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Kendall´s tau values for SPI and SPEI values calculated from gridded data of Xavier et al. (2022) for the period 1980–2019 and for different timescales. Colored pixels indicate statistically significant values (p < 0.05)

Kendall´s tau values for SPI and SPEI values calculated from gridded data of Xavier et al. (2022) for the period 1980–2019 and for different timescales. Colored pixels indicate statistically significant values (p < 0.05)

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Unlabelled: Drought indices are a numerical representation of drought conditions aimed to provide quantitative assessments of the magnitude, spatial extent, timing, and duration of drought events. Since the adverse effects of droughts vary according to the characteristics of the event, the socioeconomic vulnerabilities, exposed communities or envi...

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... the SPEI derived from the gridded data of Xavier et al. (2016) was validated with other sources of information, we analyzed trends of SPI and SPEI for the period 1980-2019. Figure 4 shows Kendall´s tau values for the SPI and SPEI values derived from the gridded data of Xavier et al. (2022) for different timescales. Colored pixels indicate statistical significance for a confidence level below 0.05. ...
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... ( Hastenrath and Heller 1977). On the other hand, Northern Amazonia shows significant positive trends, which are consistent with the intensification of the hydrological cycle in northern Amazonia ( Gloor et al. 2013). Positive trends were also detected in a region close to the coastal area of the Brazilian Northeast and South. More importantly, Fig. 4 clearly illustrates that the trends are much more significant and spatially homogeneous in the case SPEI compared to SPI. Consequently, it is clear that the magnitude of the trends are enhanced for the index that include reference ...
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... with several previous studies (for instance, Salviano et al. 2016;Penereiro et al. 2018). On the other hand, the bottom row shows that significant trends for monthly precipitation are present only in a few areas in Brazil, mostly concentrated in the northern region. Besides, it shows a spatial distribution similar to SPI on the shorter time scale (Fig. 4). In contrast, the difference in P-ETo shows more significant decrease trends (dryness trends) than P, mainly in central Brazil. However, the significant areas are also smaller than those identified by SPEI on longer time scales (Fig. 4). Although the magnitude of trends in P-ETo is not more pronounced such as in the case of ...
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... in the northern region. Besides, it shows a spatial distribution similar to SPI on the shorter time scale (Fig. 4). In contrast, the difference in P-ETo shows more significant decrease trends (dryness trends) than P, mainly in central Brazil. However, the significant areas are also smaller than those identified by SPEI on longer time scales (Fig. 4). Although the magnitude of trends in P-ETo is not more pronounced such as in the case of temperature, it is clear that those trends become more significant for increasing time-steps, as indicated by Fig. 4. Based on this analysis, it is possible to conclude that there are statistically significant negative trends in both SPI and SPEI ...
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... than P, mainly in central Brazil. However, the significant areas are also smaller than those identified by SPEI on longer time scales (Fig. 4). Although the magnitude of trends in P-ETo is not more pronounced such as in the case of temperature, it is clear that those trends become more significant for increasing time-steps, as indicated by Fig. 4. Based on this analysis, it is possible to conclude that there are statistically significant negative trends in both SPI and SPEI over the period 1980-2019 in most of Central Brazil, which becomes more significant for SPEI mostly related to the increase in evaporation associated with higher temperatures. Those trends become pronounced ...
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... area most affected by the negative trends of Fig. 4 includes regions heavily populated to the east, and almost the whole region of the country known as the new agricultural frontier in central Brazil within the Cerrado Biome, which is an area undergoing intense land use dynamics in recent decades and is responsible for the increase in grain production in Brazil ( Vieira et al. 2021a, ...
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... addition, the areas affected by negative trends in Fig. 4 correspond to the headwaters of the Paraná, Paraguay, São Francisco, and Tocantins rivers. Besides the importance of these basins for navigation and water supply, they host more than 90% of the country's hydropower installed capacity (ONS 2021). In this context, the blue line of Fig. 5 shows the stored energy in hydropower plants of ...
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... a decrease in the number of consecutive dry days. This result indicates that intense precipitation is concentrated in fewer days separated by longer dry spells, which can be partly explained by natural climate variability, global warming and/ or urbanization ( Marengo et al. 2020) and provides an additional explanation for the results shown in Fig. ...
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... it is worth mentioning that the projections of the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2021) show the same spatial patterns observed in Fig. 4, i.e., wetter conditions in the south of Brazil and drier conditions in the rest of the country. IPCC scenarios indicate the same pattern even in the case of the milder climate change scenario (Paris agreement), though changes are exacerbated under higher ...

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... In this context, there is a marked increase in the maximum number of consecutive dry days from the coast (~30 days) to the interior of the state (~50 days) (Luiz- Silva & Oscar-Júnior, 2022). Additionally, recent studies report a significant trend in drought severity for cumulative water 440 imbalances on time scales of 12 months and longer (Tomasella et al., 2022). In addition, Cordeiro has registered the largest precipitation reduction in the State of Rio de Janeiro over the period 1979-2009(Sobral et al., 2019. ...
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... Aggregated data eliminates the need to interpolate values between different gauge stations, considering that all gaps are filled with observed data, ensuring higher reliability in the results (Gao et al. 2022). Precipitation distribution and trends can be analysed using different indices, allowing for the examination of longer historical data from various perspectives (Teixeira and Satyamurty 2011;Hänsel, Schucknecht, and Matschullat 2016), reducing uncertainty regarding conclusions about changes in precipitation patterns (Salviano, Groppo, and Pellegrino 2016;Tomasella et al. 2023). ...
... The 12-and 24-month SPI showed a reduction in precipitation occurring with greater intensity, suggesting an increase in hydrological droughts (Gonçalves et al. 2021), which led to the depletion of surface and groundwater reservoirs (Hobeichi et al. 2022). Tomasella et al. (2023) observed similar results, with a significant negative trend for most of Goiás State and the Federal District using SPI for 3, 6, 12 and 24 months from 1980 to 2019, in association with an increase in evapotranspiration due to higher temperatures. Such events cause water scarcity, and the results provide a foundation for the development of waterscarcity mitigation strategies to ensure water supply for different sectors. ...
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