In this paper we study the Lorenz energy cycle of the Walker circulation associated with ENSO. The robust formulation of the energetics allows drawing a clear picture of the global energy and conversion terms associated with the three dimensional domains appropriate to qualify the large scale transfers that influence, and are influenced by, the anomalies during ENSO. A clear picture has emerged in that El Niño and La Niña years have approximately opposite anomalous energy fluxes, regardless of a non-linear response identified in the potential energy fields (zonal and eddy). During El Niños the tropical atmosphere is characterized by an increase of zonal available potential energy, decrease of eddy available potential energy and decrease of kinetic energy fields. This results in weaker upper level jets and a slowingdown of the overall Walker cell. During La Niñas reversed conditions are triggered, with an acceleration of the Walker cell as observed from the positive anomalous kinetic energy. The potential energy in the Walker circulation domain during the cold phase is also reduced. An equally opposite behavior is also experienced by the energy conversion terms according to the ENSO phase. The behavior of anomalous energetics seems to be triggered at about the same time when ENSO starts to manifest for both the positive and negative phases, suggesting a coupled mechanism in which atmospheric and oceanic anomalies interact and feed back onto each other.

Although much effort has been made to characterize and understand extreme rainfall's causes and effects, little is known about their frequency and intensity. Moreover, knowledge about their contribution to the total rainfall climatology is still minimal, especially over the Amazon where rainfall data are very scarce. In this paper we propose to classify extreme rainfall events by type and analyze their frequency and intensity over South America with a focus on the Amazon basin. Gridded daily data from the MERGE/CPTEC product over a period of 15 years (1998-2013) was used. An adaptation of Rx5d climate index was applied to select different kinds of extreme rainfall for the purpose of quantifying their frequency and intensity as well as their contribution to the accumulated rainfall climatology. According to the results, all kinds of extreme rainfall events can be observed over the studied area. However, the quantity of rainfall produced by each type is different, and consequently their percent contributions to the total accumulated rainfall climatology also differ. For example: in the Amazon region EET-I is responsible for 15% -40% of the total accumulated rainfall. Moreover, in the Brazilian northeast there are regions where EET-I exceeds 40% of the total rainfall. In northeast Brazil EET-II is responsible up to 30% of the total accumulated rainfall. EET-III is responsible for 5% -15% in the Amazon basin, 25% -45% in northeast Brazil and 10% -45% over Roraima State. Area-mean time variation shows that the quantity of rainfall extremes over the

The main purpose of the study is to explore in more detail the Upper Tropospheric Cyclonic Vortices (UTCVs) features over Northeast Brazil (NEB) in an attempt to improve weather forecasts. The various aspects of the life cycle features of the UTCVs over NEB are presented here, because these aspects have not been investigated in previous studies. Initially, the UTCVs were identified at 200 hPa, and then, they were identified at lower levels to analyse their vertical structure, using 6-hr data for a 30-year period (1984-2013) from the European Center for Medium Range Weather Forecasts' reanalysis (ERA Interim). An objective method was improved to obtain at first-hand the trajectory and the vertical extent of the UTCVs over NEB. Some statistics results were consistent with previous studies related to relative frequency, duration and direction of movement. However, further results were obtained too. An average distance of 2,000 km for the UTCVs total travel was found. Of this average distance, 750 km was reached by UTCVs on the first day of the life cycle, leading to the presumption of a possible suppression of vortex movement that depends on a diabatic mechanism. We also found predominance of UTCVs without vertical tilt or with east tilt with increasing height. When considering life cycle stages (formation, maximum depth and dissipation), diversity was observed in intensity with stages, levels and seasons of the year, with spring exhibiting the most intense UTCVs over all seasons. Finally, our finding about interannual variability is novel. There was a tendency for the average number of UTCVs to be slightly higher during El Niño summers compared with La Niña summers. K E Y W O R D S features, life cycle stages, Northeast Brazil, upper tropospheric cyclonic vortices 1 | INTRODUCTION A typical feature of the summer atmospheric circulation in the upper troposphere over South America is the existence of well-defined regional circulation systems such as the thermal anticyclone centred over Bolivia, also known as the Bolivian High (BH), and a trough near the coast of

Resumo Este trabalho possui dois objetivos principais, o primeiro é apresentar uma descrição de como o modelo atmosférico BRAMS foi estruturado com o intuito de capacitá-lo a simular a emissão, dispersão e sedimentação de cinzas vulcânicas; o segundo é fazer uma análise de sensibilidade com relação a diversas configurações do modelo, com o intuito de obter uma configuração adequada para prever a concentração de cinzas vulcânicas após eventos eruptivos. Avaliando os resultados do modelo com dados observados, principalmente com relação ao satélite CALIPSO, concluiu-se que o modelo BRAMS foi capaz de simular e prever com relativa precisão a posição e concentração das cinzas vulcânicas na atmosfera.