José Maria Brabo Alves

Reservoir Management Using Coupled Atmospheric and Hydrological Models: The Brazilian Semi-Arid Case

This study investigated the sensitivity of a dynamic downscaling atmospheric model system coupled with a rainfall-runoff model to hindcast an example of reservoir water management in the semi-arid region of Northeast Brazil (NEB). A regional atmospheric spectral model (RSM) is driven by the outputs of an atmospheric general circulation model (AGCM), itself forced by the observed sea surface temperature over the World Ocean. Daily precipitation simulated by the RSM was then used as the input to a hydrological rainfall-runoff model for the Upper Jaguaribe River Basin to estimate inflows at the Orós Reservoir in the state of Ceará. A hindcast analysis of precipitation was performed during the rainy season over NEB (January to June) from 1971 to 2000. The RSM captured the precipitation variability relatively well when a probability density function (PDF) was used to correct the numerical bias. Three hindcast series of inflow using (i) the observed rainfall, (ii) the simulated rainfall before the PDF correction, and (iii) the simulated rainfall after the PDF correction were performed during the study period and then compared to the series of observed inflow. The atmospheric-rainfall-runoff “cascade” model efficiency was evaluated by comparing the Orós Reservoir release decisions from different scenarios based on observed, simulated (RSM, RSM-PDF), and mean historical reservoir inflows. The cascade model has the potential, relatively well balanced during dry, normal or wet years, to be a useful tool to correctly forecast the decision managements of reservoirs in the semi-arid region of NEB. Additional progress in the numerical simulation is however necessary to improve the performance.

Um estudo inter-comparativo de previsão sazonal estatística-dinâmica de precipitação no nordeste do Brasil

Despite significant advances of the dynamic atmosphere models over the last decades of the 20th century, the empirical atmospheric models have been widely used due mostly to both its general applicability and its little dependence on the computational resources. This study is show comparison of precipitation simulation to Northeast Brazil (NEB) - 1971-2000 from large scale dynamical modeling and regional model (downscaling) and the forecast of empirical modeling (K-nearest-neighbor (k-NN). Were user the general circulation model ECHAM4.5 together two regional models, the Regional Spectral Model (RSM/97) from the National Centers for Atmospheric Prediction-NCEP and the Regional Atmospheric Model System (RAMS) developed at Colorado State University. The regional models were nested in ECHAM4.5, forced with the observed Sea Surface Temperature as a boundary condition, for the period from February to May. The results show that the empirical model presented a smaller absolute error than the dynamic models for the periods February to April (FMA) and March to May (MAM) in isolated areas of the north of Maranhao and Piaui states, west and south of Ceara, center-south of Piaui and west and northeast of Bahia state. Regarding model biases, ECHAM4.5 and the RSM/97 produced, to a large extent, a humid bias over large areas of NEB, however with an average precipitation for the northern sector of NEB (2oS-12oS and 45oW-37oW) close to the observations. RAMS and the analog method had a dominance of a dry bias over NEB, with precipitation totals below the observed values. The model skills (using the Heidke score) were evaluated for three categories Dry (S), Normal (N), Rainy (C), showed that the analogous method has low skills, between 0,1 and 0,3 in all categories, while dynamic models presented superior skills, with larger values for categories S and C (of the order of 0,4 the 0,5), exceeding 0,6 in some areas of the northern sector of NEB for category C as seen in the models ECHAM4.5 and RSM/97 models.

Sobre o sinal de um downscaling dinâmico às oscilações intrassazonais de precipitação no setor norte do Nordeste do Brasil

Oscilacoes intrassazonais sao fatores controladores da variabilidade pluviometrica interanual de areas tropicais. O conhecimento de como os modelos numericos reproduzem suas variabilidades e importante para entender melhor suas atuacoes e subsidiar operacoes de previsao de tempo e clima. Neste artigo investiga-se a sensibilidade de um modelo de downscaling dinâmico de precipitacao na reproducao das oscilacoes intrassazonais observadas no setor norte do Nordeste do Brasil (SNNEB - 45oW-37oW e 2oS-12oS) no periodo de 1974 a 2000. Os resultados mostraram que a precipitacao simulada sobre o SNNEB explicou aproximadamente 70% da variabilidade da precipitacao observada no trimestre fevereiro a abril nesta regiao. Estatisticas de medias, desvios normalizados e percentuais neste trimestre, nessa regiao, em anos de contrastes climaticos nos Oceanos Pacifico e Atlântico Tropicais, tambem foram bem capturadas pela precipitacao simulada atraves do downscaling. Analises espectrais com uso de ondeletas mostraram que o downscaling dinâmico tem potencial para reproduzir picos espectrais de precipitacao observada no SNNEB nas escalas acima de 8 dias, e nas escalas entre 64 e 128 dias para o periodo de 01 de janeiro a 30 de junho.

Sensibilidade intrasazonal de um downscaling dinâmico de precipitação (1971-2000): uma análise na bacia hidrográfica do Açude Castanhão-CE

In arid regions as northeast part of Brazil (NEB) artificial water reservoirs are essences to accumulate water in the rainy period and to supply its demand for release in the dry period. For this fact, the knowledge of the pluviometric variability in the hydrographic basin of these reservoirs is important. The results presented here show comparisons between observed data and simulation from dynamic modeling for the basin of the Castanhao-Ce Dam with emphases the intra seasonal scale. The interanual variability of intra-seasonal precipitation (1971-2000) simulated by the spectral regional model (MRE) has a systematic bias that underestimation the observed totals (pentads and biweekly), mainly in the period of February the May, and overestimates these totals in January and June. However, were also verified bigger (lesser) quantitative differences in these totals in the sub estimation in the decades of 1970-1980-1990 e (1990-2000). For climatic years of contrast (La Nina, El Nino and Normal), the MRE in the scales pentad, biweekly and monthly captured with good performance the signal of the anomaly in relation to the precipitation observed, predominating positive anomaly for the years of La Nina, and around the average the refusal for the Normal years and of El Nino, in particular during February the May. This characteristic also was verified in the precipitation data observed in the basin.

Estimativa dos recursos eólicos no litoral cearense usando a teoria da regressão linear

The current study deals with the estimation of wind resources in the coast of Ceara using the linear regression theory. Its main objective is to estimate average wind speed values at different altitudes from observed data at surface. Two areas located in the State of Ceara are investigated: Paracuru and Camocim. For each region the same procedure will be adopted. Initially the region is characterized by the daily and monthly mean wind speed profile obtained from the local Platform for Data Collection (PCD) and anemometric tower (TA) raw data. The prevailing wind direction data are also used. The logarithmic wind profile equation is used to estimate the values of average wind speed at altitudes of 20, 40 and 60 meters from the observed data at 10m surface, then calculating the correlation coefficients between the estimated altitude data and the observed TA data in the region. Then, the linear regression model is used to estimate new values in altitude. Initially this procedure is done for a period of model calibration and then for a period of validation. In both periods the linear regression model showed a good performance either by the high correlation coefficient values between the estimated and observed data series, or the low values of the errors between the series.

Um estudo de downscaling dinâmico de precipitação intrasazonal acoplado a modelo chuva-vazão na bacia hidrográfica alto-médio São Francisco

Este estudo mostra a aplicacao de modelagem hidroclimatica dinâmica (hydroclimate downscaling) de precipitacao acoplada a um modelo hidrologico chuva-vazao, para as Bacias hidrograficas denominadas Cachoeira Manteiga e Porto da Extrema, localizadas na Bacia do Alto-Medio Sao Francisco no Estado de Minas Gerais. Enfase foi dada a simulacao na escala intrasazonal (mensal). Os resultados sugerem que a simulacao de precipitacao pode ser usada como variavel de entrada em modelos de estimativa de vazao para periodos na escala de um mes, dando subsidio a um melhor aproveitamento dos recursos hidricos na bacia hidrografica estudada. Estes ainda sugerem que a simulacao de precipitacao, quando corrigida pela tecnica Probability Density Function (PDFs), e mais eficiente na estimativa de precipitacao simulada quando comparada com a precipitacao observada na bacia, resultando em uma melhor simulacao de vazao afluente na bacia.

Modeling of Wind Resources on Mozambique Considering a Climate Change Scenario

Abstract This work presents the application of the dynamic downscaling technique on the Regional Atmospheric Modeling Sys-tem (RAMS6.0) forced by output fields of the global circulation model HadGEM2-ES, to estimate the wind potentialover the regions of Mozambique considering the climate change scenario defined by IPCC. The results showed satisfac-tory performance of the RAMS6.0 model in the reproduction of mean patterns of wind fields obtained in the reanalysiscomparedtoCFSRandMERRAduringtheperiod1985-2005.Windsfieldsat10,50and100metersConsideringcondi-tions of the IPCC emission scenario (RCP8.5) for the period 2079-2099 showed higher values in relation to the windfieldsfortheperiod1985-2005.Furthermore,thereisevidenceofanincreaseinthewindpoweroverregionsofMozam-bique for the period 2079-2099, particularly during winter in the central and southern regions of the country. Keywords: wind energy, climate change, Mozambique. 1. Introducao A energia eolica e uma fonte de energia renovavelque tem apresentado um crescimento acelerado no mundo,dada a contribuicao que esta fonte pode desempenhar naprovisao de energia no futuro, bem como pela sua contri-buicao na mitigacao de alteracoes climaticas, pois e consi-derada uma das fontes de energia limpa, por apresentarbaixa emissao de gases do efeito estufa (Oliveira

Evaluation of the AR4 CMIP3 and the AR5 CMIP5 Model and Projections for Precipitation in Northeast Brazil

With the simulations of the models used in the latest reports from the Intergovernmental Panel on Climate Change (IPCC), comparative studies are necessary between observations and the so-called historical run (C20) and future projections of the AR4 (A2) and AR5 (RCP8.5) experiments, in order to assess whether the AR5 models had a better performance in the representation of physical processes. This article compares the sensitivity of IPCC models (AR4 and AR5) in representing the anuall average and seasonal rainfall variation (summer and autumn) in three regions of the Northeast of Brazil between 1979 and 2000, using the CMAP - CPC (Merged Analysis of Precipitation) data as reference. The projections made by these models for the period 2040-2070 were also analyzed.

Uma aplicação de conjuntos difusos na otimização do prognóstico de consenso sazonal de chuva no Nordeste do Brasil

This study presents the application of fuzzy sets theory as a tool for sazonal rain forecast of Semi-Arid Northeast Region of Brazil for the period of 1985-1996. Thermodynamic parameters in Tropical Atlântic and Pacific Oceans were used as input variables. The results have shown that qualitatively, in an annual scale, this technique was able to forecast at least one of the categories of the output variable (total February/May rain in the of Semi-Arid Northeast Region of Brazil). Quantitatively, the smallest errors have been observed for the years classified according to the output variable in the categories of Normal (N), Rainy (C), and Very Rainy (MC), with correlation coefficients ranging fron 0.8 to 0.85, depending on the defuzzification method used. This technique allows for the unification of all the climatic information used in the rain foreceast of Semi-Arid Northeast Region of Brazil and leads to a forecast grouped in more than one category, informing the one most likely to occur as a function of its membership value.

Estudo dos Padrões de Ventos Offshore no Litoral do Ceará Utilizando Dados Estimados pelo Produto de Satélites BSW

To know the spatial distribution of the wind patterns of a coastal region for monitoring the onshore and offshore wind potential goes through to the existence of a network of meteorological stations on the coast. On the coast of Ceará, a systematic analysis of the results obtained through prospective studies can be beneficial with the use of the results at 10 m estimated by satellites, BSW, with spatial and temporal resolution of 0.25° and six hours, respectively. In this work, BSW winds are validated in the vicinity of the coast of Ceará through oceanic buoys and anemometric towers. Verified its accuracy, these data are used to study spatial variability of sea winds in Ceará, in seasonal and interannual scale, and their correlation with the coastal winds.