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Southeastern Brazil, the most populous and developed region of the country, faces various environmental problems associated with the growth of its population in urban areas. It is the most industrialized area in the country, comprising the metropolitan areas of São Paulo, Rio de Janeiro, Belo Horizonte, and other major cities. Air quality is a major concern, because the reported concentrations of certain regulated pollutants, typically ozone and fine particulate, have exceeded national standards. Due to the difficulty in taking measurements over many different areas, air quality modeling is a useful tool to estimate air pollutant concentrations. For southeastern Brazil, air quality modeling has been performed mostly with the Brazilian Regional Atmospheric Modeling System with Simplified Photochemical Module and the Weather Research and Forecast with Chemistry models. One of the main objectives was to study the evolution of air quality associated with improved vehicle emission factors in urban areas, the impact of climate change on air quality, and the relationship between pollutant concentrations and health. Knowledge of mobile source emission factors has been continuously expanded by in-tunnel measurements and dynamometer protocols, which provide accurate data as inputs to photochemical air quality models. The spatial distribution of the mobile source emissions was constructed based on open access data related to the streets and traffic distribution. The mobile emission module was combined to the chemistry modeling and this implementation can be an example to be applied to other places that do not have a spatial distribution of this source. Forecasts of pollutant concentrations can inform public policies, including those addressing the effects of pollutants on health of the general population, and studies of the impacts of using different fuels and implementation of emissions regulations programs.

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RESUMO: Na Região Metropolitana do Rio de Janeiro, altos índices de concentrações de material particulado inalável (PM10) com violações dos limites estabelecidos pela Resolução CONAMA n0 03/90 são registrados rotineiramente. Analisando dados registrados entre 1998 e 2008, foram identificados 146 dias com concentrações acima dos valores estabelecidos. Nesses dias, foi possível verificar a influência da atuação do Anticiclone Subtropical do Atlântico Sul, a ausência de precipitação e a ocorrência de inversões térmicas na baixa troposfera, o que confirma a forte relação entre a ocorrência de altas concentrações de PM10 e as condições atmosféricas na região.

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The objective of this work was to investigate the mean and variability of a dataset of pollutant concentrations from measurements taken over the metropolitan area of São Paulo city, Brazil. Wavelet analysis was applied to the time series of pollutant concentrations, revealing the strongest harmonics influencing the signals. A mode of variability of 4-8 days was significant until the middle of the last decade and is likely associated with the approach and passage of meteorological systems. A dataset representing the number of frontal systems moving across the state helped to explain the interannual variability during wintertime. Years with fewer frontal systems had higher levels of pollutants in several locations. Weather events such as inversions and the passage of frontal systems influence the concentration of pollutants. Public policies on air quality should focus not only on reducing the long-term exposure of city-dwellers to the negative effects of pollutants but also account for the possible short-term effects of the weather on air quality.

Este estudo identificou e analisou o comportamento de circulações locais induzidas pela topografia no Vale do Paraíba e na Serra da Mantiqueira, entre os dias 16 e 22 de agosto de 2010, por meio de uma simulação numérica com o modelo WRF. O modelo foi dirigido com as saídas do GFS-FNL e a simulação validada com dados de estações meteorológicas. Os maiores valores de correlação entre simulação e observação foram obtidos para a temperatura do ar e menores para a intensidade e direção dos ventos. Mesmo assim, o WRF foi capaz de representar as mudanças no sentido do vento associadas à circulação de brisa vale e montanha. O modelo simulou durante o dia a brisa de vale e durante à noite, a brisa de montanha. A brisa de vale iniciou-se aproximadamente entre 10 UTC e 14 UTC e a de montanha às 22 UTC, sendo que a fase de transição entre a brisa de montanha para a de vale ocorreu entre as 16 e 20 UTC. Os resultados obtidos também são apresentados por meio de seções verticais das células de circulação de brisa.