Extremos de precipitação na Região Hidrográfica do Paraná: climatologia, tendências e influência dos modos de variabilidade do Atlântico

Abstract

The Brazilian power grid is largely dominated by hydroelectric generation, accounting for approximately 50% of the country's total energy production. The operation and planning of the energy sector are intrinsically linked to precipitation variability, which directly influences reservoir levels and inflow rates. The Paraná Hydrographic Region (PHR) plays a strategic role in this context, standing out for its high economic development, intense demand for water resources, and concentration of hydroelectric plants. Given its socioeconomic and environmental relevance, this study aims to develop a detailed climatology of precipitation extremes in the PHR and identify trends in recent decades. For this purpose, daily precipitation data from the Brazilian Daily Weather Gridded Data dataset for the period 1961-2020 were used. The analysis employed climate extreme indicators calculated using the xClim library, complemented by the MannKendall statistical test (significance) and Sen’s slope (trend magnitude). The results reveal striking spatial and temporal contrasts in precipitation patterns. The southern portion of the PHP shows statistically significant increasing trends in total annual precipitation (PRCPTOT), daily intensity (SDII), and frequency of extreme events (R95p, Rx1day). In contrast, the northern region exhibits greater seasonality, with a significant increase in consecutive dry days (CDD), indicating a higher risk of prolonged droughts, and a decrease in consecutive wet days (CWD), suggesting more frequent interruptions in rainy periods. Seasonal analysis demonstrates that summer concentrates the highest precipitation volumes, while winter is the driest season. Climate variability patterns, like Tropical North Atlantic (TNA), Tropical South Atlantic (TSA) and Southwest South Atlantic (SWSA), had distinct impacts on precipitation extremes in the Paraná River Basin. TNA was associated with drier summers and fewer extreme events, while TSA reduced rainfall and increased dry spells in autumn and winter. SWSA mainly influenced summer and spring, with opposite effects between the northern and southern regions. These results have important implications for energy planning and water resource management, highlighting the need for regionalized approaches to mitigate climate change impacts.