. Experimental results are productive as the proposed ICMS model achieves enhancement of the performance of service distribution for a variety of criteria such as service execution times, makespan, turnaround times, utilization levels and energy consumption rates for various inter-cloud entities, e.g. users, hosts and VMs. For example, ICMS optimizes the performance of a non-meta-brokering inter-cloud by 3%, while ICMS with full optimal schemes achieves 9% optimization for the same configurations. The whole experimental platform is implemented into the inter-cloud Simulation toolkit (SimIC) developed by the author, which is a discrete event simulation framework.
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Smith, Helen. "Scattering ice clouds." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/scattering-ice-clouds(949032cc-fbdd-4fde-a942-163d870a5ddd).html.
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The 2013 meeting of the Intergovernmental Panel on Climate Change concluded that the coupling of clouds to the Earth's climate is one of the biggest uncertainties faced in predicting climate change today. Cirrus clouds are of particular interest because the extensive variability in particle size, shape and complexity poses a number of challenges in the accurate modelling of optical properties. The dependence of the single-scattering properties on particle shape demand accurate representation of the crystal geometries in scattering models, geometries which can vary from simple hexagonal prisms to complex multi-branched aggregates. This work, presented as a series of papers, uses laboratory studies to investigate the single scattering properties of ice crystals. Of particular focus here are columns with internal cavities. The first paper investigates the phase function, P11 and asymmetry parameter, g of varying crystal habits, whilst the second paper focuses on polarised scattering. One of the main findings is the difference in internal structure between hollow columns grown at warmer temperatures (-7 degrees C) and those grown at colder temperatures (-30 degrees C). Measurements were used to create new particle geometries for use in scattering models. The third paper makes use of findings from papers 1 & 2 to create an optical parametrization for cirrus, utilizing the new particle geometry.
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Smith, Neil Tyler. "Suppression of marina stratocumulus clouds due to reduced cloud condensation nuclei." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA384672.
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Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, Sept. 2000.Thesis advisor(s): Durkee, Philip A. Includes bibliographical references (p. 43-44). Also available online.
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Xhagjika, Vamis. "Resource, data and application management for cloud federations and multi-clouds." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/409728.
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Distributed Real-Time Media Processing refers to classes of highly distributed, delay no-tolerant applications that account for the majority of the data traffic generated in the world today. Real-Time audio/video conferencing and live content streaming are of particular research interests as technology forecasts predict video traffic surpassing every other type of data traffic in the world in the near future. These applications are very sensitive to both communication properties such as latency, jitter, packet loss, bit rate as well as backend stream processing load profiles. In this work we provide a novel and generalized large-scale Multi-Cloud architectural blueprint for ISP and Carrier providers, that permits smart geo-distributed service placement in order to optimize latency/locality of stream processing applications. We provide as a well self-managed Intra-Cloud federation algorithm based on gradient topologies in order to optimize routes in a live media streaming backend. Additionally we introduce a novel distributed Network Bandwidth Manager that optimizes system stability by arbitrating network bandwidth between multiple Cloud services sharing the same network infrastructure. At last, an empirical study is provided connecting media quality parameters and Cloud backend load profiles, including an algorithm for stream allocation on Cloud Selective Forwarding units.El procesamiento de medios en tiempo real distribuido se refiere a clases de aplicaciones altamente distribuidas, no tolerantes al retardo, que representan la mayoría del tráfico de datos generado en el mundo actual. Las conferencias de audio y video en tiempo real y la transmisión de contenido en vivo tienen especial interés en investigación, ya que la prospectiva tecnológica estima que el tráfico de video supere a cualquier otro tipo de tráfico de datos en el futuro cercano. La transmisión en vivo se refiere a aplicaciones en las que flujos de audio/vídeo de una fuente se han de entregar a un conjunto de destinos en lugares geográficos diferentes mientras se mantiene baja la latencia de entrega del flujo (como por ejemplo la cobertura de eventos en vivo). Las plataformas de conferencia en tiempo real son plataformas de aplicación que implementan comunicaciones de audio/video en tiempo real entre muchos participantes. Ambas categorías presentan una alta sensibilidad tanto al estado de la red (latencia, jitter, pérdida de paquetes, velocidad de bits) como a los perfiles de carga de la infraestructura de procesamiento de flujo (latencia y jitter introducidos durante el procesamiento en la nube de paquetes de datos multimedia). Esta tesis trata de mejorar el procesamiento de datos multimedia en tiempo real tanto en los parámetros de nivel de red como en las optimizaciones en la nube.
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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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Otepka, Johannes, Sajid Ghuffar, Christoph Waldhauser, Ronald Hochreiter, and Norbert Pfeifer. "Georeferenced Point Clouds: A Survey of Features and Point Cloud Management." MDPI AG, 2013. http://dx.doi.org/10.3390/ijgi2041038.
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This paper presents a survey of georeferenced point clouds. Concentration is, on the one hand, put on features, which originate in the measurement process themselves, and features derived by processing the point cloud. On the other hand, approaches for the processing of georeferenced point clouds are reviewed. This includes the data structures, but also spatial processing concepts. We suggest a categorization of features into levels that reflect the amount of processing. Point clouds are found across many disciplines, which is reflected in the versatility of the literature suggesting specific features. (authors' abstract)
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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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Broman, Beijar Lina. "Using cloud resolving model simulations of tropical deep convection to study turbulence in anvil cirrus." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-303942.
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Identifying the dynamical processes that are active in tropical cirrus clouds is important for understanding the role of cirrus in the tropical atmosphere. This study focuses on analyzing turbulent motions inside tropical anvil cirrus with the use of a Cloud Resolving Model. Convection in the transition from shallow to deep convection has been simulated with Colorado State University Large Eddy Simulator/Cloud Resolving Model System for Atmospheric Model (SAM 6.3) in a high resolution three-dimensional simulation and anvil cirrus formed in the end of this simulation has been analyzed. For model set up, data gathered during the Tropical Rainfall Measuring Mission Large-Scale Biosphere-Atmosphere (TRMM LBA) field experiment in Amazonas, Brazil have been used as large scale forcing. 31 anvil clouds have been localized from a single time step of the simulation, “a snapshot”, of the entire simulated cloud field consisting of convective clouds of different scales and subsequently divided into three categories that represent different stages of the anvil lifetime; growing, mature and dissipating anvil stages. The classification is based on in-cloud properties such as cloud condensate content and vertical velocities. The simulated anvils have been analyzed both individually and as groups to examine the transition from isotropic three-dimensional turbulence in the convective core of the thunderstorm to stratified two-dimensional turbulence in the anvil outflow. A dimensionless number F is derived and used as a measure of the “isotropic” behavior of the turbulence inside the cloud. F is expressed as the ratio between the horizontal part of TKE and the total (horizontal + vertical) Experiments show that SAM 6.3 clearly can resolve turbulent structures and that the transition from isotropic three-dimensional turbulence to stratified two-dimensional turbulence occurs in the middle layers of the mature and dissipating anvil stages.Sammanfattning av ”Studier av turbulenta rörelser i städmoln med hjälp av numeriska simuleringar av tropisk konvektion” Städmoln i tropikerna har stor inverkan på strålningsballansen på grund av de är så vanligt förekommande och att de ligger på hög höjd i atmosfären. Att förstå de drivande krafterna som är aktiva i skapandet och underhållandet av städmoln är viktiga för att få en bra bild av rollen städmoln spelar i den tropiska atmosfären. Den här uppsatsen fokuserar på att studera turbulenta rörelser inuti tropiska städmoln med hjälp av en molnmodell. Tropisk konvektion har simulerats med Colorado State University’s molnmodell SAM 6.3 i en högupplöst tredimensionell simulering. Data från en ”ögonblicksbild” av det simulerade molnfältet har analyserats och 31 städmoln har valts ut och studerats vidare. De simulerade städmolnen indelades i tre olika kategorier baserat på utvecklingsstadier; växande städmoln, moget städmoln och skingrade städmoln. Stadieklassificeringen bestämdes beroende på isvatteninnehåll och vertikalhastigheter i molnet. Städmolnen har därefter analyserats både individuellt och som grupper för att lokalisera och analysera övergången från tredimensionell isotropisk turbulens i kärnan av Cb-molnet till tvådimensionell stratifierad turbulens i städmolnet. För att initiera simuleringen användes mätdata insamlade under fältexperimentet TRMM LBA (Tropical Rainfall Measuring Mission Large-Scale Biosphere-Atmosphere) i Amazonas, Brasilien. För att beskriva turbulenta rörelser i molnen togs det dimensionslösa talet 𝐹 fram som ett mått på isotropin. 𝐹 uttrycks som kvoten mellan den horisontella delen av TKE och den totala (horisontell och vertikal). Den här studien visar att den undersökta molnmodellen SAM 6.3 klart kan simulera turbulenta i rörelser i övergången mellan isotropisk till horisontell turbulens i olika stadier av städmolnens livscykel. Mina analyser visar att övergången sker främst i de mellersta skikten av de mogna och skingrade stadierna av städmolnets utveckling.
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Wyant, Matthew C. "A modeling study of the subtropical stratocumulus-to-trade-cumulus transition /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/10039.
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Mahesh, Ashwin. "Ground-based infrared remote sensing of cloud properties over the Antarctic Plateau /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/6834.
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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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Reuter, Gerhard Wilhelm. "Observations and numerical simulations of mixing mechanisms in South African cumulus conqestus clouds." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=71976.
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The mixing mechanism of South African cumulus congestus clouds is investigated using a combined observational and modeling approach. The experimental data consists of aircraft measurements collected in developing cloud towers near Nelspruit on three case study days. The observations are analyzed to determine the source regions of the entrained air. The mixing processes are simulated using both axially and slab symmetric cumulus models with very high spatial and temporal resolutions. The simulated clouds have a structured organization with small scale features such as in-cloud downdrafts. The mixing processes are examined by analyzing the time variation of dynamic and thermodynamic quantities along computed parcel trajectories.Both observations and simulations indicate that most of the entrainment occurs at the cloud top. Evaporative cooling causes downdrafts that transport highly diluted air from the cloud top down to lower levels. The trajectory analysis shows that the penetrative downdrafts are also affected by pressure perturbations.
In the presence of wind shear the downshear sides of the clouds become more diluted, cooler and have stronger downdrafts. The asymmetric organisation is attributed to turbulent exchange of horizontal momentum at the cloud top.
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Wilson, Ashley Kristen. "Like Water, Like Clouds." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/77499.
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This collection of short fiction explores femininity – a difficult term, in and of itself, because it implies that to be a woman is to be feminine in the traditional sense, or feminist in the revolutionary sense – rarely do the connotations allow for much in between. But I choose this term over “womanhood," for example, because it is more difficult, and culturally loaded, and conflicted, and even offensive. In truth, these stories attempt to portray the multi-faceted nature of how we see the feminine. They hope to convey the most fragile and complicated net of relationships, with men and with women, with mothers and fathers and children and lovers and enemies, each of whom make their own demands about what sort of femininity they require. Considering all this, I tend to think that there is no such thing as the much-talked-about “strong woman" in real life, not completely. She is constantly being pushed into corners where she is weak, or careless, or cruel–secretly unsure of who she is expected and ought to be. The result is a female psyche that is always shifting and disintegrating and dissolving, becoming someone or something else, like the characters in these eight stories. The modern woman is no sure thing. She is in flux and changing shape. And really, it is for those of us who watch to decide if it is for better, or for worse.Master of Fine Arts
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Leonard, Jenny. "This mountain of clouds." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/12499.
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Jenkins, Annabel Ka Lai. "Geoengineering marine stratocumulus clouds." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/6824/.
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Marine cloud brightening (MCB) geoengineering has been proposed as a means of ameliorating anthropogenic climate change. High concentrations of nanometre-sized aerosols would be emitted from seagoing vessels, with the intention of increasing the albedo of low-lying marine stratocumulus clouds (MSc) via indirect aerosol effects. Realistic estimates of the potential effectiveness of MCB are needed to inform policy-making on climate change. However, in spite of increasing model complexity and developments in representing MCB, the relatively coarse resolution of global-scale models prevents implementation details from being captured. This work identified three previously unrepresented implementation details, and examined their importance in achieving realistic estimates of MCB effectiveness. For this, the Weather Research and Forecasting model incorporating aerosol processes (WRF/Chem) was used, allowing clouds to be resolved over a kilometre-scale domain. Firstly, for a weakly precipitating cloud regime, cloud brightening was found to be sensitive to the timing of MCB aerosol emissions. The largest cloud albedo increase occurred for early morning emissions, with little change occurring for daytime emissions. Timing was less important for the non-precipitating regime where cloud albedo perturbations were generally smaller owing to the absence of a large second indirect (or ‘cloud lifetime’) effect. Secondly, near-surface evaporative cooling resulting from the more realistic simulation of MCB emissions as wet droplets rather than the previously assumed dry aerosols reduced aerosol plume heights by up to 30% (40 m), reducing cloud albedo increases by up to one-third. Finally, aerosol coagulation within the MCB aerosol plume (simulated at sub-metre resolution) resulted in number concentration decreases of up to 50%, consequentially reducing the cloud albedo increases by approximately half for the non-precipitating regime. These findings suggest that in omitting these details, global-scale model estimates of MCB effectiveness may be exaggerated. The inclusion of these details in global-scale MCB modelling could therefore materially improve the realism of future effectiveness estimates.
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Tai, Chih-Che. "Classrooms in the Clouds." Digital Commons @ East Tennessee State University, 2010. https://dc.etsu.edu/etsu-works/3292.
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FONTANA, SIMONE. "Robust Point Clouds Registration." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2017. http://hdl.handle.net/10281/180707.
Full textAbstract:
L’allineamento di Point Cloud (nuvole di punti) è un problema attuale e molto studiato, per il quale esistono molte soluzioni efficaci. Non di meno, gli approcci presenti in letteratura fanno affidamento su una buona inizializzazione e su un set di parametri adeguato. Questi approcci potrebbero venir divisi in due categorie: quelli basati sulle feature e quelli basati sulla distanza tra punti. Gli approcci che ricadono nella prima categoria, di solito, allineano due point cloud sfruttando dei punti salienti, keypoints, e un qualche tipo di descrittore, nello stesso modo che viene di solito usato con le immagini 2D.
Gli approcci appartenenti alla seconda categoria, invece, non calcolano esplicitamente nessuna corrispondenza, ma queste vengono approssimate utilizzando il punto più vicino, senza la necessità di calcolare alcuna feature. L'algoritmo più importante in questa categoria è Iterative Closest Point (ICP). La maggior parte degli altri algoritmi, infatti, è una variante di ICP e lo stesso vale per uno degli approcci qui proposti.
In questo lavoro introduciamo due nuove tecniche.
La prima è una variante di ICP con una differente data association, basata su un modello probabilistico. Benché sia nata con l’obiettivo di allineare una point cloud molto sparsa, con una densa, ha dimostrato di essere capace di ottenere risultati qualitativamente migliori degli altri approcci anche su problemi di allineamento classici. Di notevole importanza, inoltre, è la sua bassa sensibilità ai parametri, un problema che, al contrario, affligge molti lavori presenti nella letteratura, come mostreremo, e che ne limita il loro utilizzo nel campo della robotica.
Il secondo algoritmo da noi ideato è volto all’allineamento di due point cloud, senza la necessità di fornire alcuna stima iniziale sul loro allineamento. Questo è un vantaggio molto importante rispetto alle altre tecniche descritte nella letteratura. Mentre quelle basate su feature, benché siano in grado di allineare due nuvole di punti globalmente, senza necessità di una stima iniziale, non sono applicabili a point cloud sparse (uno dei casi che abbiamo dovuto affrontare durante questo lavoro), quelle basate su ICP hanno necessariamente bisogno di una stima iniziale adeguata, altrimenti convergeranno ad una soluzione sbagliata.
L’approccio da noi utilizzato combina i vantaggi di entrambe le tecniche. E’ infatti applicabile ad ogni point cloud, indipendentemente dalla possibilità di estrarne feature, ma allo stesso tempo non ha bisogno di una stima iniziale. Per ottenere ciò abbiamo sfruttato un famoso algoritmo di ottimizzazione, Particle Swarm Optimization, che, benché non dia alcuna garanzia di convergenza ad un ottimo globale, in pratica ha mostrato una buona abilità nello uscire dagli ottimi locali, dove invece molti altri algoritmi rimangono intrappolati.Point clouds registration is a very well studied problem, with many different and efficient solutions. Nevertheless, the approaches in the literature rely heavily on a good initialization and on a good set of parameters. These approaches could be roughly divided into two categories: those based on features and the so-called closest-point-based. The first category aims at aligning two point clouds by first detecting some salient points, the keypoints, and calculating their descriptors so that they can be compared, in the same way it is usually done with 2D images. On the other hand, the latter category approximates correspondences by iteratively choosing the closest point, without the need for any kind of feature. The most important algorithm in this category is Iterative Closest Point (ICP). Most other algorithms are variants of ICP, so is one of the proposed approaches. In this work we introduce two novel solutions to point clouds registration. The first one is a variant of ICP, with a different data association, derived from a probabilistic model. The experiments show that is very effective at aligning a sparse point cloud with a dense one, one of the issues we had to face during this work. On the other hand, it showed very good results also on standard alignment problems, often better than other popular state of the art algorithms. We show that, for the most common approaches, the quality of the result is heavily dependent on some parameters that, thus, need to be carefully calibrated before the algorithms could be used in real applications. Moreover, a new calibration is usually required when facing a new scenario. For this reasons we propose this innovative technique, that aims, besides at being capable of aligning two generic point clouds, independently from their density, at being more robust w.r.t. wrong parameter sets. The second technique we developed is a global point cloud registration algorithm. ICP-like techniques requires, in order to converge to the right solution, an initial estimate of the transformation between the two point clouds. Without a proper initial guess, the algorithm will probably remain stuck in a local minima. On the other hand, feature-based techniques do not require any initial estimate but are not applicable to sparse point clouds, because they do not contain enough information to extract meaningful descriptors. The approach we developed combines the advantages of both approaches. It is based on a soft-computing technique, Particle Swarm Optimization, that is known for being able to escape from local optima. The result is an algorithm capable of aligning any kind of point cloud, without the need of any initial estimate of the transformation.
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Young, Gillian. "Understanding the nucleation of ice particles in polar clouds." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/understanding-the-nucleation-of-ice-particles-in-polar-clouds(4f80f81b-ed06-480a-944b-6e3594ba8471).html.
Full textAbstract:
Arctic clouds are poorly represented in numerical models due to the complex, small-scale interactions which occur within them. Modelled cloud fractions are often significantly less than observed in this region; therefore, the radiative budget is not accurately simulated and forecasts of the melting cryosphere are fraught with uncertainty. Our ability to accurately model Arctic clouds can be improved through observational studies. Recent in situ airborne measurements from the springtime Aerosol-Cloud Coupling and Climate Interactions in the Arctic (ACCACIA) campaign are presented in this thesis to improve our understanding of the cloud microphysical interactions unique to this region. Aerosol-cloud interactions - where aerosol particles act as ice nucleating particles (INPs) or cloud condensation nuclei (CCN) - are integral to the understanding of clouds on a global scale. In the Arctic, uncertainties caused by our poor understanding of these interactions are enhanced by strong feedbacks between clouds, the boundary layer, and the sea ice. In the Arctic spring, aerosol-cloud interactions are affected by the Arctic haze, where a stable boundary layer allows aerosol particles to remain in the atmosphere for long periods of time. This leads to a heightened state of mixing in the aerosol population, which affects the ability of particles to act as INPs or CCN. Aerosol particle compositional data are presented to indicate which particles are present during the ACCACIA campaign, and infer how they may participate in aerosol-cloud interactions. Mineral dusts (known INPs) are identified in all flights considered, and the dominating particle classes in each case vary with changing air mass history. Mixed particles, and an enhanced aerosol loading, are identified in the final case. Evidence is presented which suggests these characteristics may be attributed to biomass burning activities in Siberia and Scandinavia. Additionally, in situ airborne observations are presented to investigate the relationship between the Arctic atmosphere and the mixed-phase clouds - containing both liquid cloud droplets and ice crystals - common to this region. Cloud microphysical structure responds strongly to changing surface conditions, as strong heat and moisture fluxes from the comparatively-warm ocean promote more turbulent motion in the boundary layer than the minimal heat fluxes from the frozen sea ice. Observations over the transition from sea ice to ocean show that the cloud liquid water content increases four-fold, whilst ice crystal number concentrations, N_ice, remain consistent at ~0.5/L. Following from this study, large eddy simulations are used to illustrate the sensitivity of cloud structure, evolution, and lifetime to N_ice. To accurately model mixed-phase conditions over sea ice, marginal ice, and ocean, ice nucleation must occur under water-saturated conditions. Ocean-based clouds are found to be particularly sensitive to N_ice, as small decreases in N_ice allow glaciating clouds to be sustained, with mixed-phase conditions, for longer. Modelled N_ice also influences precipitation development over the ocean, with either snow or rain depleting the liquid phase of the simulated cloud.
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Farrington, Robert. "Testing mixed phase cloud parametrizations through confronting models with in-situ observations." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/testing-mixed-phase-cloud-parametrizations-through-confronting-models-with-insitu-observations(e2b7e31b-fa4a-4501-9f30-2ca2452c58fa).html.
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Accurate representations of clouds are required in large-scale weather and climate models to make detailed and precise predictions of the Earth's weather and climate. Representations of clouds within these models are limited by the present understanding of the role of aerosols in the microphysical processes responsible for cloud formation and development. As part of a NERC funded CASE studentship with the Met Office, this thesis aims to test new aerosol-dependent mixed-phase cloud parametrizations by obtaining extensive cloud microphysical measurements in-situ and comparing and contrasting them with model simulations. Cloud particle concentrations were measured during the Ice NUcleation Process Investigation And Quantification (INUPIAQ) field campaign at Jungfraujoch in Switzerland. A new probe was used to separate droplet and small ice concentrations by using depolarisation ratio and size thresholds. Whilst the new small ice crystal and droplet number concentrations compared favourably with other instruments, the size and depolarisation ratio thresholds were found to be subjective, and suggested to vary from cloud to cloud. An upwind site was chosen to measure out-of-cloud aerosol particle concentrations during INUPIAQ. During periods where the site was out-of-cloud and upwind of Jungfraujoch, several large-scale model simulations were run using the aerosol concentrations in an aerosol-dependent ice nucleation parametrization. The inclusion of the parametrization failed to increase the simulated ice crystal number concentrations, which were several orders of magnitude below those observed in-situ at Jungfraujoch. Several possible explanations for the high observed ice crystal number concentrations at Jungfraujoch are tested using further model simulations. Further primary ice nucleation was ruled out, as the inclusion of additional ice nucleating particles in the model simulations suppressed the liquid water content, preventing the simulation of the mixed-phase clouds observed during INUPIAQ. The addition of ice crystals produced via the Hallett-Mossop process upwind of Jungfraujoch into the model only infrequently provided enough ice crystals to match the observed concentrations. The inclusion of a simple surface flux of hoar crystals into the model simulations was found to produce ice crystal number concentrations of a similar magnitude to those observed at Jungfraujoch, without depleting the simulated liquid water content. By confronting models with in-situ observations of cloud microphysical process, this thesis highlights interactions between surface ice crystals and mixed-phase clouds, and their potential impact on large-scale models.
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Szczodrak, Malgorzata. "Variability of cloud optical depth and cloud droplet effective radius in layer clouds : satellite based analysis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0019/NQ27255.pdf.
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Brösamlen, Gerd. "Radiative transfer in lognormal multifractal clouds and analysis of cloud liquid water data." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68158.
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The study of radiative transfer in multifractal clouds is of great interest, an important application being to Global Climate Models. In this work we develop a formalism analogous to the multifractal singularity formalism for understanding photon scattering statistics in radiative transfer in multifractals, and test the results numerically on lognormal multifractals. Although the results are only exactly valid in the thick cloud limit, the approximation is found to be quite accurate down to optical thickness of $ tau approx1$-10, so the results may be widely applicable. Furthermore we show the possibility of "renormalizing" the multifractal by replacing it with a near equivalent homogeneous medium but with a "renormalized" optical thickness $ tau sp{1/(1+C sb1)}$ where C$ sb1$ is the codimension of the mean singularity of the cloud. We argue that this approximation is likely to continue to be valid for multiple scattering, and is also compatible with recent results for diffusion on multifractals. Finally we analyze cloud liquid water content data and estimate the universal multifractal indices. We find that the scaling is respected over the whole range 5m-330km and that the cloud can in fact be reasonably described by a lognormal multifractal.
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Uriarte, Rafael Brundo. "Supporting Autonomic Management of Clouds: Service-Level-Agreement, Cloud Monitoring and Similarity Learning." Thesis, IMT Alti Studi Lucca, 2015. http://e-theses.imtlucca.it/163/1/RafaelBrundoUriarte_Thesis_Final_A5.pdf.
Full textAbstract:
Cloud computing has grown rapidly during the past few
years and has become a fundamental paradigm in the Information
Technology (IT) area. Clouds enable dynamic, scalable
and rapid provision of services through a computer network,
usually the Internet. However, managing and optimising
clouds and their services in the presence of dynamism and
heterogeneity is one of the major challenges faced by industry
and academia. A prominent solution is resorting to selfmanagement
as fostered by autonomic computing.
Self-management requires knowledge about the system and
the environment to enact the self-* properties. Nevertheless,
the characteristics of cloud, such as large-scale and dynamism,
hinder the knowledge discovery process. Moreover, cloud systems
abstract the complexity of the infrastructure underlying
the provided services to their customers, which obfuscates
several details of the provided services and, thus, obstructs
the effectiveness of autonomic managers.
While a large body of work has been devoted to decisionmaking
and autonomic management in the cloud domain,
there is still a lack of adequate solutions for the provision of
knowledge to these processes.
In view of the lack of comprehensive solutions for the provision
of knowledge to the autonomic management of clouds,
we propose a theoretical and practical framework which addresses
three major aspects of this process: (i) the definition
of services’ provision through the specification of a formal
language to define Service-Level-Agreements for the cloud domain;
(ii) the collection and processing of information through
an extensible knowledge discovery architecture to monitor
autonomic clouds with support to the knowledge discovery
process; and (iii) the knowledge discovery through a machine
learning methodology to calculate the similarity among services,
which can be employed for different purposes, e.g. service
scheduling and anomalous behaviour detection. Finally,
in a case study, we integrate the proposed solutions and show
the benefits of this integration in a hybrid cloud test-bed.
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Williams, Robyn D. "Studies of Mixed-Phase Cloud Microphysics Using An In-Situ Unmanned Aerial Vehicle (UAV) Platform." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7252.
Full textAbstract:
Cirrus clouds cover between 20% - 50% of the globe and are an essential
component in the climate. The improved understanding of ice cloud
microphysical properties is contingent on acquiring and analyzing in-situ and
remote sensing data from cirrus clouds. In ??u observations of microphysical
properties of ice and mixed-phase clouds using the mini-Video Ice Particle Sizer
(mini-VIPS) aboard robotic unmanned aerial vehicles (UAVs) provide a promising
and powerful platform for obtaining valuable data in a cost-effective, safe, and
long-term manner.
The purpose of this study is to better understand cirrus microphysical
properties by analyzing the effectiveness of the mini-VIPS/UAV in-situ platform.
The specific goals include:
(1) To validate the mini-VIPS performance by comparing the mini-VIPS data
retrieved during an Artic UAV mission with data retrieved from the millimeterwavelength
cloud radar (MMCR) at the Barrow ARM/CART site.
(2) To analyze mini-VIPS data to survey the properties of high latitude mixedphase
clouds
The intercomparison between in-situ and remote sensing measurements
was carried out by comparing reflectivity values calculated from in-situ
measurements with observations from the MMCR facility. Good agreement
between observations and measurements is obtained during the time frame
where the sampled volume was saturated with respect to ice. We also have
1 2
shown that the degree of closure between calculated and observed reflectivity
strongly correlates with the assumption of ice crystal geometry observed in the
mini-VIPS images. The good correlation increases the confidence in mini-VIPS
and MMCR measurements. Finally, the size distribution and ice crystal geometry
obtained from the data analysis is consistent with published literature for similar
conditions of temperature and ice supersaturation.
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Aslam, Mudassar. "Bringing Visibility in the Clouds : using Security, Transparency and Assurance Services." Doctoral thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-25376.
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The evolution of cloud computing allows the provisioning of IT resources over the Internet and promises many benefits for both - the service users and providers. Despite various benefits offered by cloud based services, many users hesitate in moving their IT systems to the cloud mainly due to many new security problems introduced by cloud environments. In fact, the characteristics of cloud computing become basis of new problems, for example, support of third party hosting introduces loss of user control on the hardware; similarly, on-demand availability requires reliance on complex and possibly insecure API interfaces; seamless scalability relies on the use of sub-providers; global access over public Internet exposes to broader attack surface; and use of shared resources for better resource utilization introduces isolation problems in a multi-tenant environment. These new security issues in addition to existing security challenges (that exist in today's classic IT environments) become major reasons for the lack of user trust in cloud based services categorized in Software-as-a-Service (SaaS), Platform-as-a-Service (PaaS) or Infrastructure-as-a-Service (IaaS). The focus of this thesis is on IaaS model which allows users to lease IT resources (e.g. computing power, memory, storage, etc.) from a public cloud to create Virtual Machine (VM) instances. The public cloud deployment model considered in this thesis exhibits most elasticity (i.e. degree of freedom to lease/release IT resources according to user demand) but is least secure as compared to private or hybrid models. As a result, public clouds are not trusted for many use cases which involve processing of security critical data such as health records, financial data, government data, etc. However, public IaaS clouds can also be made trustworthy and viable for these use cases by providing better transparency and security assurance services for the user. In this thesis, we consider such assurance services and identify security aspects which are important for making public clouds trustworthy. Based upon our findings, we propose solutions which promise to improve cloud transparency thereby realizing trustworthy clouds. The solutions presented in this thesis mainly deal with the secure life cycle management of the user VM which include protocols and their implementation for secure VM launch and migration. The VM launch and migration solutions ensure that the user VM is always hosted on correct cloud platforms which are setup according to a profile that fulfills the use case relevant security requirements. This is done by using an automated platform security audit and certification mechanism which uses trusted computing and security automation techniques in an integrated solution. In addition to provide the assurance about the cloud platforms, we also propose a solution which provides assurance about the placement of user data in correct and approved geographical locations which is critical from many legal aspects and usually an important requirement of the user. Finally, the assurance solutions provided in this thesis increase cloud transparency which is important for user trust and to realize trustworthy clouds.
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Barahona, Donifan. "On the representation of aerosol-cloud interactions in atmospheric models." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/41169.
Full textAbstract:
Anthropogenic atmospheric aerosols (suspended particulate matter) can modify the radiative balance (and climate) of the Earth by altering the properties and global distribution of clouds. Current climate models however cannot adequately account for many important aspects of these aerosol-cloud interactions, ultimately leading to a large uncertainty in the estimation of the magnitude of the effect of aerosols on climate. This thesis focuses on the development of physically-based descriptions of aerosol-cloud processes in climate models that help to address some of such predictive uncertainty. It includes the formulation of a new analytical parameterization for the formation of ice clouds, and the inclusion of the effects of mixing and kinetic limitations in existing liquid cloud parameterizations. The parameterizations are analytical solutions to the cloud ice and water particle nucleation problem, developed within a framework that considers the mass and energy balances associated with the freezing and droplet activation of aerosol particles. The new frameworks explicitly account for the impact of cloud formation dynamics, the aerosol size and composition, and the dominant freezing mechanism (homogeneous vs. heterogeneous) on the ice crystal and droplet concentration and size distribution. Application of the new parameterizations is demonstrated in the NASA Global Modeling Initiative atmospheric and chemical and transport model to study the effect of aerosol emissions on the global distribution of ice crystal concentration, and, the effect of entrainment during cloud droplet activation on the global cloud radiative properties. The ice cloud formation framework is also used within a parcel ensemble model to understand the microphysical structure of cirrus clouds at very low temperature. The frameworks developed in this work provide an efficient, yet rigorous, representation of cloud formation processes from precursor aerosol. They are suitable for the study of the effect of anthropogenic aerosol emissions on cloud formation, and can contribute to the improvement of the predictive ability of atmospheric models and to the understanding of the impact of human activities on climate.
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Chen, Xiaojun. "Multiple Scattering from Bubble Clouds." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_theses/36.
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Multiple scattering effects from bubble clouds are investigated in this study. A high performance, general purpose numerical tool for multiple scattering calculations is developed. This numerical tool is applied in three computational scenarios in this study. The total scattering cross section of a bubble cloud is investigated. Numerical results indicate that the resonant frequency of the bubble cloud is much lower than that of a single bubble. The variation of resonant frequency of multiple scattering is also studied. It is found that the resonant frequency decreases as the number of bubbles increases, or as the void fraction of the bubble cloud decreases. Phase distributions of bubble oscillations in various multiple scattering scenarios are presented. It is found that, at resonance, the bubbles synchronize to the same phase, which is indicative of the lowest mode of collective oscillation. At wave localization, half of the bubbles oscillate at phase 0 while the other half oscillate at phase Pi. An intuitive interpretation of this behavior is given.
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Sethi, Madhuri. "Generating clouds in computer graphics." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq29782.pdf.
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Kessaci, Yacine. "Ordonnancement multi-critère sur Clouds." Phd thesis, Université des Sciences et Technologie de Lille - Lille I, 2013. http://tel.archives-ouvertes.fr/tel-00915043.
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Le cloud computing a émergé au cours de la dernière décennie pour être largement adopté aujourd'hui dans plusieurs domaines de l'informatique. Il consiste à proposer des ressources axées, ou non, sur le marché sous forme de services qui peuvent être consommés de manière souple et transparente. Dans cette thèse, nous traitons le problème d'ordonnancement, un des enjeux majeurs du cloud. Selon la configuration de cloud ciblée, nous avons identifié trois niveaux d'ordonnancement : niveau service, niveau tâche et niveau machine virtuelle. Nous revisitons la modélisation du problème, la conception et l'implémentation des métaheuristiques multiobjectives pour chaque niveau d'ordonnancement du cloud. Les ordonnanceurs à base de métaheuristiques que nous proposons portent sur différents critères notamment la consommation d'énergie, les émissions de gaz à effet de serre, le profit et la qualité du service (coût et temps de réponse). Nous prouvons leur capacité d'adaptation aux contraintes du cloud en les intégrant au sein du gestionnaire de cloud OpenNebula. De plus, nos ordonnanceurs ont été largement expérimentés utilisant des configurations réalistes de cloud sur Grid'5000, en tant qu'infrastructure en tant que service (IAAS), et des scénarios concrets basés sur les instances et les tarifications d'Amazon EC2. Les résultats présentés montrent que les méthodes que nous proposons surpassent les approches l'ordonnancement existantes sur tous les critères cités précédemment.
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Sethi, Madhu. "Generating clouds in computer graphics." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27406.
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This thesis presents a method for synthesizing highly realistic-looking clouds. This method produces a complete 3-dimensional model of a cloud so that an image can be synthesized from any viewing direction so long as the camera is above the cloud.We take a satellite image of a cloud or cloud field (which is a scene of several clouds), along with a height field for the scene and construct a cloud model which could have produced the input picture.
This approach combines several image synthesis techniques, such as the construction and rendering of parametric bicubic surfaces, texture mapping, and transparency effects. The appropriate selection of these techniques provide a new physically motivated yet heuristic approach to the problem.
This model produces more realistic clouds than any other model, and our techniques for representing satellite data have made this otherwise cumbersome operation highly efficient and computationally inexpensive.
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Brown, Ian David. "The velocity of molecular clouds." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293612.
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Cameron-Smith, Philip J. "Spectroscopic studies of Jovian clouds." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300814.
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Francis, Peter N. "Infrared radiative properties of clouds." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302829.
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Emerson, Jessica Merrill Thurston. "Tag clouds in software visualisation." Thesis, University of Canterbury. Computer Science and Software Engineering, 2014. http://hdl.handle.net/10092/10120.
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Developing and maintaining software is a difficult task, and finding effective methods of understanding software is more necessary now than ever with the last few decades seeing a dramatic climb in the scale of software. Appropriate visualisations may enable greater understanding of the datasets we deal with in software engineering. As an aid for sense-making, visualisation is widely used in daily life (through graphics such as weather maps and road signs), as well as in other research domains, and is thought to be exceedingly beneficial. Unfortunately, there has not been widespread use of the multitude of techniques which have proposed for the software engineering domain.
Tag clouds are a simple, text-based visualisation commonly found on the internet. Typically, implementations of tag clouds have not included rich interactive features which are necessary for data exploration. In this thesis, I introduce design considerations and a task set for enabling interaction in a tag cloud visualisation system. These considerations are based on an analysis of challenges in visualising software engineering data, and the perceptive influences of visual properties available in tag clouds.
The design and implementation of interactive system Taggle based on these considerations is also presented, along with its broad-based evaluation. Evaluation approaches were informed by a systematic mapping study of previous tag cloud evaluation, providing an overview of existing research in the domain. The design of Taggle was improved following a heuristic evaluation by domain experts. Subsequent evaluations were divided into two parts - experiments focused on the tag cloud visualisation technique itself, and a task-based approach focused on the whole interactive system. As evidenced in the series of evaluative studies, the enhanced tag cloud features incorporated into Taggle enabled faster visual search response time, and the system could be used with minimal training to discover relevant information about an unknown software engineering dataset.
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Bretherton, Derek. "Star formation in molecular clouds." Thesis, Liverpool John Moores University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402927.
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Bylin, Victor. "Hybrid Clouds: Implementation and obstacles." Thesis, Umeå universitet, Institutionen för datavetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-126886.
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Hybrid cloud is the approach companies want to adopt for its future in the cloud since hybrid cloud allows you to boost the capacity or the capability of a cloud service by aggregation, integration or customization with another cloud service. Those services can be both private or public. Implementing a hybrid cloud is a big process and companies have difficulties finding a good standard for it. In this thesis, the key points and obstacles in the implementation of the hybrid cloud are pinpointed. One obstacle, workflows are studied closer. Workflows are the result of cloud orchestration, arrangement and coordination of automated tasks. The thesis covers the implementation process of workflows. The result of the thesis is key findings and motivation for the implementation of hybrid cloud and how workflows should be implemented
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Clarke, Seamus. "Numerical simulations of filamentary clouds." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/100557/.
Full textAbstract:
Filamentary structures are observed to be common over a wide range of spatial scales and are strongly linked to star formation. In this thesis I present the results of a range of numerical simulations which investigate the stability, collapse and fragmentation of filaments. The global longitudinal collapse timescale for filaments is found to be considerably longer than for equally dense spheres, allowing sufficient time for local collapse to occur, and to solely occur via the distinctive end-dominated mode. A new freefall timescale equation for filaments is presented, as well as a semi-analytic model of longitudinal collapse. The fragmentation of accreting filaments is found to be more complicated than that of equilibrium filaments, and is dominated by the behaviour of longitudinal gravo-acoustic oscillations. This results in the fastest growing perturbation mode being independent of filament width. The non-equilibrium model presented here allows observers to estimate the age of a fragmenting filament and the mass accretion rate. Simulations of filaments accreting from a inhomogenous, turbulent medium show that turbulence has a large impact on the fragmentation of a filament. When the turbulence is sub-sonic, a filament fragments in a two-tiered hierarchical manner. As the energy in the turbulent field increases, the filament fragments into elongated fibre-like sub-structures. The formation of these fibre-like structures is intimately linked to the vorticity of the velocity field in the filament and the accretion onto the filament. In addition, I present synthetic C18O observations and show that the fibrelike sub-structures appear as velocity-coherent structures, well separated in velocity space, similar to the fibres observed by Hacar & Tafalla (2011).
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Lumpa, Mushashu Mwansa. "Digital Repositories in Private Clouds." Master's thesis, Faculty of Science, 2019. https://hdl.handle.net/11427/31717.
Full textAbstract:
This study explores the use of digital repositories in private cloud environments. Private cloud computing is a cloud computing deployment model where compute and storage infrastructure are hosted on-premise by institutions. Digital repositories are used to manage institutions’ generated content. The advancement in cloud computing, the promise of elasticity, and the on-demand resource provisioning features of cloud systems are attractive characteristics that institutions can leverage on in delivering digital content to their audiences. In this study, a cloud computing operating system is deployed, and a means to install, monitor, manage and customise a repository system is developed. The repository system used is DSpace. Eucalyptus cloud software was used to setup a private cloud environment. A prototype application was developed to manage the installation and customisation of DSpace in the cloud environment. The prototype also included a feature to monitor the status of the running DSpace instances. To evaluate the efficiency, installation and customisation of DSpace in the cloud environment, two types of evaluations were carried out – a performance evaluation and a usability study. The performance evaluation was used to ascertain how long it takes to ingest and view items in DSpace. The experiments were carried out with varying numbers of running virtual machine instances in the cloud. The usability study evaluated the ease of installing and customising DSpace with the developed tool, called Lilu. A total of 22 participants took part in the usability study that was carried out within the premises of the University of Cape Town’s Computer Science Department. The participants belonged to 3 groups – experts, intermediate and beginners – based on their technical skill levels. The results show that private cloud environments can run institutional repositories with negligible performance degradation as the number of virtual machine instances in the cloud are increased. From the usability study, the tool developed was positively perceived. Participants in the study were able to install and customise DSpace. Institutional repositories can efficiently be installed and used in private cloud environments. Building tools that enable users to create single-click installations of the repositories, and creating user friendly interfaces to customise repositories would potentially increase the adoption and utilisation of private cloud environments by institutions.
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Piçarra, Pedro Miguel Ribeiro. "Armazenamento integrado em múltiplas clouds." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17571.
Full textAbstract:
Mestrado em Engenharia de Computadores e TelemáticaCom o avanço da tecnologia, o armazenamento de dados tem escalado de uma forma exponencial. Com o rápido desenvolvimento de técnicas e hardware para processamento de dados e capacidade de armazenamento de dispositivos, há cada vez mais uma menor preocupação no tamanho dos cheiros gerados para um dado propósito. Simultaneamente, com o desenvolvimento de sistemas cloud e com o aumento das velocidades de transferência de dados na Internet, possuir cópias de dados armazenados em sistemas remotos tornou-se popular e até disponibilizada gratuitamente. Hoje em dia, adquirir o computador está muito mais acessível a todos e o número de cheiros por cada utilizador está a aumentar devido ao incremento massivo de documentos em suporte digital. Esse número leva a que a ocupação dos sistemas de armazenamento remotos disponibilizados para utilizadores atinja o seu máximo. Uma forma de contornar este problema e utilizando múltiplas clouds gratuitas. Porém, o crescimento do armazenamento disponibilizado gratuito, mesmo utilizando múltiplas contas, não acompanha o crescimento do tamanho de alguns tipos de cheiros, como por exemplo os multimédia. O problema reside, desta forma, em armazenar cheiros cujo tamanho singular exceda o tamanho de um dado serviço de armazenamento cloud e no processo imprático de possuir vários serviços deste tipo na medida em que se apresentam individualmente separados perante o utilizador. Desta forma, esta dissertação pretende o desenvolvimento de uma aplicação que tenha um funcionamento idêntico ao dos vários serviços de armazenamento cloud, integrando vários serviços deste género, fundindo-os num único, de uma forma transparente para o utilizador.
Technological progress led to the exponencially increase of data storage. With the quick development of data processing hardware and techniques and devices' storage capacity, les that are generated for a certain purpose have a tendency to become bigger without any concern attached. Simultaneously, with the speedy development of cloud systems and with the Internet data transfer speeds step-up, having backup data storaged in remote systems became popular and even provided free of charge. Today, getting a computer is much more accessible to everyone and the number of les per user is growing due to the massive increase of digital format documents. That number leads to the maximum quota of the provided remote storage systems to end-users being achieved. One way around this problem is using multiple free of charge cloud services. However, the free of charge provided storage doesn't increase at the same rate of some les, for example, multimedia ones. The problem lies in les that exceed the size of a certain cloud storage service and in the impractical process of having several services of this kind in a way that they present themselves individually separated to the user. This way, this dissertation aims to develop an application that allows the identical features of several cloud storage services integrating diverse services of this kind, merging them into a single one, in a transparent way to the user.
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Garrett, Timothy J. "Radiative properties of arctic clouds /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/10090.
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Ye, Taisheng. "Nebulae in the Magellanic clouds." Thesis, The University of Sydney, 1988. https://hdl.handle.net/2123/26240.
Full textAbstract:
In this thesis I am primarily concerned with radio observations of the nebulae in the Magellanic Clouds, with particular emphasis on the regions of ionised gas in the Small Magellanic Cloud (SMC).
Nebulae (Latin for ‘clouds’) are luminous fuzzy celestial objects with diverse size, shape and brightness. After several generations of observational and theoretical work, nebulae have been classified into four categories: external galaxies, H II regions, supernova remnants (SNRs) and planetary nebulae (PN). External galaxies are no longer regarded as true nebulae. H II regions are ionised hydrogen and are excited by the intense ultraviolet radiation of central or nearby hot stars. A planetary nebula is an extended, low density envelope which has expanded outward from a red giant star at a late stage in its evolution. SNRs are formed by the high velocity and high temperature material ejected when a star ends its life with a violent explosion.
The current matters of interest in nebulae research concentrate on their classification and evolution, and their relation to the interstellar medium and to nucleosynthesis in their parent galaxies. Specifically, many investigations are directed toward the measurements of physical parameters such as electron temperature, density and elemental abundances, the morphologies of individual nebulae, spatial distributions of each type of nebula in galaxies, the number counts of sources within different luminosity ranges (the luminosity functions) and within different diameter ranges (diameter functions), the global absorption, scattering or reflection by dust (extinction) inside or outside of a nebula and the extinction distribution over a nebula.
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Delport, Waldo. "Forensic evidence isolation in clouds." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/33490.
Full textAbstract:
Cloud computing is gaining acceptance and also increasing in
popularity. Organisations often rely on cloud resources as an
effective replacement for their `in-house' computer systems. In the
cloud, virtual resources are provided from a larger pool of resources,
these resources being available to multiple different clients.
When something suspicious happens within a digital environment, a
digital forensic investigation may be conducted to gather information
about the event. When conducting such an investigation digital
forensic procedures are followed. These procedures involve the steps
to be followed to aid in the successful completion of the
investigation. One of the possible steps that may be followed involves
isolating possible evidence in order to protect it from contamination
and tampering.
Clouds may provide a multi-tenancy solution across multiple
geographical locations. When conducting an investigation into physical
equipment the equipment may be isolated. This may be done, for
example, by placing a cell phone in a Faraday bag in order to block
signals or unplugging a computer's network cable to stop the computer
from either sending or receiving of network traffic. However, in the
cloud it may not be applicable to isolate the equipment of the cloud
because of the multi-tenancy and geographically separated nature of
the cloud. There is currently little research available on how
isolation can be accomplished inside the cloud environment.
This dissertation aims at addressing the need for isolation on the
cloud by creating new methods and techniques that may be incorporated
into an investigation in order to isolate cloud resources. Isolation
can be achieved by moving the unnecessary evidence to a different
location and retaining the required evidence or by moving the required
evidence in such a manner that the evidence would not be contaminated.
If isolated evidence were to be moved to a digital forensic
laboratory, the question arises as to whether it would be possible to
create such a laboratory on the cloud utilise the benefits of cloud
computing and enable the investigation to be conducted on the cloud
without moving the isolated evidence from the cloud. The dissertation
will develop various models of isolation. These models are then tested
in experimental conditions. The experiments were conducted on Nimbula
Director 1.0.3 and VMware vSphere 5.0.
The models were successfully applied in the experiments. It was found
that investigations could benefit from the use of the proposed models
for isolation. However, the experiments also highlighted that some of
the models are not applicable or that a combination should be used.
The experiments also indicated that the methods to be used would
depend on the circumstances of the investigation. A preliminary "cloud
laboratory" was designed and described in terms of which a digital
forensic laboratory can be created on the cloud resources, thus
enabling an investigation to be conducted inside the cloud
environment.Dissertation (MSc)--University of Pretoria, 2013.
Computer Science
unrestricted
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Zygmuntowska, Marta, Thorsten Mauritsen, Johannes Quaas, and Lars Kaleschke. "Arctic clouds and surface radiation." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-185357.
Full textAbstract:
Clouds regulate the Earth’s radiation budget, both by reflecting part of the incoming sunlight leading to cooling and by absorbing and emitting infrared radiation which tends to have a warming effect. Globally averaged, at the top of the atmosphere the cloud radiative effect is to cool the climate, while at the Arctic surface, clouds are thought to be warming. Here we compare a passive instrument, the AVHRR-based
retrieval from CM-SAF, with recently launched active instruments
onboard CloudSat and CALIPSO and the widely used ERA-Interim reanalysis. We find that in particular in winter months the three data sets differ significantly. While passive satellite instruments have serious difficulties, detecting only half the cloudiness of the modeled clouds in the reanalysis, the active instruments are in between. In summer, the
two satellite products agree having monthly means of 70–80 percent, but the reanalysis are approximately ten percent higher. The monthly mean long- and shortwave components of the surface cloud radiative effect obtained from the ERAInterim reanalysis are about twice that calculated on the basis of CloudSat’s radar-only retrievals, while ground based measurements from SHEBA are in between. We discuss these
differences in terms of instrument-, retrieval- and reanalysis
characteristics, which differ substantially between the analyzed
datasets.