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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Ozone et transport dans la haute troposphère tropicale de l'océan Indien et de l'Asie du Sud : apport des données spatiales (IASI) et de la modélisation / Ozone and transport in tropical upper troposphere over Indian ocean and south Asia : contributon of spatial data (IASI) and modelling

Tocquer, Flore 30 January 2015 (has links)
Afin de mieux comprendre les processus responsables de la distribution de l'ozone (O3) dans la haute troposphère (UT) tropicale, cette thèse étudie différents aspects du transport de la pollution depuis les régions sources jusque dans l'UT. La première étude repose sur les observations spatiales IASI qui identifient un évènement de transport de masses d'air enrichies en O3 dans l'UT depuis l'Afrique vers l'Inde. Pour la saison de pré-mousson de tels enrichissement d'O3 dans l'UT au-dessus de l'Océan Indien sont essentiellement attribués à des intrusions stratosphériques. Afin de déterminer son origine des simulations ont été effectuées permettant d'exclure une origine stratosphérique et montrent l'impact prépondérant des NOx produit par les éclairs (LiNOx) en Afrique pour expliquer cet enrichissement d'O3. Cette étude pourra être étendue à d'autres saisons, pour consolider les conclusions obtenues dans le cadre du projet INDOEX. La deuxième partie porte sur l'étude de l'impact d'un système convectif très profond sur la composition de l'UT pendant la mousson asiatique d'été. La simulation avec un traceur passif montre la capacité du système situé le long de l'Himalaya centrale à soulever des masses d'air polluées jusqu'à 100 hPa, altitudes auxquelles la pollution est transportée rapidement par la circulation de l'anticyclone de la mousson asiatique. Confirmant le conduit privilégié de transport vers l'UTLS identifié par Bergman et al. 2013. Cependant l'activation du schéma chimique montre une surestimation des LiNOx produites, un ajustement de leur paramétrisation devra être effectué ainsi que des simulations de sensibilité pour correctement quantifier la production d'O3. Ce travail prend place dans des problématiques actuellement au centre d'une collaboration internationale, ACAM (Atmospheric Composition and the Asian Monsoon) visant à étudier les interactions complexes de la mousson asiatique d'été entre dynamique et chimie, jusqu'à l'échelle du changement climatique. / To better understand the processes controling for the distribution of upper tropospheric (UT) ozone (O3) in the tropics, this thesis examines different aspects of pollution transport from sources regions to UT level, through two case studies that take place in the still debated issues.. First study is based on IASI space observations identified an event of transport of UT enriched O3 air masses from Africa to India. During the pre-monsoon season, events of O3 enrichment in UT above the Indian Ocean were essentially attributed to stratospherics intrusions. Simulations have been used to determine its origin, it excludes a stratospheric origin for the event and indicates a probable important contribution by lightning (LiNOx) that occurs over Africa regions. This study could be extended to the whole region and other seasons with a focus on the spring season in order to complete the conclusions obtained during the INDOEX program. The second part focuses on the characterisation of the impact of a deep convective system upon the UTLS composition during the asian summer monsoon. Simulation with a passive tracer highlights the potential of the convective system located over the central Himalaya foothills, to uplift polluted air masses in UTLS to 100 hPa, where the pollutants are rapidly transported by the asian monsoon anticyclone circulation. In agreement with transport pipe towards the UTLS identified by Bergman et al. 2013. However simulation including reactive chemistry show an overestimation by the model of the amount of LiNOx produced, so an adjustment of their parameterization must be made and sensitivity analysis are foreseen to determine precisely O3 production. This study is established in connection with actual major problematic at the center of general debate of the international collaboration. Like ACAM (Atmospheric Composition and the Asian Monsoon) whose targeting the complexe interaction of asian summer monsoon to atmospheric dynamics and chemistry, as well as climate change impact.
22

L'adaptation des étudiants en période de transition : une étude comparative franco-canadienne des étudiants primo-entrants et des étudiants internationaux vietnamiens / Students' adaptation in transition : a French-Canadian comparison between freshmen students and Vietnamese international students

Brisset, Camille 10 December 2009 (has links)
Cette thèse porte sur l’adaptation des étudiants en période de transition. Elle repose sur une comparaison franco-canadienne entre étudiants primo-entrants et étudiants internationaux vietnamiens. Dans l’objectif d’apporter un éclairage nouveau sur les processus de leur adaptation, nous avons intégré deux modèles théoriques permettant de distinguer deux niveaux d’adaptation, l’un dit « local » commun à tous les étudiants, l’autre dit « international » spécifique aux Vietnamiens (Black, Mendenhall & Oddou, 1991), dans lesquels viennent s’imbriquer deux dimensions du processus : l’adaptation psychologique et l’adaptation socioculturelle (Ward & Searle, 1991). La personnalité anxieuse, suivie de l’attachement adulte et des tracas quotidiens, apparaissent comme le fondement explicatif de l’adaptation des étudiants, quels qu’ils soient, tant à un niveau psychologique que socioculturel. A ces aspects « locaux » pour les Vietnamiens, s’ajoutent deux enjeux interculturels : l’identification à la culture d’origine et les différents réseaux de socialisation. Les résultats soulignent également pour les différents groupes d’étudiants une fragilisation des modèles internes de l’attachement, des différences culturelles dans leurs potentialités à former un corps étudiant et à se socialiser au sein de l’université ainsi que la présence d’individus à risques : ces derniers seraient dans l’incapacité de faire face efficacement au stress induit par la période de transition. / This dissertation focuses on students’ adaptation in transition. It is based on a French-Canadian comparison between freshmen students and international Vietnamese students. With the aim to shed a new light on the process of their adaptation, we integrated two theoretical models which allowed us to distinguish two levels of adaptation, one considered as “local” and common to all students, the other as “international” and specific to Vietnamese students (Black, Mendenhall & Oddou, 1991), in which are embedded two dimensions: psychological adaptation and sociocultural adaptation (Ward & Searle, 1991). Anxious personality, followed by adult attachment and daily hassles, appeared as the root of students’ adaptation both at a psychological and sociocultural level. In addition to these “local” aspects, Vietnamese have to deal with two cross-cultural issues: their identification with culture of origin and the different social networks in their environment. Results also highlighted for all students a weakening in their working models of attachment, cultural differences in their potential to form a student body and to socialize within the university and, the existence of individuals “at risk”: these students appeared to be unable to cope effectively with the stress induced by the transition. / Lu?n án này d? c?p d?n s? h?i nh?p c?a sinh viên trong quá trình chuy?n d?i. Lu?n án du?c th?c hi?n d?a trên m?t so sánh Pháp và Canada gi?a nh?ng sinh viên m?i vào d?i h?c và sinh viên qu?c t? Vi?t Nam. V?i mong mu?n dem l?i m?t cái nhìn m?i m? v? qúa trình h?i nh?p c?a h?, chúng tôi dã trình bày hai mô hình lý thuy?t nh?m phân bi?t hai m?c d? h?i nh?p, m?t « mô hình c?c b? » chung cho m?i sinh viên và m?t « mô hình qu?c t? » d?c trung cho sinh viên Vi?t Nam (Black, Mendenhall & Oddou, 1991). Trong hai mô hình này, hai m?t c?a quá trình dan xen l?n nhau : s? h?i nh?p tâm lý và s? h?i nh?p van hóa xã h?i (Ward & Searle, 1991). Tính cách hay lo, ti?p d?n là s? g?n bó sâu s?c và nh?ng khó khan trong cu?c s?ng thu?ng ngày là co s? lý gi?i cho s? h?i nh?p c?a sinh viên c? v? m?t tâm lý và van hóa xã h?i. ? khía c?nh « c?c b?», sinh viên Vi?t Nam còn ph?i d?i phó v?i hai v?n d? mang tính ch?t liên van hóa : s? d?ng nh?t v?i n?n van hóa g?c và các m?ng xa h?i khác nhau. K?t qu? c?a lu?n án dã nh?n m?nh r?ng d?i v?i nh?ng nhóm sinh viên khác nhau, có s? không b?n v?ng c?a các m?u bên trong c?a các m?i liên h? (working models of attachment), c?a s? khác bi?t v? van hóa trong xu hu?ng hình thành m?t t?p th? sinh viên (student body) và xu hu?ng xã h?i hóa trong tru?ng d?i h?c cung nhu là s? t?n t?i nh?ng cá nhân thu?ng xuyên có v?n d?, nhi?u tâm : nh?ng sinh viên này du?ng nhu không th? d?i phó m?t cách hi?u qu? v?i nh?ng cang th?ng trong quá trình chuy?n d?i này.
23

Β-Adrenergic Receptor-Stimulated Apoptosis in Cardiac Myocytes Is Mediated by Reactive Oxygen Species/C-Jun NH<sub>2</sub>-Terminal Kinase-Dependent Activation of the Mitochondrial Pathway

Remondino, Andrea, Kwon, Susan H., Communal, Catherine, Pimentel, David R., Sawyer, Douglas B., Singh, Krishna, Colucci, Wilson S. 07 February 2003 (has links)
Stimulation of β-adrenergic receptors (βARs) causes apoptosis in adult rat ventricular myocytes (ARVMs). The role of reactive oxygen species (ROS) in mediating βAR-stimulated apoptosis is not known. Stimulation of βARs with norepinephrine (10 μmol/L) in the presence of prazosin (100 nmol/L) for 24 hours increased the number of apoptotic myocytes as determined by TUNEL staining by 3.6-fold. The superoxide dismutase/catalase mimetics Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin pentachloride (MnTMPyP; 10 μmol/L) and Euk-134 decreased βAR-stimulated apoptosis by 89±6% and 76±10%, respectively. Infection with an adenovirus expressing catalase decreased βAR-stimulated apoptosis by 82±15%. The mitochondrial permeability transition pore inhibitor bongkrekic acid (50 μmol/L) decreased βAR-stimulated apoptosis by 76±8%, and the caspase inhibitor zVAD-fmk (25 μmol/L) decreased βAR-stimulated apoptosis by 62±11%. βAR-stimulated cytochrome c release was inhibited by MnTMPyP. βAR stimulation caused c-Jun NH2-terminal kinase (JNK) activation, which was abolished by MnTMPyP. Transfection with an adenovirus expressing dominant-negative JNK inhibited βAR-stimulated apoptosis by 81±12%, and the JNK inhibitor SP600125 inhibited both βAR-stimulated apoptosis and cytochrome c release. Thus, βAR-stimulated apoptosis in ARVMs involves ROS/JNK-dependent activation of the mitochondrial death pathway.
24

Β-Adrenergic Receptor-Stimulated Apoptosis in Adult Cardiac Myocytes Involves MMP-2-Mediated Disruption of β<sub>1</sub> Integrin Signaling and Mitochondrial Pathway

Menon, Bindu, Singh, Mahipal, Ross, Robert S., Johnson, Jennifer N., Singh, Krishna 01 January 2006 (has links)
Stimulation of β-adrenergic receptors (β-AR) induces apoptosis in adult rat ventricular myocytes (ARVMs) via the JNK-dependent activation of mitochondrial death pathway. Recently, we have shown that inhibition of matrix metalloproteinase-2 (MMP-2) inhibits β-AR-stimulated apoptosis and that the apoptotic effects of MMP-2 are possibly mediated via its interaction with β1 integrins. Herein we tested the hypothesis that MMP-2 impairs β1 integrin-mediated survival signals, such as activation of focal adhesion kinase (FAK), and activates the JNK-dependent mitochondrial death pathway. Inhibition of MMP-2 using SB3CT, a selective gelatinase inhibitor, significantly increased FAK phosphorylation (Tyr-397 and Tyr-576). TIMP-2, tissue inhibitor of MMP-2, produced a similar increase in FAK phosphorylation, whereas treatment of ARVMs with purified active MMP-2 significantly inhibited FAK phosphorylation. Inhibition of MMP-2 using SB3CT inhibited β-AR-stimulated activation of JNKs and levels of cytosolic cytochrome c. Treatment of ARVMs with purified MMP-2 increased cytosolic cytochrome c release. Furthermore, inhibition of MMP-2 using SB3CT and TIMP-2 attenuated β-AR-stimulated decreases in mitochondrial membrane potential. Overexpression of β1 integrins using adenoviruses expressing the human β1A-integrin decreased β-AR-stimulated cytochrome c release and apoptosis. Overexpression of β1 integrins also inhibited apoptosis induced by purified active MMP-2. These data suggest that MMP-2 interferes with the β1 integrin survival signals and activates JNK-dependent mitochondrial death pathway leading to apoptosis.
25

A complex intervention to reduce avoidable hospital admissions in nursing homes: a research programme including the BHiRCH-NH pilot cluster RCT

Downs, Murna G., Blighe, A., Carpenter, R., Feast, A., Froggatt, K., Gordon, S., Hunter, R., Jones, L., Lago, N., McCormack, B., Marston, L., Nurock, S., Panca, M., Permain, H., Powell, Catherine, Rait, G., Robinson, L., Woodward-Carlton, B., Wood, J., Young, J., Sampson, E. 14 May 2021 (has links)
Yes / An unplanned hospital admission of a nursing home resident distresses the person, their family and nursing home staff, and is costly to the NHS. Improving health care in care homes, including early detection of residents’ health changes, may reduce hospital admissions. Previously, we identified four conditions associated with avoidable hospital admissions. We noted promising ‘within-home’ complex interventions including care pathways, knowledge and skills enhancement, and implementation support. Objectives: Develop a complex intervention with implementation support [the Better Health in Residents in Care Homes with Nursing (BHiRCH-NH)] to improve early detection, assessment and treatment for the four conditions. Determine its impact on hospital admissions, test study procedures and acceptability of the intervention and implementation support, and indicate if a definitive trial was warranted. Design: A Carer Reference Panel advised on the intervention, implementation support and study documentation, and engaged in data analysis and interpretation. In workstream 1, we developed a complex intervention to reduce rates of hospitalisation from nursing homes using mixed methods, including a rapid research review, semistructured interviews and consensus workshops. The complex intervention comprised care pathways, approaches to enhance staff knowledge and skills, implementation support and clarity regarding the role of family carers. In workstream 2, we tested the complex intervention and implementation support via two work packages. In work package 1, we conducted a feasibility study of the intervention, implementation support and study procedures in two nursing homes and refined the complex intervention to comprise the Stop and Watch Early Warning Tool (S&W), condition-specific care pathways and a structured framework for nurses to communicate with primary care. The final implementation support included identifying two Practice Development Champions (PDCs) in each intervention home, and supporting them with a training workshop, practice development support group, monthly coaching calls, handbooks and web-based resources. In work package 2, we undertook a cluster randomised controlled trial to pilot test the complex intervention for acceptability and a preliminary estimate of effect. Setting: Fourteen nursing homes allocated to intervention and implementation support (n = 7) or treatment as usual (n = 7). Participants: We recruited sufficient numbers of nursing homes (n = 14), staff (n = 148), family carers (n = 95) and residents (n = 245). Two nursing homes withdrew prior to the intervention starting. Intervention: This ran from February to July 2018. Data sources: Individual-level data on nursing home residents, their family carers and staff; system-level data using nursing home records; and process-level data comprising how the intervention was implemented. Data were collected on recruitment rates, consent and the numbers of family carers who wished to be involved in the residents’ care. Completeness of outcome measures and data collection and the return rate of questionnaires were assessed. Results: The pilot trial showed no effects on hospitalisations or secondary outcomes. No home implemented the intervention tools as expected. Most staff endorsed the importance of early detection, assessment and treatment. Many reported that they ‘were already doing it’, using an early-warning tool; a detailed nursing assessment; or the situation, , assessment, recommendation communication protocol. Three homes never used the S&W and four never used care pathways. Only 16 S&W forms and eight care pathways were completed. Care records revealed little use of the intervention principles. PDCs from five of six intervention homes attended the training workshop, following which they had variable engagement with implementation support. Progression criteria regarding recruitment and data collection were met: 70% of homes were retained, the proportion of missing data was < 20% and 80% of individuallevel data were collected. Necessary rates of data collection, documentation completion and return over the 6-month study period were achieved. However, intervention tools were not fully adopted, suggesting they would not be sustainable outside the trial. Few hospitalisations for the four conditions suggest it an unsuitable primary outcome measure. Key cost components were estimated. Limitations: The study homes may already have had effective approaches to early detection, assessment and treatment for acute health changes; consistent with government policy emphasising the need for enhanced health care in homes. Alternatively, the implementation support may not have been sufficiently potent. Conclusion: A definitive trial is feasible, but the intervention is unlikely to be effective. Participant recruitment, retention, data collection and engagement with family carers can guide subsequent studies, including service evaluation and quality improvement methodologies. Future work: Intervention research should be conducted in homes which need to enhance early detection, assessment and treatment. Interventions to reduce avoidable hospital admissions may be beneficial in residential care homes, as they are not required to employ nurses. / This project was funded by the National Institute for Health Research (NIHR) Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 9, No. 2. See the NIHR Journals Library website for further project information.
26

Quantum Chemical Feasibility Study of Methylamines as Nitrogen Precursors in Chemical Vapor Deposition

Rönnby, Karl January 2015 (has links)
The possibility of using methylamines instead of ammonia as a nitrogen precursor for the CVD of nitrides is studied using quantum chemical computations of reaction energies: reaction electronic energy (Δ𝑟𝐸𝑒𝑙𝑒𝑐) reaction enthalpy (Δ𝑟𝐻) and reaction free energy (Δ𝑟𝐺). The reaction energies were calculated for three types of reactions: Uni- and bimolecular decomposition to more reactive nitrogen species, adduct forming with trimethylgallium (TMG) and trimethylaluminum (TMA) followed by a release of methane or ethane and surface adsorption to gallium nitride for both the unreacted ammonia or methylamines or the decomposition products. The calculations for the reaction entropy and free energy were made at both STP and CVD conditions (300°C-1300°C and 50 mbar). The ab inito Gaussian 4 (G4) theory were used for the calculations of the decomposition and adduct reactions while the surface adsorptions were calculated using the Density Functional Theory method B3LYP. From the reactions energies it can be concluded that the decomposition was facilitated by the increasing number of methyl groups on the nitrogen. The adducts with mono- and dimethylamine were more favorable than ammonia and trimethylamine. 𝑁𝐻2 was found to be most readily to adsorb to 𝐺𝑎𝑁 while the undecomposed ammonia and methylamines was not willingly to adsorb.
27

Studien zum frühen römischen Kaiserkult in den Provinzen Achaia, Epirus und Macedonia

Johr, Jana 25 October 2016 (has links)
Nach der Schlacht von Actium am 2. September 31 v. Chr. war alles anders. Mit seinem Aufstieg zum unumstrittenen Alleinherrscher des Imperium Romanum wurde Augustus in den östlichen Reichsteilen kultisch verehrt. In Griechenland waren aus der hellenistischen Tradition heraus die Bedingungen für eine göttergleiche Ehrung des Herrschers gut bereitet. Das Anliegen dieser Studie ist es zu untersuchen, wie sich der Kult in den römischen Provinzen Griechenlands entwickeln und festigen konnte. Dabei werden zunächst Vorläufer kultischer Ehrungen römischer Staatsmänner in republikanischer Zeit betrachtet. Spannend ist dann in frühaugusteischer Zeit vor allem der bauliche Übergang, oftmals wurde der neue Kult des Kaisers in bereits bestehende Heiligtümer integriert. Gegenstand der Untersuchung sind nicht nur die Kaiser selbst, sondern auch ihre Familienmitglieder. Für die Betrachtungen werden Kultorte, Tempel und Altäre herangezogen. Kaiserfeste und ihre Ausrichtung spielen eine Rolle, ebenso das Amt der kaiserlichen Priester und Priesterinnen sowie Stifter und Stifterinnen. Unter kultur- und religionsgeschichtlichen Aspekten werden Fragen nach den Formen des Kaiserkultes aufgeworfen: Wie wurde dieser formal dargestellt und in welche städtischen und architektonischen Kontexte wurde der Kult eingebunden? Fragen nach der Praxis kultischer Verehrung sollen im Hintergrund stehen, wenn ausgewählte Zeugnisse des Kaiserkults von iulisch-claudischer bis in flavische Zeit betrachtet werden. Dabei bildet Athen einen hervorragenden Ausgangspunkt für einen provinzübergreifenden Vergleich, der anhand selektiver Beispiele von lokalen Kaiserkultstätten in den Provinzen Achaia, Epirus und Macedonia bereichert wird. Dabei werden Gemeinsamkeiten und Unterschiede in den genannten Regionen herausgestellt, die das Phänomen Kaiserkult beleuchten. / Early Roman imperial cult in the provinces of Achaia, Epirus and Macedonia After Actium everything changed. With his rise to the sole ruler of the Imperium Romanum, Augustus began to be worshiped in the eastern Empire. Because of its Hellenic tradition Greece had been well prepared for emperor worship. The aim of this study is to investigate how emperor worship came to be established in the Roman provinces of Greece. It first considers the precursors of worshipping Roman statesmen in the Republican period. In the following early Augustan period, there is a fascinating architectural transformation in which the new cult for the emperor was often integrated into preexisting sanctuaries. The focus of this investigation is not only the emperor himself, but also his family members. It is thus necessary to consider cult sites, sanctuaries and altars. Imperial festivals also play a role, as do imperial priests and benefactors. Questions are raised about the forms of emperor worship within their cultural and religious contexts: how was imperial cult integrated into and physically represented in its urban and architectural spaces? The actual practices of cultic worship constitute the necessary background for interpreting the evidence of Julio-Claudian and Flavian emperor worship. Athens is thus an excellent starting point for a comparison between provinces, based on case studies of imperial cult sites in the provinces of Achaia, Epirus and Macedonia. By virtue of these comparisons, similarities and differences across the regions come to the fore and ultimately help illuminate the phenomenon of emperor worship.
28

Kvalitetsundersökning av de globala höjdmodellerna Copernicus GLO-30 DEM och FABDEM över tre områden i Sverige

Jakobsson, Jennifer, Stolpe, Louise January 2022 (has links)
Höjddata är fundamentala inom en mängd applikationer. Genom att skapa en digital höjdmodell (DEM), d.v.s. en matematisk modell av terrängens fysiska form, kan höjddata nyttjas på ett effektivt sätt. Tillgång till digitala höjdmodeller underlättar både vid hållbar samhällsplanering och övervakning av klimatförändringar. Vid tillämpning av en DEM är det av största intresse att veta hur väl modellen representerar jordytan. Den centrala delen av studien innefattar en granskning av de två globala höjdmodellerna Copernicus GLO-30 DEM och FABDEM (Forest And Buildings removed Copernicus DEM) som jämförs med svenska referensmodeller baserade på nationella LiDAR-data (Light Detection And Ranging). Genom generering av en egen ytmodell från punktmolnet Laserdata NH framställdes referensdata för jämförelser med Copernicus GLO-30 DEM. Som referensdata för jämförelser med FABDEM användes GSD-Höjddata Grid 2+, vilket är ett markmodellsraster. Utvärderingen utfördes över tre provytor i Sverige. Dessa provytor representerar karaktäristiska marktyper inom landet. I granskningen av kvaliteten för de globala modellerna analyserades statistik för jämförelserna. Dessutom skapades plottar för att kunna visualisera höjdskillnaderna. Studien innehåller även en litteraturstudie om hur de globala modellerna har skapats. Skaparna av Copernicus GLO-30 DEM garanterar en utvidgad standardosäkerhet med täckningsgraden 90% (LE90) på 4 m. Den här studien resulterade i lite högre utvidgade osäkerheter, mellan ca 4,3 och 6,1 meter. Den lägsta osäkerheten uppnåddes i provytan över Stockholm som innehåller höga byggnader, vatten och en del vegetation. De mest avgörande avvikelserna för FABDEM kan kopplats till svagheter i metoden att framställa en markmodell från ytmodellen Copernicus GLO-30 DEM, men FABDEM påverkas också signifikant av brister i den underliggande modellen, d.v.s. i Copernicus GLO-30 DEM. / Elevation data is fundamental in a variety of applications. By creating a digital elevation model (DEM), i.e. a mathematical model representing the physical shape of the surface of the Earth, altitude data can be used effectively. Access to digital elevation models facilitates both sustainable spatial planning and monitoring of climate change. When applying a DEM, it is of greatest interest to know how well the model represents the earth's surface. The central part of the study includes a review of the two global height models Copernicus GLO-30 DEM and FABDEM (Forest And Buildings removed Copernicus DEM), which are compared with reference models based on Swedish national LiDAR data (Light Detection And Ranging). By generating its own surface model from the point cloud Laserdata NH, reference data was produced for comparisons with Copernicus GLO-30 DEM. GSD-Elevation data Grid 2+, which is a terrain model in grid format, was used as reference data for comparisons with FABDEM. The evaluation was performed over three test areas in Sweden. These test areas represent characteristic land types within the country. In the review of the quality of the global models, statistics for the comparisons were analysed. In addition, plots were created to be able to visualize the height differences. The study also includes a literature study on how the global models have been created. The creators of the Copernicus GLO-30 DEM guarantee an extended standard uncertainty at 90 % coverage probability (LE90) of 4 m. This study resulted in somewhat larger expanded uncertainties (90 %), between about 4.3 and 6.1 meters. The lowest uncertainty was achieved in the sample area over Stockholm, which contains tall buildings, water and some vegetation. The most significant deviations for FABDEM can be linked to weaknesses in the method of producing a terrain model from the surface model Copernicus GLO-30 DEM, but FABDEM is also significantly affected by the deficiencies in the underlying model, i.e. in Copernicus GLO-30 DEM.
29

Caractéristiques de l'écoulement et des précipitations observés durant MAP: une analyse par radar et simulation numérique

Pradier, Stephanie 21 October 2002 (has links) (PDF)
Le massif Alpin est régulièrement soumis à l'automne à des systèmes dépressionnaires amenant un flux d'air méditerranéen chaud et humide sur son versant sud . De par la forme et la topographie du massif, ce phénomène peut conduire localement à des précipitations intenses souvent à l'origine d'inondations éclairs, dommageables pour l'homme. L'un des objectifs de l'expérience internationale MAP (Mesoscale Alpine Program) est l'étude des mécanismes dynamiques et microphysiques de ces précipitations, dans le but d'en améliorer la prévision. La campagne s'est déroulée durant l'automne 1999 et a donné lieu à 17 Périodes d'Observations Intensives (POI).<br />Les travaux de recherche effectués durant cette thèse sont basés sur l'analyse de plusieurs d'entre elles, ceci au moyen de données de radars Doppler sole et aéroportés, et du modèle numérique méso-échelle non-hydrostatique Méso-NH. Ces travaux visent à établir le scénario et les processus fondamentaux qui ont mené à leur occurrence. Différents types d'évènements pluvieux ont été étudiés : 2 cas de précipitations convectives, le premier à fort cumul de pluie dans la région du Lac Majeur (ouest des Alpes, POI 2B), et un autre sur la région du Frioul (est des Alpes, POI 5) ; puis des conditions pour lesquelles les précipitations se sont révélées plus modérées sur la région du Lac Majeur (POIs 4, 8, 9 et 15) permettant d'étudier un autre mécanisme lié au relief ou non : le processus de blocage.<br />Sur ces 6 cas d'étude, le facteur dominant responsable du cumul de pluie au sol est le facteur durée : la persistance des précipitations associée au ralentissement du système dépressionnaire au niveau des Alpes mène aux plus forts cumuls. Ceux-ci ont été enregistrés pour les POIs 2B et 8, soit des évènements convectif et stratiforme respectivement. Dans le cas de la POI 2B, c'est un système quasi-stationnaire d'altitude qui est responsable du ralentissement, alors que pour la POI 8 il s'agit de la nature stable du flux incident sur les flancs alpins, et par la suite de son blocage au niveau du relief. Les POIs 4 et 15, caractérisées également par la stabilité du flux d'alimentation des précipitations, illustrent des acs pour lesquels l'arrivée du front froid associé au système dépressionnaire, et par conséquent d'un flux post-frontal antagoniste au flux d'alimentation, est responsable du déplacement des cellules précipitantes. La POI5 est une situation caractérisant le passage rapide du front froid, et l'évolution d'une ligne de cellules convectives associée.<br />L'effet du relief a été mis en évidence, dans les épisodes pluvieux stratiforme et convectif. Dans tous les cas, ce dernier contribue à renforcer/déclencher les précipitations. Il est responsable de la déviation vers l'ouest des flux incidents stables. L'impact de l'orographie de petite échelle a également été démontré à l'aide de tests numériques, en particulier les irrégularités du relief de l'ordre du kilomètre ont joué un rôle important dans la progression du système précipitant de la POI 5.
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SIMULATIONS NUMERIQUES D'EPISODES DE PRECIPITATIONS INTENSES DOCUMENTES LORS DE LA CAMPAGNE DE MESURES MAP (MESOSCALE ALPINE PROGRAMME)

Lascaux, Franck 14 November 2005 (has links) (PDF)
Des épisodes de précipitations intenses se produisent fréquemment sur les Alpes durant la saison automnale, occasionnant régulièrement de nombreux dégâts matériels et humains.<br />L'amélioration de leur prévision est un enjeu majeur de la météorologie opérationnelle actuelle.<br />En 1999, le programme MAP (Mesoscale Alpine Programme) a été mis en place afin de recueillir une base de données importante décrivant plusieurs de ces épisodes.<br />Certains de ces épisodes ont été simulés à l'aide du modèle non-hydrostatique Meso-NH.<br />L'attention est d'abord portée sur la sensibilité de la prévision d'un épisode fortement convectif au schéma microphysique utilisé, ainsi qu'aux conditions initiales. Ensuite l'étude est élargie à deux autres évènements et il est mis en évidence des comportements microphysiques différents en fonction des caractéristiques du flux incident.

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