Weather radar imagery is important for several remote sensing applications including tracking of storm fronts and radar echo classification. In particular, tracking of precipitation events is useful for both forecasting and classification of rain/non-rain events since non-rain events usually appear to be static compared to rain events. Recent weather radar imaging-based forecasting approaches [3] consider that precipitation events can be modeled as a combination of localized functions using Radial Basis Function Neural Networks (RBFNNs). Tracking of rain events can be performed by tracking the parameters of these localized functions. The RBFNN-based techniques used in forecasting are not only computationally expensive, but also moderately effective in modeling small size precipitation events. In this thesis, an existing RBFNN technique [3] was implemented to verify its computational efficiency and forecasting effectiveness. The feasibility of modeling precipitation events using RBFNN effectively was evaluated, and several modifications to the existing technique have been proposed.

Lake Superior is a forcing factor for local weather systems, causing substantial amounts of lake effect snow in the winter (particularly on the south shore). This study assesses decreasing ice cover of Lake Superior and its effects upon synoptic weather factors. Data were collected from eleven National Weather Service (NWS) stations located on the south shore of the lake. Rainfall and snowfall amounts from December to May were regressed on percent ice coverage and average monthly temperatures from 1972-2002. Ice coverage and average monthly temperature had a negative relationship with snowfall and rainfall.

Para tornar uma estrutura hidrÃulica segura e economicamente viÃvel à preciso que seu projeto seja concebido de forma a suportar eventos extremos, mas sempre seguindo a linha tÃnue entre os custos de execuÃÃo e os riscos calculados pelas consequÃncias da obra nÃo suportar os excessos de chuva. A relaÃÃo Intensidade-DuraÃÃo-FrequÃncia (IDF) da chuva à uma das ferramentas mais comumente utilizadas em engenharia de recursos hÃdricos para definir a vazÃo de projeto. As IDF sÃo determinadas atravÃs de dados pluviogrÃficos, porÃm, muitas vezes estes dados sÃo escassos levando a determinaÃÃo de equaÃÃes atravÃs de dados pluviomÃtricos diÃrios desagregados. Dada a escassez de dados pluviogrÃficos e equaÃÃes IDF no Estado do Cearà foi desenvolvido neste trabalho um programa computacional na linguagem Java que sistematizou a metodologia desenvolvida por Fechine Sobrinho (2011) para elaboraÃÃo de equaÃÃes IDF com base no mÃtodo de desagregaÃÃo de chuva atravÃs de isozonas, possibilitando a elaboraÃÃo das equaÃÃes IDF para os 30 municÃpios que compÃe a mesorregiÃo do Cariri cearense. A ferramenta computacional permite a geraÃÃo das equaÃÃes IDF a partir do processamento dos dados obtidos na base de informaÃÃes da FundaÃÃo Cearense de Meteorologia e Recursos HÃdricos â FUNCEME, apresentando grande potencial para o desdobramento das aplicaÃÃes, como à o caso da espacializaÃÃo dos parÃmetros. A sistematizaÃÃo do mÃtodo foi validada comparando os valores obtidos com os valores de equaÃÃes IDF consagradas na literatura e formuladas atravÃs de dados pluviogrÃficos. Foram obtidas correlaÃÃes acima de 95% para as funÃÃes de distribuiÃÃo empregadas e realizada a espacializaÃÃo dos parÃmetros. / In order to design a safe and economically viable hydraulic structure it is necessary to design a project to withstand extreme events, but always following the fine line between execution costs and calculated risks. The Intensity-Duration-Frequency (IDF) relationship of rainfall is one of the most commonly used tools in water resources engineering to define the design outflow. The IDF is determined by rainfall-duration recorded data, however, these data are often scarce, leading to determination of equations using disaggregated daily rainfall data. Due to insufficient data about rainfall-duration and IDF equations in the state of CearÃ, this work developed a computational program in Java which systematized the methodology developed by Fechine Sobrinho (2011) for IDF equations establishment. This methodology was based on the isozone disaggregation of rain method, allowing the establishment of IDF equations for the 30 municipalities of the Cariri region located in the southern state. The computational tool allows the generation of IDF equations from the data obtained in the FundaÃÃo Cearense de Meteorologia e Recursos HÃdricos - FUNCEME, showing great applications, such as the spatial distribution of the parameters. The systematization of the IDF equations establishment through isozone method was validated by comparison of the obtained values with existing equations on the technical literature. Correlations above 95% were obtained for the distribution functions for the employed and performed the spatial parameters

Les matières organiques dissoutes (MOD), en tant que sources de nutriments ou potentiels vecteurs de pollution, sont impliquées dans de nombreuses problématiques environnementales. Bien qu'elles fassent l'objet de nombreuses études depuis plusieurs décennies, les mécanismes gouvernant leur solubilisation et leur transfert depuis les sols vers les systèmes aquatiques demeurent sujets à discussion. En s'appuyant sur l'étude de la composition moléculaire des MOD par hydrolyse et méthylation assistée par température et couplée à la chromatographie en phase gazeuse et à la spectrométrie de masse (HMT-CPG-SM), cette thèse a pour objectif d'apporter une meilleure compréhension de leurs mécanismes de solubilisation et de transfert à l'échelle d'un bassin versant agricole. Ce travail s'est appuyé sur le bassin versant expérimental de Kervidy-Naizin (Morbihan, Observatoire de Recherche en Environnement AgrHys) afin d'observer les processus mis en jeux à deux échelles temporelles différentes. A l'échelle de la crue, ce travail a permis de préciser l'impact des conditions hydrologiques spécifiques sur la dynamique des MOD. A l'échelle annuelle, l'utilisation conjointe de la signature isotopique du carbone (δ13C) et de la composition moléculaire des MOD a permis de préciser les mécanismes de transfert de MOD impliqués à l'échelle du versant. L'utilisation de la HMT-CPG-SM s'est avéré un outil adéquat pour l'étude de la dynamique des MOD. L'ensemble des résultats ainsi obtenus ont permis de souligner l'importance des conditions hydrologiques et en particulier de la dynamique de nappe dans les processus de solubilisation et de transfert des MOD. / Dissolved organic matter (DOM), as sources of nutrient or pollutant dissemination pathway are implied in numerous environmental issues. Although DOM have been the subject of numerous studies for several decades, the mechanisms implied for their solubilization and their transport from soils to aquatic systems are still a matter of discussion. Based on DOM molecular composition determined using thermally assisted hydrolysis and methylation –gas chromatography – mass spectrometry (THM-GC-MS), this thesis aims to provide a better understanding of their solubilization and transfer mechanisms at the scale of an agricultural headwater catchment. This work was conducted on the experimental headwater catchment of Kervidy-Naizin (France, Environmental Research Observatory AgrHys) in order to determine the processes implied at two temporal scales. At the scale of a rain event, this work has clarified the impact of hydrological conditions on the DOM dynamics. At annual scale, the use of carbon isotope signature (δ13C) and DOM molecular composition allowed to clarify the DOM transfer mechanisms at the slope scale. The use of THM-GC-MS appears to be a suitable tool for the study of DOM dynamics. The results thus obtained allowed to highlight the role of hydrological conditions and in particular the water-table level in the solubilization and transfer of DOM.