Several studies suggest that deep convection that penetrates the tropical tropopause layer may influence the long-term trends in lower stratospheric water vapor. This thesis investigates the relationship between penetrating deep convection and lower stratospheric water vapor variability using historical infrared (IR) observations. However, since infrared observations do not directly resolve cloud vertical structure and cloud top height, and there has been some debate on their usefulness to characterize penetrating deep convective clouds, CloudSat/Calipso and Aqua MODIS observations are first combined to understand how to best interpret IR observations of penetrating tops. The major findings of the combined CloudSat/Calipso and Aqua MODIS analysis show that penetrating deep convection predominantly occur in the western tropical Pacific Ocean. This finding is consistent with IR studies but is in contrast to previous radar studies where penetrating deep convective clouds predominantly occur over land regions such as equatorial Africa. Estimates on the areal extent of penetrating deep convection show that when using IR observations with a horizontal resolution of 10 km, about two thirds of the events are large enough to be detected. Evaluation of two different IR detection schemes, which includes cold cloud features/pixels and positive brightness temperature differences (+BTD), show that neither schemes completely separate between penetrating deep convection and other types of high clouds. However, the predominant fraction of +BTD distributions and cold cloud features/pixels ≤ 210 K is due to the coldest and highest penetrating tops as inferred from collocated IR and radar/lidar observations. This result is in contrast to previous studies that suggest the majority of cold cloud features/pixels ≤ 210 K are cirrus/anvil cloud fractions that coexist with deep convective clouds. Observations also show that a sufficient fraction of penetrating deep convective cloud tops occur in the extratropics. This provides evidence that penetrating deep convection should be documented as a pathway of stratospheric-tropospheric exchange within the extratropical region. Since the cold cloud feature/pixel ≤ 210 K approach was found to be a sufficient method to detect penetrating deep convection it was used to develop a climatology of the coldest penetrating deep convective clouds from GridSat observations covering years 1998-2008. The highest frequencies of the coldest penetrating deep convective clouds consistently occur in the western-central Pacific and Indian Ocean. Monthly frequency anomalies in penetrating deep convection were evaluated against monthly anomalies in lower stratospheric water vapor at 82 mb and show higher correlations for the western-central Pacific regions in comparison to the tropics. At a lag of 3 months, the combined western-central Pacific had a small but significant anticorrelation, where the largest amount of variance explained by the combined western-central Pacific region was 8.25%. In conjunction with anomalies in the 82 mb water vapor mixing ratios, decreasing trends for the 1998-2008 period were also observed for tropics, the western Pacific and Indian Ocean. Although none of these trends were significant at the 95% confidence level, decreases in the frequency of penetrating deep convection over the 1998-2008 shows evidence that could explain in part some of the 82 mb lower stratospheric water vapor variability.

A base case modelling investigation was conducted to explore the chemical and physical behaviour of ground-level ozone (O3) and its precursor nitrogen dioxide (NO2) in Ontario using the U.S. Environmental Protection Agency (EPA) Community Multiscale Air Quality (CMAQ) model. Two related studies were completed to evaluate the performance of CMAQ in reproducing the behaviour of these species in both rural and urban environments by comparing to surface measurements collected by the Ontario Ministry of the Environment (MOE) network of air quality stations. The first study was a winter examination and the second study was conducted for a period during the summer of the same year. The municipality of North Bay was used to represent a rural setting given its smaller population relative to the city of Ottawa which was the base of the urban site. Statistical and graphical analyses were used to validate the model output. CMAQ was found to replicate the spatial variation of O3 and NO2 over the domain in both the winter and summer, but showed some difficulty in simulating the temporal allocation of the species. Validation statistics for North Bay and Ottawa showed overall O3 mean biases (MB) of 3.35 ppb and 2.25 ppb, respectively, and overall NO2 MB of -8.75 ppb and -4.37 ppb, respectively for the winter. Summer statistics generated O3 MB of 4.66 ppb (North Bay) and 10.05 ppb (Ottawa) while both MB for NO2 were between -2.20 ppb to -2.55 ppb. Graphical analysis showed that the model was not able to reproduce the lower levels of O3, especially at night, or the higher levels of NO2 during the day at the North Bay site for either season. This was expected since the comparisons were made between point measurements and 36 km grid-averaged model results. The presence of high amounts of NO2 emissions local to the monitoring sites compared to the levels represented in the emissions inventory may also be a contributing factor. The simulations for Ottawa demonstrated better agreement between model results and measurements as CMAQ provided a more accurate reproduction of both the higher and lower mixing ratios of O3 and NO2 during the winter and summer seasons. Results indicate that CMAQ is able to simulate urban environments better than rural ones.

O ozônio troposférico (O3) é um dos poluentes mais importantes da atualidade, sendo formado pela interação de óxidos de nitrogênio, hidrocarbonetos e radiação ultravioleta. Ele ou seus radicais livres estão associados ao aumento da incidência de doenças pulmonares em seres humanos, além de causar danos à vegetação e à produtividade agrícola em diversas regiões do mundo. Portanto, é de fundamental importância que sejam pesquisadas e padronizadas espécies e/ou cultivares sensíveis a este poluente, para que se possa fazer a bioindicação da qualidade do ar, uma vez que esta apresenta custo baixo e fácil implementação. Desta forma, o objetivo do presente trabalho foi avaliar o potencial bioindicador de 4 cultivares de feijão (Phaseolus vulgaris L.), desenvolvidas pela FEPAGRO (Fundação de Pesquisa Agropecuária) Litoral Norte do Rio Grande do Sul, através de sua comparação com a cultivar reconhecidamente sensível ao ozônio, a US Pinto 111. Para tanto, foram empregados parâmetros fotossintéticos, vazamento relativo de eletrólitos, abscisão foliar e medidas de biomassa. Plântulas de 8 dias (contados a partir da semeadura) das cultivares Fepagro 26, Guapo Brilhante, Iraí, Macotaço e US pinto 111 foram submetidas, em câmaras de topo-aberto, aos tratamentos sem e com adição de ozônio ao ar ambiente. Ao todo, foram realizados 7 eventos de fumigação, com duração de uma semana cada, e fumigação diária das 10:00 às 16:00 horas. Em cada um desses 7 eventos de fumigação, foram utilizadas 5 plântulas/tratamento/cultivar, totalizando 25 plântulas por câmara. A exposição ao ozônio causou, em algum momento, decréscimos significativos na assimilação líquida de todas as cultivares, exceto na Iraí. Esses decréscimos na assimilação líquida foram associados principalmente à atividade da Rubisco in vivo e, secundariamente, à capacidade de transporte de elétrons. A exposição ao ozônio causou também um aumento significativo no vazamento relativo de eletrólitos da cultivar Pinto, mas apenas quando a soma das concentrações horárias acima 40 ppb (AOT40) foi a mais elevada. Além disso, o tratamento com ozônio causou uma antecipação significativa no tempo de abscisão foliar apenas nas cultivares Pinto, Fepagro e Guapo, sendo que isto ocorreu em pelo menos um dos dois experimentos realizados para avaliação desse parâmetro. Quanto às medidas de biomassa da raiz, parte aérea e total da planta, pode-se dizer que períodos mais longos de exposição ao ozônio são necessários para ocorrerem modificações significativas e confiáveis nesse parâmetro. Embora tenha havido bastante instabilidade nos resultados, devido, provavelmente, a fatores ambientais não mensurados, pôde-se, com este estudo, confirmar a sensibilidade da cultivar US Pinto 111 ao ozônio e mostrar que a cultivar Fepagro 26 tem um ótimo potencial para ser empregada em estudos futuros como um bioindicador sensível ao ozônio, enquanto a cultivar Iraí poderia ser considerada resistente. Além disso, entre os parâmetros avaliados, a assimilação líquida e a abscisão foliar mostraram ser os mais eficientes para fazer a classificação das cultivares em níveis de sensibilidade. / Today, tropospheric ozone (O3) is one of the most important pollutants. It is formed by the interaction of oxides of nitrogen, hydrocarbons and ultraviolet radiation. It or its free radicals are associated with the increased incidence of lung diseases in humans, in addition to damage to vegetation and crop yield in different regions of the world. It is essential, therefore, to research and standardize species and/or cultivars sensitive to this pollutant, in order to be able to perform the bioindicator air quality, since this is low cost and easy to implement. The present study, thus, deal to evaluate the bioindicator potential of 4 bean (Phaseolus vulgaris L.) cultivars, developed by FEPAGRO (Fundação Estadual de Pesquisa Agropecuária) North Coast from Rio Grande do Sul, by comparing it with the cultivar that is known to be sensitive to ozone, US Pinto 111, using some parameters such as photosynthesis, relative leakage of electrolytes, foliar abscission and biomass measures. For this 8-day seedlings, counting from the date of sowing, of Fepagro 26, Guapo Brilhante, Iraí, were used for treatments with and without addition of ozone to the ambient air. In all, 7 fumigation events were performed, lasting one week each, and daily fumigation from 10 am to 4 pm. In each of these 7 fumigation events, 5 seedlings/treatment/cultivar were used, a total of 25 seedlings per chamber. Exposure to ozone at some point caused significant reductions in the net assimilation of all cultivars except Iraí. These reductions in net assimilation were associated mainly with the in vivo activity of Rubisco, and secondarily with the electron transport capacity. Exposure to ozone also caused a significant increase in the relative leakage of electrolytes from Pinto cultivar, but only when sum of daily concentrations above 40 ppb (AOT40) was highest. In addition, treatment with ozone caused a significant anticipation in foliar abscission time only in the Pinto, Fepagro and Guapo cultivars. This occurred in a least one of the two experiments performed to evaluate this parameter. As to the measures of root biomass, aerial part and total plant, it might be said that longer periods of exposure to the pollutant are necessary for significant, reliable changes to occur in this parameter. Although the results were quite unstable, probably due to unmeasured environmental factors, with this study one can confirm the sensitivity of US Pinto 111 cultivar to ozone and show that the Fepagro 25 cultivar has an excellent potential for future use as an ozonesensitive bioindicator, while the Iraí cultivar could be considered resistant. In addition, among the parameters evaluated in this study, net assimilation and leaf abscission proved to be most efficient to classify the cultivars as to levels of sensitivity.

O ozônio troposférico (O3) é um dos poluentes mais importantes da atualidade, sendo formado pela interação de óxidos de nitrogênio, hidrocarbonetos e radiação ultravioleta. Ele ou seus radicais livres estão associados ao aumento da incidência de doenças pulmonares em seres humanos, além de causar danos à vegetação e à produtividade agrícola em diversas regiões do mundo. Portanto, é de fundamental importância que sejam pesquisadas e padronizadas espécies e/ou cultivares sensíveis a este poluente, para que se possa fazer a bioindicação da qualidade do ar, uma vez que esta apresenta custo baixo e fácil implementação. Desta forma, o objetivo do presente trabalho foi avaliar o potencial bioindicador de 4 cultivares de feijão (Phaseolus vulgaris L.), desenvolvidas pela FEPAGRO (Fundação de Pesquisa Agropecuária) Litoral Norte do Rio Grande do Sul, através de sua comparação com a cultivar reconhecidamente sensível ao ozônio, a US Pinto 111. Para tanto, foram empregados parâmetros fotossintéticos, vazamento relativo de eletrólitos, abscisão foliar e medidas de biomassa. Plântulas de 8 dias (contados a partir da semeadura) das cultivares Fepagro 26, Guapo Brilhante, Iraí, Macotaço e US pinto 111 foram submetidas, em câmaras de topo-aberto, aos tratamentos sem e com adição de ozônio ao ar ambiente. Ao todo, foram realizados 7 eventos de fumigação, com duração de uma semana cada, e fumigação diária das 10:00 às 16:00 horas. Em cada um desses 7 eventos de fumigação, foram utilizadas 5 plântulas/tratamento/cultivar, totalizando 25 plântulas por câmara. A exposição ao ozônio causou, em algum momento, decréscimos significativos na assimilação líquida de todas as cultivares, exceto na Iraí. Esses decréscimos na assimilação líquida foram associados principalmente à atividade da Rubisco in vivo e, secundariamente, à capacidade de transporte de elétrons. A exposição ao ozônio causou também um aumento significativo no vazamento relativo de eletrólitos da cultivar Pinto, mas apenas quando a soma das concentrações horárias acima 40 ppb (AOT40) foi a mais elevada. Além disso, o tratamento com ozônio causou uma antecipação significativa no tempo de abscisão foliar apenas nas cultivares Pinto, Fepagro e Guapo, sendo que isto ocorreu em pelo menos um dos dois experimentos realizados para avaliação desse parâmetro. Quanto às medidas de biomassa da raiz, parte aérea e total da planta, pode-se dizer que períodos mais longos de exposição ao ozônio são necessários para ocorrerem modificações significativas e confiáveis nesse parâmetro. Embora tenha havido bastante instabilidade nos resultados, devido, provavelmente, a fatores ambientais não mensurados, pôde-se, com este estudo, confirmar a sensibilidade da cultivar US Pinto 111 ao ozônio e mostrar que a cultivar Fepagro 26 tem um ótimo potencial para ser empregada em estudos futuros como um bioindicador sensível ao ozônio, enquanto a cultivar Iraí poderia ser considerada resistente. Além disso, entre os parâmetros avaliados, a assimilação líquida e a abscisão foliar mostraram ser os mais eficientes para fazer a classificação das cultivares em níveis de sensibilidade. / Today, tropospheric ozone (O3) is one of the most important pollutants. It is formed by the interaction of oxides of nitrogen, hydrocarbons and ultraviolet radiation. It or its free radicals are associated with the increased incidence of lung diseases in humans, in addition to damage to vegetation and crop yield in different regions of the world. It is essential, therefore, to research and standardize species and/or cultivars sensitive to this pollutant, in order to be able to perform the bioindicator air quality, since this is low cost and easy to implement. The present study, thus, deal to evaluate the bioindicator potential of 4 bean (Phaseolus vulgaris L.) cultivars, developed by FEPAGRO (Fundação Estadual de Pesquisa Agropecuária) North Coast from Rio Grande do Sul, by comparing it with the cultivar that is known to be sensitive to ozone, US Pinto 111, using some parameters such as photosynthesis, relative leakage of electrolytes, foliar abscission and biomass measures. For this 8-day seedlings, counting from the date of sowing, of Fepagro 26, Guapo Brilhante, Iraí, were used for treatments with and without addition of ozone to the ambient air. In all, 7 fumigation events were performed, lasting one week each, and daily fumigation from 10 am to 4 pm. In each of these 7 fumigation events, 5 seedlings/treatment/cultivar were used, a total of 25 seedlings per chamber. Exposure to ozone at some point caused significant reductions in the net assimilation of all cultivars except Iraí. These reductions in net assimilation were associated mainly with the in vivo activity of Rubisco, and secondarily with the electron transport capacity. Exposure to ozone also caused a significant increase in the relative leakage of electrolytes from Pinto cultivar, but only when sum of daily concentrations above 40 ppb (AOT40) was highest. In addition, treatment with ozone caused a significant anticipation in foliar abscission time only in the Pinto, Fepagro and Guapo cultivars. This occurred in a least one of the two experiments performed to evaluate this parameter. As to the measures of root biomass, aerial part and total plant, it might be said that longer periods of exposure to the pollutant are necessary for significant, reliable changes to occur in this parameter. Although the results were quite unstable, probably due to unmeasured environmental factors, with this study one can confirm the sensitivity of US Pinto 111 cultivar to ozone and show that the Fepagro 25 cultivar has an excellent potential for future use as an ozonesensitive bioindicator, while the Iraí cultivar could be considered resistant. In addition, among the parameters evaluated in this study, net assimilation and leaf abscission proved to be most efficient to classify the cultivars as to levels of sensitivity.

O ozônio troposférico (O3) é um dos poluentes mais importantes da atualidade, sendo formado pela interação de óxidos de nitrogênio, hidrocarbonetos e radiação ultravioleta. Ele ou seus radicais livres estão associados ao aumento da incidência de doenças pulmonares em seres humanos, além de causar danos à vegetação e à produtividade agrícola em diversas regiões do mundo. Portanto, é de fundamental importância que sejam pesquisadas e padronizadas espécies e/ou cultivares sensíveis a este poluente, para que se possa fazer a bioindicação da qualidade do ar, uma vez que esta apresenta custo baixo e fácil implementação. Desta forma, o objetivo do presente trabalho foi avaliar o potencial bioindicador de 4 cultivares de feijão (Phaseolus vulgaris L.), desenvolvidas pela FEPAGRO (Fundação de Pesquisa Agropecuária) Litoral Norte do Rio Grande do Sul, através de sua comparação com a cultivar reconhecidamente sensível ao ozônio, a US Pinto 111. Para tanto, foram empregados parâmetros fotossintéticos, vazamento relativo de eletrólitos, abscisão foliar e medidas de biomassa. Plântulas de 8 dias (contados a partir da semeadura) das cultivares Fepagro 26, Guapo Brilhante, Iraí, Macotaço e US pinto 111 foram submetidas, em câmaras de topo-aberto, aos tratamentos sem e com adição de ozônio ao ar ambiente. Ao todo, foram realizados 7 eventos de fumigação, com duração de uma semana cada, e fumigação diária das 10:00 às 16:00 horas. Em cada um desses 7 eventos de fumigação, foram utilizadas 5 plântulas/tratamento/cultivar, totalizando 25 plântulas por câmara. A exposição ao ozônio causou, em algum momento, decréscimos significativos na assimilação líquida de todas as cultivares, exceto na Iraí. Esses decréscimos na assimilação líquida foram associados principalmente à atividade da Rubisco in vivo e, secundariamente, à capacidade de transporte de elétrons. A exposição ao ozônio causou também um aumento significativo no vazamento relativo de eletrólitos da cultivar Pinto, mas apenas quando a soma das concentrações horárias acima 40 ppb (AOT40) foi a mais elevada. Além disso, o tratamento com ozônio causou uma antecipação significativa no tempo de abscisão foliar apenas nas cultivares Pinto, Fepagro e Guapo, sendo que isto ocorreu em pelo menos um dos dois experimentos realizados para avaliação desse parâmetro. Quanto às medidas de biomassa da raiz, parte aérea e total da planta, pode-se dizer que períodos mais longos de exposição ao ozônio são necessários para ocorrerem modificações significativas e confiáveis nesse parâmetro. Embora tenha havido bastante instabilidade nos resultados, devido, provavelmente, a fatores ambientais não mensurados, pôde-se, com este estudo, confirmar a sensibilidade da cultivar US Pinto 111 ao ozônio e mostrar que a cultivar Fepagro 26 tem um ótimo potencial para ser empregada em estudos futuros como um bioindicador sensível ao ozônio, enquanto a cultivar Iraí poderia ser considerada resistente. Além disso, entre os parâmetros avaliados, a assimilação líquida e a abscisão foliar mostraram ser os mais eficientes para fazer a classificação das cultivares em níveis de sensibilidade. / Today, tropospheric ozone (O3) is one of the most important pollutants. It is formed by the interaction of oxides of nitrogen, hydrocarbons and ultraviolet radiation. It or its free radicals are associated with the increased incidence of lung diseases in humans, in addition to damage to vegetation and crop yield in different regions of the world. It is essential, therefore, to research and standardize species and/or cultivars sensitive to this pollutant, in order to be able to perform the bioindicator air quality, since this is low cost and easy to implement. The present study, thus, deal to evaluate the bioindicator potential of 4 bean (Phaseolus vulgaris L.) cultivars, developed by FEPAGRO (Fundação Estadual de Pesquisa Agropecuária) North Coast from Rio Grande do Sul, by comparing it with the cultivar that is known to be sensitive to ozone, US Pinto 111, using some parameters such as photosynthesis, relative leakage of electrolytes, foliar abscission and biomass measures. For this 8-day seedlings, counting from the date of sowing, of Fepagro 26, Guapo Brilhante, Iraí, were used for treatments with and without addition of ozone to the ambient air. In all, 7 fumigation events were performed, lasting one week each, and daily fumigation from 10 am to 4 pm. In each of these 7 fumigation events, 5 seedlings/treatment/cultivar were used, a total of 25 seedlings per chamber. Exposure to ozone at some point caused significant reductions in the net assimilation of all cultivars except Iraí. These reductions in net assimilation were associated mainly with the in vivo activity of Rubisco, and secondarily with the electron transport capacity. Exposure to ozone also caused a significant increase in the relative leakage of electrolytes from Pinto cultivar, but only when sum of daily concentrations above 40 ppb (AOT40) was highest. In addition, treatment with ozone caused a significant anticipation in foliar abscission time only in the Pinto, Fepagro and Guapo cultivars. This occurred in a least one of the two experiments performed to evaluate this parameter. As to the measures of root biomass, aerial part and total plant, it might be said that longer periods of exposure to the pollutant are necessary for significant, reliable changes to occur in this parameter. Although the results were quite unstable, probably due to unmeasured environmental factors, with this study one can confirm the sensitivity of US Pinto 111 cultivar to ozone and show that the Fepagro 25 cultivar has an excellent potential for future use as an ozonesensitive bioindicator, while the Iraí cultivar could be considered resistant. In addition, among the parameters evaluated in this study, net assimilation and leaf abscission proved to be most efficient to classify the cultivars as to levels of sensitivity.

Este trabalho teve como objetivo analisar as condições meteorológicas favoráveis e desfavoráveis à dispersão de poluentes, com ênfase no ozônio, nas áreas urbanas associadas à Região Metropolitana de São Paulo (RMSP) e a Grande Santiago (GS). Medidas de concentração de estações localizadas em ambas as áreas de estudo foram utilizadas para determinar o comportamento médio, o número de ocorrências de ultrapassagens de padrão de qualidade do ar e o aumento noturno das concentrações de ozônio num período de dez anos. Foi encontrado que o máximo horário acontece próximo das 14 horas (horário local) nas duas regiões, e que existe uma tendência à diminuição no número de ultrapassagens do padrão de qualidade do ar associado a este poluente. Na RMSP é possível observar um máximo secundário durante a madrugada, enquanto que este fenômeno não é claramente observado nos valores médios de concentração na GS. Com dados da Reanálise do NCEP/NCAR foi visto que a ocorrência deste fenômeno está associada a configurações sinóticas específicas na GS, enquanto que na RMSP não existe padrão sinótico específico que diferencie casos com e sem aumento de ozônio noturno. Um novo módulo fotoquímico (NPM), contendo 95 reações foi inserido no modelo BRAMS na tentativa de melhorar o prognóstico das concentrações de poluentes, principalmente em relação ao ozônio. O NPM mostrou melhor desempenho que o módulo fotoquímico original do modelo (SPM; Simple Photochemical Module) para todos os poluentes considerados, salvo o ozônio, para o qual o SPM apresentou melhores índices estatísticos em 5 das 7 estações avaliadas. As características locais associadas à ocorrência simultânea ou não de aumento na concentração de ozônio foram estudadas utilizando o modelo BRAMS com o módulo SPM ativado, sendo verificado que o aumento de ozônio na RMSP está associado, principalmente, ao transporte vertical deste poluente a partir de níveis mais elevados da atmosfera, enquanto que o transporte horizontal é a maior contribuição para o aumento das concentrações de ozônio durante o período noturno na GS. / This work aimed to analyze the favorable and unfavorable meteorological conditions for pollutant dispersion, especially ozone, at the Metropolitan Area of São Paulo (MASP) and the Greater Santiago (GS). Ozone concentration measurements from stations located in both urban areas were used to determinate the mean behavior, the number of standard air quality exceedances and the increase on nocturnal ozone concentration over a 10 years period. It was found that the diurnal maximum occurs around 14 local time in both urban areas, and that there is a diminishment tendency of the total cases of standard air quality exceedances during all period. A secondary maximum of ozone concentration was observed in MASP at night, which was not clearly seen on mean values over GS. By using the NCEP/NCAR Reanalysis data it was seen that the occurrence of this phenomenon is associated to specific synoptic patterns for GS, while there is no specific synoptic pattern for the MASP cases, with or without nocturnal increase in ozone concentrations. A New Photochemical Module (NPM), containing 95 reactions was coupled to BRAMS model in an attempt to improve the prediction of air pollutants, especially ozone. The NPM showed a better performance than the original module, the SPM (Simple Photochemical Module), for all considered pollutants but ozone. For this pollutant, the SPM presents better statistical indexes for 5 of the 7 stations analyzed. The local characteristics related to simultaneous occurrence of nocturnal ozone increase was studied using the SPM-BRAMS model, which showed that the secondary nocturnal maximum of ozone concentrations in MASP are related to vertical transport of this pollutant from higher levels of the atmosphere to the surface, while the horizontal transport is a major contributor to the increase of ozone concentrations in the GS during the night.

Made available in DSpace on 2014-08-20T14:25:52Z (GMT). No. of bitstreams: 1 dissertacao_gustavo_cuchiara.pdf: 35782355 bytes, checksum: 0606b9c213fa2c0a65dc1b1bf8a4bc6a (MD5) Previous issue date: 2011-02-23 / One of the main problems related to air pollution in urban areas is caused by photochemical oxidants.... / Um dos maiores problemas originados pela poluição do ar em áreas urbanas é o provocado pelos oxidantes fotoquímicos....

Satellite data have shown that east-west oriented cloud bands, known as Intertropical convergence zone (ITCZ), propagate eastwards along the equator throughout the year and northwards during boreal summer on intraseasonal time scales. The northward propagations over Bay of Bengal have important connection with onset of south Asian monsoon and active-break cycles of the Indian monsoon. Some studies on mean structure of ITCZ have concluded that preferred location of ITCZ is governed by meridional variation of sea surface temperature (SST) while other studies have stressed the importance of heating in the free atmosphere. Studies on the migration of ITCZ have shown that northward migration of maximum convergence zone is due to generation of positive barotropic vorticity north of the convection in the boundary layer due to internal dynamics of the atmosphere. In the present study mean and transient structure of northward migration of ITCZ over Bay of Bengal is simulated with the help of a general circulation model (GCM). The mean ITCZ is found not to occur at SST maximum or SST gradient maxima. A new simple model for the mean state of ITCZ based on moisture budget, linear friction and hydrostatic assumption is proposed. It highlights the relative importance of SST and atmospheric effects in generation of maximum convergence. The large cancellation between the effect of SST on boundary layer and thermodynamic effects in free troposphere is shown to control convergence. The model also shows that latitude and time independent linear friction parameterization in a simple model is able to predict monthly mean location of ITCZ in a GCM. The results give a quantitative understanding about the relative role of surface effects and atmospheric effects in determining location of the mean ITCZ. A simple linear model for understanding the mechanism of instability that governs the northward migration of ITCZ is proposed. Vertical shear in mean winds couples the barotrpic and baroclinic modes in free troposphere in this model. The model is able to predict the correct scale with standard values of friction and diffusion parameters. The mechanism of instability is found to be due to internal dynamics of troposphere. It is shown that direction of propagation is decided by vertical shear in zonal as well as meridional mean winds. This is contrary to the previous studies which conclude that either vertical shear in zonal winds or vertical shear in meridional winds control the direction of propagation.

No description available.

The ENSO-monsoon system is known to have a biennial component. Here we show using high resolution satellite data, mainly daily rainfall and sea surface temperature (SST) from the Tropical Rainfall Measuring Mission (TRMM), and daily scatterometer surface winds from QuickSCAT, that there is a clear biennial oscillation (TBO) in summer monsoon rainfall over Central India – Bay of Bengal (Cl-BoB) and the far west Pacific in the period 1999-2005. Summer (JJAS) mean rainfall oscillates between high and low values in alternate years; the rainfall is high in the odd years 1999, 2001, 2003, and 2005, and low in even years 2000, 2002 and 2004. The amplitude of the oscillation is significant, as measured against the long term standard deviation of seasonal rain based on 1979-2005 Global Precipitation Climatology Project (GPCP) data. We find that the TBO in rainfall is associated with TBO of SST over the tropical Indian, west Pacific and Atlantic Oceans in different seasons. There is no TBO in east Pacific SST, and no strong El Nino in this period. The TBO of SST is related to change in evaporation due to TBO of surface wind speed. A TBO of the surface branch of the Walker circulation in the eastern Indian and western Pacific basins is clearest in the autumn season during 1999-2005. There is a clear relation between a large-amplitude TBO of winter surface air temperature over north Asia associated with TBO of the Arctic oscillation (AO), and the TBO of summer monsoon rainfall. High rainfall over CI-BoB lin summer is followed by a relatively high value of the AO Index, and warm air termperature over north Asia in the succeeding winter. The Inter Tropical Convergence Zone(ITCZ) over the central Pacific and Atlantic Oceans shift north by about two degrees when the northern hemisphere is warm, reminiscent of the behaviour of the climate system of ENSO, decadal and palaeoclimate time scales. In this thesis we document the biennial oscillation of monsoon rain and its spatial structure in the recent period, and its relation with biennial oscillation of surface climate over the global tropics and extratropical regions. The existence of TBO in the tropical Atlantic, and its relation with the monsoon, is a new finding. We demonstrate that the interannual variability of the summer monsoon during 1999-2005, including the drought of 2002, is part of a pervasive TBO of global surface climate.