The thesis approaches the problem of systematic errors that arise in measuring precipitation. These errors lead to underestimation of total rainfall. Size of losses can reach in our latitudes even tens of percent. The systematic errors that contribute most to the underestimation include losses caused by the rain gauge walls wetting, evaporation losses and losses due to aerodynamic effects on the rain gauge precipitation particles. A major section of the thesis is formed by background research, which deals with the issue of systematic measurement errors precipitation. The background research tackles the lack of literature on this topic in the Czech Republic. In the research section of the thesis, two existing correction methods for estimating the size of systematic errors for the Czechoslovak manual rain gauge Metra (method developed in the 80's by Slovak Hydrometeorological Institute and the method described by the dissertation thesis Radoslav Tihlárik) were applied to data of selected four stations in the Czech Republic (Milešovka, Bedřichov - Přehrada, Čáslav - Nové Město and Svratouch) . The first mentioned method was applied to all stations in the Slovak Republic in the nineties. Nevertheless, it has not been used in the Czech Republic so far. The results show that the Tihlárik method gives...

The aim of this paper is to determine suitable term of summer holidays. It should be as long as current holidays in Czech republic, it means 62 days. The paper builds on the bachelor's thesis titled "Optimal timing of summer vacances with regard to climate". The convenient term has been evaluated on basis of characteristics of air temperature, duration of sunshine and the length of day there in the bachelor's thesis. This paper contains the analysis of duration of rain, showers, drizzle, fog and mist. Thus, several terms have been found in both papers. But these are suitable with regard to only one meteorological element or phenomenon. The summer holidays should undoubtedly provide days with the best possible values of more meteorological elements. So the final term was calculated as mean and weighted mean of several dates of the beginning of holidays with the highest values of daily average air temperature, length of day and with the shortest total duration of the complex of rain, showers and drizzle and the complex of fog and mist. The weights of individual elements have been determined in two ways, so we have obtained three terms of holidays: two as result of the weighted mean and one as result of the mean. The best periods for holidays, determined by the weighted mean, are 11th June - 11th...

L’étude du cycle de l’eau est d’une importance cruciale pour toutes les sociétés et plus particulièrement pour celles du pourtour méditerranéen qui souffrent à la fois de sécheresses en été et d’inondations dues à des événements de précipitations extrêmes survenant en automne et en hiver. La température est l’un des principaux facteurs qui gouvernent l’intensité maximale des précipitations via la relation de Clausius-Clapeyron (CC). Cette loi exprime la quantité maximale de vapeur d’eau que peut contenir l’atmosphère à une température donnée. À l’aide de simulations climatiques régionales et d’observations, nous avons montré que les relations température-précipitations extrêmes du bassin méditerranéen présentent une forme en crochet avec une augmentation des précipitations extrêmes proche de CC aux basses températures puis une augmentation moins forte (voire une diminution) aux hautes températures. Présents en grande quantité sur le pourtour méditerranéen, les aérosols absorbent et réfléchissent une partie du rayonnement, ce qui contribue à refroidir les basses couches de l’atmosphère. Par leur action sur la température de surface, les aérosols réduisent les précipitations. L’étude de simulations numériques montre également une modification de la relation température-précipitations par les aérosols (leur effet sur les nuages) dans la région euro-méditerranéenne. En plus de faire baisser le contenu en vapeur d'eau disponible, les aérosols stabilisent l’atmosphère en refroidissant davantage les basses couches de l’atmosphère par rapport aux couches supérieures. On étudie souvent la relation température-précipitations d’un climat donné dans le but de prédire l’évolution des précipitations dans un climat futur plus chaud. Cependant cette extrapolation suppose que la relation entre la température et les précipitations ne change pas entre le climat présent et le climat futur, une hypothèse qui s’avère fragile au vu de la sensibilité de cette relation au contenu en aérosols de l’atmosphère, mais aussi au vu du changement de la disponibilité en vapeur d’eau dans un climat futur. Au cours de cette thèse, nous avons ainsi montré que pour plusieurs stations côtières les projections dans le futur de plusieurs modèles de climat régionaux suggèrent que les précipitations extrêmes devraient augmenter proportionnellement à l’augmentation des températures selon la loi de CC. Un phénomène que nous n’avons pas pu observer pour des régions plus isolées de la mer et où l’afflux de vapeur d’eau serait moindre. / The study of the water cycle is of crucial importance for all societies and more particularly for those around the Mediterranean which suffer both from droughts in summer and floods due to extreme precipitation events occurring in the autumn and in winter. Temperature is one of the main factors that govern the maximum intensity of precipitation through the Clausius-Clapeyron (CC) relationship. This law expresses the maximum amount of water vapor that the atmosphere can contain at a given temperature. Using regional climate simulations and observations, we have shown that the temperature-precipitation extremes relationships of the Mediterranean basin have a hooked shape with an increase in extreme precipitation near CC at low temperatures and then a smaller increase (or even a decrease) at higher temperatures. Aerosols, which are present in large quantities around the Mediterranean, absorb and reflect part of the radiation, helping to cool the lower layers of the atmosphere. By their action on the surface temperature, aerosols reduce precipitation. The study of numerical simulations also shows a modification of the temperature-precipitation relationship by aerosols (their effect on clouds) in the Euro-Mediterranean region. In addition to the lowering the available water vapor content, aerosols stabilize the atmosphere by further cooling the lower layers of the atmosphere relatively to the upper layers. The temperature-precipitation relationship of a given climate is often studied in order to predict precipitation trends in a warmer future climate. However, this extrapolation assumes that the relationship between temperature and precipitation does not change between the present climate and the future climate, a hypothesis which proves to be fragile when looking at the sensitivity of this relationship to the aerosol content of the atmosphere, but also in view of the change in the availability of water vapor in a future climate. In this thesis, we have shown that for several coastal stations, projections in the future of several regional climate models suggest that extreme precipitation should increase in proportion to the temperature increases according to CC law. A phenomenon that we have not been able to observe for more isolated areas from the sea and where the influx of water vapor would be reduced.

Resumo: Modelos de geração de precipitações são de extrema importância nos dias atuais, pois com o conhecimento do padrão de precipitação em certa área, pode-se planejar obras de forma a minimizar os efeitos das precipitações de grande intensidade. No presente trabalho, aplica-se o modelo de Neyman-Scott e, particularmente, o de Poisson na geração de precipitações de grande intensidade na região da Bacia do Tietê Superior, no Estado de São Paulo, Brasil. Essa região sofre anualmente com as enchentes devido às fortes precipitações e a alta densidade populacional nesta área. Para a aplicação dos modelos de distribuição espacial de precipitações Neyman-Scott e Poisson, foram considerados os dados coletados de 1980 a 1997 de uma rede pluviométrica constituída de treze pluviômetros. / Abstract: Models related with precipitations generation have extremely importance nowadays because with the standard knowledge about an specific area, we can plan projects to minimize the effects caused by high intensity precipitations. At the present work, we applies Neyman-Scott’s model and particularly the one from Poisson, in the precipitations generations with high intensity in the Superior Tietê Bays’ region, São Paulo state, Brazil. This region suffer annually with the floods due to the strong precipitations and the high human density. To use the Neyman-Scott and Poisson models related to spatial precipitations distribution, we have considered data collected during 1980 to 1997 from a pluviometric network consisted by thirteen rain gauges. / Orientador: Roberto Naves Domingos / Coorientador: José Silvio Govone / Banca: José Manoel Balthazar / Banca: Marco Aurélio Sicchiroli Lavrador / Mestre

This study computed trends in extreme precipitation events of Florida for 1950-2010. Hourly aggregated rainfall data from 24 stations of the National Climatic Data Centre were analyzed to derive time-series of extreme rainfalls for 12 durations, ranging from 1 hour to 7 day. Non-parametric Mann-Kendall test and Theil-Sen Approach were applied to detect the significance of trends in annual maximum rainfalls, number of above threshold events and average magnitude of above threshold events for four common analysis periods. Trend Free Pre-Whitening (TFPW) approach was applied to remove the serial correlations and bootstrap resampling approach was used to detect the field significance of trends. The results for annual maximum rainfall revealed dominant increasing trends at the statistical significance level of 0.10, especially for hourly events in longer period and daily events in recent period. The number of above threshold events exhibited strong decreasing trends for hourly durations in all time periods.

Les eaux superficielles sont nécessaires à toute forme de vie en tant que parties intégrantes de tout processus de vie sur Terre. Quantifier les eaux de surface et suivre leurs variations est primordial en raison du lien direct qui existe entre les variables hydrologiques et le changement climatique. La télédétection par satellite, de l’hydrologie continental offre l’opportunité unique d’étudier, depuis l’espace, les processus hydrologiques à différentes échelles (régionale et globale). Dans cette thèse, différentes techniques ont été développées afin d’étudier les variations des eaux superficielles ainsi que d’autres variables hydrologiques, au niveau du bassin inférieur du Mékong (entre le Vietnam et le Cambodge) et ce en utilisant plusieurs estimations satellitaires différentes. Cette thèse s’articule autour de quatre points principaux. Premièrement, l’utilisation d’observations satellitaires dans le visible et dans l’infrarouge (MODIS) est étudiée et comparée afin d’évaluer les eaux de surface au niveau du bassin inférieur du Mékong. Quatre méthodes de classification ont été utilisées afin de différencier les types de surface (inondés ou pas) dans le bassin. Les différentes méthodes ont donné des cartes d’eaux de surface aux résultats semblables en terme de dynamique saisonnière. La classification la plus adaptée aux régions tropicales a été ensuite choisie pour produire une carte des eaux de surface à la résolution de 500 m entre janvier 2001 et aujourd’hui. La comparaison des séries temporelles issues de cette carte et de celles issues du produit de référence MODIS donne une forte corrélation temporelle (> 95%) pour la période 2001-2007. Deuxièmement, l’utilisation des observations issues du satellite SAR Sentinel-1 est examinée à des fins identiques. L’imagerie satellitaire optique est ici remplacée i par les images SAR qui grâce aux longueurs d’ondes utilisées dans le micro-ondes, permettent de « voir » à travers les nuages. Un jeu d’images Landsat-8-sans-nuage est alors utilisé pour entraîner un Réseau de Neurones (RN) afin de restituer des cartes d’eaux de surface par l’utilisation d’un seuillage sur les sorties du modèle RN. Les cartes sont à la résolution spatiale de 30 m et disponibles depuis janvier 2015. Comparées aux cartes de référence Landsat-8-sans-nuage, les sorties de modèles RN montre une très grande corrélation (90%) ainsi qu’une détection "vraie" à 90%. Les cartes restituées d’eaux de surface utilisant la technologie SAR sont enfin comparées aux cartes d’inondation issues de données topographiques. Les résultats montrent une fois encore une très grande consistance entres les deux cartes avec 98% des pixels considérés comme inondés dans cartes SAR se trouvant dans les régions de très grande probabilité d’inondation selon la topographie (>60%). Troisièmement, la variation volumique des eaux de surface est calculée comme le produit de l’étendue de la surface avec la hauteur d’eau. Ces deux variables sont validées à l’aide d’autres produits hydrologiques et montrent de bons résultats. La hauteur d’eau superficielle est linéairement interpolée aux régions non inondées afin de produire des cartes mensuelles à la résolution spatiale de 500 m. La hauteur d’eau est ensuite analysée pour estimer les variations volumiques. Ces résultats montrent une très bonne corrélation avec la variation volumique induite par la mesure du contenu en eau du satellite GRACE (95%) ainsi qu’avec la variation des mesures in situ de débit des rivières. Finalement, deux produits globaux et multi-satellites d’eaux superficielles sont comparés à l’échelle régionale et globale sur la période 1993-2007: GIEMS et SWAMPS. Lorsqu’elles existent, les données auxiliaires sont utilisées afin de renforcer l’analyse. Les deux produits montrent une dynamique similaire, mais 50% des pixels inondés dans SWAMPS se trouvent le long des côtes. / Surface water is essential for all forms of life since it is involved in almost all processes of life on Earth. Quantifying and monitoring surface water and its variations are important because of the strong connections between surface water, other hydrological components (groundwater and soil moisture, for example), and the changing climate system. Satellite remote sensing of land surface hydrology has shown great potential in studying hydrology from space at regional and global scales. In this thesis, different techniques using several types of satellite estimates have been made to study the variation of surface water, as well as other hydrological components in the lower Mekong basin (located in Vietnam and Cambodia) over the last two decades. This thesis focuses on four aspects. First, the use of visible/infrared MODIS/Terra satellite observations to monitor surface water in the lower Mekong basin is investigated. Four different classification methods are applied, and their results of surface water maps show similar seasonality and dynamics. The most suitable classification method, that is specially designed for tropical regions, is chosen to produce regular surface water maps of the region at 500 m spatial resolution, from January 2001 to present time. Compared to reference data, the MODIS-derived surface water time series show the same amplitude, and very high temporal correlation for the 2001-2007 period (> 95%). Second, the use of SAR Sentinel-1 satellite observations for the same objective is studied. Optical satellite data are replaced by SAR satellite data to benefit the ability of their microwave wavelengths to pass through clouds. Free-cloud Landsat-8 satellite imagery are set as targets to train and optimize a Neural Network (NN). Predicted surface water maps (30 m spatial resolution) are built for the studied region from January 2015 to present time, by applying a threshold (0.85) to the output of the NN. Compared to reference free-cloud Landsat-8 surface water maps, results derived from the NN show high spatial correlation (_90%), as well as true positive detection of water pixels (_90%). Predicted SAR surface water maps are also compared to floodability maps derived from topography data, and results show high consistency between the two independent maps with 98% of SAR-derived water pixels located in areas with a high probability of inundation (>60%). Third, the surface water volume variation is calculated as the product of the surface water extent and the surface water height. The two components are validated with other hydrological products, and results show good consistencies. The surface water height are linearly interpolated over inundated areas to build monthly maps at 500 m spatial resolution, then are used to calculate changes in the surface water volume. Results show high correlations when compared to variation of the total land surface water volume derived from GRACE data (95%), and variation of the in situ discharge estimates (96%). Fourth, two monthly global multi-satellite surface water products (GIEMS & SWAMPS) are compared together over the 1993-2007 period at regional and global scales. Ancillary data are used to support the analyses when available. Similar temporal dynamics of global surface water are observed when compared GIEMS and SWAMPS, but _50% of the SWAMPS inundated surfaces are located along the coast line. Over the Amazon and Orinoco basins, GIEMS and SWAMPS have very high water surface time series correlations (95% and 99%, respectively), but SWAMPS maximum water extent is just a half of what observed from GIEMS and SAR estimates. SWAMPS fails to capture surface water dynamics over the Niger basin since its surface water seasonality is out of phase with both GIEMS- and MODIS-derived water extent estimates, as well as with in situ river discharge data.

Les bassins versants nord-méditerranéens sont fréquemment soumis à des crues extrêmes liées à des précipitations convectives intenses et aux caractéristiques hydrologiques locales. La région méditerranéenne est considérée comme une des régions les plus affectées par le réchauffement climatique, ce qui laisse présager des changements dans le cycle hydrologique. L’objectif de cette thèse CIFRE est d’évaluer les impacts du changement climatique sur les précipitations extrêmes à travers une méthode dite de « futurisation », dans laquelle une fonction de transfert est construite en comparant la distribution des quantiles de précipitations du climat présent et futur. Les impacts du changement climatique sur les précipitations extrêmes sont évalués à travers les simulations à haute résolution EMCORDEX. L’exercice se focalise sur le bassin versant de l’Orbieu dans le sud de la France. La méthode de futurisation est appliquée à six épisodes majeurs de précipitations ayant généré des crues éclair. Les impacts hydrologiques des équivalents statistiques futurs des épisodes de précipitations sont ensuite évalués à travers un modèle hydrologique évènementiel conceptuel. Une estimation des changements d’humidité du sol liés au changement climatique est réalisée et couplée à la quantification des impacts hydrologiques. Le choix d’une modélisation hydrologique conceptuelle a été motivé par ses futures applications opérationnelles. Les conséquences de ce choix sont évaluées à travers une comparaison avec un modèle hydrologique à base physique. Ce dernier est mis en place grâce à une caractérisation du fonctionnement hydrologique du bassin versant de l’Orbieu appuyée par plusieurs campagnes de terrain. / Northern mediterranean meso-scale river catchments are submitted to extremes floods events linked to intense convective precipitation and local hydrologic features. The Mediterranean region is known to be one of the most affected areas by global warming, and it is likely that changes can be expected in the hydrological cycle. The aim of this CIFRE thesis is to assess the climate change impacts on extreme precipitation events using a so-called “futurization” method, in which a transfer function is built by comparing the quantiles of distribution for both present and future climate precipitation. The climate change impact on extreme precipitation events is assessed over high-resolution EMCORDEX simulations. The focus is on the Orbieu catchment located in southwestern France. The futurization method is applied to six major events of precipitation that trigger flash floods. The hydrological impacts of those future statistical counterpart precipitation events are therefore assessed through a conceptual event-based hydrological model. An assessment of soil moisture changes under climate change is performed and coupled to the hydrological impact quantification. The conceptual hydrological model chosen, have been motivated by its future operational applications. The consequences of that choice are assessed through a comparison to a physically based hydrological model. It has been implemented through the hydrological functioning caracterisation of the Orbieu catchment supported by several field campaigns.

In the present work the effect of isothermal ageing treatment on the microstructure and on the localized corrosion resistance of a duplex stainless steel (DSS) was investigated. Specimens taken from a hot rolled cylindrical duplex stainless bar with 22% Cr grade were solution annealed at 1050&deg / C and then sensitization heat treatments were conducted at 650, 725 and 800&deg / C with duration ranging from 100 to 31622 min. The microstructural changes were examined by the light optical microscopy (LOM) and scanning electron microscopy (SEM). XRD technique and EDS analysis were used for microstructural evolution. Double Loop Electrochemical Potentiodynamic Reactivation (DLEPR) and standard weight loss immersion acid tests were performed in order to determine the degree of sensitization (DOS) to intergranular corrosion. The surfaces remained after the DLEPR test and the weight loss immersion test were also examined to observe the attack locations and their relationship with the chromium depleted zones. The degree of sensitization is measured by determining the ratio of the maximum current generated by the reactivation (reverse) scan to that of the anodic (forward) scan, (Ir/Ia) x 100. Ir is very small (less than 10-5 A/cm2) for solution annealed samples at 1050&deg / C for 1 hr and those aged at 650&deg / C for 100 and 316 min after the solution heat treatment, with the Ir/Ia ratios of 0.027634%, 0.033428% and 0.058928% respectively. Hence these samples were considered as unsensitized and their microstructure was composed of primary ferrite and austenite. However, Ir increased to values as high as 10-2 A/cm2 and even approached Ia for all samples aged for other temperatures and times, associated with high Ir/Ia ratios. The increased degree of sensitization can be attributed to stronger effect of chromium and molybdenum depleted areas. The microstructure was composed of primary ferrite and austenite including also sigma phase and the secondary austenite that would be responsible for the localized chromium impoverishment. The time required for sensitization was shorter in samples aged at higher temperatures. Accordingly ageing times of 1000 min at 725&deg / C and of 316 min at 800&deg / C were sufficient, whereas times longer than 10000 min was needed to achieve a sensitized structure at 650&deg / C.

No description available.

Made available in DSpace on 2014-06-11T19:25:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2003-02-26Bitstream added on 2014-06-13T19:53:23Z : No. of bitstreams: 1 diniz_ec_me_rcla.pdf: 610866 bytes, checksum: 86834ae8acca4f4532e7d39107c9c8c7 (MD5) / Modelos de geração de precipitações são de extrema importância nos dias atuais, pois com o conhecimento do padrão de precipitação em certa área, pode-se planejar obras de forma a minimizar os efeitos das precipitações de grande intensidade. No presente trabalho, aplica-se o modelo de Neyman-Scott e, particularmente, o de Poisson na geração de precipitações de grande intensidade na região da Bacia do Tietê Superior, no Estado de São Paulo, Brasil. Essa região sofre anualmente com as enchentes devido às fortes precipitações e a alta densidade populacional nesta área. Para a aplicação dos modelos de distribuição espacial de precipitações Neyman-Scott e Poisson, foram considerados os dados coletados de 1980 a 1997 de uma rede pluviométrica constituída de treze pluviômetros. / Models related with precipitations generation have extremely importance nowadays because with the standard knowledge about an specific area, we can plan projects to minimize the effects caused by high intensity precipitations. At the present work, we applies Neyman-Scott s model and particularly the one from Poisson, in the precipitations generations with high intensity in the Superior Tietê Bays region, São Paulo state, Brazil. This region suffer annually with the floods due to the strong precipitations and the high human density. To use the Neyman-Scott and Poisson models related to spatial precipitations distribution, we have considered data collected during 1980 to 1997 from a pluviometric network consisted by thirteen rain gauges.