<p>Global mean surface air temperature (GMST) is one of the most well-known and robust measures of global climate change both contemporarily as well as through deep time. In contemporary climate science, the most often discussed causes of GMST change are referred to as external radiative forcings, which are considered to be exogenous to the land-atmosphere-ocean system and which impose a radiative energy imbalance (N) at the top of the earth’s atmosphere. Examples of external radiative forcings include changes in well-mixed greenhouse gas concentrations, changes in volcanic or anthropogenic aerosol loading, anthropogenic changes in land use, and changes in incoming solar radiation. The climate system can also produce unforced variability in GMST that spontaneously emerges from the internal dynamics of the land-atmosphere-ocean system. Unforced GMST variability can emerge via a vertical redistribution of heat within the climate system. For example, there can be a net transport of energy from below the ocean’s mixed layer to the surface during an El-Niño event. Additionally, unforced GMST variability can be due to an unforced change in N. For example, an internally generated change in the strength of an ocean circulation could alter the extent of sea ice and thus change the Earth’s albedo.</p><p>Understanding the magnitude and mechanisms underlying unforced GMST variability is relevant for both the attribution of past climate change to various causes, as well to the prediction of future changes on policy-relevant timescales. However, the literature on unforced GMST variability, particularly at interdecadal and longer timescales, is inconsistent and there is significant disagreement on its magnitude, on its primary geographic origins, and on the physical mechanisms that are most responsible.</p><p>This dissertation seeks to advance the scientific understanding of unforced GMST variability by addressing seven primary scientific goals: 1) To identify the geographic locations (and by proxy modes of variability) that are most responsible for unforced GMST variability in both the instrumental record and in climate models. 2) To identify the primary reasons why AOGCMs disagree on the magnitude of interdecadal unforced GMST variability. 3) To quantify the magnitude of unforced GMST variability in observations over the instrumental record as well as in multi-proxy reconstructions over the past millennium. 4) To quantify the degree to which unforced GMST variability is influenced by internally generated N energy imbalances. 5) To understand how anomalous N fluxes can influence large scale modes of surface temperature variability that affect GMST, such as the Atlantic Multidecadal Oscillation (AMO). 6) To understand the nature of the restoring force responsible for returning a perturbed GMST anomaly back to equilibrium; and 7) To understand how the magnitude and mechanisms of GMST variability might change in the future as the climate warms. </p><p>This research relies on the analysis of coupled Atmosphere-Ocean general circulation models (AOGCMs) that participated in Phase 5 of the Coupled Model Intercomparison Project (CMIP5), satellite observations of the Earth’s energy budget from the Clouds and Earth’s Radiant Energy System (CERES), instrumental surface temperature observations from NASA GISS Surface Temperature Analysis (GISTEMP), atmospheric reanalysis data from the European Center for Medium-Range Weather Forecasts interim reanalysis (ERA-I) and surface temperature reconstructions over the past millennium from numerous multiproxy archives.</p><p>This work has yielded six primary conclusions: I) Dynamics over the tropical Pacific Ocean represent the primary contributor to unforced GMST variability at interdecadal and longer timescales with lesser contributions from dynamics in the subpolar north Atlantic and Southern Ocean. II) AOGCMs tend to underestimate the magnitude of unforced GMST variability at interdecadal and longer timescales relative to both instrumental and reconstructed surface temperature datasets. III) N imbalances can act to significantly enhance interdecadal GMST variability. IV) GMST is able to restore equilibrium after an internally generated perturbation via the transport of energy to high-latitude locations and via the rearrangement the atmospheric circulation; both of which allow for much more efficient release of outgoing longwave radiation (OLR) than would otherwise be expected. V) N imbalances can significantly enhance internal modes of variability such as the AMO; and VI) The magnitude of interdecadal GMST variability is likely to decline and the generating mechanisms of such variability may be fundamentally altered as climate warms over the 21st century. These results advance our understanding of unforced GMST variability and they have implications for attribution studies and may inform projections of climate change on interdecadal timescales.</p> / Dissertation

Resumo: 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. / Abstract: 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. / Orientador: João Francisco Galera Monico / Coorientador: João Augusto Toledo Machado / Banca: José Antonio Aravequia / Banca: Paul J. de Jonge / Banca: José Tadeu Garcia Tommaselli / Banca: Paulo de Oliveira Camargo / Doutor

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.

Diploma thesis was dealing with design of the device for measuring the mean temperature in a channel of any cross-section. First, the theory of heat, heat transfer and fluid flow was summarized. Theory was focused specially on the uneven temperature distribution in the flowing medium. Furthermore, a general overview of commercially used temperature sensors and developed sensors with applicability to the investigated problematics was elaborated. Then, a device for sensing mean temperature in a flow channel for several different diameters has been fully designed and developed. The device included the temperature sensor itself, the necessary measurement electronics and its programming, and a simple measurement data application.