Publicações

Rainfall variability change under global warming is a crucial issue that may have a substantial impact on society and the environment, as it can directly impact biodiversity, agriculture, and water resources. Observed precipitation trends and climate change projections over Brazil indicate that many sectors of society are potentially highly vulnerable to the impacts of climate change. The purpose of this study is to assess model projections of the change in rainfall variability at various temporal scales over sub-regions of Brazil. For this, daily data from 30 CMIP5 models for historical (19002005) and future (20502100) experiments under a high-emission scenario are used. We assess the change in precipitation variability, applying a band-pass filter to isolate variability on daily, weekly, monthly, intra-seasonal, and El Nino Southern Oscillation (ENSO) time scales. For historical climate, simulated precipitation is evaluated against observations to establish model reliability. The results show that models largely agree on increases in variability on all timescales in all sub-regions, except on ENSO timescales where models do not agree on the sign of future change. Brazil will experience more rainfall variability in the future that is, drier or more frequent dry periods and wetter wet periods on daily, weekly, monthly, and intra-seasonal timescales, even in sub-regions where future changes in mean rainfall are currently uncertain. This may provide useful information for climate change adaptation across, for example, the agriculture and water resource sectors in Brazil.

The marine reservoir of dissolved organic carbon (DOC) is equivalent to the atmospheric carbon reservoir and represents the largest reduced carbon stock in the ocean. However, the role of DOC in the global carbon cycle is not fully understood. In this study, we analyzed the distribution of DOC in the water column of the Bransfield Strait, Northern Antarctic Peninsula. Data were collected during two summer cruises of the NAUTILUS project conducted by the Brazilian High Latitude Oceanography Group in February 2015 and 2016. We investigated the possible effects of the El Nino – Southern Oscillation (ENSO) and Southern Annular Mode (SAM) climate modes on DOC variability based on correlations between DOC and temperature, salinity, and dissolved oxygen. Concentrations of DOC ranged from 40.70 to 122.82 mu mol kg(-1) in 2015 and 33.12 to 112.20 mu mol kg(-1) in 2016. The analysis shows that the vertical distribution of DOC in the Bransfield Strait may be controlled by a combination of vertical stratification, vertical export of organic matter and biological activity in the upper mixed layer during summertime. The significant interannual differences observed between DOC concentration and most physicochemical parameters may be linked to ENSO and SAM climate modes. The highest DOC concentration was observed in February 2015, associated with a layer of warm surface water, due to the higher stratification of the water column. The ENSO and SAM climate modes were low and positive in that year, favoring intrusions of waters from the Antarctic Circumpolar Current. In contrast, February 2016 was characterized by record positive ENSO and SAM modes. The intensification of the Weddell Gyre induced the advection of cold, more oxygenated and recently formed shelf waters into the Bransfield Strait, which may have contributed to the lower DOC concentrations. This study contributes to a better understanding of the role of DOC in the global carbon cycle in a region of complex ocean circulation and mixing, and sensitive to global climate change.

The marine reservoir of dissolved organic carbon (DOC) is equivalent to the atmospheric carbon reservoir and represents the largest reduced carbon stock in the ocean. However, the role of DOC in the global carbon cycle is not fully understood. In this study, we analyzed the distribution of DOC in the water column of the Bransfield Strait, Northern Antarctic Peninsula. Data were collected during two summer cruises of the NAUTILUS project conducted by the Brazilian High Latitude Oceanography Group in February 2015 and 2016. We investigated the possible effects of the El Nino – Southern Oscillation (ENSO) and Southern Annular Mode (SAM) climate modes on DOC variability based on correlations between DOC and temperature, salinity, and dissolved oxygen. Concentrations of DOC ranged from 40.70 to 122.82 mu mol kg(-1) in 2015 and 33.12 to 112.20 mu mol kg(-1) in 2016. The analysis shows that the vertical distribution of DOC in the Bransfield Strait may be controlled by a combination of vertical stratification, vertical export of organic matter and biological activity in the upper mixed layer during summertime. The significant interannual differences observed between DOC concentration and most physicochemical parameters may be linked to ENSO and SAM climate modes. The highest DOC concentration was observed in February 2015, associated with a layer of warm surface water, due to the higher stratification of the water column. The ENSO and SAM climate modes were low and positive in that year, favoring intrusions of waters from the Antarctic Circumpolar Current. In contrast, February 2016 was characterized by record positive ENSO and SAM modes. The intensification of the Weddell Gyre induced the advection of cold, more oxygenated and recently formed shelf waters into the Bransfield Strait, which may have contributed to the lower DOC concentrations. This study contributes to a better understanding of the role of DOC in the global carbon cycle in a region of complex ocean circulation and mixing, and sensitive to global climate change.

Land surface/ecosystem models (LSEMs) play a key role in understanding the Earths climate. They represent ecosystem dynamics by simulating fluxes occurring between the biosphere and atmosphere. However, for a correct flux simulation, it is critical to calibrate the model using robust and state-of-the-art calibration techniques. In this work, we optimize parameters of the Integrated Model of Land Surface Processes (INLAND) using the hierarchical multi-objective calibration method (AMALGAM) to improve the representation of surface processes in a natural ecosystem over the Pampa biome in South America. The calibration was performed using experimental data of energy and CO2 flux collected in a native field located in southern Brazil. We compared simulations using the default and calibrated parameter set. The results show that the calibration of the model significantly improved all fluxes analyzed. The mean errors and bias values were significantly reduced, and the seasonality of fluxes was better represented. This work is one of the first to apply a multi-objective calibration in an LSEM to represent surface fluxes in the Pampa biome, presenting a consistent set of parameters for future applications used in studies of biome land use and land cover.

This study is concerned with the effects of a decrease in the air pollution concentration on the lightning characteristics of two large Brazilian cities. The decrease in air pollution happened from March 20, till April 02, 2020, and it was caused by the social distancing effort to contain the COVID-19 spread in the cities. In Sao Paulo, the ratio between cloud-to-ground to intracloud flashes and the average peak current of negative cloud-to-ground flashes significantly decreased; whereas in Belo Horizonte, the ratio between positive and negative cloud-toground flashes significantly increased with respect to the values in previous years.

Eutrophication is the prime water quality issue in inland waters. Eutrophication and its key symptom, harmful cyanobacterial blooms, is expected to further increase in the future, which highlights the importance of managing the issue. The reduction of external nutrient load is crucial but might not bring fast relief to eutrophic waters due to ongoing diffuse pollution and legacy nutrients in the sediment. In this context, in-lake measures are needed to speed-up recovery. In this review, we discuss different in-lake measures based on coagulation and precipitation of cyanobacteria and/or phosphate for different lake categories (e.g., shallow or deep, mainly external or internal nutrient load, occurrence of perennial or summer blooms). In deep lakes with an external nutrient load higher than the internal load, a Floc and Sink method could be used in which a coagulant (e.g. aluminium salts, Al-salts; chitosan) combined with a ballast (e.g. soil, clay) removes a cyanobacterial bloom out of the water column. In case the deep lake suffers from high internal load, a phosphate (P)-fixative (e.g. lanthanum modified bentonite or Al-salts) can be used to Lock the legacy P, possibly combined with a coagulant a Floc and Lock technique. The latter approach will target both the particulate P in a bloom and the internal P load. A shallow lake that suffers from summer blooms and in which the internal load is higher than the external load, a Lock strategy of winter application of a P-fixative is proposed to prevent bloom development. In shallow lakes with perennial blooms, an agent to damage the cells (such as H2O2) is required together with a coagulant and a ballast to avoid recolonization of the water column due to resuspension a Kill, Floc and Sink/ Lock method. The selection of the most promising in-lake measures and materials should be based on a proper system diagnosis and tests prior to a full-scale intervention. These methods can be effective, but evidently reduction of external nutrient loads, both from point- and non-pointed sources, is an absolute necessity to restore aquatic ecosystems in a holistic sense.

Como principal fonte de energia do sistema Terra/Atmosfera, o conhecimento sobre a radiação solar e os processos físicos que ocorrem até a incidência na superfície do planeta éuma condi­ção básica para a meteorologia e climatologia. A radiação solar éa principal fonte de energia do sistema Terra/Atmosfera e regula o equilíbrio termodinâmico e climático do planeta. Ademais, o conhecimento da irradiação solar também desempe­nha papel importante em diversas áreas das atividades humanas, tais como o agronegócio, a arquitetura e construção civil. No momento atual, a conversão da energia solar em eletricidade está em forte crescimento em várias regiões do mundo, incluindo o Brasil, de modo que a capacidade de estimar e prever o recurso energético solar é fundamental para o planejamento e operação do sistema elétrico e de plantas de geração solar. No entanto esse crescimento também traz desafios tecnológicos associados às incertezas e à intermitência natural da radiação solar incidente na superfície, e que serão superados com a formação de recursos humanos baseada em sólido conhecimento científico para dar suporte ao desenvol­vimento de tecnologias e inovações que promovam a viabilidade técnica e econômica do recurso solar. O livro pretende preencher uma importante lacuna na disseminação do conhecimento visando à promoção da inserção da energia solar na matriz elétrica brasileira. Este livro é resultado de uma parceria longa que teve início com uma visita ao Prof. Enio Pereira em São José dos Campos no final dos anos 90. Ali, discutimos as diretrizes para minha pesquisa de doutorado envolvendo modelagem numérica para avaliação da irradiação solar incidente no território brasileiro desenvol­vida no INPE sob sua orientação e com financiamento da FAPESP. Desde então, trilhamos um bom percurso em projetos de pesquisa e desenvolvimento tecnológico que nos proporcionou a experiência e oportunidade de elaborar este livro. O material que compõe o livro foi desenvolvido, utilizado e aprimorado inúmeras vezes como resultado de atividades de treinamento, minicursos e capacitação técnica ministrados pela equipe de pesquisadores do Laboratório de Modelagem e Estudos de Recursos Renováveis de Energia ao longo dos últimos anos. Somado a isso, tivemos também a oportunidade de participar juntos de vários projetos internacionais com foco nos estudos e levanta­mentos dos recursos de energia solar e eólica, entre eles o SWERA (Solar and Wind Energy Resource Assessment), cujos resultados são até hoje bastante utilizados pelo setor de energia. O foco dessas ativi­dades sempre foi o de promover a disseminação de conhecimento científico adquirido utilizando as tecnologias de sensoriamento remoto, modelagem numérica e bases de dados georeferenciadas sobre o recurso de energia solar no Brasil. Esta publicação visa a consolidar esse esforço ampliando o alcance a um público mais amplo e utilizando uma sólida abordagem técnica, porém com uma linguagem que facilite a compreensão daqueles que estão iniciando suas atividades e aprimorando suas habilidades e competências na avaliação da disponibilidade e variabilidade espaço-temporal deste recurso de energia. Acreditamos que o livro pode ser utilizado como texto de suporte pedagógico em unidades curriculares de cursos de Engenharia e de outras ciências exatas que tratem sobre o aproveitamento do recurso solar uma vez que aborda tópicos diretamente relacionados à avaliação e prospecção do recurso energético. Seu escopo, porém, não aborda as tecnologias de conversão da energia solar em eletri­cidade e/ou em energia térmica, uma vez que esse tema já é tratado em literaturas específicas. O foco desta obra está na abordagem de tópicos que permitem compreender o que é a radiação solar e como avaliar o recurso energético incidente na superfície para aproveita­mento e geração de energia. O livro aborda os aspectos astronômicos e atmosféricos que influenciam na distribuição espacial e nas variabilidades sazonais da incidência de radiação solar na superfície. Descreve, ainda, os aspectos e cuidados necessários para aquisição de dados de campo e importância que apresentam no desenvolvimento de metodologias e ferramentas computacionais para o levantamento, a previsão e a variabilidade deste recurso energético. O livro termina apresentando e discutindo métodos numéricos com uso de técnicas de sensoria­mento remoto utilizar tanto no mapeamento espacial da energia solar no território brasileiro. Temos esperança que o conteúdo deste livro seja útil e pedimos que nos informem se identificarem incorreções ou tenham sugestões para o aprimoramento deste material.

Digital cameras deployed on the surface are frequently used for monitoring atmospheric conditions. Several methods were developed to use the images for synoptic observations, cloud assessments, validation of satellite models, short term forecasting and so on. However, there are some restrictions not considered by these methods, especially when a linear camera sensor is used to observe logarithmic ranges of atmospheric luminance. Cameras usually accommodate the scene to a linear scale causing distortions on pattern distributions by pixel value saturation (PVS) and drifts from its original hues. This solution brings on some simplifying practices commonly found in the literature to overcome these problems. But those practices result in loss of data, misinterpretation of valid pixels and restriction on the use of computer vision algorithms. The present work begins by illustrating these problems performing supervised learning and analysis for two reasons: all observation systems seek out automation of human synoptic observation in order to provide a sound mathematical modeling of the observed patterns. A new modeling paradigm is proposed to map the sky patterns to represent the existent physical atmospheric phenomena not considered by the approaches found over the literature. In order to validate the proposed method, we compared the results of the analysis of 1630 images against two well-established methods. A hypothesis test showed that results are compatible with currently used dichotomizer approach with advantages, although the proposed method was downgraded to a common comparison ground. Differences were due to PVS and as well as other restrictions not considered by the methods existent on literature. Finally, the present work concludes that the new paradigm presents more meaningful results of sky patterns interpretation, allowing extended daylight observation periods and uses a higher dimensional domain of color space available for the analysis.