LIDAR, an acronym for LIght Detection And Ranging, is a system used for studying the scattering of laser light incident on a parcel of air. This thesis investigates the atmosphere above the Durban region using two atmospheric LIDARs, referred to, in this study, as the "old LIDAR" and the "new LIDAR". The old LIDAR was used in a campaign of observation from July to October 1997 in a study of aerosol concentrations over Durban. This thesis will focus on, among other things, the local aerosol profiles for low altitude (0 to 10 km) and high altitude (10 to 35 km). In particular, the focus will shift on any long persistence in this region (it was found that the aerosol layer observed by M. Kuppen (1996) on June 1994 at 25 km may have moved to the higher altitude of 28 km in October 1997. This may be explained by stratospheric upwelling, carrying the layer to higher altitude. These aerosols are known to influence the local climate). This investigation will give some useful insight into the local atmospheric dynamics. The new LIDAR system (Rayleigh-Mie LIDAR) has been used to measure atmospheric temperatures from 20 to 60 km as well as aerosol extinction coefficients from 15 to 40 km. Height profiles of temperature have been measured by assuming that the LIDAR returns are solely due to Rayleigh scattering by molecular species and that the atmosphere obeys the perfect gas law and is in hydrostatic equilibrium (Hauchecorne and Chanin 1980). Since its installation in April 1999, the new LIDAR has been used to monitor stratospheric temperatures and aerosol concentrations from 10 to 40 km. In this study, we discuss in chapter 7 the results of a validation campaign conducted during the period of April 1999 to December 2000. Average monthly LIDAR temperatures are computed from April 1999 to December 1999 and compared with radiosonde temperatures obtained from the South African Weather Service (SAWS) at Durban. The monthly LIDAR temperature profiles over two years (1999 and 2000) were also computed and compared with the climatological model Cospar International Reference Atmosphere (CIRA)-1986 and with the average monthly European Centre for Medium Range Weather Forecast (ECMWF) temperatures . The results show that there is good agreement between LIDAR and SAWS radiosonde temperatures in the 20 and 30 km altitude range. Between 20 and 40 km, the monthly LIDAR temperatures agree closely with the CIRA-86 and ECMWF profiles. However, during winter, in the altitude range 40 to 60 km, LIDAR temperatures are warmer than CIRA-1986 and ECMWF temperatures, and they show large variability. These variations could be due to relatively fast transient phenomena like gravity waves or planetary waves propagating vertically in the stratosphere. As part of the validation process, the aerosol extinction coefficients retrieved from the LIDAR data have also been compared with the extinction coefficients measured by Stratospheric Aerosol and Gas Experiment (SAGE) II close to the LIDAR location and on coincident days. Appendix E of this thesis also investigates the concept of refraction by atmospheric gases as applied to gas lenses. A simple spinning pipe gas lens (SPGL) has been used as the objective lens of a camera to take pictures of the moon and sun spots. The SPGL is a varifocal length lens which depends on the temperature of the pipe and the angular velocity at which it spins. For our purpose a focal length of 8 m has been used. The moon pictures are compared with a lunar map so as to identify the maria. / Thesis (Ph.D.)-University of Natal, Durban, 2002.

Copies of author's previously published articles inserted. / Bibliography: p. 227-245. / xiii, 245 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Describes the observations of gravity waves and turbulence in the lower atmosphere and their analysis using theory and modeling studies. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 2000?

Made available in DSpace on 2014-06-11T19:22:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-03Bitstream added on 2014-06-13T20:08:31Z : No. of bitstreams: 1 berardo_bl_me_bauru.pdf: 467989 bytes, checksum: 1b7cb5967b4080092b9a0c9ae7a58c49 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho mostra o estudo de uma linha de transmissão onde ocorreram desligamentos causados por descargas atmosféricas. Esse estudo foi feito a partir de informações de desligamentos de linhas de transmissão da concessionária e dados extraídos de um sistema de análise e monitoramento de descargas atmosféricas. Para esse trecho da linha de transmissão foram identificadas incidências de descargas atmosféricas que causaram desligamentos, bem como descargas que não causaram desligamentos. Baseados nestas informações foram efetuadas medições em campo de resistência de aterramento dos contrapesos e da resistividade do solo, onde foi possível constatar através dos resultados que algumas torres apresentaram valores que ultrapassaram os valores normatizados. O levantamento dessas informações é o principal foco deste estudo, que visa fornecer subsídios para a identificação de torres problemáticas. Uma proposta clássica utilizada para melhorar o desempenho desta linha de transmissão frente à incidência de descargas atmosféricas foi testada mas seu resultado não foi muito satisfatário / This paper shows the study of a transmission line where outages occurred because of lightnings. The study was made from information that came from the power utility transmission line disconnection and data obtained from lightnings analyses and monitoring system. For this part of the transmission line it was identified incidence of lightning that caused outages, as well as incidences that did not cause outages. Based on this information, it was performed field measurements of ground resistance counterpoise and resistivity where is was possible to find, trough the results that some of the towers present numbers trepassed the normal values. Coming up with this information is this information is the main goal of this study that aims to offer to identify the towers that contains problems. A classical proposal used to improve the performance of this transmission line facing the incidence of lightnings was tested but the result wasn't very satisfactory

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20183号 / 理博第4268号 / 新制||理||1613(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 家森 俊彦, 教授 田口 聡, 教授 塩谷 雅人 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Microfiche copy available in Archives and Science. / Bibliography: leaves 122-123. / by Charles A. Moo. / Ph.D.

A pesquisa teve como objetivo central investigar se os furacões do Oceano Atlântico Tropical Norte são capazes de influenciar a América do Sul (AS), principalmente no que se refere aos padrões de precipitação e circulação atmosférica. No entanto, como os furacões possuem uma gama de variedades de trajetórias, gêneses e decaimento, a pesquisa se restringiu apenas a avaliação dos furacões que poderiam causar maiores impactos na atmosfera da AS, sobretudo no norte do continente. Nesse sentido duas hipóteses foram estabelecidas concernente a trajetória e intensidades dos furacões. Para a trajetória a hipótese era de que quanto mais próximo da AS os furacões transitassem maior seria seu grau de interação com o continente ao passo que os furacões que atingissem a categoria 5 na escala de intensidade Saffir-Simpson também poderiam exercer maiores influências. Assim, através desses critérios, 6 furacões foram selecionados entre os anos de 1988-2017 e estes foram avaliados com base nos dados do CHIRPS e da reanálise ERA Interim, além de simulações numéricas com o modelo dinâmico GCM DREAM. Os resultados mostraram que, de fato, os furacões conseguiam impactar a atmosfera da AS uma vez que nos baixos níveis da troposfera foram observados modificações nos alísios, interferência na posição da Zona de Convergência Intertropical (ZCIT) e influência na nebulosidade, pressão, temperatura e umidade do norte da AS. Além disso, foram constatadas interações entre os furacões e a Alta Subtropical do Atlântico Sul (ASAS), onde essa última canalizava parte dos seus escoamentos para os furacões que, por sua vez, se intensificavam. Já para os altos níveis da troposfera, foram observados o surgimento de um anticiclone no Noroeste (NO) da AS como resposta a existência dos furacões, sendo que após formado esse anticiclone sugere uma possível interação com os furacões uma vez que ele se deslocava segundo o movimento dos mesmos. Além dessas duas abordagens a pesquisa também se utilizou das Funções dos Modos Normais no sentido de reconstituir o campo de vento horizontal através da contribuição individual de cada onda atmosférica excitada a partir de um furacão. Nessa etapa escolheu-se um dos furacões selecionados e os resultados indicaram que as principais ondas envolvidas nas características observadas nos baixos níveis da troposfera como, por exemplo, ciclones ou sistemas frontais, vinham das ondas de Rossby e Gravidade-Inercial (GI). Já para os altos níveis as ondas atmosféricas envolvidas no processo de formação do anticiclone no NO da AS foram as ondas de Rossby, GI e as ondas Mistas de Rossby-Gravidade (MRG), sendo que essa última indicava justamente uma comunicação entre os dois hemisférios. No que se refere as ondas de Rossby elas se sobressaíram em todos nos níveis atmosféricos devido a relação delas com a geostrofia ao passo que as ondas GI ficaram restritas em mostrar apenas processos de divergência, logo elas foram úteis para identificar regiões ligadas a precipitação. Com relação aos resultados para os padrões de precipitação foram observadas durante a passagem dos furacões anomalias positivas no norte da AS e anomalias negativas no Brasil Central, sendo que esse resultado foi interpretado como sendo um reflexo do aumento das concentrações de momento e umidade na região norte da AS por onde os furacões transitavam. Por fim, foi avaliado o caso do furacão Irma que teve uma trajetória distante da AS. Esse furacão foi avaliado no sentindo de testar as hipóteses feitas anteriormente e os resultados mostraram que esse furacão não conseguiu exercer impacto na atmosfera da AS. Desse modo, concluiu-se que os furacões do Oceano Atlântico conseguem impactar a atmosfera da AS como indicou os resultados, porém que isso só ocorrerá se eles descreverem uma trajetória muito próxima ao continente sul-americano. / The main objective of this research is to investigate whether hurricanes from the North Tropical Atlantic Ocean can influence the South Americans atmosphere, especially in terms of circulation and precipitation patterns. However, since hurricanes have a great range of trajectories, genesis and decay this research only focused the study of hurricanes that may impact the South American, particularly in the northern continental region. In this sense, two hypotheses were established about the trajectory and intensities of hurricanes. For the trajectory, the hypothesis is that the closer the hurricanes pass by South America the greater would be their degree of interaction with the South American atmosphere variability. Also, the higher the Hurricanes classification, for instance, category 5 on the Saffir-Simpson Scale, the influence could be increased. Following this criteria 6 hurricanes were selected between the years 1988-2017 and they were evaluated based on ERA Interim reanalysis and CHIRPS data, as well as numerical simulations using the dynamic GCM DREAM model. The results showed that these hurricanes really impacted the atmosphere of the South America. At lower levels of the troposphere, the passage of hurricanes caused trade winds deformation, interference in the Intertropical Convergence Zones (ITCZ) position, besides of the influence on the cloudiness, pressure, temperature and moist in the north of the continent. In addition, it was detected interactions between hurricanes and the South Atlantic Subtropical High (SASH), where the SASH sustained the wind flows towards the hurricanes, supporting their intensification. Regarding the results for the upper levels of the troposphere it was observed the development of an anticyclone in the Northwest of South America as a response to the hurricane presence. It was noticed that this anticyclone interacts with the hurricanes once it moves according to their movement. In addition to these two approaches, it was also used the Normal Mode Functions in order to reconstruct the horizontal wind field through the individual contribution of each atmospheric waves excited from a hurricane. One of the selected hurricanes was chosen and the results indicated the main waves related to the characteristics observed at lower levels of the troposphere are the Rossby and Gravity-Inertial (GI) waves. For the upper levels, the atmospheric waves related with the formation of the anticyclone in northwestern South Americas were the Rossby, GI and the Mixed Rossby-Gravity (MRG) modes, where the MRG waves clearly show the interaction between the two hemispheres. The Rossby waves excelled at all atmospheric levels due to their relationship to the geostrophic approach, while the GI waves only showed divergence processes, being useful to identify regions linked to precipitation. The precipitation patterns during the hurricanes passage generates positive anomalies in the north of the South America and negative anomalies in central Brazil. This result was interpreted as an increase of momentum and moist concentrations in the South Americas northern region due to the interaction with the hurricanes. As a case study the hurricane Irma was investigated. This hurricane was intense but its track was distant of the South America being evaluated in the order to test the hypotheses previously assumed. The results indicated that the hurricane Irma did not have any impact in the South Americans atmosphere, where not interations with SASH, temperature or moist were observed. In summary, it was observed that North Atlantic Ocean hurricanes can influence the South Americas atmosphere when their trajectories are close to the South American continent.

Orientador: André Christóvão Pio Martins / Coorientador: André Nunes de Souza / Banca: Oscar Armando Maldonado Astorga / Banca: Pedro da Costa Junior / Resumo: Este trabalho mostra o estudo de uma linha de transmissão onde ocorreram desligamentos causados por descargas atmosféricas. Esse estudo foi feito a partir de informações de desligamentos de linhas de transmissão da concessionária e dados extraídos de um sistema de análise e monitoramento de descargas atmosféricas. Para esse trecho da linha de transmissão foram identificadas incidências de descargas atmosféricas que causaram desligamentos, bem como descargas que não causaram desligamentos. Baseados nestas informações foram efetuadas medições em campo de resistência de aterramento dos contrapesos e da resistividade do solo, onde foi possível constatar através dos resultados que algumas torres apresentaram valores que ultrapassaram os valores normatizados. O levantamento dessas informações é o principal foco deste estudo, que visa fornecer subsídios para a identificação de torres problemáticas. Uma proposta clássica utilizada para melhorar o desempenho desta linha de transmissão frente à incidência de descargas atmosféricas foi testada mas seu resultado não foi muito satisfatário / Abstract: This paper shows the study of a transmission line where outages occurred because of lightnings. The study was made from information that came from the power utility transmission line disconnection and data obtained from lightnings analyses and monitoring system. For this part of the transmission line it was identified incidence of lightning that caused outages, as well as incidences that did not cause outages. Based on this information, it was performed field measurements of ground resistance counterpoise and resistivity where is was possible to find, trough the results that some of the towers present numbers trepassed the normal values. Coming up with this information is this information is the main goal of this study that aims to offer to identify the towers that contains problems. A classical proposal used to improve the performance of this transmission line facing the incidence of lightnings was tested but the result wasn't very satisfactory / Mestre

We examine the eastern Pacific Ocean Intertropical Convergence Zone (ITCZ) both in its mean state and transient phases using a combined diagnostic, theoretical and numerical modeling approach. We note that the ITCZ is perpetually in a transient state with strong variability occurring on 4-8 day time scales. Transients, about half the amplitude of the mean ITCZ, propagate northwards from the near-equatorial southern hemisphere eventually increasing the convection in the vicinity of the mean ITCZ convection. It is argued that the mean ITCZ is continually inertially unstable with incursions of anticyclonic vorticity advected across the equator resulting in the creation of a divergence-convergence doublet. The low-level convergence generates convection and vortex tube stretching which generates cyclonic vorticity counteracting the northward advection of anticyclonic vorticity. During a cycle, the heating in the mid-troposphere near 10°N oscillated between 6 and 12 K/day at the inertial frequency of the latitude of the mean convection. The shallow meridional circulation, noted in the mean field in other studies, appears to be a result of the transient nature of the ITCZ. It is hypothesized that westward propagating equatorial waves result from the inertial oscillation of the ITCZ. To test that the waves are formed in situ in the eastern Pacific and not remnants of waves propagating from the Atlantic or promoted by the Central and South American orography, several numerical experiments are undertaken using a high-resolution regional model spanning the western Atlantic Ocean and the eastern Pacific. In the control case, the model is initialized at all boundaries with full high-frequency observations. In two additional experiments, these transients are filtered out, and a third experiment is run with the topography over a large part of Central and South America removed. In all experiments, westward propagating waves are formed in the region of high CEPG suggesting that the hypothesis of in situ development may be correct.

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2018-06-15T14:03:10Z No. of bitstreams: 1 PDF - Luciana Rodrigues de Araújo.pdf: 65021055 bytes, checksum: ca14397fd5976fb51f30eb8b9769c237 (MD5) / Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2018-06-18T18:12:06Z (GMT) No. of bitstreams: 1 PDF - Luciana Rodrigues de Araújo.pdf: 65021055 bytes, checksum: ca14397fd5976fb51f30eb8b9769c237 (MD5) / Made available in DSpace on 2018-06-18T18:12:06Z (GMT). No. of bitstreams: 1 PDF - Luciana Rodrigues de Araújo.pdf: 65021055 bytes, checksum: ca14397fd5976fb51f30eb8b9769c237 (MD5) Previous issue date: 2017-02-17 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Wind data obtained between 1999 and 2016 from measuments by meteor radar at Cachoeira Paulista (22.7°S, 45.0°W), Brazil, were used to investigate the behavior of the dynamics on upper mesosphere and lower thermosphere region, the interannual variability in the winds, in the diurnal tide and 2-day wave amplitudes and the possible causes. The results show that zonal wind is characterized by a semiannual variation below 90 km and annual above, while the meridional wind exhibits an annual cycle at all altitudes. Monthly winds did not show quasi-biennial variation (QBO), however the seasonal winds in the zonal direction observed during the summer and fall show QBO variations type in altitudes below 90 km. The results also suggest that the zonal and meridional winds are intensified during the years of solar maximum, especially in the summer and winter seasons. The monthly amplitudes of diurnal tide show an annual variation, in which the amplitudes are greater during the eastward phase of QBO at 30 hPa. The spectrum obtained from the deseasonalized amplitudes shows a 26 months peak in the meridional component, which may to be associated with stratospheric QBO phase. The modulation of the diurnal tide amplitude by QBO shows a quasi ten-year variation, and is stronger for the solar cycle maximum. The amplitude of the 2-day wave exhibit interannual variability, however, do not shows to be affected by the QBO phase during the summer season. The amplitudes of the 2-day show interannual variability, but, only in winter it is affected by the QBO phase. Good agreement between the variation of the amplitude of the 2-day wave for meridional wind and the solar radio flux was observed for most of the summers with a significant correlation, suggesting a possible wave modulation by the 11-year solar cycle. / Dados de ventos obtidos entre 1999 e 2016 a partir de medidas por radar meteórico em Cachoeira Paulista (22,7°S, 45,0°O), Brasil, foram utilizados para investigar o comportamento da dinâmica da região da alta mesosfera e baixa termosfera, a variabilidade interanual dos ventos, das amplitudes da maré diurna e da onda de 2 dias e as possíveis causas. Os resultados mostram que o vento zonal é caracterizado por uma variação semianual abaixo de 90 km e anual acima, enquanto o vento meridional exibe um ciclo anual em todas as alturas. Os ventos mensais não mostraram variação quase bienal (QBO), contudo os ventos sazonais na direção zonal observados durante o verão e o outono mostram variações tipo QBO nas alturas abaixo de 90 km. Os resultados sugerem ainda que os ventos zonal e meridional são intensificados durante os anos de máxima atividade solar, principalmente nas estações de verão e inverno. As amplitudes mensais da maré diurna exibem variação interanual, em que as amplitudes são maiores durante a fase para leste da QBO em 30 hPa. O espectro obtido a partir das amplitudes dessazonalizadas mostra um pico próximo de 26 meses na componente meridional, o qual pode estar associado à fase da QBO estratosférica. A modulação da amplitude da maré diurna pela QBO mostra uma variação quase decenal, e é mais forte durante o máximo do ciclo solar. As amplitudes da onda de 2 dias exibem variabilidade interanual para ambas as componentes, contudo, apenas no inverno mostra ser afetada pela fase da QBO. Boa concordância entre a variação da amplitude meridional da onda de 2 dias e o fluxo de rádio solar foi observada para a maioria dos verões com correlação significativa, sugerindo uma possível modulação da onda pelo ciclo solar de 11 anos.

The middle atmosphere transport is mostly controlled by a large-scale meridional circulation, namely the Brewer-Dobson circulation. In this thesis, climatology and variability of the Brewer-Dobson circulation and the middle atmosphere has been analysed using the Canadian Middle Atmosphere Model (CMAM30-Ext). A number of key variables are used including the age of air, residual velocities, residual stream function, temperature and zonal wind. The analysis of the climatology of the age of air shows, in particular, that young air gets generated near the tropical tropopause, which then travels poleward. The residual stream function shows that the Brewer-Dobson circulation dominates the winter hemispheres around the solstices and becomes nearly symmetrical, with respect to the equator, around the equinoxes. The empirical orthogonal function analysis is applied to explore the modes of variability in the middle atmosphere. The analysis identifies, in particular, the semi-annual oscillation, the quasi-biennial oscillation with moderate explained variance compared to the variance explained by the annual cycle. In addition, the analysis also reveals the emergence of the solar cycle. Powered by TCPDF (www.tcpdf.org)