Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-04-03T23:20:24Z No. of bitstreams: 1 GilvanLuteroDeCarvalhoFilho_DISSERT.pdf: 2534911 bytes, checksum: 6e5346023d8898ac72d6969006150e15 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-04-12T00:06:08Z (GMT) No. of bitstreams: 1 GilvanLuteroDeCarvalhoFilho_DISSERT.pdf: 2534911 bytes, checksum: 6e5346023d8898ac72d6969006150e15 (MD5) / Made available in DSpace on 2017-04-12T00:06:08Z (GMT). No. of bitstreams: 1 GilvanLuteroDeCarvalhoFilho_DISSERT.pdf: 2534911 bytes, checksum: 6e5346023d8898ac72d6969006150e15 (MD5) Previous issue date: 2016-09-28 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A t?cnica de an?lise de sinais GNSS (Global Navigation Satellite System) emitidos por sat?lites tem sido largamente utilizada no campo da geodin?mica e da geodesia, como sensor para medidas de velocidades e deslocamentos de placas tect?nicas e da representa??o da forma e da superf?cie da Terra. No entanto, o sinal proveniente do sat?lite sofre atrasos ao atravessar a atmosfera terrestre, especificamente em duas das suas camadas: (a) a camada ionosf?rica, na qual o sinal sofre atraso pela presen?a de ?tomos ionizados nesta regi?o, e (b) a camada troposf?rica, onde o atraso acontece devido a presen?a de vapor d??gua na regi?o, sendo fortemente relacionado ? quantidade de vapor d??gua precipit?vel presente na mesma. Neste trabalho apresenta-se uma an?lise de dados de sinais GNSS, coletados em esta??es receptoras de superf?cie, visando aplica??es relacionadas ao c?lculo da quantidade de vapor d??gua na troposfera. Os dados dos sinais GNSS foram obtidos diretamente do IBGE (Instituto Brasileiro de Geografia e Estat?stica) atrav?s da RBMC (Rede Brasileira de Monitoramento Continuo dos Sistemas GNSS). O processamento dos dados foi realizado utilizando-se o software GIPSY (GPS Inferred Positioning System) do JPL-NASA (Jet Propulsion Laboratory), que processa os dados observados dos sat?lites e fornece os valores de ZTD (Zenital Tropospheric Delay) ou Atraso Zenital Troposf?rico. A partir do conhecimento da temperatura e da press?o na posi??o da antena receptora dos sinais, determinou-se o IWV (Integrated Water Vapor), que representa o vapor d??gua integr?vel na coluna atmosf?rica e est? relacionado ? pluviometria local. Aplica??es foram feitas para as cidades de Natal e Mossor?. Das s?ries temporais dos par?metros ZWD, IWV e Pluviometria ? obtidas do INMET (Instituto Nacional de Meteorologia) - foram realizadas as correla??es estat?sticas entre estas vari?veis, utilizando-se o software R. Correla??es estat?sticas entre sinais de GNSS e de Pluviometria v?m sendo usada como ferramenta de aux?lio para a PNT (Previs?o Num?rica de Tempo). Este trabalho mostra, sem sombra de d?vida, que o par?metro IWV pode ser utilizado como dado de entrada para aplica??es de Nowcasting. / The GNSS signal analysis (Global Navigation Satellite System) issued by satellites has been widely used in the field of geodynamics and geodesy, as a sensor for speed measurements and displacement of tectonic plates and the representation of the shape and the Earth's surface. However, the satellite signal is delayed as it crosses the earth's atmosphere, specifically in two of its layers: (a) the ionospheric layer, where the signal is delayed by ionized atoms present in this region, and (b) the tropospheric layer, due to the presence of water vapor, and is strongly related to the amount of water vapor precipitable present in that region. This work presents data analysis of GNSS signals obtained from surface gauge stations, aiming applications related to the amount of water vapor in the troposphere. Data from the GNSS signals were obtained directly from the IBGE (Instituto Brasileiro de Geografia e Estat?stica) through its link with RBMC (Rede Brasileira de Monitoramento Continuo dos Sistemas GNSS). Data processing was performed using the GIPSY (GPS Inferred Positioning System) software, from JPL-NASA (Jet Propulsion Laboratory), which processes the observed data from satellites and provides ZTD values (Zenithal Tropospheric Delay). From the knowledge of temperature and pressure in the gauge station antenna, one can estimate IWV (Integrated Water Vapor), that means the water vapor in the atmospheric column and is related to the local pluviometry. Applications has been made on Natal and Mossor? cities and were made correlations between the variables from the time series obtained from INMET (Instituto Nacional de Meteorologia), for the ZTD parameters, IWV and Pluviometry, using statistical analysis from the R-software. Statistical correlations between GNSS and Pluviometry data could be used as a tool for NWP (Numerical Weather Prediction). This work shows, without a doubt, that this happen when IWV is used as input data for Nowcasting applications.

Radio signals from Global Navigation Satellite Systems (GNSS) satellites suffer delay as they propagate through the atmosphere (neutral and non-neutral) and this delay is partially driven by the water vapour content in the atmosphere. The delay component due to the non-neutral atmosphere (ionosphere) is removed through the use of dual frequency GNSS receivers. The main tropospheric parameter is the zenith tropospheric (or total) delay (ZTD), which is a widely accepted parameter with which to express the total delay in the signal from all satellites due to the neutral atmosphere. The ZTD is a measure of the integrated tropospheric condition over a GNSS receiver station. Accordingly, the integrated water vapour or precipitable water vapour (PWV) can be obtained from a portion of the ZTD, if the atmospheric pressure and temperature at the station are known through a concept often referred to as GNSS meteorology. A number of GNSS receivers have been deployed for mapping and geodetic services in Nigeria under the African reference frame initiative, but unfortunately most of these receivers do not have co-located meteorological sensors for pressure and temperature measurements. The prospect of incorporating GNSS meteorology into weather monitoring and climate analysis in Nigeria was investigated and is reported in this thesis. During the first task of this research, the technical basis for ground-based GNSS meteorology was reviewed and the potentials and challenges of the approach to meteorological activities in Africa (including Nigeria) were identified. Thereafter an in-depth analysis of the spatial and temporal variability of ZTD over Nigeria for the period of 2010-2014 was conducted; results revealed weak spatial dependence among the stations. Tidal oscillations (of the diurnal and semidiurnal components) were observed at the GNSS stations of which the diurnal ZTD cycles exhibited significant seasonal dependence, affirming the prospective relevance of ground-based GNSS data to atmospheric studies. Also in this research, the accuracy and suitability of using reanalysis datasets (ERA-Interim and NCEP/NCAR) and a GPT2 neutral model in retrieving PWV from GNSS observations over Nigeria were investigated; results showed that PWV can be retrieved to within a precision of about 1 mm, provided GNSS-derived ZTD is of high precision. A fundamental issue for GNSS meteorology in the West African region was yet again addressed in this research; this is the development of a weighted tropospheric mean temperature model for use in current and future GNSS meteorology activities in the region. A multitechnique comparison of PWV estimates showed good agreement between GNSS estimates and other techniques (i.e. the atmospheric infrared sounder, and ERAInterim reanalysis). This result is suggestive of the potential of assimilating GNSS atmospheric products into reanalysis and climate models. Diurnal and seasonal variability of GNSS PWV estimates exhibits strong correlation with weather events that influence the region (i.e. solar activity and rainfall events); this further demonstrated the immense contribution of the approach to efficient weather forecasting and climate monitoring for Nigeria. / Thesis (PhD)--University of Pretoria, 2017. / Geography, Geoinformatics and Meteorology / PhD / Unrestricted

Made available in DSpace on 2014-06-11T19:31:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-12-07Bitstream added on 2014-06-13T20:01:31Z : No. of bitstreams: 1 sapucci_lf_dr_prud.pdf: 3782471 bytes, checksum: af4cccfc2f5cb3b6dd4ba86dfb21c180 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A quantificação do vapor d'água integrado na atmosfera (IWV - Integrated Water Vapor), ao contrário de outras variáveis meteorológicas, é algo que ainda se apresenta como um grande desafio para as Ciências Atmosféricas. Diversos mecanismos, envolvendo diferentes técnicas, têm sido empregados e testados para esse fim em diferentes regiões do globo por pesquisa dores das mais variadas áreas da ciência. Essa tese apresenta uma contribuição a esse tema ao empregar receptores GPS (Global Positioning System) em bases terrestres, localizados no Brasil, envolvendo instituições de pesquisa na área de Geodésia e de Meteorologia. Os objetivos principais desse trabalho são validar os valores do IWV obtidos a partir das observações GPS e contribuir com a viabilização da utilização de redes ativas de receptores GPS, existentes atualmente e futuras, no monitoramento do IWV como suporte às atividades da Meteorologia e Climatologia no Brasil. Os resultados obtidos mostram que, com a efetivação desse processo, poderá ser obtida uma fonte adicional de informações da umidade para Previsão Numérica de Tempo (PNT). Além disso, é mostrado também que a alta resolução temporal dos valores do IWV obtidos a partir das observações GPS pode contribuir para a melhoria dos resultados gerados por outras técnicas empregadas na mesma tarefa. Em contrapartida, um modelo de PNT é utilizado para gerar previsões da influência da troposfera nos sinais GPS, visando beneficiar aplicações GPS em tempo real. Os resultados gerados nesse trabalho são frutos da sinergia entre as duas áreas envolvidas e mostram que, atualmente, há boas perspectivas para essa parceria no Brasil. / Quantification of Integrated Water Vapor (IWV), unlike other meteorological variables, still represents a significant challenge to the Atmospheric Sciences. In this task several techniques using different mechanisms have been employed and tested in different regions of the planet. Many researchers from several areas of science have been involved in this process. This thesis presents a contribution to this theme, employing ground-based GPS receivers installed on Brazilian territory, involving Geodesy and Meteorology research institutes. The main aim of this work is to contribute in order to make enable the use of the existing networks of continuously operating GPS receivers, and those that will be installed in the future, in IWV monitoring to support meteorological and climatological activities in Brazil. The results generated show that in this process it is possible to obtain an additional source of humidity information for Numerical Weather Prediction (NWP). Furthermore, the prospect of using the ground-based GPS receivers to monitor atmospheric water vapor is promising because thehigh temporal resolution of IWV values from GPS observations can improve the results generated from other techniques employed in the same task. At the same time, a NWP model is applied to generate predictions of the atmosphere's influence over radiofrequency signals, to improve real time GPS applications. The results of this work stem from the synergy between the two areas of science involved. They show that the current outlook for this partnership in Brazil is good, and that both Meteorology and Geodesy will benefit.

La zone Cévennes-Vivarais et son extension jusque la Méditerranée a été choisie par l'OHM-CV (Observatoire Hydrométéorologique-Méditerranéen des Cévennes-Vivarais) pour la fréquence et la représentativité des événements de pluies intenses qu'elle subit. Depuis 2002, des campagnes automnales de mesures GPS y sont menées dans le but d'améliorer notre connaissance du champ de vapeur d'eau troposphérique associé aux événements de pluie intense. Les observations GPS météorologiques sont les ZTD (délais troposphériques au zénith) et les gradients de délais. Exprimé par une composante Est-Ouest (Gew) et une composante Nord-Sud (Gns), le gradient de délai traduit l'anisotropie du champ de vapeur d'eau à proximité du site GPS.Pour le traitement des observations GPS des réseaux permanents et temporaires de la région de l'OHM-CV, une configuration optimale a été recherchée à partir de différents tests de sensibilité. Une précision de 5 mm sur les ZTD peut être obtenue avec cette stratégie d'analyse pour le réseau régional GPS de la région de l'OHM-CV ; Gew est précis à 6 mm près, alors que Gns apparaît moins précis (à 12 mm près) du fait de l'absence de satellite survolant le pôle Nord.Afin de préparer l'assimilation des observations GPS par les systèmes d'assimilation de données à méso-échelle de Météo-France (modèle de Météo-France AROME), des simulateurs d'observations GPS (ZTD, STD et gradients) ont été implémentés dans le modèle non-hydrostatique à haute résolution Méso-NH. Le laboratoire numérique que constitue le modèle Méso-NH a été un moyen efficace de quantifier la sensibilité des simulations de délais à différentes formulations de la réfractivité atmosphérique.

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