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The objective of this work is to study the atmospheric conditions during cloud-to-ground (CG) lightning activity and the associated meteorological systems. A more comprehensive study of the CG lightning characteristics may lead to a better understanding of the thunderstorm severity. For these developments, it was selected two cases of severe thunderstorms that occur in Southeastern Brazil. The synoptic and mesoscale conditions previous to and during the CG lightning activity was analyzed. Furthermore, the number of CG strokes and its polarity are also evaluated in time in order to verify the electrical behavior of the thunderstorm. As a main result, it was observed that some patterns in CG lightning activity might indicate some level of severity in such thunderstorms. A storm occurred on November 17, 2008 has its genesis around 12:00 Z on the state of Sao Paulo. Its a gradual evolution over time, but since its inception has caused heavy rain over the state, and this accompanied by lightning occurrence. The number of negative flashes during the whole time the storm was higher than the positive flashes, indicating a not so intense severity. But on June 27, 2009 a storm reaches State of the Sao Paulo near 12:00 Z, isnt a gradual evolution over time. The number of negative flashes is much higher than the positive in a few hours. But at other times, the number of positive flashes is closer to the number of negative flashes, particularly from 21:00 Z to 22:00 Z, where both number are almost equal. This behavior indicates a much higher severity in this case compared to the previous case. Among the results, considering storms with similar characteristics, not necessarily they present the same severity. Thus, the study of the lightning occurrence is important for the assessment a storm severity. As a future proposal other cases of severe storms including a more detailed study of lightning will be studied. The idea is to create a severity rating from the set of meteorological data based also in the lightning characteristics.

Belém is the capital of the state of Pará, in the North region of Brazil. It is located at 1°27S 48°30 W, near to the equator. The thunderstorm activity in this region receives direct influence of global climatological parameters like ENSO (El Niño Southern Oscillation) and Tropical Atlantic Dipole. It may be also influenced by variations in solar activity, large scale volcanic eruptions, anthropogenic activity (Greenhouse Gases GHG), PDO (Pacific Decadal Oscillation), QBO (Quasi-biennial oscillation), average global air temperature (from Climatic Research Unit), and local air temperature. To find the relative influence of these parameters on atmospheric electrical activity in Belém, thunderstorm days (TD), also called keraunic level, records were used. The TD observations began in the 1950s and continued until nowadays allowing a robust statistical multivariate regression of the keraunic level in the city with respect to these parameters. Preliminary results show a positive trend of TD over the period that is correlated mainly with anthropogenic activity, followed by temperature of the city, ENSO and average global temperature. The monthly average TD presents its maximum in autumn and minimum in spring, while the monthly average air temperature of the city has a maximum in spring and minimum in summer. It was also found a strong (weak) trend to observe high TD in summer (winter) in La Niña events as compared to El Niño events.

O crescente aumento da quantidade de dados na área de ciências ambientais gera uma demanda de análise e interpretação. Este trabalho faz uso de dados meteorológicos e hidrológicos, e utiliza técnicas de mineração de dados na análise de variáveis climatológicas. O objetivo é apontar as variáveis mais relevantes em situações de secas severas para a região na Amazônia na primeira década do século XXI.

Períodos prolongados com temperatura máxima do ar superiores a 34°C na floração e maturação do cafeeiro causam abortamento floral, prejudicando a produção dessa cultura. O objetivo desse estudo foi quantificar ocorrências de temperaturas máximas diárias acima de 34°C durante os períodos fenológicos floração-maturação do café arábica, para o clima presente e em simulações futuras do cenário A1B geradas pelo modelo Eta/CPTEC. As regiões produtoras do estado de São Paulo selecionadas foram: Campinas, Mococa, Pindorama e Ribeirão Preto. A partir das séries históricas de temperatura para esses locais, foram avaliadas e ajustadas as simulações do modelo Eta para o clima presente. Após a identificação e remoção do erro sistemático observou-se que o modelo apresentou um bom desempenho nas estimativas das temperaturas máximas do ar, mostrando valores próximos aos observados. As projeções indicaram aumento na freqüência de dias com temperaturas máximas acima de 34°C, atingindo, em média, até 13 dias/mês a mais para o cenário futuro.