This study investigated the erosion of the nocturnal boundary layer (NBL) over the central Amazon using a high-resolution model of large-eddy simulation (LES) named PArallel Les Model (PALM) and observational data from Green Ocean Amazon (GoAmazon) project 2014/5. This data set was collected during four intense observation periods (IOPs) in the dry and rainy seasons in the years 2014 (considered a typical year) and 2015, during which an El Niño–Southern Oscillation (ENSO) event predominated and provoked an intense dry season. The outputs from the PALM simulations represented reasonably well the NBL erosion, and the results showed that it has different characteristics between the seasons. During the rainy season, the IOPs exhibited slow surface heating and less intense convection, which resulted in a longer erosion period, typically about 3 h after sunrise (that occurs at 06:00 local time). In contrast, dry IOPs showed more intensive surface warming with stronger convection, resulting in faster NBL erosion, about 2 h after sunrise. A conceptual model was derived to investigate the complete erosion during sunrise hours when there is a very shallow mixed layer formed close to the surface and a stable layer above. The kinematic heat flux for heating this layer during the erosion period showed that for the rainy season, the energy emitted from the surface and the entrainment was not enough to fully heat the NBL layer and erode it. Approximately 30% of additional energy was used in the system, which could come from the release of energy from biomass. The dry period of 2014 showed stronger heating, but it was also not enough, requiring approximately 6% of additional energy. However, for the 2015 dry period, which was under the influence of the ENSO event, it was shown that the released surface fluxes were sufficient to fully heat the layer. The erosion time of the NBL probably influenced the development of the convective boundary layer (CBL), wherein greater vertical development was observed in the dry season IOPs (~1500 m), while the rainy season IOPs had a shallower layer (~1200 m).

The use of stable isotopes of hydrogen and oxygen is a tool widely used to trace water paths along the hydrological cycle, providing support for understanding climatic conditions in different spatial scales. One of the main synoptic scale events acting in southeastern Brazil is the South Atlantic Convergence Zone (SACZ), which causes a large amount of precipitation from southern Amazonia to southeastern Brazil during the southern summer. In order to determine the isotopic composition of precipitation during the action of SACZ in São Francisco Xavier in southeastern Brazil, information from the Weather Forecasting and Climate Studies Center of the National Institute for Space Research (CPTEC) was used regarding SACZ performance days, the retrograde trajectories of the HYSPLIT model, and images from the GOES-16 satellite, in addition to the non-parametric statistical tests by Spearman and Kruskal–Wallis. A high frequency of air mass trajectories from the Amazon to southeastern Brazil was observed when the SACZ was operating. During the SACZ events, the average isotopic composition of precipitation was more depleted, with a δ¹⁸O of −9.9‰ (±2.1‰), a δ²H of −69.3‰ (±17.9‰), and d-excess of 10.1‰ (±4.0‰). When disregarding the SACZ performance, the annual isotopic composition can present an enrichment of 1.0‰ for δ¹⁸O and 8.8‰ for the δ²H. The long-term monitoring of trends in the isotopic composition of precipitation during the SACZ events can assist in indicating the evapotranspiration contribution of the Amazon rainforest to the water supply of southeastern Brazil.

Para a tomada de decisões voltadas para a preservação dos recursos naturais faz-se necessário levantar a maior quantidade possível de informações hidrológicas, climatológicas, agroclimáticas e agroecológicas. Assim, este estudo constitui uma análise do clima e das disponibilidades dos recursos hídricos superficiais e subterrâneos do município de Cabaceiras, área com o menor índice pluviométrico do Nordeste do Brasil (NEB), apresentando núcleos de desertificação espalhados por todo seu território. A caracterização climática foi realizada através do levantamento dos principais elementos do clima e tempo como: precipitação pluviometria, vento, umidade relativa do ar, balanço hídrico e dos recursos hídricos superficiais e subterrâneos. De acordo com a classificação de Köppen, o clima da área de estudo é considerado do tipo As - clima quente; a temperatura média anual é de 24,0°C; a umidade relativa do ar média anual é de 63,8%; a evaporação real total média anual é de 338,4 mm/ano. Seu principal rio é o Taperoá, de regime intermitente que nasce na Serra do Teixeira e desemboca no rio Paraíba, no Açude de Boqueirão (Açude Presidente Epitácio Pessoa). Recebe contribuições de cursos da água como os rios São José dos Cordeiros, Floriano, Soledade e Boa Vista e dos riachos Carneiro, Mucuim e da Serra. As vazões dos poços são bastante modestas, ou seja, inferiores a 3,25 m³/h para rebaixamento do nível da água de 25 metros, com capacidade específica 47 inferior a 0,13 m³/h/m, em média. Palavras-chave: recursos hídricos, balanço hídrico e climatologia. Hydroclimatic Analysis of Cabaceiras`s City, PB ABSTRACT To make decisions aimed at preserving natural resources it is necessary to raise as much information as possible hydrological, climatological, agro-climatic and agro-ecology. This study is an analysis of climate and the availability of surface and underground water resources of the municipality of Cabaceiras, area with the lowest rainfall in Northeast Brazil (NEB), with desertification nuclei scattered throughout their territory. The climatic characterization was performed using the survey of the main elements of weather and climate as rainfall precipitation, wind, relative humidity, water balance and surface and underground water resources. According to Köppen, the climate of the study area is considered the type As - warm climate, the average annual temperature is 24.0 ° C, the relative humidity annual average is 63.8%, the total actual annual average evaporation is 338.4 mm / year. Its main river is the Taperoá of intermittent which rises in the Serra do Teixeira and flows into the Paraiba River, dam in Boqueirão (Dam President Pessoa). Receives contributions from the water courses such as rivers São José dos Cordeiros, Floriano, Soledade and Boa Vista and streams Carneiro, Mucuim and Sierra. The flow of the wells are quite modest, ie less than 3.25 m 3 / h for lowering the water level of 25 meters, with the specific capacity of less than 0.13 m3/h/m 47 on average. Keywords: water resources, water balance and climate.