The purpose of this work is to evaluate the applicability of five drought indices (Surface Water Supply Index—SWSI, Reclamation Drought Index—RDI, Streamflow Drought Index—SDI, Standardized Precipitation Index—SPI, and Evaporative Demand Drought Index—EDDI) as tools for monitoring, in identifying the duration, intensity, and frequency of hydrological droughts in the basins of the Banabuiú, Castanhão, and Orós reservoirs, located in the state of Ceará, Brazil. The analysis focused on determining the performance of the indexes for capturing the droughts characteristics from 2002 to 2020. Thus, the comparison of the values of the indexes with the Target Levels of the reservoir’s operation were used, as well as the analysis of six decision criteria: robustness, tractability, transparency, sophistication, extensibility, and dimensionality, to compare the behavior of drought indices. The results of the evaluation criteria showed that the SPI was superior to the other indices, being able to significantly represent the drought episodes, capturing a greater number of events. Thus, SPI received the highest total weighted score (118), followed by SWSI (97), EDDI (95), SDI (95), and RDI (88). In this context, it was found that the SPI and SWSI are the most suitable indices to monitor drought in the region and that the use of longer time scales can be recommended to manage hydrological droughts, in order to improve planning and management of water resources.

Climate change impacts may influence hydropower generation, especially with the intensification of extreme events and growing demand. In this study, we analyzed future hydroelectric generation using a set of scenarios considering both climate change and consumptive demands in the São Francisco River Basin. This project will increase consumptive demands for the coming decades. Five models from the recently released Coupled Model Intercomparison Project Phase 6 and two scenarios, SSP2-4.5 and SSP5-8.5, were considered to estimate climate change projections. The affluent natural flows, regulated flows, and the hydroelectric energy generated were estimated for four multi-purpose reservoirs considering all existing and new demands. The conjunction of scenarios indicated a possible significant reduction in water availability, increased consumptive demands, especially for irrigation, and reduced power generation. Only at the Sobradinho hydroelectric plant, the decrease ranged from −30% to −50% for the period 2021 to 2050 compared to the historical period (1901 to 2000). The results can provide insights into future energy generation and water resources management in the basin.

Resumo O presente artigo faz uma revisão bibliográfica e aborda os principais índices utilizados no monitoramento e análise de secas. Além disso, o texto ainda discorre sobre as metodologias empregadas mundialmente no monitoramento e previsão desses eventos. As secas ocorrem quando existe um déficit de precipitação comparado à média histórica da região. Elas podem ser diagnosticadas por meio de índices que identificam os períodos de escassez ou de disponibilidade hídrica através de equações. Dessa forma, é possível determinar a intensidade, frequência e duração dos eventos de seca. Nesse âmbito, alguns países implementaram seus próprios sistemas de monitoramento e alerta precoce das secas como o Monitor de Secas dos Estados Unidos, o Monitor de Secas da Europa e o Monitor de Secas do Brasil. Onde estes, utilizam de forma conjunta ou isolada as informações provenientes dos índices, a fim de identificar e caracterizar os eventos de seca. Desse modo, pode haver um melhor planejamento das instituições responsáveis, adoção de planos emergenciais e mitigação de impactos.

Este trabalho apresenta análises de projeções de mudanças nos campos de precipitação e temperatura em simulações de downscaling dinâmico no contexto do projeto CORDEX. O domínio da simulação corresponde às Américas Tropicais, mas a região de estudo se restringe a duas sub-regiões do Nordeste Brasileiro: Norte (NNEB) e Sul (SNEB). O modelo regional utilizado nas simulações foi o RAMS6.0, forçado por dados do modelo global HadGEM2-ES. Foram analisados os períodos presente e três "fatias de tempo" futuras sob o cenário climático RCP8.5. Para a precipitação e temperatura no clima presente, a simulação foi comparada com os dados do CRU com finalidade de avaliar o desempenho e os erros de viés dos modelos. O RAMS6.0 mostra-se superior ao HadGEM2-ES em aspectos como, a representação da fase do ciclo anual de precipitação e temperatura, redução do viés seco na estação seca sobre o NNEB e distribuição espacial de ambas as variáveis, especialmente temperatura. Entretanto, o RAMS6.0 também exacerba alguns erros do modelo global, como o viés úmido na estação chuvosa. No clima futuro, foram analisadas as mudanças nos valores climatológicos e nos campos anuais das duas variáveis. Alguns padrões projetados pelos dois modelos incluem redução da precipitação no inverno austral e aumento da temperatura no decorrer do século.

The Northern Northeast Brazil (NNB) has two rainy periods, namely Pre-Wet Season (PWS) and Wet Season (WES), which are usually treated as one system. The precipitation pattern on NNB is influenced by sea surface temperature (SST) anomalies in the Atlantic and Pacific Ocean on interannual timescales particularly by the Interhemispheric Gradient of SST anomalies (IGS) and El Niño Southern Oscillation (ENSO). On intraseasonal time scales, the MJO is especially important. This study investigates the variability of the PWS/WES. The PWS is largely associated with the development of the South America Monsoon System and South Atlantic Convergence Zone (SAMS/SACZ); the onset is depicted by incursion of the SAMS/SACZ northward. Anomalous atmospheric cyclonic circulation over the southeastern Brazil along with easterlies over the northern Tropical Atlantic marks the early onset of the PWS, while easterlies over the southern Tropical Atlantic are related to late onset episodes. The demise of the PWS is significantly associated with propagation of the MJO, specifically during phases 4-5 of the MJO lifecycle. A Rossby wave train in 200-hPa geopotential height with positive anomalies over central-southern Brazil is depicted during transition between PWS and WES.